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PubMed1994

Diversity within diversity: molecular approaches to studying microbial interactions with insects.

DNA sequence information has greatly augmented the number of characters available for analysis in phylogenetic research. Nowhere is this more evident than in studies of microbial evolution. Ribosomal DNA sequence data has simultaneously permitted the distinction between individual species and the inference of their phylogenetic relationships in many cases where both were formerly impossible. These have contributed to our understanding of the ecology of particular microbe-host interactions and the history of these relationships over evolutionary time. We describe examples from two ends of the ecological spectrum in insect/bacterial associations: one in which bacteria mediate host cytoplasmic incompatibility and parthenogenesis, and the other in which mycetocyte bacteria augment host nutrition. In the former, the pattern of bacterial interaction is general, with the same or closely related strains of the genus Wolbachia associating with a wide range of insect taxa. In the latter, concordance between host and microbe phylogenies suggests cospeciation between bacteria and host, although it is as yet unclear whether this process has involved step-wise, reciprocal coevolution. We conclude with a discussion of how developments in molecular techniques may aid in analyzing more complex interactions between insects and microbes.

Animals↗
PubMed2004

Unravelling rhizosphere-microbial interactions: opportunities and limitations.

The rhizosphere is a biologically active zone of the soil around plant roots that contains soil-borne microbes including bacteria and fungi. Plant-microbe interactions in the rhizosphere can be beneficial to the plant, the microbes or to neither of them. One of the major difficulties that plant biologists and microbiologists face when studying these interactions is that many groups of microbes that inhabit this zone are not cultivable in the laboratory. Recent developments in molecular biology methods are shedding some light on rhizospheric microbial diversity. This review discusses recent findings and future challenges in the study of plant-microbe interactions in the rhizosphere.

Bacteria↗
PubMed2002

How host-microbial interactions shape the nutrient environment of the mammalian intestine.

Humans and other mammals are colonized by a vast, complex, and dynamic consortium of microorganisms. One evolutionary driving force for maintaining this metabolically active microbial society is to salvage energy from nutrients, particularly carbohydrates, that are otherwise nondigestible by the host. Much of our understanding of the molecular mechanisms by which members of the intestinal microbiota degrade complex polysaccharides comes from studies of Bacteroides thetaiotaomicron, a prominent and genetically manipulatable component of the normal human and mouse gut. Colonization of germ-free mice with B. thetaiotaomicron has shown how this anaerobe modifies many aspects of intestinal cellular differentiation/gene expression to benefit both host and microbe. These and other studies underscore the importance of understanding precisely how nutrient metabolism serves to establish and sustain symbiotic relationships between mammals and their bacterial partners.

Animals↗
PubMed2026

Microbial Interactions with Protein Intake and Preterm Infant Body Composition: Secondary Analysis of a Randomized Trial.

BACKGROUND: Enteral protein supplementation improves preterm infant growth and may impact body composition and the gut microbiota. OBJECTIVES: This study aimed to identify the effects of additional enteral protein supplementation on the gut microbiota and microbial and clinical drivers of body composition. METHODS: Secondary analysis of a masked randomized trial of additional enteral protein vs. standard fortification in preterm infants born at 25 to 28 weeks of gestation (NCT03586102) was conducted. Stool samples at weeks 4 and 8 underwent 16S rRNA sequencing; functional potential was predicted by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2). Body composition was measured by air-displacement plethysmography at 36 wk postmenstrual age (PMA). Least absolute shrinkage and selection operator (LASSO) regression with multivariable linear regression identified body composition predictors. RESULTS: Among 46 infants, gestational age (P = 0.16) and sex (P = 0.55) did not differ between groups. The protein group had higher week 4 Shannon diversity than standard fortification (median 1.2 vs. 0.87, P = 0.049). Week 4 Shannon diversity was positively correlated with fat-free mass z-score at 36 wk PMA (r2 = 0.34, P = 0.02). Adjusting for covariates, the protein group had higher Peptoniphilus (&#x3b2; = 1.6, Padj = 0.10) and lower Vibrio centered log-ratio abundance (&#x3b2; = -0.98, Padj = 0.10); 62 predicted metabolic pathways were lower in the protein group (false discovery rate < 0.20). In combined LASSO models, Bacillus abundance at week 4 was the strongest predictor of fat-free mass z-score (&#x3b2; = -0.17, P < 0.001; R2 = 0.80) and fat mass z-score (&#x3b2; = -0.31, P < 0.001; R2 = 0.66). CONCLUSIONS: Additional protein supplementation is associated with fat-free mass z-score and alterations to the gut microbiota. Clinical variables and microbial variables are key predictors of body composition, suggesting that nutrition, clinical factors, and the gut microbiota jointly contribute to body composition in extremely preterm infants. This study was registered at clinicaltrials.gov as NCT03586102 https://clinicaltrials.gov/study/NCT03586102 (registered in March 2020).

Humans↗
PubMed1992

Microbial interaction with animal cell surface carbohydrates.

Microbes have selected primarily carbohydrates for attachment to host animal cells. Recent studies have revealed essential characteristics in the recognition of receptor carbohydrates. Of importance is the property of recognizing also sequences placed inside an oligosaccharide chain, which differs from most animal antibodies. This is the basis for series of isoreceptors with the minimum receptor sequence in common but with separate neighbouring groups. There are families of microbial ligands that show different preferences for members within one series of isoreceptors, indicating only slight differences in the complementary binding sites of the proteins. Such differences may explain shifts in the selectivity of separate host tissues for infection. A second characteristic is the low affinity interaction often found where simple receptor-containing saccharides are unable to inhibit attachment. Technical possibilities are rapidly developing for the design of synthetic receptor analogues to be used in the therapy of clinical infections. This is urgently needed in cases where no rational therapy exists today.

Adhesins, Escherichia coli↗
PubMed2004

Biooxidation of pyrite by defined mixed cultures of moderately thermophilic acidophiles in pH-controlled bioreactors: significance of microbial interactions.

The oxidative dissolution of pyrite (FeS2) by pure and mixed cultures of moderately thermophilic acidophiles was studied in shake flask cultures and in pH-controlled bioreactors, incubated at 45 degrees C. Various combinations of seven eubacteria (a Leptospirillum sp. (MT6), Acidimicrobium ferrooxidans, Acidithiobacillus caldus, an Alicyclobacillus sp. (Y004), and three Sulfobacillus spp.) and one archaeon (Ferroplasma sp. MT17) were examined. Pyrite dissolution was determined by measuring changes in soluble iron and generation of acidity, and microbial populations were monitored using a combined culture-dependent (plate counts) and culture-independent (fluorescent in situ hybridization) approach. In pure cultures, the most efficient pyrite-oxidizing acidophile was Leptospirillum MT6, which was unique among the prokaryotes used in being obligately autotrophic. Mixed cultures of Leptospirillum MT6 and the sulfur-oxidizer At. caldus generated more acidity than pure cultures of the iron-oxidizer, though this did not necessarily enhance pyrite dissolution. In contrast, a mixed culture of Leptospirillum MT6 and the obligate heterotroph Alicyclobacillus Y004 oxidized pyrite more rapidly and more completely than a pure culture of Leptospirillum MT6, in synchronized bioreactors. Although the autotroph, At. caldus, and the "heterotrophically inclined" iron-oxidizer, Am. ferrooxidans, were both ineffective at leaching pyrite in pure culture, a mixed culture of the two bacteria was able to accelerate dissolution of the mineral. Concentrations of dissolved organic carbon accumulated to >100 mg/L in some mixed cultures, and the most effective bioleaching systems were found to be consortia containing both autotrophic and heterotrophic moderate thermophiles. A mixed culture comprising the autotrophs Leptospirillum MT6 and At. caldus, and the heterotroph Ferroplasma MT17, was the most efficient of all of those examined. Mutualistic interactions between physiologically distinct moderately thermophilic acidophiles, involving transfer of organic and inorganic carbon and transformations of iron and sulfur, were considered to have critical roles in optimizing pyrite dissolution.

Acidithiobacillus↗
PubMed2005

Neutrophil-anti-microbial interaction in the established infection: effect on Staphylococcus aureus.

OBJECTIVES: To determine if differences in drug-related Staphylococcus aureus killing, associated in vivo with neutropenia, is neutrophil-related in vitro, and the mechanisms of this interaction. METHODS: To evaluate the influence of living neutrophils on drug-S. aureus interactions, cell wall enzymes, the PBPs, were isolated and their binding to five (beta lactam and other) antibiotics was evaluated following incubation (or not) with neutrophils. S. aureus killing by the test drugs was assayed in growth media of sterile filtered abscess fluid, either neutropenic infected or normal infected. At MBCs for the test isolate, each drug or saline control was incubated with S. aureus 10(6)and dilution-plated. RESULTS: Neutrophil incubation with S. aureus eliminated the S. aureus PBP-2 band in all Western blots irrespective of the drug used to tag the PBPs. Time-kill of S. aureus grown in neutropenic or normal abscess fluid showed greater kill by all drugs in neutropenic abscess fluid (p=0.029 6h incubation). Killing difference between the media correlates with drug PBP-2 activity. CONCLUSIONS: Drug activity against S. aureus in vitro is changed by neutrophil incubation. The neutrophil-induced loss of S. aureus PBP-2 drug binding suggests novel host-bacterial interaction that may impinge on drug treatment of S. aureus infections.

Abscess↗
PubMed2005

NOD-LRR proteins: role in host-microbial interactions and inflammatory disease.

Nods are cytosolic proteins that contain a nucleotide-binding oligomerization domain (NOD). These proteins include key regulators of apoptosis and pathogen resistance in mammals and plants. A large number of Nods contain leucine-rich repeats (LRRs), hence referred to as NOD-LRR proteins. Genetic variation in several NOD-LRR proteins, including human Nod2, Cryopyrin, and CIITA, as well as mouse Naip5, is associated with inflammatory disease or increased susceptibility to microbial infections. Nod1, Nod2, Cryopyrin, and Ipaf have been implicated in protective immune responses against pathogens. Together with Toll-like receptors, Nod1 and Nod2 appear to play important roles in innate and acquired immunity as sensors of bacterial components. Specifically, Nod1 and Nod2 participate in the signaling events triggered by host recognition of specific motifs in bacterial peptidoglycan and, upon activation, induce the production of proinflammatory mediators. Naip5 is involved in host resistance to Legionella pneumophila through cell autonomous mechanisms, whereas CIITA plays a critical role in antigen presentation and development of antigen-specific T lymphocytes. Thus, NOD-LRR proteins appear to be involved in a diverse array of processes required for host immune reactions against pathogens.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Microbial interaction in cooked cured meat products under vacuum or modified atmosphere at 4 degrees C.

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 degrees 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 the spoilage 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.

Animals↗
PubMed1996

A model of host-microbial interactions in an open mammalian ecosystem.

The maintenance and significance of the complex populations of microbes present in the mammalian intestine are poorly understood. Comparison of conventionally housed and germ-free NMRI mice revealed that production of fucosylated glycoconjugates and an alpha1, 2-fucosyltransferase messenger RNA in the small-intestinal epithelium requires the normal microflora. Colonization of germ-free mice with Bacteroides thetaiotaomicron, a component of this flora, restored the fucosylation program, whereas an isogenic strain carrying a transposon insertion that disrupts its ability to use L-fucose as a carbon source did not. Simplified models such as this should aid the study of open microbial ecosystems.

Animals↗
PubMed1996

Microbial interactions with aluminium.

Although aluminium is the most abundant metal in the Earth's crust, it lacks biological functions and shows a low bioavailability. Acid rain, however, solubilizes aluminium to toxic levels. Most research on the biological effects of aluminium has been centred on the analysis of aluminium-tolerant plants as well as its possible relationship with neurological disorders in humans. Also, several studies have been reported concerning aluminium effects on microorganisms, with more interest directed to cyanobacteria, soil bacteria and mycorrhizal fungi. Competition with iron and magnesium, and binding to DNA, membranes or cell walls are considered the main toxic effects of aluminium in microbes.

Aluminum↗
PubMed1987

[Immunoglobulin A and its significance for mucosa immunity--a contribution to the understanding of microbial interactions].

The secretory immunoglobulin A is still dominating with regard to knowledges and further investigations of the causes of mucosal immunity. Origin, formation, structure and mode of action of s-IgA are extensively explored. In the clinical range results of researches on symptoms and consequences of selective IgA deficiency are gaining importance, increasingly. Patients with IgA defect suffer up to 40 times more frequently from allergies and autoimmunopathies. In the induction of the immune response cellular components of mucosa immunity attaining the Lamina propria and the epithelium with the effector cells of Peyer's patches play a particular role.

Animals↗
PubMed2006

Microbial interactions in Staphylococcus epidermidis biofilms.

Medical device-associated infections, most frequently caused by coagulase-negative staphylococci, especially Staphylococcus epidermidis, are of increasing importance in modern medicine. The formation of adherent, multilayered bacterial biofilms is the most important factor in the pathogenesis of these infections, which regularly fail to respond to appropriate antimicrobial therapy. Progress in elucidating the factors functional in elaboration of S. epidermidis biofilms and the regulation of their expression with a special emphasis on the role of quorum sensing are reviewed. Significant progress has been made in recent years, which provides the rationale for developing better preventive, therapeutic and diagnostic measures.

Bacterial Physiological Phenomena↗
PubMed2005

Cystic fibrosis lung disease: genetic influences, microbial interactions, and radiological assessment.

Cystic fibrosis (CF) is a multiorgan disease caused by mutation of the CF transmembrane conductance regulator (CFTR) gene. Obstructive lung disease is the predominant cause of morbidity and mortality; thus, most efforts to improve outcomes are directed toward slowing or halting lung-disease progression. Current therapies, such as mucolytics, airway clearance techniques, bronchodilators, and antibiotics, aim to suppress airway inflammation and the processes that stimulate it, namely, retention and infection of mucus plaques at the airway surface. New approaches to therapy that aim to ameliorate specific CFTR mutations or mutational classes by restoring normal expression or function are being investigated. Because of its sensitivity in detecting changes associated with early airway obstruction and regional lung disease, high-resolution CT (HRCT) complements pulmonary function testing in defining disease natural history and measuring response to both conventional and experimental therapies. In this review, perspectives on the genetics and microbiology of CF provide a context for understanding the increasing importance of HRCT and other imaging techniques in assessing CF therapies.

Alleles↗
PubMed2000

A novel microbial interaction: obligate commensalism between a new gram-negative thermophile and a thermophilic Bacillus strain.

Obligately commensal interaction between a new gram-negative thermophile and a thermophilic Bacillus strain was investigated. From compost samples, a mixed culture showing tyrosine phenol-lyase activity was enriched at 60 degrees C. The mixed culture consisted of a thermophilic gram-negative strain, SC-1, and a gram-positive spore-forming strain, SK-1. In mixed cultures, strain SC-1 started to grow only when strain SK-1 entered the stationary phase. Although strain SC-1 showed tyrosine phenol lyase activity, we could not isolate a colony with any nutrient medium. For the isolation and cultivation of strain SC-1, we added culture supernatant and cell extract of the mixed culture to the basal medium. The supernatant and cell extract of the mixed culture contained heat-stable and heat-labile factors, respectively, that are essential to the growth of strain SC-1. During pure cultures of strain SK-1, the heat-stable growth factors were released during the growth phase and the heat-labile growth factors were produced intracellularly at the early stationary phase. Strain SC-1 was gram-negative and microaerophilic, and grows optimally at 60 degrees C. Based on these results, we propose a novel commensal interaction between a new gram-negative thermophile, strain SC-1, and Bacillus sp. strain SK-1.

Bacillus↗