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The role of metabolic cross-feeding between strains of Bifidobacterium adolescentis that are able to utilize starch or fructo-oligosaccharides (FOS) as growth substrates and strains of butyrate-producing bacteria that cannot themselves utilize starch or FOS but can use the lactate and acetate formed by B. adolescentis is examined.

Research reveals that human large intestine harbors distinct groups of butyrate-producing bacteria of different functionality. Data show that strains of Roseburia sp. and Faecalibacterium prausnitzii and strain L2-50 of Coprococcus sp. possess different functional enzyme systems.

The properties of the 808-amino acid cellulase produced by the endB gene in Ruminococcus flavefaciens 17 are described. The EndB protein may bind to celluloase via a cellulose-binding module or via its involvement in a cellulosome-like multienzyme complex.

Of 313 butyrate-producing bacteria isolated from fecal samples of three people, 80% fell within the XIVa cluster of gram-positive bacteria. Most of the isolates were related to known species, but many represented new uncharacterized phylogenetic groups.

Molecular analysis has been carried out for study of microbial diversity in the colonic wall, colonic lumen, and cecal lumen of the pig. This is the first effort to identify the main types of bacteria by direct retrieval and analysis of small-subunit ribosomal DNA (rDNA) sequences, free of cultural bias and to compare with cultured pig colon isolates. A significant part of the microbial diversity, especially that of the colonic wall sample, is related only distantly to cultured bacterial types, the sequences of which are in databases. Phylogenetic analysis is used to find the positions of the unidentified bacterial strains relative to known rDNA sequences.

The survival of free DNA in human saliva and its degradation have been studied by using competitive polymerase chain reaction. The free DNA is a 520-bp target sequence from a recombinant plasmid, pVACMC1, after the admixture of the plasmid with freshly-sample human saliva. Results reveal that the plasmid DNA that has been exposed to degradation by human saliva can transform naturally-competent Streptococcus gordonii DL1 to erythromycin resistance. The transformation decreased rapidly with a half-life of 50 seconds.

A study described an approach for determining the genetic composition of Bacteroides and Prevotella populations in gut contents based on selective amplification of 16S rRNA gene sequences followed by cleavage of the amplified material with restriction enzymes. The contributions of various ribotypes to total Bacteroides and Prevotella 16S rDNA were estimated followed by the estimation of the contribution of the sequences to total eubacterial 16S rDNA. The approach was found to be a rapid, convenient and widely applicable method for comparing the genotypic composition of bacterial populations in gut samples.

A 25-kDa extracellular enzyme that acts against Beta-(1,3-1,4)-glucans was generated by Steptococcus bovis JB1 (S bovis). Constructs derived from the plasmid vector pIL253 or pTRW10 were employed to reintroduce the cloned Beta-glucanase gene into S bovis. The glucanase was found to influence the bacterium's capacity to use starch by degrading endosperm cell wall polysaccharides.

Microbiological research has established the presence of a transmissible chromosomal element with tetracycline resistance in the obligately anaerobic rumen bacterial species Butyrivibrio fibrisolvens. Pulsed-field gel electrophoretic analysis demonstrates the transconjugant's altered chromosomal band profile. Evidence suggests that a distantly related Tc(super r) genetic determinant is transferred.

The XynB enzyme in Prevotella ruminicola B14, a ruminal anaerobe, appears to be an oxygen-senstive exoxylanase whose sequence homology to two beta-xylosidases establishes a new family of beta-(1,4)-glycosidases. The xynB gene is closely linked to xynA, which encodes an endoxylanase, and the two enzyme products appear to act in synergy in releasing reducing sugars from oat spelt xylan.

Research has been conducted on the verocytotoxigenic bacteriophage isolated from the enterohemorragic Escherichia coli strain. The use of this bacteriophage in infecting the Enterobacteriaceae strains is discussed.

Human colonic anaerobe Roseburia imulinivorans A2-194 is a transfer recipient for two conjugative transposons. Findings reveal the occurrence of transfer of antibiotic resistance genes in both directions between rumen and human gut representatives of gut Firmicutes.

A new degenerate real-time PCR approach is described to simultaneously quantify phylogenetically different butyrate-producing bacteria based on the detection of butyryl-coenzyme A (CoA) CoA transferase genes. The transferase gene pathway is present in numerically important groups of butyrate producers within the human colon and could be used to estimate the butyrate-producing ability of the microbiota.

A study was conducted to investigate the effect of reduced carbohydrate intake upon bacterial populations and metabolites detected in fecal samples. The close correlation between the population densities of Roseburia and Eubacterium rectale species and fecal butyrate concentrations in response to altered carbohydrate supply supports a dominant role for these bacteria in butyrate production.

The cultivation and abundance of Roseburia- and Eubacterium rectale-related human gut bacteria in human feces was examined by comparing 16S rRNA sequences from 19 cultured human gut strains with 356 related sequences derived from clone libraries. Five out of six Roseburia- and E. rectale-related phylotypes or operational taxonomic units (OTUs) were defined by molecular diversity analyses through isolation under strict anaerobiosis, leading to the possibility of recovering a very high proportion of the total bacterial diversity present in the normal human gut as pure cultures.

The isolation of bacteria from human feces that can convert lactate largely into butyrate is reported. The study identified several abundant groups of lactate-utilizing bacteria belonging to clostridial cluster XIVa from human feces for which butyrate is a major product.

A mean population distribution of 2.3, 3.8, and 0.6% in a population comprising three different bacteria is detected using 16S rRNA-targeted oligonucleotide prones from 10 human feces samples. Data indicate that a mean of 7.7% , of the total fecal microbiota produce butyrate.

Research investigates the changes in a community of human fecal bacteria due to changes in the carbohydrate substrates. Results show that dahlia inulin substrate markedly increases the number of Ruminococcus and eubacterium bacterial species. Different levels of ability to use different substrates by selected anaerobic bacteria indicate that low G+C content gram-positive obligate anaerobes may be selected against during fermentation.