Sam:LabNotes/Microbiome-new/2010-12-10: Difference between revisions
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**Some peaks are missing in long-amplified libraries but still shown in short-amplified libraries (see pooled figure). | **Some peaks are missing in long-amplified libraries but still shown in short-amplified libraries (see pooled figure). | ||
*'''A significant difference between short and long-amplified libraries was shown at the Y-axis range -1 ~ 0''', where it showed one read(Y=0) in short-amplified libraries but no read (Y=-1) in long amplified libraries at the same bin. | *'''A significant difference between short and long-amplified libraries was shown at the Y-axis range -1 ~ 0''', where it showed one read(Y=0) in short-amplified libraries but no read (Y=-1) in long amplified libraries at the same bin. | ||
Revision as of 17:49, 26 January 2011
Read distribution analysis (unique mapplabe reads) - HC-MDA-Ecoli-SAGs-Ind1to8(SE - down-sampled reads)
Background
- Genome coverage is just one indication to assess the amplification bias.
- It is more informative to evaluate the mappable reads distribution from each library. A more even distribution (across E.coli genome) of mappable reads should be expected to see on samples with less amplification bias.
Analysis
- Running bowtie alignment on previous down-sampled datasets and transform the output to sam-format
- Using samtools to convert the output from sam-format to bam-format and then to pileup-format.
- Script: fastq2pileup-hc2
- Data resource: down-sampled raw reads (meet 1,000,000 unique mappable reads): e.g. s_4_ID1_cut_2262955.txt
- Template:E.coli-k12-mg1655 template
- Bowtie setting: -k 1 -l 28 -n 2 -m 1 --best --best --phred64-quals
- Output the data: e.g. s_4_ID1_cut_2262955.bowtie.pileup
- In UNIX, extract data from column 1, 2 and column9 with "^" symbol ("^" read starting sign in pileup-format) from each line
- Output the data: e.g. s_4_ID1_cut_2262955.bowtie.pileup.readstart
- Using perl to calculate "^" symbol in defined bin size (10,000 bp)
- Script: CountReadStart-hc2
- Output the data: e.g. s_4_ID1_cut_2262955.bowtie.pileup.readstart.count
- Use excel to plot the Read-start counts vs. bin numbers (genome position)
Plotting
- Since the bin number data is not continuous (the bin number containing no reads will not be reported in previous step).
- I need to create a bin-ladder (from bin 0 to 463) and pool my data set with bin-ladder by matching bin number.
- Without doing this step will cause Excel draw the plot with discontinuous bin interval (since Excel regard bin number as a new data set but not X-axis).
- I pooled the data set using Excel Add-Ins function "Join (merge)Talbes"(from DigDB).
- Take the log10 value of total reads for Y-axis.
- IMPORTANT: Since log10 value can't be taken from no read (count=0/10,000bp), I manually assign the value of log10 of "no read data" as "-1".
- The reason to do so is that there are lots of bins containing "0 read" exclusively in long-amplified SAGs' data sets.
Results
File:Sam121510-read-distribution - ID1 - ID3.jpg File:Sam121510-read-distribution - ID1 - ID3-pooled.jpg File:Sam121510-read-distribution - ID2 - ID4.jpg File:Sam121510-read-distribution - ID2 - ID4-pooled.jpg File:Sam121510-read-distribution - ID5 - ID7.jpg File:Sam121510-read-distribution - ID5 - ID7-pooled.jpg File:Sam121510-read-distribution - ID6 - ID8.jpg File:Sam121510-read-distribution - ID6 - ID8-pooled.jpg
Excel files: Media:Bias-plot-all-pooled ID1-ID3-office2003.xls Media:Bias-plot-all-pooled ID2-ID4-office2003.xls Media:Bias-plot-all-pooled ID5-ID7-office2003.xls Media:Bias-plot-all-pooled ID6-ID8-office2003.xls *For unknown reason the wikinote doesn't allow me to upload Excel 2007 files(.xlsx), so I saved as Excel 2003 file format(.xls)
Discussion
- Short-amplified and long-amplified libraries showed very high overlapped on reads distribution.
- Reads from short-amplified libraries are more evenly distributed than that from long-amplified libraries.
- Some peaks are missing in long-amplified libraries but still shown in short-amplified libraries (see pooled figure).
- A significant difference between short and long-amplified libraries was shown at the Y-axis range -1 ~ 0, where it showed one read(Y=0) in short-amplified libraries but no read (Y=-1) in long amplified libraries at the same bin.