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Microbial Interactions (microbial + interaction)
Selected AbstractsMicrobial interaction in cooked cured meat products under vacuum or modified atmosphere at 4°CJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2002J. Metaxopoulos Aims: To investigate the antagonistic activity of two lactic acid strains against the spoilage microflora in cooked cured meat products, vacuum or modified atmosphere packed at 4°C and to determine the inhibitory capacity of their bacteriocins. Methods and Results: Frankfurter-type sausages and sliced cooked cured pork shoulder were inoculated with Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442 or with their bacteriocins. The microbial, physico-chemical (pH, l - and d -lactate, acetate and ammonia) and colour changes were studied. Results under vacuum packaging showed that in the uninoculated samples of the pork product the spoilage microflora grew but in the inoculated ones the spoilage microorganisms (e.g. Brochothrix thermosphacta and enterococci) reduced during the storage. This observation was more pronounced in the samples with the addition of bacteriocins. In the frankfurter-type sausages the spoilage microflora did not grow in the uninoculated and inoculated samples. In the modified atmosphere enriched in CO2 the population of spoilage microflora remained at low levels in both products, indicating that CO2 has an effect on thespoilage microorganisms' growth. In the pork product the concentrations of acetate and d -lactate increased while l -lactate decreased, but in the frankfurter-type sausages increase of acetate and d -lactate was not observed. Conclusions: Lactic acid strains had an effect on the spoilage microflora growth but did not affect, negatively, the organoleptic properties of the products. These strains may be used as biopreservative cultures or their bacteriocins could be an important contribution to microbiological quality of meat products. Significance and Impact of Study: Establishment of biopreservation as a method for extension of shelf life of meat products. [source] Microbial interactions and differential protein expression in Staphylococcus aureus ,Candida albicans dual-species biofilmsFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 3 2010Brian M. Peters Abstract The fungal species Candida albicans and the bacterial species Staphylococcus aureus are responsible for a majority of hospital-acquired infections and often coinfect critically ill patients as complicating polymicrobial biofilms. To investigate biofilm structure during polymicrobial growth, dual-species biofilms were imaged with confocal scanning laser microscopy. Analyses revealed a unique biofilm architecture where S. aureus commonly associated with the hyphal elements of C. albicans. This physical interaction may provide staphylococci with an invasion strategy because candidal hyphae can penetrate through epithelial layers. To further understand the molecular mechanisms possibly responsible for previously demonstrated amplified virulence during coinfection, protein expression studies were undertaken. Differential in-gel electrophoresis identified a total of 27 proteins to be significantly differentially produced by these organisms during coculture biofilm growth. Among the upregulated staphylococcal proteins was l -lactate dehydrogenase 1, which confers resistance to host-derived oxidative stressors. Among the downregulated proteins was the global transcriptional repressor of virulence factors, CodY. These findings demonstrate that the hyphae-mediated enhanced pathogenesis of S. aureus may not only be due to physical interactions but can also be attributed to the differential regulation of specific virulence factors induced during polymicrobial growth. Further characterization of the intricate interaction between these pathogens at the molecular level is warranted, as it may aid in the design of novel therapeutic strategies aimed at combating fungal,bacterial polymicrobial infection. [source] Microbial interactions affecting the natural transformation of Bacillus subtilis in a model aquatic ecosystemFEMS MICROBIOLOGY ECOLOGY, Issue 3 2003Kazuaki Matsui Abstract The involvement of microbial interactions in natural transformation of bacteria was evaluated using an aquatic model system. For this purpose, the naturally transformable Bacillus subtilis was used as the model bacterium which was co-cultivated with the protist Tetrahymena thermophila (a consumer) and/or the photosynthetic alga Euglena gracilis (a producer). Co-cultivation with as few as 102 individuals ml,1 of T. thermophila lowered the number of transformants to less than the detectable level (<1×100 ml,1), while co-cultivation with E. gracilis did not. Metabolites from co-cultures of T. thermophila and B. subtilis also decreased the number of transformants to less than the detectable level, while metabolites from co-culture of T. thermophila and B. subtilis with E. gracilis did not. Thus, the introduction of transformation inhibitory factor(s) by the grazing of T. thermophila and the attenuation of this inhibitory factor(s) by E. gracilis is indicated. These observations suggest that biological components do affect the natural transformation of B. subtilis. The study described is the first to suggest that ecological interactions are responsible not only for the carbon and energy cycles, but also for the processes governing horizontal transfer of genes, in microbial ecosystems. [source] Phyllosphere microbiology with special reference to diversity and plant genotypeJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008J.M. Whipps Summary The phyllosphere represents the habitat provided by the aboveground parts of plants, and on a global scale supports a large and complex microbial community. Microbial interactions in the phyllosphere can affect the fitness of plants in natural communities, the productivity of agricultural crops, and the safety of horticultural produce for human consumption. The structure of phyllosphere communities reflects immigration, survival and growth of microbial colonists, which is influenced by numerous environmental factors in addition to leaf physico-chemical properties. The recent use of culture-independent techniques has demonstrated considerable previously unrecognized diversity in phyllosphere bacterial communities. Furthermore, there is significant recent evidence that plant genotype can play a major role in determining the structure of phyllosphere microbial communities. The main aims of this review are: (i) to discuss the diversity of phyllosphere microbial populations; (ii) to consider the processes by which microbes colonize the phyllosphere; (iii) to address the leaf characteristics and environmental factors that determine the survival and growth of colonists; (iv) to discuss microbial adaptations that allow establishment in the phyllosphere habitat and (v) to evaluate evidence for plant genotypic control of phyllosphere communities. Finally, we suggest approaches and priority areas for future research on phyllosphere microbiology. [source] Host collagen signal induces antigen I/II adhesin and invasin gene expression in oral Streptococcus gordoniiMOLECULAR MICROBIOLOGY, Issue 2 2003Catherine Heddle Summary Microbial interactions with host molecules, and programmed responses to host environmental stimuli, are critical for colonization and initiation of pathogenesis. Bacteria of the genus Streptococcus are primary colonizers of the human mouth. They express multiple cell-surface adhesins that bind salivary components and other oral bacteria and enable the development of polymicrobial biofilms associated with tooth decay and periodontal disease. However, the mechanisms by which streptococci invade dentine to infect the tooth pulp and periapical tissues are poorly understood. Here we show that production of the antigen I/II (AgI/II) family polypeptide adhesin and invasin SspA in Streptococcus gordonii is specifically upregulated in response to a collagen type I signal, minimally the tri-peptide Gly-Pro-Xaa (where Xaa is hydroxyproline or alanine). Increased AgI/II polypeptide expression promotes bacterial adhesion and extended growth of streptococcal cell chains along collagen type I fibrils that are characteristically found within dentinal tubules. These observations define a new model of host matrix signal-induced tissue penetration by bacteria and open the way for novel therapy opportunities for oral invasive diseases. [source] Growth inhibition of Listeria monocytogenes by a nonbacteriocinogenic Carnobacterium piscicolaJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2005L. Nilsson Abstract Aims:, This study elucidates the mechanisms by which a nonbacteriocinogenic Carnobacterium piscicola inhibits growth of Listeria monocytogenes. Methods and Results:,Listeria monocytogenes was exposed to live cultures of a bacteriocin-negative variant of C. piscicola A9b in co-culture, in a diffusion chamber system, and to a cell-free supernatant. Suppression of maximum cell density (0,3·5 log units) of L. monocytogenes was proportional to initial levels of C. pisciola (103,107 CFU ml,1). Cell-to-cell contact was not required to cause inhibition. The cell-free C. piscicola supernatant caused a decrease in L. monocytogenes maximum cell density, which was abolished by glucose addition but not by amino acid, vitamin or mineral addition. The fermentate also gave rise to a longer lag phase and a reduction in growth rate. These effects were independent of glucose and may have been caused by acetate production by C. piscicola. 2D gel-electrophoretic patterns of L. monocytogenes exposed to C. piscicola or to L. monocytogenes fermentate did not differ. Treatment with C. piscicola fermentate resulted in down-regulation (twofold) of genes involved in purine- or pyrimidine metabolism, and up-regulation (twofold) of genes from the regulon for vitamin B12 biosynthesis and propanediol and ethanolamine utilization. Conclusions:, A nonbacteriocinogenic C. piscicola reduced growth of L. monocytogenes partly by glucose depletion. Significance and Impact of the Study:, Understanding the mechanism of microbial interaction enhances prediction of growth in mixed communities as well as use of bioprotective principles for food preservation. [source] Innate immune responses of gingival epithelial cells to nonperiodontopathic and periodontopathic bacteriaJOURNAL OF PERIODONTAL RESEARCH, Issue 6 2007S. Ji Background and Objective:, We have previously reported different susceptibilities of periodontopathic and nonperiodontopathic bacteria to antimicrobial peptides and phagocytosis by neutrophils. Differences between the two groups of bacteria may exist also in their ability to induce immune responses from the host. Therefore, we evaluated the effects of various oral bacteria on innate immune responses by gingival epithelial cells. Material and Methods:, HOK-16B cells were cocultured with live or lysed nonperiodontopathic (n = 3) and periodontopathic (n = 5) bacterial species. The levels of human beta defensin-1, -2 and -3, and of the cathelicidin, LL-37, were examined by real-time reverse transcription-polymerase chain reaction, and the accumulated interleukin-8 and interleukin-1, were measured by enzyme-linked immunosorbent assay. Results:, Nonperiodontopathic bacteria up-regulated some antimicrobial peptides without affecting the levels of cytokines. In the periodontopathic group, the orange-complex bacteria induced antimicrobial peptides and interleukin-8 efficiently, but the red-complex bacteria often demonstrated suppressive effects. In contrast to live bacteria, bacterial lysates had no suppressive effects. In addition, some bacterial lysates demonstrated a reduced ability to induce antimicrobial peptides compared with live bacteria. Conclusion:, The nonperiodontopathic, the orange-complex, and the red-complex bacteria had different effects on the innate immune responses from gingival epithelial cells, which may affect the outcome of their host,microbial interaction in gingival sulcus. [source] Possible role of reactive chlorine in microbial antagonism and organic matter chlorination in terrestrial environmentsENVIRONMENTAL MICROBIOLOGY, Issue 6 2009Per Bengtson Summary Several studies have demonstrated that extensive formation of organically bound chlorine occurs both in soil and in decaying plant material. Previous studies suggest that enzymatic formation of reactive chlorine outside cells is a major source. However, the ecological role of microbial-induced extracellular chlorination processes remains unclear. In the present paper, we assess whether or not the literature supports the hypothesis that extracellular chlorination is involved in direct antagonism against competitors for the same resources. Our review shows that it is by no means rare that biotic processes create conditions that render biocidal concentrations of reactive chlorine compounds, which suggest that extracellular production of reactive chlorine may have an important role in antagonistic microbial interactions. To test the validity, we searched the UniprotPK database for microorganisms that are known to produce haloperoxidases. It appeared that many of the identified haloperoxidases from terrestrial environments are originating from organisms that are associated with living plants or decomposing plant material. The results of the in silico screening were supported by various field and laboratory studies on natural chlorination. Hence, the ability to produce reactive chlorine seems to be especially common in environments that are known for antibiotic-mediated competition for resources (interference competition). Yet, the ability to produce haloperoxidases is also recorded, for example, for plant endosymbionts and parasites, and there is little or no empirical evidence that suggests that these organisms are antagonistic. [source] Interactions between arbuscular mycorrhizal fungi and bacteria and their potential for stimulating plant growthENVIRONMENTAL MICROBIOLOGY, Issue 1 2006Veronica Artursson Summary Arbuscular mycorrhizal (AM) fungi and bacteria can interact synergistically to stimulate plant growth through a range of mechanisms that include improved nutrient acquisition and inhibition of fungal plant pathogens. These interactions may be of crucial importance within sustainable, low-input agricultural cropping systems that rely on biological processes rather than agrochemicals to maintain soil fertility and plant health. Although there are many studies concerning interactions between AM fungi and bacteria, the underlying mechanisms behind these associations are in general not very well understood, and their functional properties still require further experimental confirmation. Future mycorrhizal research should therefore strive towards an improved understanding of the functional mechanisms behind such microbial interactions, so that optimized combinations of microorganisms can be applied as effective inoculants within sustainable crop production systems. In this context, the present article seeks to review and discuss the current knowledge concerning interactions between AM fungi and plant growth-promoting rhizobacteria, the physical interactions between AM fungi and bacteria, enhancement of phosphorus and nitrogen bioavailability through such interactions, and finally the associations between AM fungi and their bacterial endosymbionts. Overall, this review summarizes what is known to date within the present field, and attempts to identify promising lines of future research. [source] Bacterial community structure of glacier forefields on siliceous and calcareous bedrockEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2009A. Lazzaro Summary Forefields of retreating glaciers represent unique opportunities to investigate the initial phases of soil formation and microbial interactions with mineral surfaces. An open question concerns the physical and chemical driving-factors affecting the establishment of microbial communities in these young ecosystems. In this study we compared the bacterial community structure of six glacier forefield soils belonging to two contrasting bedrock categories (calcareous and siliceous) through T-RFLP profiling of the 16S rRNA gene. The community profiles were correlated with an array of physical (soil texture, water holding capacity, hours of sunshine, temperature, rainfall and exposure) and chemical (TC, TN, DOC, extractable nutrients and pH) factors using canonical correspondence analysis (CCA). A first comparison of the T-RFLP profiles suggested that the degree of operational taxonomic unit (OTU) diversity of these soils was similar, and that community structure was dominated by ubiquitous taxa. CCA showed that both physical (e.g. hours of sunshine or rainfall) and chemical factors (e.g. SO2,4 or PO3,4) played an equal role in shaping the soil bacterial communities. OTUs unique to specific sites appeared to be strongly influenced by the climatic regime and by texture. Overall, the community structure of the six glacial forefields showed no clear dependence on the bedrock categories. [source] Microbial interactions affecting the natural transformation of Bacillus subtilis in a model aquatic ecosystemFEMS MICROBIOLOGY ECOLOGY, Issue 3 2003Kazuaki Matsui Abstract The involvement of microbial interactions in natural transformation of bacteria was evaluated using an aquatic model system. For this purpose, the naturally transformable Bacillus subtilis was used as the model bacterium which was co-cultivated with the protist Tetrahymena thermophila (a consumer) and/or the photosynthetic alga Euglena gracilis (a producer). Co-cultivation with as few as 102 individuals ml,1 of T. thermophila lowered the number of transformants to less than the detectable level (<1×100 ml,1), while co-cultivation with E. gracilis did not. Metabolites from co-cultures of T. thermophila and B. subtilis also decreased the number of transformants to less than the detectable level, while metabolites from co-culture of T. thermophila and B. subtilis with E. gracilis did not. Thus, the introduction of transformation inhibitory factor(s) by the grazing of T. thermophila and the attenuation of this inhibitory factor(s) by E. gracilis is indicated. These observations suggest that biological components do affect the natural transformation of B. subtilis. The study described is the first to suggest that ecological interactions are responsible not only for the carbon and energy cycles, but also for the processes governing horizontal transfer of genes, in microbial ecosystems. [source] Linkage of microbial ecology to phenotype: correlation of rumen microbial ecology to cattle's feed efficiencyFEMS MICROBIOLOGY LETTERS, Issue 1 2008Le Luo Guan Abstract Linkage of rumen microbial structure to host phenotypical traits may enhance the understanding of host,microbial interactions in livestock species. This study used culture-independent PCR-denaturing gradient gel electrophoresis (PCR-DGGE) to investigate the microbial profiles in the rumen of cattle differing in feed efficiency. The analysis of detectable bacterial PCR-DGGE profiles showed that the profiles generated from efficient steers clustered together and were clearly separated from those obtained from inefficient steers, indicating that specific bacterial groups may only inhabit in efficient steers. In addition, the bacterial profiles were more likely clustered within a certain breed, suggesting that host genetics may play an important role in rumen microbial structure. The correlations between the concentrations of volatile fatty acids and feed efficiency traits were also observed. Significantly higher concentrations of butyrate (P<0.001) and valerate (P=0.006) were detected in the efficient steers. Our results revealed potential associations between the detectable rumen microbiota and its fermentation parameters with the feed efficiency of cattle. [source] Conceptual models for burrow-related, selective dolomitization with textural and isotopic evidence from the Tyndall Stone, CanadaGEOBIOLOGY, Issue 1 2004Murray K. Gingras ABSTRACT The formation of dolomite is generally explained using models that reflect larger-scale processes that describe the relationship between the supply and transport of Mg, and geochemical conditions that are amenable to the formation of dolomite. However, heterogeneities in the substrate, such as those made by bioturbating infauna, may play a more important role in dolomitization than has been previously considered. Burrow-facilitated dolomitization is evident in the Ordovician Tyndall Stone (Red River Group, Selkirk Formation) of central Canada. The diagenetic fabrics present are attributed to dolomitizing fluids that both flowed through and evolved within burrow networks. Petrographic analysis suggests that two phases of dolomite formation took place. The first formed a fine-grained, fabric-destructive type that probably accompanied early burial; the second is a fine- to medium-grained, locally sucrosic dolomite that is interpreted to have precipitated during later burial. Isotopic analysis supports the proposed paragenetic history: (1) an apparent linking of the stable isotopes 13C and 18O strongly suggests that the micrite matrix formed during very early diagenesis and was derived from seawater; (2) the initial phase of dolomitization is potentially microbially mediated, as evidenced by the enrichment of 13C; and (3) isotopic values for the second generation of dolomite reflect the mixing of ground water and resorbed early dolomite. This paper conceptualizes the physical and chemical conditions required for the formation of dolomite in association with burrow fabrics. The proposed model reveals a composite of biological and inorganic reactions that demonstrates the interdependence of sediment fabric, organic content and microbial interactions in the development of burrow-mottled dolomitic limestone. It is suggested that where burrow-associated dolomite occurs, it is most likely to develop in two stages: first, the byproducts of the degradation of organic material in burrows locally increase the permeability and porosity around burrow fabrics in shallow diagenetic depositional environments; and, second, the passing of burrowed media into deeper dysaerobic sediment is accompanied by the establishment of fermenting micro-organisms whose byproducts mediate dolomitization. [source] A role for PSK signaling in wounding and microbial interactions in ArabidopsisPHYSIOLOGIA PLANTARUM, Issue 4 2010Maaria Loivamäki PSK- , is a disulfated peptide that acts as a growth factor in plants. PSK- , is derived from preproproteins which are encoded by five PSK precursor genes in Arabidopsis thaliana (L.) Heynh and is perceived by leucine-rich repeat receptor kinases. Arabidopsis has two PSK receptor genes, PSKR1 and PSKR2. Although ligand and receptor are well characterized, the biological functions of PSK signaling are not well understood. Using reporter lines and receptor knockout mutants of Arabidopsis, a role for PSK signaling in biotic interactions and in wounding was analyzed. Treatment of Arabidopsis leaves with the fungal elicitor E-Fol, or the fungal pathogens Alternaria brassicicola and Sclerotinia sclerotiorum resulted in induction of PSK2 and PSKR1 as shown by promoter:GUS analysis. Wounding of hypocotyls or leaves induced PSK3:GUS, PSK5:GUS and PSKR1:GUS expression indicating that PSK precursor genes are differentially regulated in response to specific stresses. The receptor knockout lines pskr1-3 and pskr2-1 showed significantly reduced photosynthesis in response to the fungal elicitor E-Fol which indicates that fungal defence is impaired. pskr1-3 plants further showed reduced growth of crown galls after infection with Agrobacterium tumefaciens. A role for PSK signaling in Agrobacterium tumefaciens tumor growth was supported by the finding that PSK precursor genes and PSKR1 are expressed in crown galls. Overall, the results indicate that PSK signaling may play a previously undescribed role in pathogen or herbivore interactions and is crucial for Agrobacterium -induced cell proliferation in crown gall formation. [source] Interleukin-1 receptor phosphorylation activates Rho kinase to disrupt human gastric tight junctional claudin-4 during Helicobacter pylori infectionCELLULAR MICROBIOLOGY, Issue 5 2010Tamia K. Lapointe Summary Helicobacter pylori infects more than half of the human population worldwide. In the absence of treatment, this persistent infection leads to asymptomatic gastritis, which in some cases can progress into gastric ulcers and adenocarcinomas. The host,microbial interactions that govern the clinical outcome of infection remain incompletely understood. H. pylori is known to disrupt gastric epithelial tight junctions, which may represent a significant component of disease pathogenesis. The present study demonstrates that H. pylori disrupt epithelial tight junctional claudin-4 in a Rho kinase (ROCK)-dependent manner in human gastric epithelial (HGE-20) cell monolayers, independently of the virulence factors CagA and VacA, and without altering claudin-4 transcription. In the same epithelial cell model, interleukin (IL)-1,, mediated a similar ROCK-dependent pattern of tight junction disruption. Further experiments revealed that H. pylori infection induced IL-1 receptor type I (IL-1RI) phosphorylation, independently of epithelial secretion of its endogenous ligands IL-1,, IL-1, or IL-18. Finally, inhibition of IL-1RI activation prevented H. pylori -induced ROCK activation and claudin-4 disruption. Taken together, these findings identify a novel pathophysiological mechanism by which H. pylori disrupts gastric epithelial barrier structure via IL-1RI-dependent activation of ROCK, which in turn mediates tight junctional claudin-4 disruption. [source] Myths, legends and realities of relapsing fever borreliosisCLINICAL MICROBIOLOGY AND INFECTION, Issue 5 2009S. J. Cutler Relapsing fever borreliosis is often shrouded in mystery. From its discovery, it has evaded fulfilment of Koch's postulates. It has resulted in epidemic waves of infection, although it is now mostly localized to particular endemic pockets of infection. Structurally, this spirochaete breaks many paradigms for conventional microorganisms, e.g. through its segmented genomic structure. Disclosure of host,microbial interactions is revealing a plethora of mechanisms, from antigenic variation to binding of various host-derived proteins. We dispel some of the myths and explore current understanding of this much neglected area through a series of reviews within this theme section. [source] | ||||||||||||||||||||||||||||