Project description:Serratia marcescens, a member of the order Enterobacterales, is adept at colonizing healthcare environments and an important cause of invasive infections. Antibiotic resistance is a daunting problem in S. marcescens because in addition to plasmid-mediated mechanisms, most isolates have considerable intrinsic resistance to multiple antibiotic classes. To discover endogenous modifiers of antibiotic susceptibility in S. marcescens, a high-density transposon insertion library was subjected to sub-minimal inhibitory concentrations of two cephalosporins, cefoxitin and cefepime, as well as the fluoroquinolone ciprofloxacin. Comparisons of transposon insertion abundance before and after antibiotic exposure identified hundreds of potential modifiers of susceptibility to these agents. Using single gene deletions, we validated several candidate modifiers of cefoxitin susceptibility and chose ydgH, a gene of unknown function, for further characterization. In addition to cefoxitin, deletion of ydgH in S. marcescens resulted in decreased susceptibility to multiple 3rd generation cephalosporins, and in contrast, to increased susceptibility to both cationic and anionic detergents. YdgH is highly conserved throughout the Enterobacterales, and we observed similar phenotypes in Escherichia coli O157:H7 and Enterobacter cloacae mutants. YdgH is predicted to localize to the periplasm and we speculate that it may be involved there in cell envelope homeostasis. Collectively, our findings provide insight into chromosomal mediators of antibiotic resistance in S. marcescens and will serve as a resource for further investigations of this important pathogen.
Project description:We report the application of transcriptome sequencing technology for high-throughput profiling of Serratia marcescens for producing prodigiosin. By obtaining over 163 million bases of sequence from Serratia marcescens genome DNA, we generated transcriptome -state maps of Serratia marcescens 12h cells, 24h cells, and 36h cells at 30C and 37C,respectively. We explored the mechanism of S. marcescens response temperature regulation at the transcription level through transcriptome sequencing technology. We found that the pig gene cluster at low temperature would favor at the transcriptional level, however, higher temperature resulting in instability and loss of enzyme activity. Numerous amino acid metabolic pathways involved in prodigiosin biosynthesis in S. marcescens responded to temperature changes, and metabolic fluxes were directed towards prodigiosin biosynthesis. At the same time, quorum sensing, two-component regulatory system and sRNA were stimulated by temperature to regulate PG biosynthesis and involve strain virulence and exclusive genes. Moreover, inhibition factors was the one reason for S. marcescens incapable synthesis of prodigiosin at 37C. This study laid a good foundation for understanding the biological functions of prodigiosin, improving the temperature tolerance of industrial strains, and excavating temperature-sensitive regulatory elements.
Project description:Bacteria respond to changes in their external environment like temperature by changing the transcription of their genes, but we know little about how these regulatory patterns evolve. We used RNA-seq to study the transcriptional response of a shift from 37°C to 15°C in wild-type Escherichia coli, Salmonella enterica, Citrobacter rodentium, Enterobacter cloacae, Klebsiella pneumoniae, and Serratia marcescens, as well as ∆rpoS strains of E. coli and S. enterica. We found that these species change the transcription of between 626 and 1057 genes in response to the temperature shift, but there are only 16 genes differentially expressed in wild-type strains of all six species. GO enrichment of regulated genes suggests many species-specific phenotypic responses to temperature changes, but terms involved in iron metabolism, central metabolism, and response to osmotic stress are implicated in at least half of the species. The alternative sigma factor RpoS regulates about 200 genes at 15°C in E. coli and S. enterica, with only 83 genes in common between the two species. Divergence in the RpoS-regulon between the two species is due to both species-specific genes in each genome as well as differences in regulation of shared genes. Overall, there is limited conservation of the response to low temperature generally, or the RpoS-regulated part of the response specifically, due both to some genes being species-specific, as well as the species-specific regulation of shared genes. Regulatory responses to a common stress evolve rapidly between closely related species.
Project description:Drosophila melanogaster oral infection by the entomopathogen bacteria Serratia marcescens trigger, at the midgut level, a drastic phenotype during the early phase of the exposure. In response to Serratia marcescens virulence factors the enterocytes present a rapid formation of megamitochondria and a subsequent controlled extrusion of the cytoplasm along with damaged organelles, which may constitute a repair mechanism. This results in a thin intestinal epithelium that then recovers its original shape in just a few hours. In order to identify, at the midgut level, the transcriptional modifications induced by Serratia marcescens during this early phase of the infection, we performed a RNAseq transcriptomics analysis of the flies intestine three hours after bacteria ingestion. We found that 144 genes were significantly induced and that 34 genes were repressed at this time point in comparison to the non infected midguts.
Project description:In order to identify changes in the global mRNA transcriptome caused by deletion of the RNA-binding protein Hfq in Serratia marcescens, total mRNA was isolated from wild type Serratia marcescens Db10 and an otherwise isogenic strain carrying an in-frame deletion of the hfq gene (SMDB11_4482) and analysed by RNAseq. Four independent biological replicates were sequenced for each strain using the Illumina HiSeq platform. The data was used to identify the nature and extent of changes in transcript level between the two strains and to inform on the role of Hfq in virulence of Serratia marcescens, an opportunist bacterial pathogen.