Aminoacyl β-naphthylamides as substrates and modulators of AcrB multidrug efflux pump.

Efflux pumps of the resistance-nodulation division superfamily, such as AcrB, make a major contribution to multidrug resistance in Gram-negative bacteria. Inhibitors of such pumps would improve the efficacy of antibiotics, and ameliorate the crisis in health care caused by the prevalence of multidrug resistant Gram-negative pathogens. Phenylalanyl-arginine β-naphthylamide (PAβN), is a well-known inhibitor of AcrB and its homologs.

Impacts of hydrophilic colanic acid on bacterial attachment to microfiltration membranes and subsequent membrane biofouling.

In order to examine the interactions between physicochemical properties of specific extracellular polymeric substances (EPS) and membrane biofouling, we investigated the impacts of hydrophilic colanic acid, as a model extracellular polysaccharide component, on initial bacterial attachment to different microfiltration (MF) membranes and membrane biofouling by using Escherichia coli strains producing different amounts of colanic acid. In a newly designed microtiter plate assay, the bacterial attachment by an E. coli strain RcsF(+), which produces massive amounts of colanic acid, decreased only to a hydrophobic membrane because the colanic acid made cell surfaces more hydrophilic, resulting in low cell attachment to hydrophobic membranes.

RelE-mediated dormancy is enhanced at high cell density in Escherichia coli.

Bacteria show remarkable adaptability under several stressful conditions by shifting themselves into a dormant state. Less is known, however, about the mechanism underlying the cell transition to dormancy. Here, we report that the transition to dormant states is mediated by one of the major toxin-antitoxin systems, RelEB, in a cell density-dependent manner in Escherichia coli K-12 MG1655.

Enterobactin is required for biofilm development in reduced-genome Escherichia coli.

A variety of bacterial cell surface structures and quorum signalling molecules play a role in biofilm development in Escherichia coli. However, here we show that an engineered reduced-genome E. coli mutant that lacks 17.

Exposure of conjugative plasmid carrying Escherichia coli biofilms to male-specific bacteriophages.

Escherichia coli carrying a natural conjugative F-plasmid generates F-pili mating pairs, which is important for early biofilm formation. In this study, we investigated the effect of male-specific filamentous single stranded DNA bacteriophage (f1) and RNA bacteriophage (MS2) on the formation of biofilms by E. coli carrying a natural conjugative F-plasmid.

Characterization and global gene expression of F- phenocopies during Escherichia coli biofilm formation.

The ecological role of horizontal gene transfer within biofilms has been recently investigated, and it has been reported that conjugation directly induces bacteria to form biofilms via expression of conjugative pili. In this report, we described the contribution of bacterial conjugation during biofilm formation by Escherichia coli harboring a natural IncF conjugative F plasmid (F(+)). We showed that cell-to-cell pili interactions through the homosexual mating-pair formation among F(+) × F(+) cells (namely, F(-) phenocopy phenomenon) promote E.

Induction of multidrug resistance mechanism in Escherichia coli biofilms by interplay between tetracycline and ampicillin resistance genes.

Biofilms gain resistance to various antimicrobial agents, and the presence of antibiotic resistance genes is thought to contribute to a biofilm-mediated antibiotic resistance. Here we showed the interplay between the tetracycline resistance efflux pump TetA(C) and the ampicillin resistance gene (bla(TEM-1)) in biofilms of Escherichia coli harboring pBR322 in the presence of the mixture of ampicillin and tetracycline. E.

Increased antibiotic resistance of Escherichia coli in mature biofilms.

Biofilms are considered to be highly resistant to antimicrobial agents. Several mechanisms have been proposed to explain this high resistance of biofilms, including restricted penetration of antimicrobial agents into biofilms, slow growth owing to nutrient limitation, expression of genes involved in the general stress response, and emergence of a biofilm-specific phenotype. However, since combinations of these factors are involved in most biofilm studies, it is still difficult to fully understand the mechanisms of biofilm resistance to antibiotics.

Localized expression profiles of rpoS in Escherichia coli biofilms.

Although importance of the rpoS gene on biofilm formation by Escherichia coli has been suggested, there has not been any report showing where the rpoS is expressed during biofilm formation process. Since physiological state of the cells in the biofilms is considerably heterogeneous, the expression of the rpoS gene must be heterogeneous. In this study, in situ spatial expression of the rpoS gene during biofilm formation was investigated with an rpoS-gfp transcriptional fusion mutant strain.

Escherichia coli harboring a natural IncF conjugative F plasmid develops complex mature biofilms by stimulating synthesis of colanic acid and Curli.

It has been shown that Escherichia coli harboring the derepressed IncFI and IncFII conjugative F plasmids form complex mature biofilms by using their F-pilus connections, whereas a plasmid-free strain forms only patchy biofilms. Therefore, in this study we investigated the contribution of a natural IncF conjugative F plasmid to the formation of E. coli biofilms.

Significance of rpoS during maturation of Escherichia coli biofilms.

Presence of starved, stationary phase-like zones in biofilms seems to be an important factor for biofilm formation. In this study, roles of rpoS gene in the formation of Escherichia coli biofilms were investigated. E.