Freund oder Feind? — Die zwei Gesichter von Photorhabdus luminescens

Photorhabdus luminescens is an enteric bacterium with two faces: on the one hand these bacteria live in symbiosis with soil nematodes, on the other hand they are highly pathogenic for insects. The population is also phenotypically heterogeneous: one part lives in symbiosis with nematodes, the other part symbiotically interacts with plants. Cell-cell communication, inter-kingdom signaling, and other gene regulation processes are behind the complex decision of being friend or foe.

Salmonella enters a dormant state within human epithelial cells for persistent infection

Salmonella Typhimurium (S. Typhimurium) is an enteric bacterium capable of invading a wide range of hosts, including rodents and humans. It targets different host cell types showing different intracellular lifestyles. S. Typhimurium colonizes different intracellular niches and is able to either actively divide at various rates or remain dormant to persist. A comprehensive tool to determine these distinct S. Typhimurium lifestyles remains lacking. Here we developed a novel fluorescent reporter, Salmonella Intracellular Analyzer (SINA), compatible for fluorescence microscopy and flow cytometry in single-bacterium level quantification. This identified a S. Typhimurium subpopulation in infected epithelial cells that exhibits a unique phenotype in comparison to the previously documented vacuolar or cytosolic S. Typhimurium. This subpopulation entered a dormant state in a vesicular compartment distinct from the conventional Salmonella-containing vacuoles (SCV) as well as the previously reported niche of dormant S. Typhimurium in macrophages. The dormant S. Typhimurium inside enterocytes were viable and expressed Salmonella Pathogenicity Island 2 (SPI-2) virulence factors at later time points. We found that the formation of these dormant S. Typhimurium is not triggered by the loss of SPI-2 effector secretion but it is regulated by (p)ppGpp-mediated stringent response through RelA and SpoT. We predict that intraepithelial dormant S. Typhimurium represents an important pathogen niche and provides an alternative strategy for S. Typhimurium pathogenicity and its persistence.

Serratia no longer an opportunistic uncommon pathogen – case series & review of literature

Background: Serratia spp. is a common enteric bacterium generally thought not to be pathogenic in the gastrointestinal tract. Serratia marcescens is a member of the genus Serratia, which is a part of the family Enterobacteriales..Of all Serratia species, S. marcescens is the most common clinical isolate and the most important human pathogen. Objective: We are discussing here four cases of Serratia marcescens which we reported in our laboratory in the Department of Microbiology Government Medical College and Hospital Chandigarh during six months of duration. Method: All the samples were processed and identified as per standard microbiological techniques.The isolates of Serratia marcescens were identified, depending upon their biochemical and morphological characters and further confirmed by MALDI-TOF-MS ,PGIMER Chandigarh. Result: In one of the four cases there was polymicrobial infection and one patient was diabetic and rest three patients were immunocompetent. The importance of detection and reporting of Serratia marcescens is related to the concern regarding its increase spread in hospital settings as nosocomial infection . Conclusion: We need to identify and isolate this pathogen ,not thinking of only contaminant and opportunistic pathogen but as a pathogen which can lead to serious infections in hospital settings .

Draft Genome Sequence of the Redox-Active Enteric Bacterium Citrobacter portucalensis Strain MBL

ABSTRACT We grew a soil enrichment culture to identify organisms that anaerobically oxidize phenazine-1-carboxylic acid. A strain of Citrobacter portucalensis was isolated from this enrichment and sequenced by both Illumina and PacBio technologies. It has a genome with a length of 5.3 Mb, a G+C content of 51.8%, and at least one plasmid.

Polyphasic Characterisation of Cedecea colo sp. nov., a New Enteric Bacterium Isolated from the Koala Hindgut

The Cedecea genus is comprised of six rarely isolated species within the Enterobacteriaceae family. Representatives are Gram-negative motile bacilli, and are typically oxidase-negative, lipase-positive and resistant to colistin and cephalothin. In this study, a putative novel Cedecea species (designated strain ZA_0188T), isolated from the koala hindgut, was characterised using a polyphasic taxonomic approach. Maximum average nucleotide identity (ANI) and 16S ribosomal RNA (rRNA) similarity scores well below thresholds of species demarcation were reported, at 81.1% and 97.9%, respectively. Multilocus phylogenetic analysis indicated strain ZA_0188T was most similar to but divergent from recognised Cedecea species. The isolate’s genomic G+C content was determined as 53.0 mol%, >1% lower than previously reported in Cedecea. Phenotypically, strain ZA_0188T was distinct from recognised Cedecea species such as colistin- and cephalothin-sensitive, lipase-, sorbitol-, sucrose-, and Voges-Proskauer-negative, and melibiose-, arabinose-, arginine-, and rhamnose-positive. In preliminary experiments, strain ZA_0188T exhibited cellulase activity and high-level tolerance to eucalyptus oil compared to other enteric species surveyed. Collectively, these findings suggest that strain ZA_0188T represents a novel enteric species, for which the name Cedecea colo is proposed.

Complete Genome Sequence of Proteus mirabilis Siphophage Saba

Proteus mirabilis is a Gram-negative enteric bacterium associated with complicated human urinary tract infections. Here, we present the complete genome annotation for P. mirabilis siphophage Saba. With a 60,056-bp genome and 75 predicted genes, Saba is most similar at the nucleotide and protein levels to phage Chi and Chi-like viruses.

Identification and characterization of FtsH mediating in vivo colonization and stress adaptation in the fish pathogen Edwardsiella piscicida

ABSTRACT Edwardsiella piscicida is an important pathogenic enteric bacterium of fish. FtsH is a unique membrane-anchored AAA + protease that regulates protein homeostasis in bacteria. In cooperation with modulators HflK and HflC, FtsH is essential in enteric bacteria and controls the response to environmental stresses. Here, we used in vivo pattern analysis of conditional essentiality (PACE) and identified that ftsH and hflK/C were associated with impaired in vivo colonization in Edw. piscicida and attenuated internalization ability of ZF4 cells. The ftsH mutant displayed increased survival during prolonged treatment of starvation and high osmotic stresses in Edw. piscicida. Further analysis showed that the disruption of ftsH resulted in the overproduction of the established substrate LpxC, which is responsible for the synthesis of LPS (lipopolysaccharide), as well as the substrate YfgM, which is involved in high osmolality tolerance during stationary phase. However, the inconsistency in the abilities of the ftsH and hflK/C mutants to achieve YfgM-based osmotic resistance indicated that there might be multiple, while distinctive, pathways controlled by FtsH and the associated modulator proteins HflK/C. This investigation revealed the unique functions of FtsH and its modulator HflK/C in Edw. piscicida.

The Prophages ofCitrobacter rodentiumRepresent a Conserved Family of Horizontally Acquired Mobile Genetic Elements Associated with Enteric Evolution towards Pathogenicity

ABSTRACTProphage-mediated horizontal gene transfer (HGT) plays a key role in the evolution of bacteria, enabling access to new environmental niches, including pathogenicity.Citrobacter rodentiumis a host-adapted intestinal mouse pathogen and important model organism for attaching and effacing (A/E) pathogens, including the clinically significant enterohaemorrhagic and enteropathogenicEscherichia coli(EHEC and EPEC, respectively). Even thoughC. rodentiumcontains 10 prophage genomic regions, including an active temperate phage, ΦNP, little was known regarding the nature ofC. rodentiumprophages in the bacterium’s evolution toward pathogenicity. In this study, our characterization of ΦNP led to the discovery of a second, fully functional temperate phage, named ΦSM. We identify the bacterial host receptor for both phages as lipopolysaccharide (LPS). ΦNP and ΦSM are likely important mediators of HGT inC. rodentium. Bioinformatic analysis of the 10 prophage regions reveals cargo genes encoding known virulence factors, including several type III secretion system (T3SS) effectors.C. rodentiumprophages are conserved across a wide range of pathogenic enteric bacteria, including EPEC and EHEC as well as pathogenic strains ofSalmonella enterica,Shigella boydii, andKlebsiella pneumoniae. Phylogenetic analysis of core enteric backbone genes compared against prophage evolutionary models suggests that these prophages represent an important, conserved family of horizontally acquired enteric-bacterium-associated pathogenicity determinants. In addition to highlighting the transformative role of bacteriophage-mediated HGT inC. rodentium’s evolution toward pathogenicity, these data suggest that the examination of conserved families of prophages in other pathogenic bacteria and disease outbreaks might provide deeper evolutionary and pathological insights otherwise obscured by more classical analysis.IMPORTANCEBacteriophages are obligate intracellular parasites of bacteria. Some bacteriophages can confer novel bacterial phenotypes, including pathogenicity, through horizontal gene transfer (HGT). The pathogenic bacteriumCitrobacter rodentiuminfects mice using mechanisms similar to those employed by human gastrointestinal pathogens, making it an important model organism. Here, we examined the 10 prophages ofC. rodentium, investigating their roles in its evolution toward virulence. We characterized ΦNP and ΦSM, two endogenous active temperate bacteriophages likely important for HGT. We showed that the 10 prophages encode predicted virulence factors and are conserved within other intestinal pathogens. Phylogenetic analysis suggested that they represent a conserved family of horizontally acquired enteric-bacterium-associated pathogenic determinants. Consequently, similar analysis of prophage elements in other pathogens might further understanding of their evolution and pathology.