Number Of Gram-positive Bacteria Research Articles

Seasonality of the conjunctival microbiota in cattle from a microregion in midwestern Brazil

This study aimed to identify the bacterial and fungal organisms in the conjunctival fornix of healthy cattle in a microregion located in midwestern Brazil. Additionally, we evaluated whether seasonality and cattle category (dairy vs. beef) play a role in our findings. The conjunctival fornix of 74 Holstein x Gyr and 70 Nelore cattle were sampled from February to March (rainy season) and August to September (dry season) of 2017. Bacterial and fungal strains were isolated by classical bacteriological and mycological methods. Some bacterial species were also identified by polymerase chain reaction. From the 144 animals included in the study, a total of 12 bacterial genera were identified, with Bacillus cereus being the most prevalent agent in both seasons and cattle categories. The total number of bacteria was not influenced by seasonality or cattle category (P = 0.25). The number of Moraxella bovoculi identified in dairy (5/74) and beef cattle (7/70) did not differ statistically (P = 0.76). However, seasonality played a role in M. bovoculi identification, being found only during the rainy season in the dairy cattle (P = 0.01), and only during the dry season in the beef cattle (P = 0.04). During the dry season, the number of gram-positive bacteria was significantly higher than the number of gram-negative bacteria in beef cattle (P = 0.009). Fungi were isolated in 20/144 samples. The number of fungi isolated in dairy cattle (16/144) was significantly higher than that isolated in beef cattle (4/144) (P = 0.007). Although a higher number of fungi were isolated in both cattle categories during the rainy season, this finding was not significant (P = 0.53). In this microregion located in midwestern Brazil, Bacillus cereus was the most prevalent and Corynebacterium spp. and Streptococcus spp. the least prevalent bacteria found in the conjunctival fornix of healthy cattle. The prevalence of the conjunctival fungal microbiota (11.8%) was lower than previously reported, with a higher number of isolates found in dairy cattle. Trichosporon spp. (41.2%) and Aspergillus spp. (35.3%) were the most frequent genera, being most commonly isolated in the rainy season.

Glucosylceramide Changes Bacterial Metabolism and Increases Gram-Positive Bacteria through Tolerance to Secondary Bile Acids In Vitro.

Glucosylceramide is present in many foods, such as crops and fermented foods. Most glucosylceramides are not degraded or absorbed in the small intestine and pass through the large intestine. Glucosylceramide exerts versatile effects on colon tumorigenesis, skin moisture, cholesterol metabolism and improvement of intestinal microbes in vivo. However, the mechanism of action has not yet been fully elucidated. To gain insight into the effect of glucosylceramide on intestinal microbes, glucosylceramide was anaerobically incubated with the dominant intestinal microbe, Blautia coccoides, and model intestinal microbes. The metabolites of the cultured broth supplemented with glucosylceramide were significantly different from those of broth not treated with glucosylceramide. The number of Gram-positive bacteria was significantly increased upon the addition of glucosylceramide compared to that in the control. Glucosylceramide endows intestinal microbes with tolerance to secondary bile acid. These results first demonstrated that glucosylceramide plays a role in the modification of intestinal microbes.

Discovery of novel N4-alkylcytidines as promising antimicrobial agents.

The emergence of drug-resistant strains of pathogenic microorganisms necessitates the creation of new drugs. In order to find new compounds that effectively inhibit the growth of pathogenic bacteria and fungi, we synthesized a set of N4-derivatives of cytidine, 2'-deoxycytidine and 5-metyl-2'-deoxycytidine bearing extended N4-alkyl and N4-phenylalkyl groups. The derivatives demonstrate activity against a number of Gram-positive bacteria, including Mycobacterium smegmatis (MIC=24-200μM) and Staphylococcus aureus (MIC=50-200μM), comparable with the activities of some antibiotics in medical use. The most promising compound appeared to be N4-dodecyl-5-metyl-2'-deoxycytidine 4h with activities of 24 and 48μM against M.smegmatis and S.aureus, respectively, and high inhibitory activity of 0.5mM against filamentous fungi that can, among other things, damage works of art, such as tempera painting. Noteworthy, some of other synthesized compounds are active against fungal growth with the inhibitory concentration in the range of 0.5-3mM.

Conductive all-carbon nanotube layers: Results on attractive physicochemical, anti-bacterial, anticancer and biocompatibility properties

Physicochemical, electrochemical and biological performance of 4 types of all-carbon nanotube layers was studied. Higher oxidation state of carbon was responsible for micro-scaled uniformity of the layers and excellent electrical conductivity, while nitrogen containing functional groups yielded materials with anisotropy similar to natural tissues and reduced work function. All materials were cytocompatible with mammalian fibroblasts (viability >80%, cytotoxicity <3% at day 7) and human dermal fibroblast (viability of cells >70% at day 1), while reducing bacterial and cancer cells proliferation without adding any drug. After 8 h culture, a ~50% depletion in the number of Gram-positive bacteria was observed on materials with lower work function, while Gram-negative bacteria were more sensitive towards carbon coordination number and presence of nitrogen atoms (cell depletion of up to 48% on amidized carbon nanotubes). After 1-day culture, >80% reduction in the melanoma cells number, connected with enhanced production of reactive oxygen species (ROS) was observed. All-carbon nanotube layers decreased bacteria and cancer cell functions without negatively influencing mammalian cells nor using drugs and we believe that this can be explained by various sensitivity of the tested cells towards exogenous ROS overproduction. As the concerns over implant-related infections as well as rates of antibiotic-resistant bacteria and chemotherapeutic-resistant cancer cells are growing, such materials should pave the way for a wide range of biomedical applications.

Pre-growth conditions and strain diversity affect nisin treatment efficacy against Listeria monocytogenes on cold-smoked salmon

Listeria monocytogenes is a human pathogen that is commonly found in environments associated with cold-smoked salmon. Nisin is a natural antimicrobial that can be used as a food preservative. While nisin is active against a number of Gram-positive bacteria, including L. monocytogenes, environmental stresses encountered in cold-smoked salmon processing facilities might affect L. monocytogenes' nisin susceptibility. The objective of this study was to investigate the effect of seafood-relevant pre-growth conditions and L. monocytogenes strain diversity on nisin treatment efficacy on cold-smoked salmon. Six L. monocytogenes strains representing serotypes most commonly associated with cold-smoked salmon (1/2a, 1/2b, and 4b) were initially pre-grown under a number of seafood-relevant conditions and challenged with nisin in growth media modified to represent the characteristics of cold-smoked salmon. The pre-growth conditions with the lowest mean log reduction due to nisin and the highest strain-to-strain variability were selected for experiments on cold-smoked salmon; these included: (i) 4.65% w.p. NaCl (“NaCl”); (ii) pH = 6.1 (“pH”); (iii) 0.5 μg/ml benzalkonium chloride (“Quat”); and a control (“BHI”). Cold-smoked salmon slices with or without nisin were inoculated with L. monocytogenes pre-grown in one of the conditions above, vacuum-packed, and incubated at 7 °C. L. monocytogenes were enumerated on days 1, 15, and 30. A linear mixed effects model was constructed to investigate the effect of pre-growth condition, day in storage, serotype, source of isolation as well as their interactions on nisin efficacy against L. monocytogenes. Compared to pre-growth in “BHI”, significant reduction (P < 0.05) in nisin efficacy was induced by pre-growth in “pH” and “Quat” on both days 15 and 30, and by pre-growth in “NaCl” on day 30, indicating a time-dependent cross-protection effect. Additionally, an effect of L. monocytogenes' serotype on the cross-protection to nisin was observed; pre-growth in “pH” significantly reduced nisin efficacy against serotype 1/2a and 4b strains, but not against 1/2b strains. In conclusion, pre-exposure to mildly acidic environment, high salt content, and sublethal concentrations of quaternary ammonium compounds, is likely to provide cross-protection against a subsequent nisin treatment of L. monocytogenes on cold-smoked salmon. Therefore, challenge studies that use pre-growth in “BHI”, as well as more susceptible L. monocytogenes strains, may overestimate the efficacy of nisin as a control strategy for cold-smoked salmon.

Serine-rich repeat proteins from gut microbes

ABSTRACTSerine-rich repeat proteins (SRRPs) have emerged as an important group of cell surface adhesins found in a growing number of Gram-positive bacteria. Studies focused on SRRPs from streptococci and staphylococci demonstrated that these proteins are O-glycosylated on serine or threonine residues and exported via an accessory secretion (aSec) system. In pathogens, these adhesins contribute to disease pathogenesis and represent therapeutic targets. Recently, the non-canonical aSec system has been identified in the genomes of gut microbes and characterization of their associated SRRPs is beginning to unfold, showing their role in mediating attachment and biofilm formation. Here we provide an update of the occurrence, structure, and function of SRRPs across bacteria, with emphasis on the molecular and biochemical properties of SRRPs from gut symbionts, particularly Lactobacilli. These emerging studies underscore the range of ligands recognized by these adhesins and the importance of SRRP glycosylation in the interaction of gut microbes with the host.

COMPARISON OF THE EFFICACY OF TWO DISINFECTANTS FOR CONTROLLING GRAM-POSITIVE BACTERIA ON THERMOPLASTIC RETAINERS IN DENTAL PLAQUES

Objective: Thermoplastic retainers are believed to be able to change the ecosystem for the oral cavity microflora. To prevent oral tissue damage,it is vital that retainers are subjected to appropriate cleaning techniques. This study compared the effectiveness of two disinfectants in cleaningthermoplastic retainers against Gram-positive bacteria in the dental plaque layer.Methods: The two disinfectants used in this study were Polident and 0.1% chlorhexidine gluconate. We performed laboratory studies on Gramnegativebacteria using a single-blind setup, with three groups of subjects, each with 13 participants.Results: The results showed that there was a significant reduction in the number of Gram-positive bacterial colonies in the dental plaque layer onretainers cleaned with Polident compared with the control, whereas cleaning the retainer with 0.1% chlorhexidine gluconate showed no significantdifference in the number of Gram-positive bacteria compared with the control.Conclusion: We conclude that there is a significant difference in the number of Gram-positive bacteria on the teeth before and after insertion of athermoplastic retainer in Polident solution, whereas immersion in Minosep did not reduce bacterial numbers compared with that in the control.

Изменение микрофлоры мочи у пациентов с мочекаменной болезнью

Since the results of treatment of chronic pyelonephritis (CP) depend on timely and rationally selected targeted antibiotic therapy, when choosing a treatment regimen, it is necessary to rely on the local data obtained by monitoring the state of microflora in a particular hospital. to monitor the changes in urine microflora in patients with urinary stone disease. A total of 598 isolated bacteria and yeast-like fungi from patients with urinary stone disease who were treated in the Department of Urology during different time periods (1997-1999, 2010-2014 and 2015-2017 yy) were analyzed. A comparison of the urine microbiota in patients with single kidney stone (n=154) and staghorn stone (n=147) for the period 2015-2017 yy. was carried out. The significant changes of gram-positive and gram-negative bacteria were found with a tendency to decrease in the proportion of the latter (from 80.6% to 50.6%, p<0.05) due to a decrease in the proportion of P. mirabilis and complete absence of Enterobacter spp, Serraciae spp and Citrobacter spp. as well as an increase in the number of gram-positive bacteria (from 18 to 48.7%, p<0.05) owing to increase in the proportion of E. faecium + E. faecalis. During observation period, E. Coli has remained the leading pathogen (26.4+/-0.32%). During observation period, a permanent fourfold prevalence of gram-negative bacteria in clinically significant concentrations (>104 CFU/ml) was found: E. coli (36.8+/-4.1%). The proportion of K. Pneumonia increased from 8.5% to 17.4%, and proportion of P. mirabilis decreased from 20.3 to 10.4%. Despite a significant increase in the proportion of Enterococcus spp. (from 4.6 to 26.6%) in the general population, the incidence of microorganisms in clinically significant concentrations during analyzed period remained unchanged and did not exceed 8.46+/-4.76%. In patients with single stones and patients with staghorn stones there was no significant difference in the proportion of analyses with clinically significant concentrations of bacteria fer (p>0.05). The percentage of analyses with clinically significant concentration was 70.06%, while in all patients with urolithiasis it was 59.7%. In patients under and over 60 years old, the largest number of bacterial pathogens were represented by E. coli. (29.7% and 32.1%, respectively). E. Coli remains the leading bacterial causative agent of calculous pyelonephritis, both in the general population and in analyses with clinically significant concentrations of bacteria. There were no significant differences in urine microflora in patients with staghorn and single stones.

Antimicrobial activity of water and acetone extracts of some Eucomis taxa.

To evaluate the antibacterial and antifungal properties of acetone and water extracts of selected Eucomis taxa. The bulbs of Eucomis bicolor, Eucomis comosa (E.comosa) and E. comosa cv. were dried and examples from each experimental treatment were ground separately into powder. Each sample was divided into two groups with equal amounts of powder, and respectively extracted with water and a 70% solution of aqueous acetone. The crude water extracts were then filtered through a 0.2μm filter. The 70% aqueous acetone extracts were next concentrated at 40°C. After the evaporation of the acetone, the samples were additionally filtered through a 0.2μm filter. The antibacterial and antifungal activities of the extracts against chosen microorganisms were then determined. The results of the study demonstrated that the water and acetone extracts of Eucomis bulbs have an influence on the viability of Staphylococcus aureus and Bacillus atrophaeus strains. In the case of mediums containing E. comosa and E. comosa cv. extracts, a decrease in the number of gram-positive bacteria was dependent on the extract concentration. The best results were obtained in the case of the 25% extracts. The water and acetone extracts of Eucomis bulbs did not cause a decrease in the number of Escherichia coli cells. Additionally, antifungal activity against Aspergillus niger, Botrytis cinerea, Stachybotrys chartarum, Mucor circinelloides and Rhizopus oryzae cells were also not observed. The tested gram-negative and fungi microorganisms show resistance towards acetone and water extracts of Eucomis bulbs. The highest activity is found in the case of Aspergillus clavatus, Staphylococcus aureus and Bacillus atrophaeus strains, which shows water and acetone extracts of 25%.

Dysbiosis a risk factor for celiac disease.

Celiac disease remains one of the most challenging pathologies of the small intestine. It involves multiple pathogenic pathways and there are no disease-changing pharmacological agents available against it yet. The term microbiota refers to the community of microorganisms that inhabit a particular region of the body. Normal gut microbiota has a vital role in maintaining the intestinal homeostasis and promoting health. Celiac disease is associated with microbiota alteration, especially with an increase in the number of Gram-negative bacteria and a decrease in the number of Gram-positive bacteria. There is a strong relationship between intestinal dysbiosis and celiac disease, and recent studies are aimed at determining whether the celiac disease is a risk factor for dysbiosis or dysbiosis is for celiac disease. Therefore, the aim of this review was to assess the latest findings regarding the gut microbiota and its impact on the celiac disease, including therapeutic aspects.

Protein Secretion in Gram-Positive Bacteria: From Multiple Pathways to Biotechnology.

A number of Gram-positive bacteria are important players in industry as producers of a diverse array of economically interesting metabolites and proteins. As discussed in this overview, several Gram-positive bacteria are valuable hosts for the production of heterologous proteins. In contrast to Gram-negative bacteria, proteins secreted by Gram-positive bacteria are released into the culture medium where conditions for correct folding are more appropriate, thus facilitating the isolation and purification of active proteins. Although seven different protein secretion pathways have been identified in Gram-positive bacteria, the majority of heterologous proteins are produced via the general secretion or Sec pathway. Not all proteins are equally well secreted, because heterologous protein production often faces bottlenecks including hampered secretion, susceptibility to proteases, secretion stress, and metabolic burden. These bottlenecks are associated with reduced yields leading to non-marketable products. In this chapter, besides a general overview of the different protein secretion pathways, possible hurdles that may hinder efficient protein secretion are described and attempts to improve yield are discussed including modification of components of the Sec pathway. Attention is also paid to omics-based approaches that may offer a more rational approach to optimize production of heterologous proteins.

Physiological roles of bacillithiol in intracellular metal processing.

Glutathione (GSH) is an abundantly produced low-molecular-weight (LMW) thiol in many organisms. However, a number of Gram-positive bacteria do not produce GSH, but instead produce bacillithiol (BSH) as one of the major LMW thiols. Similar to GSH, studies have found that BSH has various roles in the cell, including protection against hydrogen peroxide, hypochlorite and disulfide stress. BSH also participates in the detoxification of thiol-reactive antibiotics and the electrophilic metabolite methylglyoxal. Recently, a number of studies have highlighted additional roles for BSH in the processing of intracellular metals. Herein, we examine the potential functions of BSH in the biogenesis of Fe-S clusters, cytosolic metal buffering and the prevention of metal intoxication.

Antimicrobial activity and brine shrimp toxicity of methanolic whole plant extract of Boerhavia repens L. (Family: Nyctaginaceae)

This study was designed to explore the phytochemicals, antioxidant, cytotoxic, and antimicrobial activity of the crude methanolic extract of Boerhavia repens L. (Family: Nytaginaceae). The phytochemical screening of the crude extract revealed the presence of alkaloid, carbohydrate, glycoside, phenol, tannin, steroid, flavonoid, protein, saponin, and terpens. For the evaluation of antioxidant activity, total phenolic content was determined which manifests moderate antioxidant property (189.67±0.5204 mg/g of gallic acid equivalent) of the plant. The cytotoxic property of the crude methanolic extract of Boerhavia repens L. was assessed by using the brine-shrimp lethality bio-assay. The crude methanolic extract showed significant cytotoxic potential (LC 50 value 4.192μg/ml and LC90 value 124.33μg/ml) comparing with vincristine sulphate, a potent cytotoxic agent. The antimicrobial activity of crude methanolic extract of Boerhavia repens L. was screened against a number of Gram positive bacteria, Gram negative bacteria and Fungi using disc diffusion method. The extract showed mild antimicrobial activity against Gram positive bacteria (10mm to 12mm) and moderate antimicrobial activities against Gram negative bacteria and fungi (15mm to 17 mm) at a concentration of 30μg/disc. Keywords: Boerhavia repens L, Phytochemical, Antioxidant activity, Antimicrobial activity, Cytotoxicity.

Oriental Plant Alkanna Orientalis Extracts Effects on Enterococcal Membrane-Associated Properties

The oriental plant Alkanna orientalis tissues extracts have been shown to have antimicrobial activity against a number of gram-positive bacteria, particularly Enterococcus hirae, however mechanisms of this activity is not clear enough.A. orientalis intact root and callus cells extracts influence on E. hirae ATCC9790 whole cells H+/K+ exchange, membrane vesicles accessible SH-groups number and ATPase activity was investigated. It was shown that 50 and 100 μl root extract inhibited H+ release ∼1.27 and ∼1.47 fold and K+ accumulation ∼1.25 and ∼1.36 fold, respectively. Whereas, callus cells extract had a stronger effect on ions fluxes rates. The inhibitor of proton translocating F0F1-ATPase, N,N'-dicyclohexylcarbodiimide (DCCD) - sensitive H+ efflux were observed upon addition of both extracts. The number of SH-groups was lowered ∼1.7 and 2 fold compared with the control in the presence of root and callus cells extracts, respectively. The strongest effect was in the case when these substances were added in the assay medium together with 0.2 mM DCCD. The ATPase activity was also decreased ∼3.1 and 3.5 fold compared with the control in the presence of 100 μl intact root and callus cells extracts, respectively. Maximum inhibition of ATPase activity was detected again when intact root and callus cells extracts were added in the assay medium with 0.2 mM DCCD simultaneously.The results point out that A. orientalis intact root and callus cells extracts can directly affect enterococcal membrane-associated FoF1-ATPase, which can be considered as a target for antimicrobial activity.

Enterocin T, a novel class IIa bacteriocin produced by Enterococcus sp. 812

Enterococcus sp. 812, isolated from fresh broccoli, was previously found to produce a bacteriocin active against a number of Gram-positive bacteria, including Listeria monocytogenes. Bacteriocin activity decreased slightly after autoclaving (121°C for 15min), but was inactivated by protease K. Mass spectrometry analysis revealed the bacteriocin mass to be approximately 4,521.34Da. N-terminal amino acid sequencing yielded a partial sequence, NH2-ATYYGNGVYXDKKKXWVEWGQA, by Edman degradation, which contained the consensus class IIa bacteriocin motif YGNGV in the N-terminal region. The obtained partial sequence showed high homology with some enterococcal bacteriocins; however, no identical peptide or protein was found. This peptide was therefore considered to be a novel bacteriocin produced by Enterococcus sp. 812 and was termed enterocin T.

Diversity of endophytic bacteria in the fruits of Coffea canephora

Endophytic bacteria colonize the internal tissues of plants without causing infection or negative effects on their hosts. This study investigates the occurrence and diversity of culturable endophytic bacteria in the fruits of Coffea canephora at three developmental stages. Isolation and quantification were performed in R2A culture medium, and the diversity was established using molecular methods and analysis of fatty acid methyl esters (FAME). α- and γ-Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes were identified in the investigated community. Kocuria turfanensis and Pantoea vaganswere identified as endophytes for the first time. Of the 18 species that were found, the following seven had not been previously described as endophytic in coffee fruits: Bacillus thuringiensis, Bacillus licheniformis, Agrobacterium tumefaciens, Escherichia coli,Enterobacter hormaechei, Chryseobacterium sp., and Ochrobactrum sp. The diversity of endophytic bacteria varied during the three developmental stages that were investigated, and the diversity was greatest in fruits during the green stage, during which Bacillus subtilis predominated. The number of Gram-positive bacteria was larger than the number of Gram-negative bacteria during the two earliest developmental stages, whereas their numbers were similar during the ripe stage. The diversity was lowest during the ripe stage, and Klebsiella oxytoca was the predominant species at this stage, probably due to the higher caffeine and sugar contents in the fruits. Key words: Coffee, bacterial community, sequencing, 16S rDNA, FAME

Aminoguanidine Down-Regulates the Expression of mreB-like Protein in Bacillus subtilis

Nitric oxide synthase (NOS), the enzyme responsible for the production of endogenous nitric oxide from arginine, has been recently discovered in a number of Gram-positive bacteria. While bacterial NOS has been implicated in mediating nitrosative stress, much remains unknown about the functional role of endogenous nitric oxide in bacteria. Using the known NOS inhibitor aminoguanidine, we examined changes in the protein expression profile using two-dimensional gel electrophoresis. Treatment with aminoguanidine induced several changes in protein expression in Bacillus subtilis. In particular, mreB-like protein (Mbl) was fully down-regulated in the aminoguanidine-treated samples. The expression of Mbl was also examined by reverse transcriptase-polymerase chain reaction and Mbl was found to be fully down-regulated at the transcriptional level as well. Given the role that Mbl plays in the maintenance of cytoskeletal structure, it appears that bacterial NOS may participate in specific biosynthetic pathways with ramifications toward the regulation of antibiotic resistance.

Enhanced production of nukacin D13E in Lactococcus lactis NZ9000 by the additional expression of immunity genes

Nukacin D13E (D13E) is a variant of type-A(II) lantibiotic nukacin ISK-1 produced by Staphylococcus warneri ISK-1. D13E exhibited a twofold higher specific antimicrobial activity than nukacin ISK-1 against a number of Gram-positive bacteria. We previously reported the heterologous production of D13E in Lactococcus lactis NZ9000 under the control of nisin-controlled gene expression system. In this study, we demonstrated enhanced production of D13E by the additional expression of immunity genes, nukFEG. The nukacin ISK-1 immunity, conferred by the ABC transporter complex, NukFEG, and the lantibiotic-binding protein, NukH, was not overwhelmed by D13E. The additional NukFEG resulted in a fourfold increase in the immunity level of the strain and a 5.2-fold increase in D13E production. The additional NukFEGH-expressing strain with the highest D13E immunity showed reduced level of production. Further improvement in D13E production was achieved by using pH-controlled batch fermentation.

New Cell Surface Protein Involved in Biofilm Formation by Streptococcus parasanguinis

Dental biofilm formation is critical for maintaining the healthy microbial ecology of the oral cavity. Streptococci are predominant bacterial species in the oral cavity and play important roles in the initiation of plaque formation. In this study, we identified a new cell surface protein, BapA1, from Streptococcus parasanguinis FW213 and determined that BapA1 is critical for biofilm formation. Sequence analysis revealed that BapA1 possesses a typical cell wall-sorting signal for cell surface-anchored proteins from Gram-positive bacteria. No functional orthologue was reported in other streptococci. BapA1 possesses nine putative pilin isopeptide linker domains which are crucial for pilus assembly in a number of Gram-positive bacteria. Deletion of the 3' portion of bapA1 generated a mutant that lacks surface-anchored BapA1 and abolishes formation of short fibrils on the cell surface. The mutant failed to form biofilms and exhibited reduced adherence to an in vitro tooth model. The BapA1 deficiency also inhibited bacterial autoaggregation. The N-terminal muramidase-released-protein-like domain mediated BapA1-BapA1 interactions, suggesting that BapA1-mediated cell-cell interactions are important for bacterial autoaggregation and biofilm formation. Furthermore, the BapA1-mediated bacterial adhesion and biofilm formation are independent of a fimbria-associated serine-rich repeat adhesin, Fap1, demonstrating that BapA1 is a new streptococcal adhesin.

Blue and Red Light Modulates SigB-Dependent Gene Transcription, Swimming Motility and Invasiveness in Listeria monocytogenes

BackgroundIn a number of gram-positive bacteria, including Listeria, the general stress response is regulated by the alternative sigma factor B (SigB). Common stressors which lead to the activation of SigB and the SigB-dependent regulon are high osmolarity, acid and several more. Recently is has been shown that also blue and red light activates SigB in Bacillus subtilis.Methodology/Principal FindingsBy qRT-PCR we analyzed the transcriptional response of the pathogen L. monocytogenes to blue and red light in wild type bacteria and in isogenic deletion mutants for the putative blue-light receptor Lmo0799 and the stress sigma factor SigB. It was found that both blue (455 nm) and red (625 nm) light induced the transcription of sigB and SigB-dependent genes, this induction was completely abolished in the SigB mutant. The blue-light effect was largely dependent on Lmo0799, proving that this protein is a genuine blue-light receptor. The deletion of lmo0799 enhanced the red-light effect, the underlying mechanism as well as that of SigB activation by red light remains unknown. Blue light led to an increased transcription of the internalin A/B genes and of bacterial invasiveness for Caco-2 enterocytes. Exposure to blue light also strongly inhibited swimming motility of the bacteria in a Lmo0799- and SigB-dependent manner, red light had no effect there.Conclusions/SignificanceOur data established that visible, in particular blue light is an important environmental signal with an impact on gene expression and physiology of the non-phototrophic bacterium L. monocytogenes. In natural environments these effects will result in sometimes random but potentially also cyclic fluctuations of gene activity, depending on the light conditions prevailing in the respective habitat.