: Investigation of Fitness in Soil Does Not Support the Relevance of Ecotypes.

() is a ubiquitous bacterium that causes the serious foodborne illness listeriosis. Although soil is a primary reservoir and a central habitat for , little information is available on the genetic features underlying the fitness of strains in this complex habitat. The aim of this study was to identify (i) correlations between the strains fitness in soil, their origin and their phylogenetic position (ii) identify genetic markers allowing to survive in the soil.

Plants as a realized niche for Listeria monocytogenes.

Listeria monocytogenes is a human pathogen. It is the causative agent of listeriosis, the leading cause of bacterial-linked foodborne mortality in Europe and elsewhere. Outbreaks of listeriosis have been associated with the consumption of fresh produce including vegetables and fruits.

Plant Growth Promoting Bacterial Consortium Induces Shifts in Indigenous Soil Bacterial Communities and Controls Listeria monocytogenes in Rhizospheres of Cajanus cajan and Festuca arundinacea.

The rhizosphere is a dynamic and complex interface between plant roots and microorganisms. Owing to exudates, a web of interactions establishes among the microbial members of this micro-environment. The present study explored the impact of a bacterial consortium (Azotobacter chroococcum, Bacillus megaterium and Pseudomonas fluorescens, ABP), on the fate of a human pathogen, Listeria monocytogenes EGD-e, in soil and in the rhizospheres of Cajanus cajan and Festuca arundinacea, in addition to its plant growth promoting effect.

LisRK is required for optimal fitness of Listeria monocytogenes in soil.

Listeria monocytogenes is a food-borne pathogen responsible for the disease listeriosis. It is ubiquitously found in the environment and soil is one of its natural habitats. Listeria monocytogenes is highly capable of coping with various stressful conditions.

Habitat Disturbances Modulate the Barrier Effect of Resident Soil Microbiota on Invasion Success.

Microbial communities are continuously exposed to the arrival of alien species. In complex environments such as soil, the success of invasion depends on the characteristics of the habitat, especially the diversity and structure of the residing bacterial communities. While most data available on microbial invasion relies on experiments run under constant conditions, the fate of invading species when the habitat faces disturbances has not yet been addressed.

Evidence of Biocontrol Activity of Bioinoculants Against a Human Pathogen, .

Due to rhizodeposits and various microbial interactions, the rhizosphere is an extremely dynamic system, which provides a conductive niche not only for bacteria beneficial to plants but also for those that might pose a potential threat to humans. The importance of bioinoculants as biocontrol agents to combat phytopathogens has been widely recognized. However, little information exists with respect to their role in inhibiting human pathogens in the rhizosphere.

The ZKIR Assay, a Real-Time PCR Method for the Detection of and Closely Related Species in Environmental Samples.

is of growing public health concern due to the emergence of strains that are multidrug resistant, virulent, or both. Taxonomically, the complex ("Kp") includes seven phylogroups, with Kp1 () being medically prominent. Kp can be present in environmental sources such as soils and vegetation, which could act as reservoirs of animal and human infections.

Exploring Listeria monocytogenes Transcriptomes in Correlation with Divergence of Lineages and Virulence as Measured in Galleria mellonella.

As for many opportunistic pathogens, the virulence potential of is highly heterogeneous between isolates and correlated, to some extent, with phylogeny and gene repertoires. In sharp contrast with copious data on intraspecies genome diversity, little is known about transcriptome diversity despite the role of complex genetic regulation in pathogenicity. The current study implemented RNA sequencing to characterize the transcriptome profiles of 33 isolates under optimal growth conditions.

Impact of temperature and soil type on Mycobacterium bovis survival in the environment.

Mycobacterium bovis, the causative agent of the bovine tuberculosis (bTB), mainly affects cattle, its natural reservoir, but also a wide range of domestic and wild mammals. Besides direct transmission via contaminated aerosols, indirect transmission of the M. bovis between wildlife and livestock might occur by inhalation or ingestion of environmental substrates contaminated through infected animal shedding.

Survival of Listeria monocytogenes in Soil Requires AgrA-Mediated Regulation.

In a recent paper, we demonstrated that inactivation of the Agr system affects the patterns of survival of Listeria monocytogenes (A.-L. Vivant, D.

The Agr communication system provides a benefit to the populations of Listeria monocytogenes in soil.

In this study, we investigated whether the Agr communication system of the pathogenic bacterium Listeria monocytogenes was involved in adaptation and competitiveness in soil. Alteration of the ability to communicate, either by deletion of the gene coding the response regulator AgrA (response-negative mutant) or the signal pro-peptide AgrD (signal-negative mutant), did not affect population dynamics in soil that had been sterilized but survival was altered in biotic soil suggesting that the Agr system of L. monocytogenes was involved to face the complex soil biotic environment.

Listeria monocytogenes differential transcriptome analysis reveals temperature-dependent Agr regulation and suggests overlaps with other regulons.

Listeria monocytogenes is a ubiquitous, opportunistic pathogenic organism. Environmental adaptation requires constant regulation of gene expression. Among transcriptional regulators, AgrA is part of an auto-induction system.

Evidence of autoinduction heterogeneity via expression of the Agr system of Listeria monocytogenes at the single-cell level.

To investigate if the primary function of the Agr system of Listeria monocytogenes is to monitor cell density, we followed Agr expression in batch cultures, in which the autoinducer concentration was uniform, and in biofilms. Expression was heterogeneous, suggesting that the primary function of Agr is not to monitor population density.

Physiological responses of Escherichia coli exposed to different heat-stress kinetics.

The effects of heat-stress kinetics on the viability of Escherichia coli were investigated. Cells were exposed to heat-stress treatments extending from 30 to 50 degrees C, with either a slope (40 min) or a shock (10 s), both followed by a 1-h plateau at 50 degrees C in nutritive medium. A higher survival rate was observed after the slope than after the shock, when both were followed by a plateau, so the heat slope induced a certain degree of thermotolerance.

Communication and autoinduction in the species Listeria monocytogenes: A central role for the agr system.

In order to withstand changes in their environment, bacteria have evolved mechanisms to sense the surrounding environment, integrate these signals and adapt their physiology to thrive under fluctuating conditions. Among these mechanisms, the ability of bacteria to exchange information between cells has become a dynamic field of interest for microbiologists over the past four decades. First described by Nelson et al.

Biofilm-detached cells, a transition from a sessile to a planktonic phenotype: a comparative study of adhesion and physiological characteristics in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a pathogenic bacterium widely investigated for its high incidence in clinical environments and its ability to form strong biofilms. During biofilm development, sessile cells acquire physiological characteristics differentiating them from planktonic cells. But after treatment with disinfectants, or to ensure survival of the species in hostile environments, biofilm cells can detach.

Partial vinylphenol reductase purification and characterization from Brettanomyces bruxellensis.

Brettanomyces is the major microbial cause for wine spoilage worldwide and causes significant economic losses. The reasons are the production of ethylphenols that lead to an unpleasant taint described as 'phenolic odour'. Despite its economic importance, Brettanomyces has remained poorly studied at the metabolic level.

Effects of yeast proteolytic activity on Oenococcus oeni and malolactic fermentation.

Alcoholic fermentation of synthetic must was performed using either Saccharomyces cerevisiae or a mutant Deltapep4, which is deleted for the proteinase A gene. Fermentation with the mutant Deltapep4 resulted in 61% lower levels of free amino acids, and in 62% lower peptide concentrations at the end of alcoholic fermentation than in the control. Qualitative differences in amino acid composition were observed.

Assessment of the roles of LuxS, S-ribosyl homocysteine, and autoinducer 2 in cell attachment during biofilm formation by Listeria monocytogenes EGD-e.

LuxS is responsible for the production of autoinducer 2 (AI-2), which is involved in the quorum-sensing response of Vibrio harveyi. AI-2 is found in several other gram-negative and gram-positive bacteria and is therefore considered a good candidate for an interspecies communication signal molecule. In order to determine if this system is functional in the gastrointestinal pathogen Listeria monocytogenes EGD-e, an AI-2 bioassay was performed with culture supernatants.

A small HSP, Lo18, interacts with the cell membrane and modulates lipid physical state under heat shock conditions in a lactic acid bacterium.

The small heat shock proteins (sHSP) are characterized by a chaperone activity to prevent irreversible protein denaturation. This study deals with the sHSP Lo18 induced by multiple stresses in Oenococcus oeni, a lactic acid bacterium. Using in situ immunocytochemistry and cellular fractionation experiments, we demonstrated the association of Lo18 with the membrane in O.

Cel9M, a new family 9 cellulase of the Clostridium cellulolyticum cellulosome.

A new cellulosomal protein from Clostridium cellulolyticum Cel9M was characterized. The protein contains a catalytic domain belonging to family 9 and a dockerin domain. Cel9M is active on carboxymethyl cellulose, and the hydrolysis of this substrate is accompanied by a decrease in viscosity.