Genomic Signatures of Distributive Conjugal Transfer among Mycobacteria
Distributive conjugal transfer (DCT) is a mechanism of lateral gene transfer (LGT) first discovered in the nonpathogenic model organism Mycobacterium smegmatis. DCT is characterized by transfer of large, noncontiguous tracts of DNA from donor to recipient cells via cell contact, which produces transconjugant genomes that are mosaics of the parental strains. Using whole genome sequencing (WGS) data from M. smegmatis transconjugants produced in experimental matings, I tested recombination detection software appropriate for bacterial WGS to identify the best methods to study recombination among mycobacterial populations. Additionally, I compared signatures of recombination produced by DCT to bacterial species with different mechanisms (e.g. natural transformation, mobile genetic elements), including length of tracts, recombination hot spots, and directionality of transfer. Using publicly available WGS data from clinical isolates of Mycobacterium canettii, I characterized recombination signatures and found that the signatures in M. canettii were most compatible with DCT. M. canettii and M. smegmatis are phylogenetically distinct; M. canettii is a slow growing pathogen closely related to Mycobacterium tuberculosis, and M. smegmatis is a rapid growing mycobacterium closely related to other environmental species, suggesting that DCT is widespread across the genus.
You can read more about this project in Genome Biology and Evolution here!