Serratia marcescens is an important opportunistic pathogen in hospitals, where quaternary ammonium compounds are often used for disinfection. The aim of this study is to elucidate the effect of a biocide on the emergence of biocide- and antibiotic-resistant mutants and to characterize the molecular mechanism of biocide resistance in Serratia marcescens . A quaternary ammonium compound-resistant strain, CRes01, was selected by exposing a wild-type strain of S. marcescens to cetylpyridinium chloride. The CRes01 cells exhibited 2- to 16-fold more resistance than the wild-type cells to biocides and antibiotics, including cetylpyridinium chloride, benzalkonium chloride, chlorhexidine gluconate, fluoroquinolones, tetracycline, and chloramphenicol, and showed increased susceptibilities to β-lactam antibiotics and N -dodecylpyridinium iodide. Mutant cells accumulated lower levels of norfloxacin than the parent cells in an energized state but not in a de-energized state, suggesting that the strain produced a multidrug efflux pump(s). To verify this assumption, we knocked out a putative efflux pump gene, sdeAB , in CRes01 and found that the knockout restored susceptibility to most quaternary ammonium compounds and antibiotics, to which the CRes01 strain showed resistance. On the basis of these and other results, we concluded that S. marcescens gains resistance to both biocides and antibiotics by expressing the SdeAB efflux pump upon exposure to cetylpyridinium chloride.

Succinoyl trehalose lipids (STLs) are promising glycolipid biosurfactants produced from n -alkanes that are secreted by Rhodococcus species bacteria. These compounds not only exhibit unique interfacial properties but also demonstrate versatile biochemical actions. In this study, three novel types of genes involved in the biosynthesis of STLs, including a putative acyl coenzyme A (acyl-CoA) transferase ( tlsA ), fructose-bisphosphate aldolase ( fda ), and alkane monooxygenase ( alkB ), were identified. The predicted functions of these genes indicate that alkane metabolism, sugar synthesis, and the addition of acyl groups are important for the biosynthesis of STLs. Based on these results, we propose a biosynthesis pathway for STLs from alkanes in Rhodococcus sp. strain SD-74. By overexpressing tlsA , we achieved a 2-fold increase in the production of STLs. This study advances our understanding of bacterial glycolipid production in Rhodococcus species.

Expression of the MexEF-OprN efflux pump in Pseudomonas aeruginosa seems to be upregulated by MexT. The region upstream of the mexEF-oprN operon cont

In this study, we describe a rational design strategy to develop a latent ratiometric fluorescent pH probe from self-assembled seminaphthorhodafluor (SNARF) derivatives in aqueous conditions. Analysis of the characteristics of SNARF derivatives with protected phenolic groups allowed classification of the threshold between the assembled and monomeric states according to the Hansch–Fujita hydrophobic parameters for a substituent inserted as a SNARF-OH phenolic-protecting group. The esterase-activated latent ratiometric fluorescent pH probe SNARF-OBn(OAc) was characterized in the application of tuneable small-molecule aggregation and disaggregation. Before esterase treatment, SNARF-OBn(OAc) formed self-assembled clusters, emitting no fluorescence. The significant fluorescence was observed after esterase treatment because the self-assembled clusters of SNARF-OBn(OAc) diffuse as SNARF-OH monomers, demonstrating the intracellular application of SNARF-OBn(OAc) as a latent ratiometric fluorescent pH probe for floating cells. Furthermore, to directly visualize the state of self-assembled SNARF derivatives for investigating the mechanism of their cellular uptake, SNARF-Dan was rationally designed and applied for cellular imaging. Through the cellular application of SNARF-Dan, it was suggested that the self-assembled SNARF derivatives were introduced into the cell via macropinocytosis.

This report describes the whole-genome sequence of an alkalitolerant microcystin-degrading bacterium, Sphingopyxis sp. strain C-1, isolated from a lake in China.