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Background: Streptococcus uberis, a Gram positive bacterial pathogen responsible for a significant proportion of bovine mastitis in commercial dairy herds, colonises multiple body sites of the cow including the gut, genital tract and mammary gland. Comparative analysis of the complete genome sequence of S. uberis strain 0140J was undertaken to help elucidate the biology of this effective bovine pathogen., Results: The genome revealed 1,825 predicted coding sequences (CDSs) of which 62 were identified as pseudogenes or gene fragments. Comparisons with related pyogenic streptococci identified a conserved core (40%) of orthologous CDSs. Intriguingly, S. uberis 0140J displayed a lower number of mobile genetic elements when compared with other pyogenic streptococci, however bacteriophage-derived islands and a putative genomic island were identified. Comparative genomics analysis revealed most similarity to the genomes of Streptococcus agalactiae and Streptococcus equi subsp. zooepidemicus. In contrast, streptococcal orthologs were not identified for 11% of the CDSs, indicating either unique retention of ancestral sequence, or acquisition of sequence from alternative sources. Functions including transport, catabolism, regulation and CDSs encoding cell envelope proteins were over-represented in this unique gene set; a limited array of putative virulence CDSs were identified., Conclusion: S. uberis utilises nutritional flexibility derived from a diversity of metabolic options to successfully occupy a discrete ecological niche. The features observed in S. uberis are strongly suggestive of an opportunistic pathogen adapted to challenging and changing environmental parameters.

The O-acetylation of the essential cell wall polymer peptidoglycan occurs in most Gram-positive bacterial pathogens, including species of Staphylococcus, Streptococcus and Enterococcus. This modification to peptidoglycan protects these pathogens from the lytic action of the lysozymes of innate immunity systems and, as such, is recognized as a virulence factor. The key enzyme involved, peptidoglycan O-acetyltransferase A (OatA) represents a particular challenge to biochemical study since it is a membrane associated protein whose substrate is the insoluble peptidoglycan cell wall polymer. OatA is predicted to be bimodular, being comprised of an N-terminal integral membrane domain linked to a C-terminal extracytoplasmic domain. We present herein the first biochemical and kinetic characterization of the C-terminal catalytic domain of OatA from two important human pathogens, Staphylococcus aureus and Streptococcus pneumoniae. Using both pseudosubstrates and novel biosynthetically-prepared peptidoglycan polymers, we characterized distinct substrate specificities for the two enzymes. In addition, the high resolution crystal structure of the C-terminal domain reveals an SGNH/GDSL-like hydrolase fold with a catalytic triad of amino acids but with a non-canonical oxyanion hole structure. Site-specific replacements confirmed the identity of the catalytic and oxyanion hole residues. A model is presented for the O-acetylation of peptidoglycan whereby the translocation of acetyl groups from a cytoplasmic source across the cytoplasmic membrane is catalyzed by the N-terminal domain of OatA for their transfer to peptidoglycan by its C-terminal domain. This study on the structure-function relationship of OatA provides a molecular and mechanistic understanding of this bacterial resistance mechanism opening the prospect for novel chemotherapeutic exploration to enhance innate immunity protection against Gram-positive pathogens. [ABSTRACT FROM AUTHOR]

Abstract: Streptococcus pneumoniae causes considerable morbidity and mortality worldwide. The need for a cheap and effective pneumococcal vaccine has necessitated the evaluation of common virulence-associated proteins as potential vaccine antigens. PiuA and PiaA are the lipoprotein components of two pneumococcal iron ABC transporters. Here, we show that patients with culture confirmed pneumococcal septicaemia have elevated levels of antibody to PiuA and PiaA in convalescent-phase, compared with acute-phase serum. Additionally, sera from septicaemic patients infected with 13 pneumococcal strains covering eight different serotypes, cross-reacted with recombinant PiuA-His6 and PiaA-His6 from a single pneumococcal strain, indicating that this immune response is serotype independent. Anti-PiuA and anti-PiaA antibodies were also found in healthy seven-month-old infants, indicating that they are immunogenic at a very early age. [Copyright &y& Elsevier]

Although Streptococcus suis is an economically important pathogen of pigs and an occasional cause of zoonotic infections of humans knowledge of crucial virulence factors, and as a consequence targets for therapeutic or prophylactic intervention, remains limited. Here we describe a detailed study of the distribution, diversity, and in vitro expression of hyaluronate lyase, a protein implicated as a virulence factor of many mucosal pathogens. The gene encoding hyaluronate lyase, hyl, was present in all 309 bona fide S. suis isolates examined representing diverse serotypes, geographic sources, and clinical backgrounds. Examination of the genetic diversity of hyl by RFLP and sequence analysis indicated a pattern of diversity shared by many gram-positive surface proteins with a variable 5' region encoding the most distal cell surface-exposed regions of the protein and a much more conserved 3' region encoding domains more closely associated with the bacterial cell. Variation occurs by several mechanisms, including the accumulation of point mutations and deletion and insertion events, and there is clear evidence that genetic recombination has contributed to molecular variation in this gene. Despite the ubiquitous presence of hyl, the corresponding enzyme activity was detected in fewer than 30% of the 309 isolates. In several cases this lack of activity correlates with the presence of mutations (either sequence duplications or point mutations) within hyl that result in a truncated polypeptide. There is a striking absence of hyaluronate iyase activity in a large majority of isolates from classic S. suis invasive disease, indicating that this protein is probably not a crucial virulence factor, although activity is present in significantly higher numbers of isolates associated with pneumonia. [ABSTRACT FROM AUTHOR]