Trends of the major porin gene (ompF) evolution

OmpF is one of the major general porins of Enterobacteriaceae that belongs to the first line of bacterial defense and interactions with the biotic as well as abiotic environments. Porins are surface exposed and their structures strongly reflect the history of multiple interactions with the environmental challenges. Unfortunately, little is known on diversity of porin genes of Enterobacteriaceae and the genus Yersinia especially. We analyzed the sequences of the ompF gene from 73 Yersinia strains covering 14 known species. The phylogenetic analysis placed most of the Yersinia strains in the same line assigned by 16S rDNA-gyrB tree. Very high congruence in the tree topologies was observed for Y. enterocolitica, Y. kristensenii, Y. ruckeri, indicating that intragenic recombination in these species had no effect on the ompF gene. A significant level of intra- and interspecies recombination was found for Y. aleksiciae, Y. intermedia and Y. mollaretii. Our analysis shows that the ompF gene of Yersinia has evolved with nonrandom mutational rate under purifying selection. However, several surface loops in the OmpF porin contain positively selected sites, which very likely reflect adaptive diversification Yersinia to their ecological niches. To our knowledge, this is a first investigation of diversity of the porin gene covering the whole genus of the family Enterobacteriaceae. This study demonstrates that recombination and positive selection both contribute to evolution of ompF, but the relative contribution of these evolutionary forces are different among Yersinia species

Molecular Evolution of the Yersinia Major Outer Membrane Protein C (OmpC)

The genus Yersinia includes species with a wide range of eukaryotic hosts (from fish, insects, and plants to mammals and humans). One of the major outer membrane proteins, the porin OmpC, is preferentially expressed in the host gut, where osmotic pressure, temperature, and the concentrations of nutrients and toxic products are relatively high. We consider here the molecular evolution and phylogeny of Yersinia ompC. The maximum likelihood gene tree reflects the macroevolution processes occurring within the genus Yersinia. Positive selection and horizontal gene transfer are the key factors of ompC diversification, and intraspecies recombination was revealed in two Yersinia species. The impact of recombination on ompC evolution was different from that of another major porin gene, ompF, possibly due to the emergence of additional functions and conservation of the basic transport function. The predicted antigenic determinants of OmpC were located in rapidly evolving regions, which may indicate the evolutionary mechanisms of Yersinia adaptation to the host immune system

Trends of the Major Porin Gene (ompF) Evolution: Insight from the Genus Yersinia

OmpF is one of the major general porins of Enterobacteriaceae that belongs to the first line of bacterial defense and interactions with the biotic as well as abiotic environments. Porins are surface exposed and their structures strongly reflect the history of multiple interactions with the environmental challenges. Unfortunately, little is known on diversity of porin genes of Enterobacteriaceae and the genus Yersinia especially. We analyzed the sequences of the ompF gene from 73 Yersinia strains covering 14 known species. The phylogenetic analysis placed most of the Yersinia strains in the same line assigned by 16S rDNA-gyrB tree. Very high congruence in the tree topologies was observed for Y. enterocolitica, Y. kristensenii, Y. ruckeri, indicating that intragenic recombination in these species had no effect on the ompF gene. A significant level of intra- and interspecies recombination was found for Y. aleksiciae, Y. intermedia and Y. mollaretii. Our analysis shows that the ompF gene of Yersinia has evolved with nonrandom mutational rate under purifying selection. However, several surface loops in the OmpF porin contain positively selected sites, which very likely reflect adaptive diversification Yersinia to their ecological niches. To our knowledge, this is a first investigation of diversity of the porin gene covering the whole genus of the family Enterobacteriaceae. This study demonstrates that recombination and positive selection both contribute to evolution of ompF, but the relative contribution of these evolutionary forces are different among Yersinia species

Yersinia enterocolitica provides the link between thyroid-stimulating antibodies and their germline counterparts in Graves' disease.

Graves' disease results from thyroid-stimulating Abs (TSAbs) activating the thyrotropin receptor (TSHR). How TSAbs arise from early precursor B cells has not been established. Genetic and environmental factors may contribute to pathogenesis, including the bacterium Yersinia enterocolitica. We developed two pathogenic monoclonal TSAbs from a single experimental mouse undergoing Graves' disease, which shared the same H and L chain germline gene rearrangements and then diversified by numerous somatic hypermutations. To address the Ag specificity of the shared germline precursor of the monoclonal TSAbs, we prepared rFab germline, which showed negligible binding to TSHR, indicating importance of somatic hypermutation in acquiring TSAb activity. Using rFab chimeras, we demonstrate the dominant role of the H chain V region in TSHR recognition. The role of microbial Ags was tested with Y. enterocolitica proteins. The monoclonal TSAbs recognize 37-kDa envelope proteins, also recognized by rFab germline. MALDI-TOF identified the proteins as outer membrane porin (Omp) A and OmpC. Using recombinant OmpA, OmpC, and related OmpF, we demonstrate cross-reactivity of monoclonal TSAbs with the heterogeneous porins. Importantly, rFab germline binds recombinant OmpA, OmpC, and OmpF confirming reactivity with Y. enterocolitica. A human monoclonal TSAb, M22 with similar properties to murine TSAbs, also binds recombinant porins, showing cross-reactivity of a spontaneously arising pathogenic Ab with Y. enterocolitica. The data provide a mechanistic framework for molecular mimicry in Graves' disease, where early precursor B cells are expanded by Y. enterocolitica porins to undergo somatic hypermutation to acquire a cross-reactive pathogenic response to TSHR

Echinimonas agarilytica gen. nov., sp. nov., a new gammaproteobacterium isolated from the sea urchin Strongylocentrotus intermedius

A novel Gram-negative, facultatively anaerobic and motile bacterial strain, designated KMM 6351(T), was isolated from the sea urchin Strongylocentrotus intermedius and examined using a polyphasic taxonomic approach. A phylogenetic analysis based on 16S rRNA gene sequencing revealed that the strain formed a distinct phyletic line in the class Gammaproteobacteria and was most closely related to the genera Aliivibrio, Photobacterium and Vibrio. Strain KMM 6351(T) grows at 4-40 A degrees C and with 0.5-12 % NaCl and decomposes aesculin, agar, gelatin, starch, chitin and DNA. The DNA G+C content of the strain was determined to be 46.1 mol%. The prevalent fatty acids were found to be C-16:0, C-18:1 omega 7c, C-12:0 3-OH and summed feature 3 (comprising C-16:1 omega 7c and/or iso-C-15:0 2-OH fatty acids). The major polar lipids were determined to be diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and an unidentified aminolipid. The predominant ubiquinone was found to be Q-8. The results of the phenotypic, chemotaxonomic and genotypic analyses clearly indicated that the novel strain should be assigned to a new genus and species within the class gamma-Proteobacteria for which the name Echinimonas agarilytica gen. nov., sp. nov. is proposed. The type strain is KMM 6351(T) (=KCTC 22996(T) = LMG 25420(T))

Phylogenetic relationships among 16S rDNA-<i>gyrB</i> sequences of <i>Yersinia</i>.

<p>The unrooted dendrogram was generated using neighbour-joining algorithm. The evolutionary distances were computed using the Kimura 2-parameter method and are expressed in number of base substitutions per site. The percentages of replicate trees in which the associated taxa clustered together in the bootstrap test are shown in nodes.</p

Phylogenetic relationships among <i>ompF</i> sequences of <i>Yersinia</i>.

<p>The unrooted dendrogram was generated using neighbour-joining algorithm. The evolutionary distances were computed using the Kimura 2-parameter method and are expressed in number of base substitutions per site. The percentages of replicate trees in which the associated taxa clustered together in the bootstrap test are shown in nodes.</p

Nucleotide divergence (Pi) in 73 <i>ompF</i> sequences.

<p>The regions predicted to correspond to the external loops (L1–L8) are colored green, regions putatively exposed to the periplasm and predicted transmembrane strands (1-16β) are indicated by black shading, the signal sequence (Sig.s.) is colored blue.</p

Location of positively selected sites in OmpF porins of <i>Yersinia</i>.

<p>Group VII-<i>Y. enterocolitica</i> WA220; Group XIII-<i>Y. intermedia</i> 1948; Group IX-<i>Y. frederiksenii</i> 4648; Group I-<i>Y. intermedia</i> ATCC 29909; Group X-<i>Y. kristensenii</i> 5868; Group VIII-<i>Y. pseudotuberculosis</i> IP 31758. Sites that show positive selection (P<0.05) are depicted as yellow spheres and (P<0.01)-as red spheres.</p

Schematic representation of recombination events with brake-points location in the <i>ompF</i> gene of <i>Yersinia</i>.

<p>Schematic representation of recombination events with brake-points location in the <i>ompF</i> gene of <i>Yersinia</i>.</p