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Human gut microbiomes (microbiotas) are highly individualistic in taxonomic composition but nevertheless are functionally similar. Thus, collectively, they comprise a "metacommunity." In ecological terminology, the assembly of human gut microbiomes is influenced by four processes: selection, speciation, drift, and dispersal. As a result of fortuitous events associated with these processes, individual microbiomes are taxonomically "tailor-made" for each host. However, functionally they are "off-the-shelf" because of similar functional outputs resulting from metabolic redundancy developed in host-microbe symbiosis. Because of this, future microbiological and molecular studies of microbiomes should emphasize the metabolic interplay that drives the human gut metacommunity and that results in these similar functional outputs. This knowledge will support the development of remedies for specific functional dysbioses and hence provide practical examples of precision medicine. [ABSTRACT FROM AUTHOR]

Background/Objectives: To assess associations between dietary fibre intake, adiposity, and odds of metabolic syndrome in Pacific and New Zealand European women. Methods: Pacific (n = 126) and New Zealand European (NZ European; n = 161) women (18–45 years) were recruited based on normal (18–24.9 kg/m2) and obese (≥30 kg/m2) BMIs. Body fat percentage (BF%), measured using whole body DXA, was subsequently used to stratify participants into low (<35%) or high (≥35%) BF% groups. Habitual dietary intake was calculated using the National Cancer Institute (NCI) method, involving a five-day food record and semi-quantitative food frequency questionnaire. Fasting blood was analysed for glucose and lipid profile. Metabolic syndrome was assessed with a harmonized definition. Results: NZ European women in both the low- and high-BF% groups were older, less socioeconomically deprived, and consumed more dietary fibre (low-BF%: median 23.7 g/day [25–75-percentile, 20.1, 29.9]; high-BF%: 20.9 [19.4, 24.9]) than Pacific women (18.8 [15.6, 22.1]; and 17.8 [15.0, 20.8]; both p < 0.001). The main source of fibre was discretionary fast foods for Pacific women and whole grain breads and cereals for NZ European women. A regression analysis controlling for age, socioeconomic deprivation, ethnicity, energy intake, protein, fat, and total carbohydrate intake showed an inverse association between higher fibre intake and BF% (β= −0.47, 95% CI = −0.62, −0.31, p < 0.001), and odds of metabolic syndrome (OR = 0.91, 95% CI = 0.84, 0.98, p = 0.010) among both Pacific and NZ European women (results shown for both groups combined). Conclusions: Low dietary fibre intake was associated with increased metabolic disease risk. Pacific women had lower fibre intakes than NZ European women. [ABSTRACT FROM AUTHOR]

Clostridium difficile infection (CDI) is the most common identifiable cause of diarrhoea in hospitalized patients. Current therapies rely on the administration of metronidazole or vancomycin, which reduce vegetative populations of C. difficile in the bowel. Recurrence of the disease when treatment with these antibiotics ceases indicates that metronidazole and vancomycin affect not only C. difficile but also commensal populations that normally mediate competitive exclusion. Fidaxomicin is a new antibiotic that inhibits C. difficile. Our study shows that fidaxomicin had little effect on the composition of the faecal microbiota in terms of its major phylogenetic clusters. Notably, clostridial clusters XlVa and IV, and Bifidobacterium, were much less affected by fidaxomicin compared to vancomycin treatment. These findings help to explain the substantially reduced rates of relapse following treatment of CDI with fidaxomicin in recent clinical trials. DOI 10.1099/mic.0.042010-0

Members of the genus Lactobacillus are common inhabitants of the proximal gastrointestinal tract of animals such as mice, rats, chickens and pigs, where they form epithelial biofilms. Little is known about the traits that facilitate biofilm formation and gut colonization. This study investigated the ecological role of a glucosyltransferase (GtfA) and inulosucrase (Inu) of Lactobacillus reuteri TMW 1.106 and a fructosyltransferase (FtfA) of L. reuteri LTH5448. In vitro experiments using isogenic mutants revealed that GtfA was essential for sucrose-dependent autoaggregation of L. reuteri TMW1.106 cells under acidic conditions, while inactivation of Inu slowed the formation of cell aggregates. Experiments using an in vitro biofilm assay showed that GtfA and Inu contributed to biofilm formation of L. reuteri TMW1.106. Experiments using ex-Lactobacillus-free mice revealed that the ecological performance of the inu mutant, but not of the gtfA or ftfA mutant, was reduced in the gastrointestinal tract when in competition with the parental strain. In the absence of competition, the gtfA mutant showed delayed colonization of the murine gut relative to the wild-type. In addition, the gtfA mutant showed reduced ecological performance in competition experiments with Lactobacillus johnsonii #21. From the evidence provided in this study we conclude that GtfA and Inu confer important ecological attributes of L. reuteri TMW1.106 and contribute to colonization of the mouse gastrointestinal tract.

Comparative studies are carried out on two Campylobacter jejuni strains, T1016 and Pstau, in relation to their prevalence in human infections and on poultry meat in a specific geographical area of New Zealand. The strain comparisons have used an in vitro cell invasion assay, microarray-based comparative genomic hybridization, flagellin A (FlaA) characteristics obtained from amino acid sequences, and competitive-exclusion experiments with chickens.

A study was conducted to measure the impact on the gut microbiota of rats of the consumption of diets supplemented with beta-glucans extracted from barley flour. The results show that HV beta-glucan could produce a prebiotic effect in the ceca of rats, at least under the specific dietary conditions that were used.

The physiological and ecological role for the luxS gene in Lactobacillus reuteri 100-23C is defined by constructing a luxS mutant by insertional mutagenesis. The results show that LuxS influences important ecological attributes of L. reuteri 100-23C, the consequences of which are niche specific.

Culture-based enumeration of selected bacterial populations, monitoring of the bifidobacterial species and strain composition by nucleic acid-based methods were used for measuring the impact of the consumption of three biscuits per day, containing oligosaccharide on the fecal microbiota of humans. Physiological methods may prove to be more informative as compared to the phylogenetic approach during the analysis of the gut ecosystem.

Researchers describe a PCR technique based on the transaldolase gene in Bifidobacterium coupled with denaturing gradient gel electrophoresis that can distinguish between species. This is possible because bifidobacteria produce 14 or more different types of transaldolase. Because they produce different electrophoretic patterns, the transaldolase genes must have variable sequences.

Researchers describe the development of PCR primers specific for Lactobacillus, Pediococcus, Leuconostoc, and Weissella. Lactic acid bacteria make up less than 1% of the intestinal microflora, and are not easily detectable using universal PCR primers.