Project SRP420678 services include NGS sequencing of the V1V3 region of the 16S rRNA gene amplicons from the samples. First and foremost, please
download this report, as well as the sequence raw data from the download links provided below.
These links will expire after 60 days. We cannot guarantee the availability of your data after 60 days.
Full Bioinformatics analysis service was requested. We provide many analyses, starting from the raw sequence quality and noise filtering, pair reads merging, as well as chimera filtering for the sequences, using the
DADA2 denosing algorithm and pipeline.
We also provide many downstream analyses such as taxonomy assignment, alpha and beta diversity analyses, and differential abundance analysis.
For taxonomy assignment, most informative would be the taxonomy barplots. We provide an interactive barplots to show the relative abundance of microbes at different taxonomy levels (from Phylum to species) that you can choose.
If you specify which groups of samples you want to compare for differential abundance, we provide both ANCOM and LEfSe differential abundance analysis.
The samples were processed and analyzed with the ZymoBIOMICS® Service: Targeted
Metagenomic Sequencing (Zymo Research, Irvine, CA).
DNA Extraction: If DNA extraction was performed, the following DNA
extraction kit was used according to the manufacturer’s instructions:
☑
ZymoBIOMICS®-96 MagBead DNA Kit (Zymo Research, Irvine, CA)
☐
N/A (DNA Extraction Not Performed)
Elution Volume: 50µL
Additional Notes: NA
Targeted Library Preparation: The DNA samples were prepared for targeted
sequencing with the Quick-16S™ NGS Library Prep Kit (Zymo Research, Irvine, CA).
These primers were custom designed by Zymo Research to provide the best coverage
of the 16S gene while maintaining high sensitivity. The primer sets used in this project
are marked below:
☐
Quick-16S™ Primer Set V1-V2 (Zymo Research, Irvine, CA)
☑
Quick-16S™ Primer Set V1-V3 (Zymo Research, Irvine, CA)
☐
Quick-16S™ Primer Set V3-V4 (Zymo Research, Irvine, CA)
☐
Quick-16S™ Primer Set V4 (Zymo Research, Irvine, CA)
☐
Quick-16S™ Primer Set V6-V8 (Zymo Research, Irvine, CA)
Additional Notes: NA
The sequencing library was prepared using an innovative library preparation process in
which PCR reactions were performed in real-time PCR machines to control cycles and
therefore limit PCR chimera formation. The final PCR products were quantified with
qPCR fluorescence readings and pooled together based on equal molarity. The final
pooled library was cleaned up with the Select-a-Size DNA Clean & Concentrator™
(Zymo Research, Irvine, CA), then quantified with TapeStation® (Agilent Technologies,
Santa Clara, CA) and Qubit® (Thermo Fisher Scientific, Waltham, WA).
Control Samples: The ZymoBIOMICS® Microbial Community Standard (Zymo
Research, Irvine, CA) was used as a positive control for each DNA extraction, if
performed. The ZymoBIOMICS® Microbial Community DNA Standard (Zymo Research,
Irvine, CA) was used as a positive control for each targeted library preparation.
Negative controls (i.e. blank extraction control, blank library preparation control) were
included to assess the level of bioburden carried by the wet-lab process.
Sequencing: The final library was sequenced on Illumina® NextSeq 2000™ with a p1
(Illumina, Sand Diego, CA) reagent kit (600 cycles). The sequencing was performed
with 25% PhiX spike-in.
Absolute Abundance Quantification*: A quantitative real-time PCR was set up with a
standard curve. The standard curve was made with plasmid DNA containing one copy
of the 16S gene and one copy of the fungal ITS2 region prepared in 10-fold serial
dilutions. The primers used were the same as those used in Targeted Library
Preparation. The equation generated by the plasmid DNA standard curve was used to
calculate the number of gene copies in the reaction for each sample. The PCR input
volume (2 µl) was used to calculate the number of gene copies per microliter in each
DNA sample.
The number of genome copies per microliter DNA sample was calculated by dividing
the gene copy number by an assumed number of gene copies per genome. The value
used for 16S copies per genome is 4. The value used for ITS copies per genome is 200.
The amount of DNA per microliter DNA sample was calculated using an assumed
genome size of 4.64 x 106 bp, the genome size of Escherichia coli, for 16S samples, or
an assumed genome size of 1.20 x 107 bp, the genome size of Saccharomyces
cerevisiae, for ITS samples. This calculation is shown below:
Calculated Total DNA = Calculated Total Genome Copies × Assumed Genome Size (4.64 × 106 bp) ×
Average Molecular Weight of a DNA bp (660 g/mole/bp) ÷ Avogadro’s Number (6.022 x 1023/mole)
* Absolute Abundance Quantification is only available for 16S and ITS analyses.
The absolute abundance standard curve data can be viewed in Excel here:
The absolute abundance standard curve is shown below:
The complete report of your project, including all links in this report, can be downloaded by clicking the link provided below. The downloaded file is a compressed ZIP file and once unzipped, open the file “REPORT.html” (may only shown as "REPORT" in your computer) by double clicking it. Your default web browser will open it and you will see the exact content of this report.
Please download and save the file to your computer storage device. The download link will expire after 60 days upon your receiving of this report.
Complete report download link:
To view the report, please follow the following steps:
1.
Download the .zip file from the report link above.
2.
Extract all the contents of the downloaded .zip file to your desktop.
3.
Open the extracted folder and find the "REPORT.html" (may shown as only "REPORT").
4.
Open (double-clicking) the REPORT.html file. Your default browser will open the top age of the complete report. Within the
report, there are links to view all the analyses performed for the project.
The raw NGS sequence data is available for download with the link provided below. The data is a compressed ZIP file and can be unzipped to individual sequence files.
Since this is a pair-end sequencing, each of your samples is represented by two sequence files, one for READ 1,
with the file extension “*_R1.fastq.gz”, another READ 2, with the file extension “*_R1.fastq.gz”.
The files are in FASTQ format and are compressed. FASTQ format is a text-based data format for storing both a biological sequence
and its corresponding quality scores. Most sequence analysis software will be able to open them.
The Sample IDs associated with the R1 and R2 fastq files are listed in the table below:
SRR23319523
Original Sample ID
SRR23319523_R1.fastq
SRR23319523_R2.fastq
SRR23319524
SRR23319524_R1.fastq
SRR23319524_R2.fastq
SRR23319525
SRR23319525_R1.fastq
SRR23319525_R2.fastq
SRR23319526
SRR23319526_R1.fastq
SRR23319526_R2.fastq
SRR23319527
SRR23319527_R1.fastq
SRR23319527_R2.fastq
SRR23319528
SRR23319528_R1.fastq
SRR23319528_R2.fastq
SRR23319529
SRR23319529_R1.fastq
SRR23319529_R2.fastq
SRR23319530
SRR23319530_R1.fastq
SRR23319530_R2.fastq
SRR23319531
SRR23319531_R1.fastq
SRR23319531_R2.fastq
SRR23319532
SRR23319532_R1.fastq
SRR23319532_R2.fastq
SRR23319533
SRR23319533_R1.fastq
SRR23319533_R2.fastq
SRR23319534
SRR23319534_R1.fastq
SRR23319534_R2.fastq
SRR23319535
SRR23319535_R1.fastq
SRR23319535_R2.fastq
SRR23319536
SRR23319536_R1.fastq
SRR23319536_R2.fastq
SRR23319537
SRR23319537_R1.fastq
SRR23319537_R2.fastq
SRR23319538
SRR23319538_R1.fastq
SRR23319538_R2.fastq
SRR23319539
SRR23319539_R1.fastq
SRR23319539_R2.fastq
SRR23319540
SRR23319540_R1.fastq
SRR23319540_R2.fastq
SRR23319541
SRR23319541_R1.fastq
SRR23319541_R2.fastq
SRR23319542
SRR23319542_R1.fastq
SRR23319542_R2.fastq
SRR23319543
SRR23319543_R1.fastq
SRR23319543_R2.fastq
SRR23319544
SRR23319544_R1.fastq
SRR23319544_R2.fastq
SRR23319545
SRR23319545_R1.fastq
SRR23319545_R2.fastq
SRR23319546
SRR23319546_R1.fastq
SRR23319546_R2.fastq
SRR23319547
SRR23319547_R1.fastq
SRR23319547_R2.fastq
SRR23319548
SRR23319548_R1.fastq
SRR23319548_R2.fastq
SRR23319549
SRR23319549_R1.fastq
SRR23319549_R2.fastq
SRR23319550
SRR23319550_R1.fastq
SRR23319550_R2.fastq
SRR23319552
SRR23319552_R1.fastq
SRR23319552_R2.fastq
SRR23319553
SRR23319553_R1.fastq
SRR23319553_R2.fastq
SRR23319554
SRR23319554_R1.fastq
SRR23319554_R2.fastq
SRR23319555
SRR23319555_R1.fastq
SRR23319555_R2.fastq
SRR23319556
SRR23319556_R1.fastq
SRR23319556_R2.fastq
SRR23319557
SRR23319557_R1.fastq
SRR23319557_R2.fastq
SRR23319558
SRR23319558_R1.fastq
SRR23319558_R2.fastq
SRR23319559
SRR23319559_R1.fastq
SRR23319559_R2.fastq
SRR23319560
SRR23319560_R1.fastq
SRR23319560_R2.fastq
SRR23319561
SRR23319561_R1.fastq
SRR23319561_R2.fastq
SRR23319562
SRR23319562_R1.fastq
SRR23319562_R2.fastq
SRR23319563
SRR23319563_R1.fastq
SRR23319563_R2.fastq
SRR23319564
SRR23319564_R1.fastq
SRR23319564_R2.fastq
SRR23319565
SRR23319565_R1.fastq
SRR23319565_R2.fastq
SRR23319566
SRR23319566_R1.fastq
SRR23319566_R2.fastq
SRR23319567
SRR23319567_R1.fastq
SRR23319567_R2.fastq
SRR23319568
SRR23319568_R1.fastq
SRR23319568_R2.fastq
SRR23319569
SRR23319569_R1.fastq
SRR23319569_R2.fastq
SRR23319570
SRR23319570_R1.fastq
SRR23319570_R2.fastq
SRR23319571
SRR23319571_R1.fastq
SRR23319571_R2.fastq
SRR23319572
SRR23319572_R1.fastq
SRR23319572_R2.fastq
SRR23319573
SRR23319573_R1.fastq
SRR23319573_R2.fastq
SRR23319574
SRR23319574_R1.fastq
SRR23319574_R2.fastq
SRR23319575
SRR23319575_R1.fastq
SRR23319575_R2.fastq
SRR23319576
SRR23319576_R1.fastq
SRR23319576_R2.fastq
SRR23319577
SRR23319577_R1.fastq
SRR23319577_R2.fastq
SRR23319578
SRR23319578_R1.fastq
SRR23319578_R2.fastq
SRR23319579
SRR23319579_R1.fastq
SRR23319579_R2.fastq
SRR23319580
SRR23319580_R1.fastq
SRR23319580_R2.fastq
SRR23319581
SRR23319581_R1.fastq
SRR23319581_R2.fastq
SRR23319582
SRR23319582_R1.fastq
SRR23319582_R2.fastq
SRR23319583
SRR23319583_R1.fastq
SRR23319583_R2.fastq
SRR23319584
SRR23319584_R1.fastq
SRR23319584_R2.fastq
SRR23319585
SRR23319585_R1.fastq
SRR23319585_R2.fastq
SRR23319586
SRR23319586_R1.fastq
SRR23319586_R2.fastq
SRR23319587
SRR23319587_R1.fastq
SRR23319587_R2.fastq
SRR23319588
SRR23319588_R1.fastq
SRR23319588_R2.fastq
SRR23319589
SRR23319589_R1.fastq
SRR23319589_R2.fastq
SRR23319590
SRR23319590_R1.fastq
SRR23319590_R2.fastq
SRR23319591
SRR23319591_R1.fastq
SRR23319591_R2.fastq
SRR23319593
SRR23319593_R1.fastq
SRR23319593_R2.fastq
SRR23319595
SRR23319595_R1.fastq
SRR23319595_R2.fastq
SRR23319596
SRR23319596_R1.fastq
SRR23319596_R2.fastq
SRR23319597
SRR23319597_R1.fastq
SRR23319597_R2.fastq
SRR23319598
SRR23319598_R1.fastq
SRR23319598_R2.fastq
SRR23319599
SRR23319599_R1.fastq
SRR23319599_R2.fastq
SRR23319600
SRR23319600_R1.fastq
SRR23319600_R2.fastq
SRR23319601
SRR23319601_R1.fastq
SRR23319601_R2.fastq
SRR23319602
SRR23319602_R1.fastq
SRR23319602_R2.fastq
SRR23319603
SRR23319603_R1.fastq
SRR23319603_R2.fastq
SRR23319604
SRR23319604_R1.fastq
SRR23319604_R2.fastq
SRR23319605
SRR23319605_R1.fastq
SRR23319605_R2.fastq
SRR23319606
SRR23319606_R1.fastq
SRR23319606_R2.fastq
SRR23319607
SRR23319607_R1.fastq
SRR23319607_R2.fastq
SRR23319608
SRR23319608_R1.fastq
SRR23319608_R2.fastq
SRR23319609
SRR23319609_R1.fastq
SRR23319609_R2.fastq
SRR23319610
SRR23319610_R1.fastq
SRR23319610_R2.fastq
SRR23319611
SRR23319611_R1.fastq
SRR23319611_R2.fastq
SRR23319612
SRR23319612_R1.fastq
SRR23319612_R2.fastq
Please download and save the file to your computer storage device. The download link will expire after 60 days upon your receiving of this report.
DADA2 is a software package that models and corrects Illumina-sequenced amplicon errors [1].
DADA2 infers sample sequences exactly, without coarse-graining into OTUs,
and resolves differences of as little as one nucleotide. DADA2 identified more real variants
and output fewer spurious sequences than other methods.
DADA2’s advantage is that it uses more of the data. The DADA2 error model incorporates quality information,
which is ignored by all other methods after filtering. The DADA2 error model incorporates quantitative abundances,
whereas most other methods use abundance ranks if they use abundance at all.
The DADA2 error model identifies the differences between sequences, eg. A->C,
whereas other methods merely count the mismatches. DADA2 can parameterize its error model from the data itself,
rather than relying on previous datasets that may or may not reflect the PCR and sequencing protocols used in your study.
Callahan BJ, McMurdie PJ, Rosen MJ, Han AW, Johnson AJ, Holmes SP. DADA2: High-resolution sample inference from Illumina amplicon data. Nat Methods. 2016 Jul;13(7):581-3. doi: 10.1038/nmeth.3869. Epub 2016 May 23. PMID: 27214047; PMCID: PMC4927377.
Analysis Procedures:
DADA2 pipeline includes several tools for read quality control, including quality filtering, trimming, denoising, pair merging and chimera filtering. Below are the major processing steps of DADA2:
Step 1. Read trimming based on sequence quality
The quality of NGS Illumina sequences often decreases toward the end of the reads.
DADA2 allows to trim off the poor quality read ends in order to improve the error
model building and pair mergicing performance.
Step 2. Learn the Error Rates
The DADA2 algorithm makes use of a parametric error model (err) and every
amplicon dataset has a different set of error rates. The learnErrors method
learns this error model from the data, by alternating estimation of the error
rates and inference of sample composition until they converge on a jointly
consistent solution. As in many machine-learning problems, the algorithm must
begin with an initial guess, for which the maximum possible error rates in
this data are used (the error rates if only the most abundant sequence is
correct and all the rest are errors).
Step 3. Infer amplicon sequence variants (ASVs) based on the error model built in previous step. This step is also called sequence "denoising".
The outcome of this step is a list of ASVs that are the equivalent of oligonucleotides.
Step 4. Merge paired reads. If the sequencing products are read pairs, DADA2 will merge the R1 and R2 ASVs into single sequences.
Merging is performed by aligning the denoised forward reads with the reverse-complement of the corresponding
denoised reverse reads, and then constructing the merged “contig” sequences.
By default, merged sequences are only output if the forward and reverse reads overlap by
at least 12 bases, and are identical to each other in the overlap region (but these conditions can be changed via function arguments).
Step 5. Remove chimera.
The core dada method corrects substitution and indel errors, but chimeras remain. Fortunately, the accuracy of sequence variants
after denoising makes identifying chimeric ASVs simpler than when dealing with fuzzy OTUs.
Chimeric sequences are identified if they can be exactly reconstructed by
combining a left-segment and a right-segment from two more abundant “parent” sequences. The frequency of chimeric sequences varies substantially
from dataset to dataset, and depends on on factors including experimental procedures and sample complexity.
Results
1. Read Quality Plots NGS sequence analaysis starts with visualizing the quality of the sequencing. Below are the quality plots of the first
sample for the R1 and R2 reads separately. In gray-scale is a heat map of the frequency of each quality score at each base position. The mean
quality score at each position is shown by the green line, and the quartiles of the quality score distribution by the orange lines.
The forward reads are usually of better quality. It is a common practice to trim the last few nucleotides to avoid less well-controlled errors
that can arise there. The trimming affects the downstream steps including error model building, merging and chimera calling. FOMC uses an empirical
approach to test many combinations of different trim length in order to achieve best final amplicon sequence variants (ASVs), see the next
section “Optimal trim length for ASVs”.
2. Optimal trim length for ASVs The final number of merged and chimera-filtered ASVs depends on the quality filtering (hence trimming) in the very beginning of the DADA2 pipeline.
In order to achieve highest number of ASVs, an empirical approach was used -
Create a random subset of each sample consisting of 5,000 R1 and 5,000 R2 (to reduce computation time)
Trim 10 bases at a time from the ends of both R1 and R2 up to 50 bases
For each combination of trimmed length (e.g., 300x300, 300x290, 290x290 etc), the trimmed reads are
subject to the entire DADA2 pipeline for chimera-filtered merged ASVs
The combination with highest percentage of the input reads becoming final ASVs is selected for the complete set of data
Below is the result of such operation, showing ASV percentages of total reads for all trimming combinations (1st Column = R1 lengths in bases; 1st Row = R2 lengths in bases):
R1/R2
251
241
231
221
211
201
233
75.66%
17.81%
14.34%
0.00%
0.00%
0.00%
223
18.24%
14.65%
0.00%
0.00%
0.00%
0.00%
213
15.02%
0.00%
0.00%
0.00%
0.00%
0.00%
203
0.01%
0.00%
0.00%
0.00%
0.00%
0.00%
193
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
Based on the above result, the trim length combination of R1 = 233 bases and R2 = 251 bases (highlighted red above), was chosen for generating final ASVs for all sequences.
This combination generated highest number of merged non-chimeric ASVs and was used for downstream analyses, if requested.
3. Error plots from learning the error rates
After DADA2 building the error model for the set of data, it is always worthwhile, as a sanity check if nothing else, to visualize the estimated error rates.
The error rates for each possible transition (A→C, A→G, …) are shown below. Points are the observed error rates for each consensus quality score.
The black line shows the estimated error rates after convergence of the machine-learning algorithm.
The red line shows the error rates expected under the nominal definition of the Q-score.
The ideal result would be the estimated error rates (black line) are a good fit to the observed rates (points), and the error rates drop
with increased quality as expected.
Forward Read R1 Error Plot
Reverse Read R2 Error Plot
The PDF version of these plots are available here:
4. DADA2 Result Summary The table below shows the summary of the DADA2 analysis,
tracking paired read counts of each samples for all the steps during DADA2 denoising process -
including end-trimming (filtered), denoising (denoisedF, denoisedF), pair merging (merged) and chimera removal (nonchim).
Sample ID
SRR23319523
SRR23319524
SRR23319525
SRR23319526
SRR23319527
SRR23319528
SRR23319529
SRR23319530
SRR23319531
SRR23319532
SRR23319533
SRR23319534
SRR23319535
SRR23319536
SRR23319537
SRR23319538
SRR23319539
SRR23319540
SRR23319541
SRR23319542
SRR23319543
SRR23319544
SRR23319545
SRR23319546
SRR23319547
SRR23319548
SRR23319549
SRR23319550
SRR23319552
SRR23319553
SRR23319554
SRR23319555
SRR23319556
SRR23319557
SRR23319558
SRR23319559
SRR23319560
SRR23319561
SRR23319562
SRR23319563
SRR23319564
SRR23319565
SRR23319566
SRR23319567
SRR23319568
SRR23319569
SRR23319570
SRR23319571
SRR23319572
SRR23319573
SRR23319574
SRR23319575
SRR23319576
SRR23319577
SRR23319578
SRR23319579
SRR23319580
SRR23319581
SRR23319582
SRR23319583
SRR23319584
SRR23319585
SRR23319586
SRR23319587
SRR23319588
SRR23319589
SRR23319590
SRR23319591
SRR23319593
SRR23319595
SRR23319596
SRR23319597
SRR23319598
SRR23319599
SRR23319600
SRR23319601
SRR23319602
SRR23319603
SRR23319604
SRR23319605
SRR23319606
SRR23319607
SRR23319608
SRR23319609
SRR23319610
SRR23319611
SRR23319612
Row Sum
Percentage
input
106,370
156,987
154,840
106,203
122,603
143,802
126,559
153,777
118,548
118,542
146,378
103,861
127,152
150,158
129,381
117,241
114,657
118,593
113,687
104,732
143,983
113,831
140,787
136,741
160,191
89,651
153,773
136,993
115,609
103,413
128,943
144,207
129,423
124,562
139,370
125,271
148,846
125,567
146,169
131,225
125,537
135,901
134,102
141,747
149,406
144,921
105,099
108,714
114,672
114,407
79,870
97,296
103,630
108,866
112,317
98,800
92,339
92,007
97,388
105,202
88,831
113,064
104,752
68,669
87,537
108,513
96,465
97,067
86,603
96,227
104,338
99,617
115,427
100,616
127,338
108,164
92,835
93,790
106,701
123,612
106,168
148,190
151,822
109,753
106,785
124,217
110,916
10,312,864
100.00%
filtered
105,757
156,103
153,953
105,581
121,892
142,962
125,851
152,914
117,888
117,892
145,556
103,311
126,426
149,278
128,668
116,580
114,002
117,871
113,031
104,082
143,106
113,203
140,016
135,912
159,208
89,140
152,926
136,217
114,959
102,818
128,272
143,373
128,643
123,874
138,547
124,555
147,930
124,841
145,291
130,509
124,821
135,096
133,288
140,938
148,572
144,066
104,480
108,081
114,016
113,766
79,430
96,758
103,055
108,212
111,669
98,234
91,998
91,474
96,818
104,622
88,360
112,409
104,157
68,306
87,036
107,898
95,928
96,559
86,114
95,705
103,738
99,017
114,745
100,014
126,589
107,518
92,330
93,252
106,095
122,923
105,602
147,317
150,976
109,132
106,140
123,482
110,294
10,253,968
99.43%
denoisedF
104,490
154,062
152,229
104,473
120,752
140,942
124,492
151,234
116,001
116,400
142,731
101,043
124,084
146,448
126,701
114,600
112,597
116,711
111,770
103,118
141,832
112,309
138,442
134,522
156,782
88,540
149,836
134,210
113,634
101,897
126,951
140,980
126,581
122,093
136,457
122,872
146,082
123,719
143,626
129,037
122,986
132,444
130,431
139,409
146,255
141,681
102,637
106,916
111,968
111,723
78,598
95,785
101,811
106,943
110,023
97,206
90,633
90,755
95,432
102,710
86,999
110,551
102,897
67,458
85,228
107,000
94,378
95,156
85,036
94,185
102,711
96,715
113,140
98,935
124,469
106,425
91,379
91,379
104,683
121,236
103,318
145,614
148,108
107,458
104,541
122,225
109,058
10,111,908
98.05%
denoisedR
102,388
150,767
149,041
102,548
118,237
138,004
122,296
148,577
113,524
114,522
139,934
98,628
121,245
143,378
124,339
112,197
109,875
114,754
109,562
101,325
139,059
110,736
135,095
132,625
153,531
86,918
146,581
131,471
111,508
100,371
124,656
138,326
123,605
118,857
133,453
120,134
143,187
121,408
140,404
126,296
120,474
129,778
127,376
136,443
143,160
138,762
100,077
104,515
108,874
109,214
76,988
93,831
99,120
104,390
107,593
95,241
86,708
88,864
92,904
100,411
85,092
108,288
100,843
66,051
83,220
104,803
92,290
92,740
83,210
91,983
100,324
94,514
110,565
96,812
121,187
103,952
89,597
89,401
102,634
117,932
100,971
141,812
144,144
104,624
102,337
119,909
107,025
9,894,345
95.94%
merged
99,010
142,385
142,825
99,663
114,135
130,278
118,224
143,107
106,902
110,337
128,486
90,508
111,708
129,750
117,711
104,419
105,117
110,373
105,533
98,487
134,600
108,188
128,699
127,714
145,398
85,763
134,471
124,270
107,353
98,108
120,702
129,320
114,730
112,911
125,808
114,698
137,630
118,244
133,049
121,003
114,977
119,377
115,443
130,924
133,416
129,915
93,786
100,857
100,002
101,957
75,457
91,189
94,547
99,546
103,242
92,335
85,047
86,772
87,417
93,230
80,842
100,355
97,041
63,099
77,607
102,276
85,907
88,440
79,178
85,987
97,048
84,765
104,803
93,128
114,344
99,643
87,266
81,629
98,431
110,651
93,248
135,518
131,298
97,619
96,121
115,303
103,048
9,385,648
91.01%
nonchim
84,767
109,894
107,823
92,810
102,291
94,774
105,002
118,725
77,480
97,773
83,712
64,011
75,960
105,429
85,921
71,534
89,296
95,428
92,229
87,642
114,065
102,117
96,402
114,840
108,706
84,259
77,728
98,554
95,242
89,471
109,014
88,801
70,033
98,195
87,469
88,989
99,480
105,233
102,997
89,847
92,467
79,647
69,651
109,280
86,424
92,845
73,603
84,499
62,245
70,936
73,601
82,915
76,770
79,605
90,046
86,218
83,220
82,049
59,191
68,693
69,433
69,473
86,149
57,583
53,145
96,945
62,627
76,042
68,601
63,520
86,277
47,176
80,645
81,862
84,990
81,166
77,974
49,298
84,698
69,236
66,569
95,329
82,442
70,057
78,615
101,082
87,864
7,396,646
71.72%
This table can be downloaded as an Excel table below:
5. DADA2 Amplicon Sequence Variants (ASVs). A total of 5883 unique merged and chimera-free ASV sequences were identified, and their corresponding
read counts for each sample are available in the "ASV Read Count Table" with rows for the ASV sequences and columns for sample. This read count table can be used for
microbial profile comparison among different samples and the sequences provided in the table can be used to taxonomy assignment.
The species-level, open-reference 16S rRNA NGS reads taxonomy assignment pipeline
Version 20210310a
The close-reference taxonomy assignment of the ASV sequences using BLASTN is based on the algorithm published by Al-Hebshi et. al. (2015)[2].
1. Raw sequences reads in FASTA format were BLASTN-searched against a combined set of 16S rRNA reference sequences - the FOMC 16S rRNA Reference Sequences version 20221029 (https://microbiome.forsyth.org/ftp/refseq/).
This set consists of the HOMD (version 15.22 http://www.homd.org/index.php?name=seqDownload&file&type=R ), Mouse Oral Microbiome Database (MOMD version 5.1 https://momd.org/ftp/16S_rRNA_refseq/MOMD_16S_rRNA_RefSeq/V5.1/),
and the NCBI 16S rRNA reference sequence set (https://ftp.ncbi.nlm.nih.gov/blast/db/16S_ribosomal_RNA.tar.gz).
These sequences were screened and combined to remove short sequences (<1000nt), chimera, duplicated and sub-sequences,
as well as sequences with poor taxonomy annotation (e.g., without species information).
This process resulted in 1,015 full-length 16S rRNA sequences from HOMD V15.22, 356 from MOMD V5.1, and 22,126 from NCBI, a total of 23,497 sequences.
Altogether these sequence represent a total of 17,035 oral and non-oral microbial species.
The NCBI BLASTN version 2.7.1+ (Zhang et al, 2000) [3] was used with the default parameters.
Reads with ≥ 98% sequence identity to the matched reference and ≥ 90% alignment length
(i.e., ≥ 90% of the read length that was aligned to the reference and was used to calculate
the sequence percent identity) were classified based on the taxonomy of the reference sequence
with highest sequence identity. If a read matched with reference sequences representing
more than one species with equal percent identity and alignment length, it was subject
to chimera checking with USEARCH program version v8.1.1861 (Edgar 2010). Non-chimeric reads with multi-species
best hits were considered valid and were assigned with a unique species
notation (e.g., spp) denoting unresolvable multiple species.
2. Unassigned reads (i.e., reads with < 98% identity or < 90% alignment length) were pooled together and reads < 200 bases were
removed. The remaining reads were subject to the de novo
operational taxonomy unit (OTU) calling and chimera checking using the USEARCH program version v8.1.1861 (Edgar 2010)[4].
The de novo OTU calling and chimera checking was done using 98% as the sequence identity cutoff, i.e., the species-level OTU.
The output of this step produced species-level de novo clustered OTUs with 98% identity.
Representative reads from each of the OTUs/species were then BLASTN-searched
against the same reference sequence set again to determine the closest species for
these potential novel species. These potential novel species were pooled together with the reads that were signed to specie-level in
the previous step, for down-stream analyses.
Reference:
Al-Hebshi NN, Nasher AT, Idris AM, Chen T. Robust species taxonomy assignment algorithm for 16S rRNA NGS reads: application
to oral carcinoma samples. J Oral Microbiol. 2015 Sep 29;7:28934. doi: 10.3402/jom.v7.28934. PMID: 26426306; PMCID: PMC4590409.
Zhang Z, Schwartz S, Wagner L, Miller W. A greedy algorithm for aligning DNA sequences. J Comput Biol. 2000 Feb-Apr;7(1-2):203-14. doi: 10.1089/10665270050081478. PMID: 10890397.
Edgar RC. Search and clustering orders of magnitude faster than BLAST.
Bioinformatics. 2010 Oct 1;26(19):2460-1. doi: 10.1093/bioinformatics/btq461. Epub 2010 Aug 12. PubMed PMID: 20709691.
3. Designations used in the taxonomy:
1) Taxonomy levels are indicated by these prefixes:
k__: domain/kingdom
p__: phylum
c__: class
o__: order
f__: family
g__: genus
s__: species
Example:
k__Bacteria;p__Firmicutes;c__Clostridia;o__Clostridiales;f__Lachnospiraceae;g__Blautia;s__faecis
2) Unique level identified – known species:
k__Bacteria;p__Firmicutes;c__Clostridia;o__Clostridiales;f__Lachnospiraceae;g__Roseburia;s__hominis
The above example shows some reads match to a single species (all levels are unique)
3) Non-unique level identified – known species:
k__Bacteria;p__Firmicutes;c__Clostridia;o__Clostridiales;f__Lachnospiraceae;g__Roseburia;s__multispecies_spp123_3
The above example “s__multispecies_spp123_3” indicates certain reads equally match to 3 species of the
genus Roseburia; the “spp123” is a temporally assigned species ID.
k__Bacteria;p__Firmicutes;c__Clostridia;o__Clostridiales;f__Lachnospiraceae;g__multigenus;s__multispecies_spp234_5
The above example indicates certain reads match equally to 5 different species, which belong to multiple genera.;
the “spp234” is a temporally assigned species ID.
4) Unique level identified – unknown species, potential novel species:
k__Bacteria;p__Firmicutes;c__Clostridia;o__Clostridiales;f__Lachnospiraceae;g__Roseburia;s__ hominis_nov_97%
The above example indicates that some reads have no match to any of the reference sequences with
sequence identity ≥ 98% and percent coverage (alignment length) ≥ 98% as well. However this groups
of reads (actually the representative read from a de novo OTU) has 96% percent identity to
Roseburia hominis, thus this is a potential novel species, closest to Roseburia hominis.
(But they are not the same species).
5) Multiple level identified – unknown species, potential novel species:
k__Bacteria;p__Firmicutes;c__Clostridia;o__Clostridiales;f__Lachnospiraceae;g__Roseburia;s__ multispecies_sppn123_3_nov_96%
The above example indicates that some reads have no match to any of the reference sequences
with sequence identity ≥ 98% and percent coverage (alignment length) ≥ 98% as well.
However this groups of reads (actually the representative read from a de novo OTU)
has 96% percent identity equally to 3 species in Roseburia. Thus this is no single
closest species, instead this group of reads match equally to multiple species at 96%.
Since they have passed chimera check so they represent a novel species. “sppn123” is a
temporary ID for this potential novel species.
4. The taxonomy assignment algorithm is illustrated in this flow char below:
Read Taxonomy Assignment - Result Summary *
Code
Category
MPC=0% (>=1 read)
MPC=0.01%(>=578 reads)
A
Total reads
7,396,646
7,396,646
B
Total assigned reads
5,780,215
5,780,215
C
Assigned reads in species with read count < MPC
0
23,465
D
Assigned reads in samples with read count < 500
0
0
E
Total samples
87
87
F
Samples with reads >= 500
87
87
G
Samples with reads < 500
0
0
H
Total assigned reads used for analysis (B-C-D)
5,780,215
5,756,750
I
Reads assigned to single species
4,043,997
4,027,007
J
Reads assigned to multiple species
1,447,517
1,442,362
K
Reads assigned to novel species
288,701
287,381
L
Total number of species
545
78
M
Number of single species
208
43
N
Number of multi-species
63
7
O
Number of novel species
274
28
P
Total unassigned reads
1,616,431
1,616,431
Q
Chimeric reads
9,902
9,902
R
Reads without BLASTN hits
1,547,585
1,547,585
S
Others: short, low quality, singletons, etc.
58,944
58,944
A=B+P=C+D+H+Q+R+S
E=F+G
B=C+D+H
H=I+J+K
L=M+N+O
P=Q+R+S
* MPC = Minimal percent (of all assigned reads) read count per species, species with read count < MPC were removed.
* Samples with reads < 500 were removed from downstream analyses.
* The assignment result from MPC=0.1% was used in the downstream analyses.
Read Taxonomy Assignment - ASV Species-Level Read Counts Table
This table shows the read counts for each sample (columns) and each species identified based on the ASV sequences.
The downstream analyses were based on this table.
The species listed in the table has full taxonomy and a dynamically assigned species ID specific to this report.
When some reads match with the reference sequences of more than one species equally (i.e., same percent identiy and alignmnet coverage),
they can't be assigned to a particular species. Instead, they are assigned to multiple species with the species notaton
"s__multispecies_spp2_2". In this notation, spp2 is the dynamic ID assigned to these reads that hit multiple sequences and the "_2"
at the end of the notation means there are two species in the spp2.
You can look up which species are included in the multi-species assignment, in this table below:
Another type of notation is "s__multispecies_sppn2_2", in which the "n" in the sppn2 means it's a potential novel species because all the reads in this species
have < 98% idenity to any of the reference sequences. They were grouped together based on de novo OTU clustering at 98% identity cutoff. And then
a representative sequence was chosed to BLASTN search against the reference database to find the closest match (but will still be < 98%). This representative
sequence also matched equally to more than one species, hence the "spp" was given in the label.
In ecology, alpha diversity (α-diversity) is the mean species diversity in sites or habitats at a local scale.
The term was introduced by R. H. Whittaker[5][6] together with the terms beta diversity (β-diversity)
and gamma diversity (γ-diversity). Whittaker's idea was that the total species diversity in a landscape
(gamma diversity) is determined by two different things, the mean species diversity in sites or habitats
at a more local scale (alpha diversity) and the differentiation among those habitats (beta diversity).
Diversity measures are affected by the sampling depth. Rarefaction is a technique to assess species richness from the results of sampling. Rarefaction allows
the calculation of species richness for a given number of individual samples, based on the construction
of so-called rarefaction curves. This curve is a plot of the number of species as a function of the
number of samples. Rarefaction curves generally grow rapidly at first, as the most common species are found,
but the curves plateau as only the rarest species remain to be sampled [7].
The two main factors taken into account when measuring diversity are richness and evenness.
Richness is a measure of the number of different kinds of organisms present in a particular area.
Evenness compares the similarity of the population size of each of the species present. There are
many different ways to measure the richness and evenness. These measurements are called "estimators" or "indices".
Below is a diversity of 3 commonly used indices showing the values for all the samples (dots) and in groups (boxes).
Printed on each graph is the statistical significance p values of the difference between the groups.
The significance is calculated using either Kruskal-Wallis test or the Wilcoxon rank sum test, both are non-parametric methods (since
microbiome read count data are considered non-normally distributed) for testing
whether samples originate from the same distribution (i.e., no difference between groups). The Kruskal-Wallis test is used to compare three or more
independent groups to determine if there are statistically significant differences between their medians. The Wilcoxon Rank Sum test, also known as
the Mann-Whitney U test, is used to compare two independent groups to determine if there is a significant difference between their distributions.
The p-value is shown on the top of each graph. A p-value < 0.05 is considered statistically significant between/among the test groups.
 
Alpha Diversity Box Plots for All Groups
 
 
 
Alpha Diversity Box Plots for Individual Comparisons at Species level
The above comparisons are at the species-level. Comparisons of other taxonomy levels, from phylum to genus, are also available:
 
Group Significance Evaluation of Alpha-diversity Indices with QIIME2
The above comparisons and significance tests were done under the R environment. For compasison (also because this was included in the pipeline
early on) we also use the Kruskal Wallis H test
provided the "alpha-group-significance" fucntion in the QIIME 2 "diversity" package. As mentioned above, Kruskal Wallis test is the non-parametric alternative
to the One Way ANOVA. Non-parametric means that the test doesn’t assume your data comes from a particular distribution. The H test is used
when the assumptions for ANOVA aren’t met (assumption of normality). It is sometimes called the one-way ANOVA on ranks,
as the ranks of the data values are used in the test rather than the actual data points. The H test determines whether the medians of two
or more groups are different.
Below are the Kruskal Wallis H test results for each comparison based on three different alpha diversity measures: 1) Observed species (features),
2) Shannon index, and 3) Simpson index.
Beta diversity compares the similarity (or dissimilarity) of microbial profiles between different
groups of samples. There are many different similarity/dissimilarity metrics [8].
In general, they can be quantitative (using sequence abundance, e.g., Bray-Curtis or weighted UniFrac)
or binary (considering only presence-absence of sequences, e.g., binary Jaccard or unweighted UniFrac).
They can be even based on phylogeny (e.g., UniFrac metrics) or not (non-UniFrac metrics, such as Bray-Curtis, etc.).
For microbiome studies, species profiles of samples can be compared with the Bray-Curtis dissimilarity,
which is based on the count data type. The pair-wise Bray-Curtis dissimilarity matrix of all samples can then be
subject to either multi-dimensional scaling (MDS, also known as PCoA) or non-metric MDS (NMDS).
MDS/PCoA is a
scaling or ordination method that starts with a matrix of similarities or dissimilarities
between a set of samples and aims to produce a low-dimensional graphical plot of the data
in such a way that distances between points in the plot are close to original dissimilarities.
NMDS is similar to MDS, however it does not use the dissimilarities data, instead it converts them into
the ranks and use these ranks in the calculation.
In our beta diversity analysis, Bray-Curtis dissimilarity matrix was first calculated and then plotted by the PCoA and
NMDS separately. Below are beta diveristy results for all groups together:
The above PCoA and NMDS plots are based on count data. The count data can also be transformed into centered log ratio (CLR)
for each species. The CLR data is no longer count data and cannot be used in Bray-Curtis dissimilarity calculation. Instead
CLR can be compared with Euclidean distances. When CLR data are compared by Euclidean distance, the distance is also called
Aitchison distance.
Below are the NMDS and PCoA plots of the Aitchison distances of the samples:
 
 
 
 
 
 
 
NMDS and PCoA Plots for Individual Comparisons at Species level
Interactive 3D PCoA Plots - Bray-Curtis Dissimilarity
 
 
 
Interactive 3D PCoA Plots - Euclidean Distance
 
 
 
Interactive 3D PCoA Plots - Correlation Coefficients
 
 
 
Group Significance of Beta-diversity Indices
To test whether the between-group dissimilarities are significantly greater than the within-group dissimilarities,
the "beta-group-significance" function provided in the QIIME 2 "diversity" package was used with PERMANOVA
(permutational multivariate analysis of variance) as the group significant testing method.
Three beta diversity matrics were used: 1) Bray–Curtis dissimilarity 2) Correlation coefficient matrix , and 3) Aitchison distance
(Euclidean distance between clr-transformed compositions).
16S rRNA next generation sequencing (NGS) generates a fixed number of reads that reflect the proportion of different
species in a sample, i.e., the relative abundance of species, instead of the absolute abundance.
In Mathematics, measurements involving probabilities, proportions, percentages, and ppm can all
be thought of as compositional data. This makes the microbiome read count data “compositional”
(Gloor et al, 2017). In general, compositional data represent parts of a whole which only
carry relative information [9].
The problem of microbiome data being compositional arises when comparing two groups of samples for
identifying “differentially abundant” species. A species with the same absolute abundance between two
conditions, its relative abundances in the two conditions (e.g., percent abundance) can become different
if the relative abundance of other species change greatly. This problem can lead to incorrect conclusion
in terms of differential abundance for microbial species in the samples.
When studying differential abundance (DA), the current better approach is to transform the read count
data into log ratio data. The ratios are calculated between read counts of all species in a sample to
a “reference” count (e.g., mean read count of the sample). The log ratio data allow the detection of DA
species without being affected by percentage bias mentioned above
In this report, a compositional DA analysis tool “ANCOM” (analysis of composition of microbiomes)
was used [10]. ANCOM transforms the count data into log-ratios and thus is more suitable for comparing
the composition of microbiomes in two or more populations. "ANCOM" generates a table of features with
W-statistics and whether the null hypothesis is rejected. The “W” is the W-statistic, or number of
features that a single feature is tested to be significantly different against. Hence the higher the "W"
the more statistical sifgnificant that a feature/species is differentially abundant.
References:
Gloor GB, Macklaim JM, Pawlowsky-Glahn V, Egozcue JJ. Microbiome Datasets Are Compositional: And This Is Not Optional. Front Microbiol.
2017 Nov 15;8:2224. doi: 10.3389/fmicb.2017.02224. PMID: 29187837; PMCID: PMC5695134.
Mandal S, Van Treuren W, White RA, Eggesbø M, Knight R, Peddada SD. Analysis of composition of
microbiomes: a novel method for studying microbial composition. Microb Ecol Health Dis.
2015 May 29;26:27663. doi: 10.3402/mehd.v26.27663. PMID: 26028277; PMCID: PMC4450248.
Starting with version V1.2, we include the results of ANCOM-BC (Analysis of Compositions of
Microbiomes with Bias Correction) (Lin and Peddada 2020) [11]. ANCOM-BC is an updated version of "ANCOM" that:
(a) provides statistically valid test with appropriate p-values,
(b) provides confidence intervals for differential abundance of each taxon,
(c) controls the False Discovery Rate (FDR),
(d) maintains adequate power, and
(e) is computationally simple to implement.
The bias correction (BC) addresses a challenging problem of the bias introduced by differences in
the sampling fractions across samples. This bias has been a major hurdle in performing DA analysis of microbiome data.
ANCOM-BC estimates the unknown sampling fractions and corrects the bias induced by their differences among samples.
The absolute abundance data are modeled using a linear regression framework.
Starting with version V1.43, ANCOM-BC2 is used instead of ANCOM-BC, So that multiple pairwise directional test can be performed (if there are more than two gorups in a comparison).
When performing pairwise directional test, the mixed directional false discover rate (mdFDR) is taken into account. The mdFDR
is the combination of false discovery rate due to multiple testing, multiple pairwise comparisons, and directional tests within
each pairwise comparison. The mdFDR is adopted from (Guo, Sarkar, and Peddada 2010 [12]; Grandhi, Guo, and Peddada 2016 [13]). For more detail
explanation and additional features of ANCOM-BC2 please see author's documentation.
References:
Lin H, Peddada SD. Analysis of compositions of microbiomes with bias correction.
Nat Commun. 2020 Jul 14;11(1):3514. doi: 10.1038/s41467-020-17041-7.
PMID: 32665548; PMCID: PMC7360769.
Guo W, Sarkar SK, Peddada SD. Controlling false discoveries in multidimensional directional decisions, with applications to gene expression data on ordered categories. Biometrics. 2010 Jun;66(2):485-92. doi: 10.1111/j.1541-0420.2009.01292.x. Epub 2009 Jul 23. PMID: 19645703; PMCID: PMC2895927.
Grandhi A, Guo W, Peddada SD. A multiple testing procedure for multi-dimensional pairwise comparisons with application to gene expression studies. BMC Bioinformatics. 2016 Feb 25;17:104. doi: 10.1186/s12859-016-0937-5. PMID: 26917217; PMCID: PMC4768411.
LEfSe (Linear Discriminant Analysis Effect Size) is an alternative method to find "organisms, genes, or
pathways that consistently explain the differences between two or more microbial communities" (Segata et al., 2011) [14].
Specifically, LEfSe uses rank-based Kruskal-Wallis (KW) sum-rank test to detect features with significant
differential (relative) abundance with respect to the class of interest. Since it is rank-based, instead of proportional based,
the differential species identified among the comparison groups is less biased (than percent abundance based).
Reference:
Segata N, Izard J, Waldron L, Gevers D, Miropolsky L, Garrett WS, Huttenhower C. Metagenomic biomarker discovery and explanation. Genome Biol. 2011 Jun 24;12(6):R60. doi: 10.1186/gb-2011-12-6-r60. PMID: 21702898; PMCID: PMC3218848.
To analyze the co-occurrence or co-exclusion between microbial species among different samples, network correlation
analysis tools are usually used for this purpose. However, microbiome count data are compositional. If count data are normalized to the total number of counts in the
sample, the data become not independent and traditional statistical metrics (e.g., correlation) for the detection
of specie-species relationships can lead to spurious results. In addition, sequencing-based studies typically
measure hundreds of OTUs (species) on few samples; thus, inference of OTU-OTU association networks is severely
under-powered. Here we use SPIEC-EASI (SParse InversECovariance Estimation
for Ecological Association Inference), a statistical method for the inference of microbial
ecological networks from amplicon sequencing datasets that addresses both of these issues (Kurtz et al., 2015) [15].
SPIEC-EASI combines data transformations developed for compositional data analysis with a graphical model
inference framework that assumes the underlying ecological association network is sparse. SPIEC-EASI provides
two algorithms for network inferencing – 1) Meinshausen-Bühlmann's neighborhood selection (MB method) and inverse covariance selection
(GLASSO method, i.e., graphical least absolute shrinkage and selection operator). This is fundamentally distinct from SparCC, which essentially estimate pairwise correlations. In addition
to these two methods, we provide the results of a third method - SparCC (Sparse Correlations for Compositional Data)(Friedman & Alm 2012)[16], which
is also a method for inferring correlations from compositional data. SparCC estimates the linear Pearson correlations between
the log-transformed components.
References:
Kurtz ZD, Müller CL, Miraldi ER, Littman DR, Blaser MJ, Bonneau RA. Sparse and compositionally robust inference of microbial ecological networks. PLoS Comput Biol. 2015 May 7;11(5):e1004226. doi: 10.1371/journal.pcbi.1004226. PMID: 25950956; PMCID: PMC4423992.
The results of this analysis are for research purpose only. They are not intended to diagnose, treat, cure, or prevent any disease. Forsyth and FOMC
are not responsible for use of information provided in this report outside the research area.