Conservation and Divergence Among Salmonella enterica Subspecies

Genome sequencing efforts of taxonomically proximate organisms successfully divulged proteomic diversity embedded within closely related organisms. The Salmonella enterica subspecies represents a group of enterobacteric pathogens known to share similar genomic content yet possess diverse host specificity and distinct disease symptoms. Study of Salmonella enterica subspecies proteomes reports an overestimation of the proximity among the subspecies. Interestingly, orthology comparison among Salmonella typhi and Salmonella typhimurium across the proteome suggested the metabolic proteins possessed the highest propensity of the divergence, while proteins involved in environment information processing and genetic information processing are least susceptible to evolution. Consistent with earlier reports, transporter proteins and transcription factors are the most populated protein families in the Salmonellae. Several of the unique domains present in Salmonella typhi and Salmonella typhimurium genomes were introduced into the genome through phage invasion and eventually selected. Redundancy and divergence is observed among the metabolic pathway proteins. Though complying with essentiality of their function, the metabolic proteins possess the highest propensity of sampling sequence space for imbibing new function. The detailed cross-genome analysis of the subspecies provides an understanding of diversity and unique attributes defined in the individual Salmonella enterica genomes.