Unknown,Transcriptomics,Genomics,Proteomics

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Molecular evolution of Acinetobacter baumannii strains (belonging to ST-2 clone) in a decade: Role of phages

ABSTRACT: Phages have emerged as prime suspects in the adaptation of pathogens to new hosts and the emergence of new pathogens or epidemic clones. Here we describe the genomic features of “swarms” of three related prophages (Ab105-1ϕ, Ab105-2ϕ and Ab105-3ϕ) present in the ST-2 epidemic clone of Acinetobacter baumannii clinical strain Ab105 GEIH-2010 and not present in genetically related Ab155 GEIH-2000 strain isolated 10 years before. The “Quasicore genome” of Ab105-1ϕ, Ab105-2ϕ and Ab105-3ϕ prophages revealed genes that promote bacterial-host fitness. The results of microarray analysis under stress conditions, SOS response and Quorum Sensing (QS) activation revealed 42% and 21% of genes expressed by Ab105-2ϕ and Ab105-3ϕ prophages (which produce bacterial lysis) in the first case and underexpression of these genes from prophages in the second case. Hence, the QS system plays a major role in the evolution of phages in their natural hosts and environments. Interestingly, in host-virus interactions, RT-PCR showed several mechanisms of overexpression of the SOS response in relation to phage defence mechanisms: i) SAM or AdoMet-MTase (methyltransferases) and MazG protein (pyrophosphohydrolase) associated with phage defence in response to bacterial attack; ii) eukaryotic-like protein kinase (glutamate 5-kinase) associated with prevention of secondary infection by the same or a closely related virus. Overexpression of secretory virulence factors such as oxidoreductase (DsbA-like), anfo-nitrogenase and chromosome segregation proteins were also observed. Moreover, under iron-deficient growth, there was an overexpression by RT-PCR of the a new interesting cluster of genes located following a “Moron” organization in the Ab105-3ϕ prophage being associated with iron uptake systems (Xanthine dehydrogenase gene cluster, Anthranilate operon, ABC transporter and TonB dependent receptor). In conclusion, study of the co-evolution of phages (virus) and bacteria may be essential in the search for means of combatting multi-resistant epidemic clones. Two parental clinical strains of A. baumannii (90% identity, indicated by PFGE, and ST2, indicated by Multilocus Sequence Typing, MLST) isolated in the same Intensive Care Unit (ICU) of a Spanish hospital, in 2000 and 2010, during the “I Multicenter Study GEIH-REIPI-Ab-2000” (Ab155 GEIH-2000) and “II Multicenter Study GEIH-REIPI-Ab-2010” (Ab105 GEIH-2010), respectively. Three replicates from RNA of the AB105 GEIH-2010 strain x 2 conditions (SOS response by Mitomycin C) and (Quorum Sensing activation by AHLs mixture).

ORGANISM(S): Acinetobacter baumannii

SUBMITTER: Maria Tomas-Carmona

PROVIDER: E-GEOD-72885 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Staphylococcus aureus is a Gram-positive human pathogen causing a variety of human diseases in both hospital and community settings. This bacterium is so closely associated with prophages that it is rare to find S. aureus isolates without prophages. Two phages are known to be important for staphylococcal virulence: the beta-hemolysin (hlb) converting phage and the Panton-Valentine Leukocidin (PVL) converting phage. The hlb-converting phage is found in more than 90% of clinical isolates of S. aureus. This phage produces exotoxins and immune modulatory molecules, which inhibit human innate immune responses. The PVL-converting phage produces the two-component exotoxin PVL, which can kill human leucocytes. This phage is wide-spread among community-associated methicillin resistant S. aureus (CA-MRSA). It also shows strong association with soft tissue infections and necrotizing pneumonia. Several lines of evidence suggest that staphylococcal prophages increase bacterial virulence not only by providing virulence factors but also by altering bacterial gene expression: 1) Transposon insertion into prophage regulatory genes, but not into the genes of virulence factors, reduced S. aureus killing of Caenorhabditis elegans.; 2) Although the toxins and immune modulatory molecules encoded by the hlb- converting phages do not function in the murine system, deletion of ϕNM3, the hlb-converting phage in S. aureus Newman, reduced staphylococcal virulence in the murine abscess formation model. 3) In a preliminary microarray experiment, prophages in S. aureus Newman altered the expression of more than 300 genes. In this research proposal, using microarray and high-throughput quantitative RT-PCR (qRT-PCR) technologies, we will identify the effects of the two important staphylococcal phages on the gene expression of S. aureus in both in vitro and in vivo conditions. This project is intended to be completed within one year. All the data – microarray, qRT-PCR and all the primer sequences- will be made available to public 6 month after completion. Data from this project will help us to understand the role of prophages in the S. aureus pathogenesis and can lead to development of a strategy to interfere with the pathogenesis process. Following strains were grown in TSA broth: Staphylococcus aureus USA300 (reference) Staphylococcus aureus USA300 with deletion of ϕSa2usa (Query) Staphylococcus aureus USA300 with deletion of ϕSa3usa (Query) Staphylococcus aureus USA300 Prophage-free mutant (Query) Staphylococcus aureus USA300 Prophage-free mutant lysogenized with ϕSa2mw (Query) Staphylococcus aureus USA300 Prophage-free mutant lysogenized with ϕSa3usa (Query) strain: Staphylococcus aureus USA300 Prophage-free mutant lysogenized with both ϕSa2mw and ϕSa3usa (Query) RNA samples were harvested at early log, midlog and stationary phase.Samples were hybridized on aminosilane coated slides with 70-mer oligos.

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Molecular evolution of Acinetobacter baumannii strains (belonging to ST-2 clone) in a decade: Role of phages

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