Abstract
The rate of gene loss was studied in the facultative pathogens, E. coli and Shigella, and was found to be greater in the more niche-limited Shigella. This is demonstrated to be due to a genome-wide reduction in the effectiveness of selection.
Highlights
Obligate pathogenic bacteria lose more genes relative to facultative pathogens, which, in turn, lose more genes than free-living bacteria
In order to focus on gene loss, we eliminated from our examination genes that are predicted to be horizontally transferred into E. coli K12 [16]
We modeled the number of genes lost along a branch as a Poisson random variable, whose mean parameter may depend on dS and on a binary strain indicator variable that receives the value one if the branch leads towards a Shigella strain and the value zero if it leads towards a pathogenic E. coli strain
Summary
Obligate pathogenic bacteria lose more genes relative to facultative pathogens, which, in turn, lose more genes than free-living bacteria. In pathway-specific reduction, specific functions that are carried out by free-living bacteria may be provided to a certain extent by the host of the pathogenic bacteria, or may not be needed once a pathogen adapts to survival within a host. For this reason, purifying selection may be less effective in preventing the loss of some genes involved in specific pathways that are no longer as useful as they were in the free-living ancestor of the pathogenic bacteria. In genome-wide reduction, population size and structure may be different in pathogens compared
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
