Genome evolution and plasticity of Serratia marcescens, an important multidrug-resistant nosocomial pathogen.
Bottom Line: Naturally, it is found in many environmental niches, and is capable of infecting plants and animals.We further show that pSMC1 is most closely related to plasmids circulating in Pseudomonas species.Our data will provide a valuable basis for future studies on S. marcescens and new insights into the genetic mechanisms that underlie the emergence of pathogens highly resistant to multiple antimicrobial agents.
Affiliation: Interdisciplinary Research Organization, University of Miyazaki, JapanPresent address: Department of Animal and Grassland Sciences, Faculty of Agriculture, University of Miyazaki, Japan.Show MeSH
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Mentions: Multiple type V secretion systems (T5SSs) are present in SM39 and Db11. T5SSs include both autotransporters and two-partner systems (Grijpstra et al. 2013; Jacob-Dubuisson et al. 2013). An archetypal example of a two-partner T5SS is ShlBA; the hemolysin ShlA is one of the known major virulence factors in S. marcescens (Goluszko and Nowacki 1989). The shlBA operon is conserved in both strains. In contrast, three additional gene clusters, encoding two-partner systems with partial similarity to ShlA and other haemagglutinin-like proteins, were identified only in SM39 (fig. 5). Two of these, SM39_2080-2077 and SM39_3145-3141, appear to encode contact-dependent inhibition (Cdi) systems. In such systems, CdiB is a translocator protein that assembles the large, hemagglutinin domain-containing CdiA passenger protein on the cell surface (Aoki et al. 2010). Variable toxin domains are found at the C-terminus of CdiA (CdiACt), which mediate contact-dependent growth inhibition of competitor bacteria. Additionally, immunity proteins (CdiI) cognate to the CdiACt are encoded downstream of CdiA. Both loci contain a typical cdiBAI arrangement. The SM39_3144 locus also includes an “orphan” CdiACt–CdiI paizr (SM39_3142-3141). Orphan CdiACt–CdiI pairs contain truncated CdiA C-termini thought to represent remnants or reservoirs of alternative toxin domains, which can be exchanged to provide new antibacterial capability (Poole et al. 2011).Fig. 5.—
Affiliation: Interdisciplinary Research Organization, University of Miyazaki, JapanPresent address: Department of Animal and Grassland Sciences, Faculty of Agriculture, University of Miyazaki, Japan.