FabR, a regulator of membrane lipid homeostasis, is involved in biofilm robustness.

Biofilm is a dynamic structure from which individual bacteria and micro-aggregates are released to subsequently colonize new niches by either detachment or dispersal. Screening of a transposon mutant library identified genes associated with the alteration of biofilm including , which encodes a transcriptional regulator involved in membrane lipid homeostasis. An isogenic ∆ mutant formed more biofilm than the wild-type (WT) strain and its trans-complemented strain.

Ubiquitination of Virulence Factor InlC Contributes to the Host Response to Infection.

is a pathogenic bacterium causing potentially fatal foodborne infections in humans and animals. While the mechanisms used by to manipulate its host have been thoroughly characterized, how the host controls bacterial virulence factors remains to be extensively deciphered. Here, we found that the secreted virulence protein InlC is monoubiquitinated by the host cell machinery on K224, restricting infection.

Colonization and immune modulation properties of biofilm-dispersed cells.

Biofilm-dispersal is a key determinant for further dissemination of biofilm-embedded bacteria. Recent evidence indicates that biofilm-dispersed bacteria have transcriptional features different from those of both biofilm and planktonic bacteria. In this study, the in vitro and in vivo phenotypic properties of cells spontaneously dispersed from biofilm were compared with those of planktonic and sessile cells.

Immunomodulatory Effects of Lactobacillus plantarum on Inflammatory Response Induced by Klebsiella pneumoniae.

Some respiratory infections have been associated with dysbiosis of the intestinal microbiota. The underlying mechanism is incompletely understood, but cross talk between the intestinal microbiota and local immune cells could influence the immune response at distal mucosal sites. This has led to the concept of enhancing respiratory defenses by modulating the intestinal microbiota with exogenous supplementation of beneficial strains.

How do environment-dependent switching rates between susceptible and persister cells affect the dynamics of biofilms faced with antibiotics?

Persisters form sub-populations of stress-tolerant cells that play a major role in the capacity of biofilms to survive and recover from disturbances such as antibiotic treatments. The mechanisms of persistence are diverse and influenced by environmental conditions, and persister populations are more heterogeneous than formerly suspected. We used computational modeling to assess the impact of three switching strategies between susceptible and persister cells on the capacity of bacterial biofilms to grow, survive and recover from antibiotic treatments.

Relating switching rates between normal and persister cells to substrate and antibiotic concentrations: a mathematical modelling approach supported by experiments.

We developed and compared two mathematical models of variable phenotypic switching rates between normal and persister cells that depend on substrate concentration and antibiotic presence. They could be used to simulate the formation of persisters in environments with concentration gradients such as biofilms. Our models are extensions of a previous model of the dynamics of normal and persistent cell populations developed by Balaban et al.

Biofilm dispersal: multiple elaborate strategies for dissemination of bacteria with unique properties.

In most environments, microorganisms evolve in a sessile mode of growth, designated as biofilm, which is characterized by cells embedded in a self-produced extracellular matrix. Although a biofilm is commonly described as a "cozy house" where resident bacteria are protected from aggression, bacteria are able to break their biofilm bonds and escape to colonize new environments. This regulated process is observed in a wide variety of species; it is referred to as biofilm dispersal, and is triggered in response to various environmental and biological signals.

Assessing Vacuolar Escape of Listeria Monocytogenes.

Listeria monocytogenes is a bacterial pathogen which invades and multiplies within non-professional phagocytes. Signaling cascades involved in cellular entry have been extensively analyzed, but the events leading to vacuolar escape remain less clear. In this chapter, we detail a microscopy FRET-based assay which allows quantitatively measuring L.

Compatibility of Injectable Anticoagulant Agents in Ethanol; In Vitro Antibiofilm Activity and Impact on Polyurethane Catheters of Enoxaparin 400 U/mL in 40% v/v Ethanol.

Background And Objectives: Interdialytic lock solutions should maintain catheter patency and prevent catheter infections. We aimed to determine in which conditions injectable anticoagulant agents (IAAs) combined with ethanol are compatible and to assess the antibiofilm activity of the selected combination and its effects on dialysis catheters (DC).

Methods: The solubility and compatibility of unfractionated heparin (UFH), low molecular weight heparins (LMWHs), heparinoids and fondaparinux (50 to 2,500 U/mL) in 30 to 70% ethanol were determined by visual observation.

Transcriptional profiling of Klebsiella pneumoniae defines signatures for planktonic, sessile and biofilm-dispersed cells.

Background: Surface-associated communities of bacteria, known as biofilms, play a critical role in the persistence and dissemination of bacteria in various environments. Biofilm development is a sequential dynamic process from an initial bacterial adhesion to a three-dimensional structure formation, and a subsequent bacterial dispersion. Transitions between these different modes of growth are governed by complex and partially known molecular pathways.

Genome Sequence of a Clinical Klebsiella pneumoniae Sequence Type 6 Strain.

We report here the genome sequence of Klebsiella pneumoniae CH1034, a sequence type 6 (ST6) strain isolated in 2012 from a central venous catheter of a hospitalized patient.

A Dual Microscopy-Based Assay To Assess Listeria monocytogenes Cellular Entry and Vacuolar Escape.

Listeria monocytogenes is a Gram-positive bacterium and a facultative intracellular pathogen that invades mammalian cells, disrupts its internalization vacuole, and proliferates in the host cell cytoplasm. Here, we describe a novel image-based microscopy assay that allows discrimination between cellular entry and vacuolar escape, enabling high-content screening to identify factors specifically involved in these two steps. We first generated L.

In silico analysis of usher encoding genes in Klebsiella pneumoniae and characterization of their role in adhesion and colonization.

Chaperone/usher (CU) assembly pathway is used by a wide range of Enterobacteriaceae to assemble adhesive surface structures called pili or fimbriae that play a role in bacteria-host cell interactions. In silico analysis revealed that the genome of Klebsiella pneumoniae LM21 harbors eight chromosomal CU loci belonging to γκп and ϭ clusters. Of these, only two correspond to previously described operons, namely type 1 and type 3-encoding operons.

Anti-biofilm activity: a function of Klebsiella pneumoniae capsular polysaccharide.

Competition and cooperation phenomena occur within highly interactive biofilm communities and several non-biocides molecules produced by microorganisms have been described as impairing biofilm formation. In this study, we investigated the anti-biofilm capacities of an ubiquitous and biofilm producing bacterium, Klebsiella pneumoniae. Cell-free supernatant from K.

Two distinct sensing pathways allow recognition of Klebsiella pneumoniae by Dictyostelium amoebae.

Recognition of bacteria by metazoans is mediated by receptors that recognize different types of microorganisms and elicit specific cellular responses. The soil amoebae Dictyostelium discoideum feeds upon a variable mixture of environmental bacteria, and it is expected to recognize and adapt to various food sources. To date, however, no bacteria-sensing mechanisms have been described.

Pyrosequencing assessment of prokaryotic and eukaryotic diversity in biofilm communities from a French river.

Despite the recent and significant increase in the study of aquatic microbial communities, little is known about the microbial diversity of complex ecosystems such as running waters. This study investigated the biodiversity of biofilm communities formed in a river with 454 Sequencing™. This river has the particularity of integrating both organic and microbiological pollution, as receiver of agricultural pollution in its upstream catchment area and urban pollution through discharges of the wastewater treatment plant of the town of Billom.

The Listeria monocytogenes InlC protein interferes with innate immune responses by targeting the I{kappa}B kinase subunit IKK{alpha}.

Listeria monocytogenes is an intracellular pathogen responsible for severe foodborne infections. It can replicate in both phagocytic and nonphagocytic mammalian cells. The infectious process at the cellular level has been studied extensively, but how the bacterium overcomes early host innate immune responses remains largely unknown.

Quorum sensing affects biofilm formation through lipopolysaccharide synthesis in Klebsiella pneumoniae.

Biofilm formation by Klebsiella pneumoniae is modulated by quorum sensing through the synthesis of interspecies AI-2 autoinducers. We characterized in K. pneumoniae the genes homologous to those described in Escherichia coli involved in AI-2 transport, and created two isogenic mutants deleted of lsrCD and tqsA.

Single-cell techniques using chromosomally tagged fluorescent bacteria to study Listeria monocytogenes infection processes.

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen which invades different cell types, including nonphagocytic cells, where it is able to replicate and survive. The different steps of the cellular infectious process have been well described and consist of bacterial entry, lysis of the endocytic vacuole, intracellular replication, and spreading to neighboring cells. To study the listerial infectious process, gentamicin survival assays, plaque formation, and direct microscopy observations are typically used; however, there are some caveats with each of these techniques.

The Listeria transcriptional landscape from saprophytism to virulence.

The bacterium Listeria monocytogenes is ubiquitous in the environment and can lead to severe food-borne infections. It has recently emerged as a multifaceted model in pathogenesis. However, how this bacterium switches from a saprophyte to a pathogen is largely unknown.

Eradication of microorganisms embedded in biofilm by an ethanol-based catheter lock solution.

Background: Interdialytic locking of catheters with antimicrobial agents is frequently used for preventing catheter-related infections, often associated with biofilm formation. We determined the bactericidal effect of 60% ethanol (ETOH) versus a 46.7% trisodium citrate (TSC) solution on biofilm embedded in silicone catheters.

The characterization of functions involved in the establishment and maturation of Klebsiella pneumoniae in vitro biofilm reveals dual roles for surface exopolysaccharides.

The ability to form biofilm is seen as an increasingly important colonization strategy among both pathogenic and environmental Klebsiella pneumoniae strains. The aim of the present study was to identify abiotic surface colonization factors of K. pneumoniae using different models at different phases of biofilm development.

Ac2-DPD, the bis-(O)-acetylated derivative of 4,5-dihydroxy-2,3-pentanedione (DPD) is a convenient stable precursor of bacterial quorum sensing autoinducer AI-2.

Ac2-DPD, the bis-(O)-acetylated derivative of 4,5-dihydroxy-2,3-pentanedione (DPD), was prepared both as a racemic mixture and in the optically active form found in naturally occurring DPD. It was shown to exhibit the same ability as DPD to induce bioluminescence in Vibrio harveyi and beta-galactosidase activity in Salmonella enterica Typhimurium, both gram-negative bacteria. Likewise, it was also shown to inhibit biofilm formation in gram-positive Bacillus cereus.

Broad-spectrum biofilm inhibition by a secreted bacterial polysaccharide.

The development of surface-attached biofilm bacterial communities is considered an important source of nosocomial infections. Recently, bacterial interference via signaling molecules and surface active compounds was shown to antagonize biofilm formation, suggesting that nonantibiotic molecules produced during competitive interactions between bacteria could be used for biofilm reduction. Hence, a better understanding of commensal/pathogen interactions within bacterial community could lead to an improved control of exogenous pathogens.