Truncated internalin A and asymptomatic Listeria monocytogenes carriage: in vivo investigation by allelic exchange

ABSTRACT Allelic exchange of the region coding for the C terminus of InlA between one epidemic (with an 80-kDa InlA) and one asymptomatic (with a 47-kDa InlA) carriage Listeria monocytogenes strain confirmed the need for this region for internalin entry in vitro. Interestingly, restoration of internalin A functionality did not result in full virulence in chicken embryo assays.

Interactions between Pisum sativum & pseudomonads, consequences on plant iron nutrition and growth and immunity

Pea has a high potential in agroecology, however, it may suffer from a susceptibility to iron deficiency in calcareous soils. This susceptibility varies depending on cultivars. Pseudomonad siderophores, pyoverdines (pvd), were shown to promote iron nutrition in Arabidopsis and tobacco. The hypothesis was therefore raised that variation in iron susceptibility between pea cultivars could be related to differences in their ability to recruit fluorescent pseudomonads (fp) contributing to siderophore-mediated iron nutrition. Our aims were to compare i) the impact of a susceptible (S) and a tolerant (T) cultivar of pea on fp biodiversity with a focus on their pvd, and in return ii) the impact of …

Influence of pea genotype on root associated fluorescent pseudomonads, impact on plant iron nutrition

International audience; Pea has a high potential in agroecology because of its ability to fix atmospheric nitrogen and for Humannutrition due to the high amino-acids content of its seeds. However, pea can suffer from a susceptibility toiron deficiency in calcareous soils as expressed by chlorosis symptoms. Previous studies have shown thatsiderophores of model strains of fluorescent pseudomonads (fp), pyoverdines, promote iron nutrition ofarabidopsis and tobacco. We hypothesized that susceptibility to iron deficiency of pea is at least partly dueto its ability to select fluorescent pseudomonad that promote differentially plant nutrition thanks to theirsiderophores.To identify siderophores po…

Contribution of fluorescent pseudomonads to iron nutrition and health of pea

Communication and Autoinduction in the species Listeria monocytogenes

International audience; 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.,1 this phenomenon often referred as either cell-cell communication, Quorum Sensing and/or AutoInduction involves the synthesis of small signal molecules called autoinducers. These signal molecules may be sensed by the bacterial population in the vicinity …

Report on the interaction between pea and fluorescent pseudomonads and the potential impact on the plant iron nutrition

Evidence of autoinduction heterogeneity via expression of the agr system of listeria monocytogenes at the single-cell level

ABSTRACT 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.

Metabolic fate of a bacterial siderophore in Arabidopsis thaliana and Pisum sativum in relationship with iron status in plants

Despite its abundance, iron is weakly bioavailable for organisms due to its poor solubility in soils under aerobic conditions. Therefore, plants and other organisms have evolved mechanisms to efficiently assimilate iron from the soil. Non-grass plants use a strategy (strategy I) based on soil acidification, reduction of the Fe3+ in Fe2+ which incorporated in the roots by iron transporters. We previously showed (Shirley et al., 2011; Vansuyt et al., 2007) that iron nutrition and growth of a strategy I plant could be promoted by the ferric-complex of the pyoverdine (Fe-pvd), a siderophore produced by microorganisms. If pyoverdine was further localized in planta using different immunological t…

Plasmid-Mediated Resistance to Antimicrobial Agents among Listeriae

The resistance to 14 antiseptic-disinfectant and dye compounds of 208 strains of Listeria (132 L. monocytogenes, 63 L. innocua, 8 L. seeligeri, 1 L. ivanovii, 1 L. welshimeri, and 3 Listeria spp.) was tested by the agar-dilution procedure. The Listeria strains were isolated from different varieties of foods, environments of cheese dairies, humans, and wild birds. A total of 14 (6.7%) Listeria strains (12 L. monocytogenes and 2 L. innocua) were resistant to benzalkonium chloride, hexamidine diisethionate, and ethidium bromide. This multiple resistance was observed more frequently from strains of Listeria spp. detected on carcasses of poultry (47%) than strains isolated from human listeriosis…

Interactions in dual species biofilms between Listeria monocytogenes EGD-e and several strains of Staphylococcus aureus.

International audience; Six environmental isolates of Staphylococcus aureus and one collection strain were investigated for their ability to form monospecies biofilms and dual species biofilms with Listeria monocytogenes EGD-e on stainless steel coupons. All isolates were able to grow as biofilms but their ability to form monospecies biofilms differed. The population of L. monocytogenes EGD-e in dual species biofilms was not affected by the presence of S. aureus isolates except for strain CIP 53.156. The effect of L. monocytogenes EGD-e on the population of S. aureus was strain dependent: S. aureus population either increased or decreased or was not affected in the presence of L. monocytoge…

Single cell analysis evidence Heterogeneous expression of the Agr communication system of Listeria monocytogenes

http://prodinra.inra.fr/record/271694EAMERSCT3 EJ3; Communication, often referred as Quorum Sensing, is involved in the adaptation of most bacteria to their environment. In the genus Listeria, the agr communication system affects the biology of Listeria monocytogenes during saprophytic life (biofilm formation) and during infection. In the present study, we investigated in situ agr expression of six isolates of L. monocytogenes by combining gfp reporters, flow cytometry and fluorescent microscopy during plantonic growth and dynamic flow cell biofilm set ups. Unexpectedly, during growth in TSB homogenised liquid cultures incubated at 25°C, while auto-inducer concentration was uniform, statist…

Resistance of Immobilized Lactic Acid Bacteria to the Inhibitory Effect of Quaternary Ammonium Sanitizers

Abstract The inhibitory effect of quaternary ammonium sanitizers (QAS) on the fermentation activity of lactic acid bacteria was investigated. Benzalkonium chloride and didecyl dimethyl ammonium chloride show the same inhibitory effect. In MRS agar medium and MRS liquid medium their minimum inhibitory concentration was below 2 μg/mL. Interfering molecules in milk increased this concentration of inhibitory QAS above 8 μg/mL. Both growth and acidification were decreased but by immobilizing cells in calcium alginate gel beads this inhibitory effect could be reduced. The longer the beads were used for successive acidification and were colonized by lactic acid bacteria, the better was the acidifi…

Influence of pea genotype on root-associated pseudomonads, impact on the plant protection against fungal pathogens

International audience

Influence of pea genotype on root associated fluorescent pseudomonads, consequences for plant iron nutrition

Pea has a high potential in agroecology because of its ability to fix atmospheric nitrogen and in Human nutrition because of the high aminoacid content of its grains. However, pea may suffer from a susceptibility to iron deficiency in calcareous soils. This susceptibility varies depending on cultivars. Pseudomonad siderophores, pyoverdines (pvd), were shown to promote iron nutrition in Arabidopsis and tobacco. Thus, we hypothesize that variations in iron susceptibility between pea cultivars could be related to differences in their ability to recruit fluorescent pseudomonad (fp) contributing to siderophore-mediated iron nutrition. Our aims were to compare i) the impact of a susceptible (S) a…

Listeria phage and phage tail induction triggered by components of bacterial-growth media (phosphate, LiCl, nalidixic acid and acriflavine)

ABSTRACT The detection of Listeria monocytogenes from food is currently carried out using a double enrichment. For the ISO methodology, this double enrichment is performed using half-Fraser and Fraser broths, in which the overgrowth of L. innocua can occur in samples where both species are present. In this study, we analyzed the induction of phages and phage tails of Listeria spp. in these media and in two brain heart infusion (BHI) broths (BHIM [bioMérieux] and BHIK [Biokar]) to identify putative effectors. It appears that Na 2 HPO 4 at concentrations ranging from 1 to 40 g/liter with an initial pH of 7.5 can induce phage or phage tail production of Listeria spp., especially with 10 g/lite…