chimeraslayer - detects likely chimeras in PCR amplified DNA
Contents
Description
ChimeraSlayer is a chimeric sequence detection utility, compatible with near-full length Sanger sequences
and shorter 454-FLX sequences (~500bp).
Chimera Slayer involves the following series of steps that operate to flag chimeric 16S rRNA sequences:
1. the ends of a query sequence are searched against an included database of reference chimera-free
16S sequences to identify potential parents of a chimera
2. candidate parents of a chimera are selected as those that form a branched best scoring alignment
to the NAST-formatted query sequence
3. the NAST alignment of the query sequence is improved in a ‘chimera-aware’ profile-based NAST
realignment to the selected reference parent sequences
4. an evolutionary framework is used to flag query sequences found to exhibit greater sequence
homology to an in silico chimera formed between any two of the selected reference parent
sequences.
To run Chimera Slayer, you need NAST-formatted sequences generated by the nast-ier utility.
ChimeraSlayer is part of the microbiomeutil suite.
Name
chimeraslayer - detects likely chimeras in PCR amplified DNA
Options
Required--query_NAST
multi-fasta file containing query sequences in alignment format
Commonoptions--db_NAST
db in NAST format (default:
/usr/share/microbiomeutil-data/RESOURCES/rRNA16S.gold.NAST_ALIGNED.fasta)
--db_FASTA
db in fasta format (megablast formatted) (default:
/usr/share/microbiomeutil-data/RESOURCES/rRNA16S.gold.fasta)
-n number of top matching database sequences to compare to (default 15)
-R min divergence ratio default: 1.007
-P min percent identity among matching sequences (default: 90)
ParameterstotuneChimeraParentSelector:
Scoring parameters:
-M match score (default: +5)
-N mismatch penalty (default: -4)
-Q min query coverage by matching database sequence (default: 70)
-T maximum traverses of the multiple alignment (default: 1)
ParameterstotuneChimeraPhyloChecker--windowSize
default 50
--windowStep
default 5
--minBS
minimum bootstrap support for calling chimera (default: 90)
--num_BS_replicates
default: 100
--low_range_finer_BS
(default: 10) If computed BS is between minBS and (minBS - low_range_finer_BS), then
num_finer_BS_replicates computed.
--num_finer_BS_replicates
(default: 1000)
-S percent of SNPs to sample on each side of breakpoint for computing bootstrap support (default: 10)
--num_parents_test
number of potential parents to test for chimeras (default: 3)
--MAX_CHIMERA_PARENT_PER_ID
Chimera/Parent alignments with perID above this are considered non-chimeras (default 100; turned
off)
Miscoptions--printFinalAlignments
shows alignment between query sequence and pair of candidate chimera parents
--printCSalignments
print ChimeraSlayer alignments in ChimeraSlayer output
--exec_dir
chdir to here before running
