Differentially evolved genes of Salmonella pathogenicity islands: insights into the mechanism of host specificity in Salmonella.
BACKGROUND
The species Salmonella enterica (S. enterica) includes many serovars that cause disease in avian and mammalian hosts. These serovars differ greatly in their host range and their degree of host adaptation. The host specificity of S. enterica serovars appears to be a complex phenomenon governed by multiple factors acting at different stages of the infection process, which makes identification of the cause/s of host specificity solely by experimental methods difficult.


RESULTS
In this study, we have employed a molecular evolution and phylogenetics based approach to identify genes that might play important roles in conferring host specificity to different serovars of S. enterica. These genes are 'differentially evolved' in different S. enterica serovars. This list of 'differentially evolved' genes includes genes that encode translocon proteins (SipD, SseC and SseD) of both Salmonella pathogenicity islands 1 and 2 encoded type three secretion systems, sptP, which encodes an effector protein that inhibits the mitogen-activated protein kinase pathway of the host cell, and genes which encode effector proteins (SseF and SifA) that are important in placing the Salmonella-containing vacuole in a juxtanuclear position.


CONCLUSIONS
Analysis of known functions of these 'differentially evolved genes' indicates that the products of these genes directly interact with the host cell and manipulate its functions and thereby confer host specificity, at least in part, to different serovars of S. enterica that are considered in this study.
Eswarappa
Sandeepa M
SM
Department of Microbiology and Cell Biology, Centre for Infectious Disease Research and Biosafety Laboratories, Indian Institute of Science, Bangalore, India.
Janice
Jessin
J
Nagarajan
Arvindhan G
AG
Balasundaram
Sudhagar V
SV
Karnam
Guruswamy
G
Dixit
Narendra M
NM
Chakravortty
Dipshikha
D
D000595:Amino Acid Sequence; D000818:Animals; D002135:Calcium-Binding Proteins; D004247:DNA; D019143:Evolution, Molecular; D005798:Genes, Bacterial; D044404:Genomic Islands; D054884:Host-Pathogen Interactions / Q000235:genetics*; D006801:Humans; D008562:Membrane Glycoproteins; D008969:Molecular Sequence Data; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D012475:Salmonella / Q000235:genetics / Q000472:pathogenicity; D019779:Salmonella enterica / Q000235:genetics* / Q000472:pathogenicity; D017422:Sequence Analysis, DNA; D012703:Serotyping; D014774:Virulence / Q000235:genetics*
D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; C066973:signal sequence receptor; D004247:DNA