Comparative genome analysis of <i>Salmonella</i> Enteritidis PT4 and <i>Salmonella</i> Gallinarum 287/91 provides insights into evolutionary and host adaptation pathways

TLDR

The authors propose using chicken and mouse models to test Enteritidis mutants carrying functional homologs of Gallinarum pseudogenes, aiming to elucidate the genetic basis of host adaptation in Salmonella enterica. They sequenced the complete genomes of a host‑promiscuous Enteritidis PT4 isolate (P125109) and a chicken‑restricted Gallinarum 287/91 isolate. Comparative genomics revealed that Gallinarum 287/91 is a recently evolved descendant of Enteritidis, with extensive genome degradation via deletions and pseudogene formation that removes many functional traits, offering insights into host and tissue adaptation mechanisms.

Abstract

We have determined the complete genome sequences of a host-promiscuous Salmonella enterica serovar Enteritidis PT4 isolate P125109 and a chicken-restricted Salmonella enterica serovar Gallinarum isolate 287/91. Genome comparisons between these and other Salmonella isolates indicate that S . Gallinarum 287/91 is a recently evolved descendent of S. Enteritidis. Significantly, the genome of S . Gallinarum has undergone extensive degradation through deletion and pseudogene formation. Comparison of the pseudogenes in S . Gallinarum with those identified previously in other host-adapted bacteria reveals the loss of many common functional traits and provides insights into possible mechanisms of host and tissue adaptation. We propose that experimental analysis in chickens and mice of S . Enteritidis–harboring mutations in functional homologs of the pseudogenes present in S. Gallinarum could provide an experimentally tractable route toward unraveling the genetic basis of host adaptation in S. enterica .