Microbial interactions in foods: meats, poultry and dairy products.
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Aerobiosis↗
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Electron microscopic studies on oral microbial interactions in plaque formation in vitro associated with Streptococcus mutans.
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Dental Plaque↗
The consequences of volatile organic compound mediated bacterial and fungal interactions.
Microbial interactions via infochemicals are fundamental to the development of spatial distribution and activity variations in ecosystems. Microorganisms produce a wide range of infochemicals, frequently secondary metabolites, most of which are soluble and many volatile. Volatile organic compounds (VOCs) have been identified in soil atmospheres and related to community structure and function. VOC profiles produced by microorganisms are consistent, relating to cultural conditions, environment and inputs, and so to population and function dynamics. VOC-mediated interactions can result in functional responses by the organisms involved that result in selective advantage to some community members. Positive, negative or neutral interactions can occur between a very wide range of soil bacteria and fungi. These effects include both stimulation and inhibition of growth, by 40 and 60%, respectively, and enzyme production. These effects are usually transient, e.g. removal of an antagonist is followed by complete recovery. Up- and down-regulation of gene expression, by mRNA and protein profiling has been demonstrated. VOCs have played an important role during the evolution of microorganisms in the context of their communities.
Bacteria↗
Antimicrobial interactions of microbial species involved in the fermentation of cassava dough into agbelima with particular reference to the inhibitory effect of lactic acid bacteria on enteric pathogens.
Lactic acid bacteria, Bacillus species and yeasts are involved in the fermentation of cassava dough into agbelima. Microbial interactions within and between these groups of microorganisms were investigated in addition to the survival of five enteric pathogens inoculated into agbelima under various conditions. Nine out of 10 cultures of lactic acid bacteria isolated at the end of agbelima fermentation showed inhibitory effect against 10 cultures of lactic acid bacteria isolated at the start of fermentation. Only 3 out of 10 isolates of Bacillus subtilis were inhibited by 10 isolates of lactic acid bacteria tested. No interactions were observed between yeasts and the lactic acid bacteria, whereas three of the Bacillus isolates showed inhibitory effects against the yeasts. Twelve isolates of Lactobacillus plantarum tested inhibited the growth of an isolate each of Lactobacillus fermentum and Lactobacillus brevis but none tested positive for bacteriocin production. The antimicrobial effect of the lactic acid bacteria was attributed to acid production. In fermenting cassava dough, enteric pathogens survived to different extents depending on pH and their sensitivity to acids. Vibrio cholerae C-230, Salmonella typhimurium 9 and Salmonella enteritidis 226 were not detectable in 10 g of sample after 4 h when inoculated into the 48-h fermented product, agbelima, whereas Shigella dysenteriae 2357T and Escherichia coli D2188 were detectable up to 8 h in the product.
Antibiosis↗
[Bacterial interactions].
The review deals with specific features of interactions in microbial biocenoses. The subdivision of the mechanisms of microbial interactions in associations into direct and indirect ones is proposed. The formation of intercellular contacts and matrix belongs to one group of mechanisms, the second group includes the products of metabolism (changes in the physical and chemical composition of the medium, specific growth regulators) and secreted factors (antibacterial substances, pheromones and signal molecules, vitamins, specific mediators). The applied aspects of the knowledge of microbial interactions in the human body are presented.
Anti-Bacterial Agents↗
Physico-chemistry of initial microbial adhesive interactions--its mechanisms and methods for study.
In this review, initial microbial adhesive interactions are divided into adhesion to substratum surfaces, coaggregation between microbial pairs and co-adhesion between sessile and planktonic microorganisms of different strains or species. The physico-chemical mechanisms underlying the adhesive interactions are described and a critical review is given of currently employed methods to study microbial adhesive interactions, with an emphasis on the use of the parallel plate flow chamber. Subsequently, for each of the three microbial adhesive interactions distinguished, the role of Lifshitz-van der Waals, acid-base and electrostatic interactions is described based on existing literature.
Bacterial Adhesion↗
The use of germ line-mutated mice in understanding host-pathogen interactions.
Microbial pathogenesis reflects an imbalance between parasite and host factors that favour pathogen multiplication and tissue destruction over those required for microbial elimination and preservation of the integrity of host tissues. In vivo analysis of host-pathogen interactions has been revolutionized by the ability to engineer specific genetic alterations including loss of function mutations and transgenes into the mouse germline. This brief review recapitulates what we have learned about the host response to Toxoplasma gondii infection to illustrate the usefulness of gene-altered mice in microbial pathogenesis research. A consideration of the pitfalls and limitations of experiments in knockout mice and ways of addressing these concerns are discussed. Finally, advances in inducible and tissue-restricted alterations in gene function are presented and their possible applications to microbiology research are considered.
Animals↗
Interactions of microbial populations in cellulose fermentation.
Fermentation of cellulose in the rumen occurs through the interactions of many microbial species. The initial degradation of cellulose is caused by cellulase-producing organisms. The soluble hydrolysis products are used by both cellulolytic and noncellulolytic organisms to produce acetate, propionate, and butyrate and the important intermediates H2 and succinate. Interactions between species are necessary for the decarboxylation of succinate to propionate. H2 is used by methanogenic bacteria to reduce CO2 to CH4. The removal of H2 by methanogenesis increases the production of acetate from carbohydrates by several important cellulose- and carbohydrate-fermenting microbial species. Monensin and lasalocid appear to alter the overall fermentation by selecting for populations that produce relatively larger amounts of propionate and against populations that produce relatively larger amounts of acetate and H2. Cellulose fermentation in the human large intestine is compared with fermentation in the rumen.
Anaerobiosis↗
Specificity of marine microbial surface interactions.
The macromolecular surface components involved in intraspecific cell surface interactions of the green microalga Chlorella vulgaris and closely associated bacteria were investigated. The specific surface attachment between this alga and its associated bacteria is mediated by lectin-like macromolecules associated with the surfaces of these cells. The binding activity of these surface polymers was inhibited by specific simple sugars; this suggests the involvement of specific receptor-ligand binding sites on the interactive surfaces. Epifluorescent microscopic evaluation of bacteria-alga interactions in the presence and absence of the macromolecules that mediate these interactions showed that the glycoproteins active in these processes were specific to the microbial sources from which they were obtained. The demonstration and definition of the specificity of these interactions in mixed microbial populations may play an important role in our understanding of the dynamics of marine microbial populations in the sea.
Adhesiveness↗
Microbial surface interactions: reduction of the haemagglutination activity of the oral bacterium Fusobacterium nucleatum by absorption with Streptococcus and Bacteroides.
Oral strains of Fusobacterium nucleatum showed haemagglutination (HA) of sheep red blood cells and attachment of HA-active F. nucleatum fragments to other microorganisms allowed a means of studying microbial surface interactions. HA-active sonicated fragments (SF) prepared from F. nucleatum were mixed with whole cell suspensions of 48 bacterial strains and, after incubation, the whole cells were separated from the non-absorbed fragments by differential centrifugation. Attachment of F. nucleatum fragments to the cells was indicated by a reduction in the HA activity of the SF in the supernatant fluid remaining after absorption with whole cells. HA activity of the microbial cells used for absorption and the detection of F. nucleatum fragments on these cells by an indirect fluorescent antibody technique provided further evidence of attachment. Of the 48 strains tested, 10 absorbed F. nucleatum HA-active fragments. They included Bacteroides gingivalis, Bacteroides fragilis subsp. distasonis, Bacteroides corrodens, Streptococcus morbillorum, Streptococcus sanguis (Blackburn and JC 74) and Streptococcus mutans AHT, BHT, 10449 and 6715. Chelators revealed that F. nucleatum attached to the microorganisms via a Ca2+-dependent interaction. Sugar inhibition demonstrated that F. nucleatum attached to the microorganisms via a D-galactose-containing moiety on their surface. A reduction in the absorption of F. nucleatum HA-active fragments by Strep. mutans grown in a higher concentration of sucrose was observed.
Absorption↗
Pseudomonas aeruginosa phenazines dictate site-specific competitive interactions with Klebsiella pneumoniae.
Pseudomonas aeruginosa and Klebsiella pneumoniae are Gram-negative opportunistic pathogens that frequently colonize the human body and are major causes of infection. These bacteria are often co-isolated in polymicrobial urinary tract and lung infections, the latter of which is associated with increased disease severity and worse clinical outcomes. Despite their overlapping niches and clinical relevance, little is known about how these two pathogens interact and how those interactions influence human health. Given the growing recognition that microbial interactions are key drivers of disease, we investigated how P. aeruginosa and K. pneumoniae influence one another. We discovered an antagonistic interaction in which P. aeruginosa restricts the growth of K. pneumoniae. This inhibition is driven by phenazine production in P. aeruginosa, specifically the secondary metabolites pyocyanin and pyorubin, which are both necessary and sufficient to suppress K. pneumoniae growth. Using a diverse set of clinical isolates, we found that this antagonism is strain dependent. Both the susceptibility of K. pneumoniae to phenazines and the ability of P. aeruginosa to restrict K. pneumoniae growth varies between strains. Moreover, the necessity of phenazine production is specific to the site of infection. Together, these findings demonstrate that strain background and environmental context are critical determinants of pathogen interactions. Our work underscores the importance of considering these variables when investigating how microbial interactions influence infection and disease outcomes.
Journal Article↗
Effects of initial corncob particle size on the short-term composting for preparation of cultivation substrates for Pleurotus ostreatus.
The short-term composting based on corncob for preparing Pleurotus ostreatus cultivation medium originated from agricultural production practices and so lacked systematic investigation. In this study, the influences of a Dafen (15 mm, DFT) and Xiaofen (5 mm, XFT) initial particle size (IPS) of corncob on the microbial succession and compost quality were examined. Results demonstrated that XFT compost was better suited for mushroom cultivation due to its high biological efficiency of 70 % and the absence of contamination. The composting microbes differed significantly between the DFT and XFT composts. During composting, the genera of Bacillus, Acinetobacter, Lactobacillus, Streptomyces, and Paenibacillus were majorly found in the DFT compost, while Acinetobacter, Lactobacillus, Puccinia, Bacteroides, and Bacillus genera dominated the XFT compost. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that throughout the thermophilic phase, XFT compost had much greater relative abundances of sequences relevant to energy, carbohydrate, and amino acid metabolism than DFT compost. Analysis of network correlations and Mantel tests indicated that IPS reduction could increase microbial interactions. Overall, adjusting the IPS of corncob to 5 mm increased microbial interactions, improved compost quality, and thereby boosted the P. ostreatus yield. These findings will be pertinent in optimizing the composting process of cultivation medium for P. ostreatus.
Composting↗
Effects of microbial community interactions on transformation rates of xenobiotic chemicals.
The effects of culture filtrates, mixed populations, and common microbial exudates on bacterial transformations of three agricultural and industrial chemicals were investigated. Test chemicals included methyl parathion, diethyl phthalate, and 2,4-dichlorophenoxyacetic acid butoxyethyl ester. The presence of various cultures, filtrates, or exudates of algae, fungi, or other bacteria either stimulated or inhibited bacterial transformation rates. Inhibition resulted from treatments that lowered the pH, and stimulation resulted from an increase in cell biomass (based on plate counts) and from a different process whereby rates of transformation per bacterial cell rapidly increased as much as 10-fold.
2,4-Dichlorophenoxyacetic Acid↗
Mycorrhizosphere interactions to improve plant fitness and soil quality.
Arbuscular mycoruhizal fungi are key components of soil microbiota and obviously interact with other microorganisms in the rhizosphere, i.e. the zone of influence of plant roots on microbial populations and other soil constituents. Mycorrhiza formation changes several aspects of plant physiology and some nutritional and physical properties of the rhizospheric soil. These effects modify the colonization patterns of the root or mycovrhizas (mycorrhizosphere) by soil microorganisms. The rhizosphere of mycorrhizal plants, in practice a mycorrhizosphere, harbors a great array of microbial activities responsible for several key ecosystem processes. This paper summarizes the main conceptual principles and accepted statements on the microbial interactions between mycorrhizal fungi and other members of rhizosphere microbiota and discusses current developments and future trends concerning the following topics: (i) effect of soil microorganisms on mycorrhiza formation; (ii) mycorrhizosphere establishment; (iii) interactions involved in nutrient cycling and plant growth; (iv) interactions involved in the biological control of plant pathogens; and (v) interactions to improve soil quality. The main conclusion is that microbial interactions in the rhizosphere of mycorrhizal plants improve plant fitness and soil quality, critical issues for a sustainable agricultural development and ecosystem functioning.
Bacteria↗
Cooperative anaerobic catabolism of chlorinated organic compounds: implications for sustainable bioremediation.
Biodegradation research historically followed a reductionist approach focused on axenic (pure) cultures capable of catabolizing the specific contaminant(s) of interest. While this approach has substantially advanced our understanding of the microbiology, physiology, biochemistry, and genetics of contaminant degradation under laboratory conditions, it does not capture the complexity of natural and engineered environments. During in situ bioremediation, microbiomes are exposed to mixtures of contaminants, and microbial interactions profoundly influence contaminant transformation and fate. In anoxic environments, degradation of chlorinated compounds is often sustained by metabolic cooperation among taxonomically and physiologically distinct microorganisms. Through the exchange of metabolites such as hydrogen, formate, acetate, and other nutrients, microbial populations establish interdependent networks that overcome thermodynamic and physiological constraints, enabling self-sustaining systems of contaminant transformations that would be inefficient or impossible with individual organisms. We highlight examples of microbial interactions that underpin anaerobic catabolism of chlorinated contaminants, including systems resulting in self-sustained anaerobic bioremediation.
Biodegradation, Environmental↗
The virulence of mixed infection with Streptococcus constellatus and Fusobacterium nucleatum in a murine orofacial infection model.
Orofacial infections are usually polymicrobial, and it is the microbial interactions of pathogenic species that cause tissue destruction. In this study, the microbial interaction between Streptococcus constellatus and Fusobacterium nucleatum was characterized using a murine orofacial infection model. A mixture of viable S. constellatus and F. nucleatum cells (both 2 x 10(8) CFU/mouse) was injected into the submandible; as a result, all of the test mice died. In contrast, none of the experimental animals monoinjected with either S. constellatus or F. nucleatum died (P<0.001), indicating that the synergism between the two resulted in the virulence. When a mixture of viable S. constellatus cells and a culture filtrate of F. nucleatum was tested, lethality and the bacterial cell count per lesion were significantly enhanced as compared with monoinjections (P<0.02). However, the virulence of F. nucleatum was not enhanced by infection of a culture filtrate of S. constellatus. The enhancement of virulence was observed even when viable S. constellatus cells and the culture filtrate of F. nucleatum were injected at separate sites. Heat treatment of the culture filtrate of F. nucleatum did not affect the enhancement. These results indicate that a heat-stable substance(s) produced by F. nucleatum contributes to the microbial synergy of S. constellatus and F. nucleatum in orofacial infections.
Abscess↗
Postmortem alterations of bacterial localization.
Localization of bacteria in mammalian gastrointestinal tracts by electron microscopy has yielded much information on our understanding of intimate host-microbial interactions, but because of difficulties in obtaining human tissue, the human host-microbial interactions have not been well studied. In this report, an attempt was made to ascertain the feasibility of using gastrointestinal tissues obtained at autopsy. A rat model was used to produce samples that would simulate conditions that autopsy samples might undergo. Rats, left at room temperature for 1 hr and then refrigerated at 2C for time intervals up to 24 hours after death were autopsied and samples from the stomach, ileum and cecum were removed and processed for light and scanning microscopy. Tissues were fixed in buffered glutaraldehyde, postfixed in buffered osmium tetroxide, dehydrated in an ethanol series, critical point dried, coated with gold-palladium and examined. Keratinized murine stomachs showed little or no changes in the localization of the gram-positive layer of bacteria over 24 hours. However, major changes were noted in the ileum and colon with the ileum showing the most dislocation of the flora. Colonic tissues were altered by invading bacteria although some regions had a relatively normal appearing host-flora relationship. Slow cooling rates of the gastrointestinal tracts were implicated as a major cause for alterations in bacterial localization. The data predict that studies of normal microbial location with human autopsy samples will be best pursued on keratinized tissue.
Animals↗
The ES-242s, novel N-methyl-D-aspartate antagonists of microbial origin, interact with both the neurotransmitter recognition site and the ion channel domain.
ES-242-1 approximately 5 are novel microbial bioxanthracenes which do not contain nitrogen. The ES-242s inhibited the binding of [3H]TCP and [3H]CGS19755 to the N-methyl-D-aspartate (NMDA) receptor complex. They had no effect on the binding of the specific ligands for the non-NMDA receptor. The biochemical and pharmacological properties of ES-242-1 were fully examined since it is the most potent of the five compounds. ES-242-1 is highly specific for the NMDA receptor; it has no effect on other receptors. Kinetic analyses indicated that ES-242-1 inhibited the binding of [3H]TCP and [3H]CGS19755 in a competitive manner, respectively, suggesting that ES-242-1 interacts with both the transmitter recognition site and the channel domain. ES-242-1 selectively inhibited NMDA-induced Ca2+ influx in primary cultures of mouse hippocampal neurons. ES-242-1 also specifically blocked the increase in cyclic GMP accumulation induced by NMDA or L-glutamate in rat cerebellar slices. In a concentration range of 0.1-1.0 microM, ES-242-1 was as potent as MK-801 in preventing glutamate-induced neurotoxicity in primary cultures of mouse hippocampal neurons. These results show that ES-242-1 is a potent and specific antagonist for the NMDA receptor. The antagonistic properties of the ES-242s appear to be due to a novel mechanism of action at the NMDA receptor.
Animals↗