No abstract

"Roseburia inulinivorans" is an anaerobic polysaccharide-utilizing firmicute bacterium from the human colon that was identified as a producer of butyric acid during growth on glucose, starch, or inulin. R. inulinivorans A2-194 is also able to grow on the host-derived sugar fucose, following a lag period, producing propionate and propanol as additional fermentation products. A shotgun genomic microarray was constructed and used to investigate the switch in gene expression that is involved in changing from glucose to fucose utilization. This revealed a set of genes coding for fucose utilization, propanediol utilization, and the formation of propionate and propanol that are up-regulated during growth on fucose. These include homologues of genes that are implicated in polyhedral body formation in Salmonella enterica. Dehydration of the intermediate 1,2-propanediol involves an enzyme belonging to the new B 12 -independent glycerol dehydratase family, in contrast to S. enterica, which relies on a B 12 -dependent enzyme. A typical gram-positive agr-type quorum-sensing system was also up-regulated in R. inulinivorans during growth on fucose. Despite the lack of genome sequence information for this commensal bacterium, microarray analysis has provided a powerful tool for obtaining new information on its metabolic capabilities.The human colon contains a dense and highly diverse microbial community consisting of over 500 different bacterial species (13,15,20,41). These bacteria are predominantly obligate anaerobes and produce fermentation products that may be beneficial (e.g., butyrate) (35) or detrimental (e.g., hydrogen sulfide) (34) to the epithelial cells lining the human colon. The main butyrate-producing colonic anaerobes belong to Clostridium clusters IV and XIVa (3,20,26) and include cluster XIVa bacteria that have been assigned to the genus Roseburia (11). Studies using fluorescent in situ hybridization have shown that bacteria related to Roseburia (including Eubacterium rectale) can comprise up to 10% of the total bacterial population in human feces (21, 43). All Roseburia spp. produce butyrate, but they differ markedly in their substrate utilization profiles (12,36).Colonic bacteria gain energy from dietary substrates that escape digestion in the upper gastrointestinal tract, including plant cell wall polysaccharides, resistant starch, inulin, and a variety of oligosaccharides. In the distal colon, host-derived secretions and mucin, including the glycoproteins and glycolipids covering the surface of gut epithelial cells, may be significant substrates. L-fucose is frequently present at the terminus of epithelial glycoconjugates (14), and several pathogenic bacteria, including Salmonella enterica serovar Typhimurium LT2 (subsequently referred to as Salmonella serovar Typhimurium LT2) and the commensal bacterium Bacteroides thetaiotaomicron, utilize fucose for growth (see references 1 and 38, respectively). B. fragilis is able to incorporate fucose into its own surface polysaccharides, a mechanism that gives it a c...

Roseburia inulinivorans is a recently identified motile representative of the Firmicutes that contributes to butyrate formation from a variety of dietary polysaccharide substrates in the human large intestine. Microarray analysis was used here to investigate substratedriven gene-expression changes in R. inulinivorans A2-194. A cluster of fructo-oligosaccharide/inulin utilization genes induced during growth on inulin included one encoding a β-fructofuranosidase protein that was prominent in the proteome of inulin-grown cells. This cluster also included a 6-phosphofructokinase and an ABC transport system, whereas a distinct inulin-induced 1-phosphofructokinase was linked to a fructose-specific phosphoenolpyruvatedependent sugar phosphotransferase system (PTS II transport enzyme). Real-time PCR analysis showed that the β-fructofuranosidase and adjacent ABC transport protein showed greatest induction during growth on inulin, whereas the 1-phosphofructokinase enzyme and linked sugar phosphotransferase transport system were most strongly up-regulated during growth on fructose, indicating that these two clusters play distinct roles in the use of inulin. The R. inulinivorans β-fructofuranosidase was overexpressed in Escherichia coli and shown to hydrolyze fructans ranging from inulin down to sucrose, with greatest activity on fructo-oligosaccharides. Genes induced on starch included the major extracellular α-amylase and two distinct α-glucanotransferases together with a gene encoding a flagellin protein. The latter response may be concerned with improving bacterial access to insoluble starch particles.anaerobic gut bacteria | differential gene expression | fructooligosaccharides | butyrate | prebiotic P lant cell wall polysaccharides, storage polysaccharides such as resistant starch and inulin, and many oligosaccharides of plant origin remain undigested in the upper gastrointestinal tract and become important substrates for the growth of colonic bacteria. Prebiotics are defined as dietary substrates that reach the colon where they selectively stimulate the growth of beneficial gut bacteria (1), with the most widely used prebiotics being the fructans inulin and fructo-oligosaccharides (FOS). Inulin is a linear polymer [degree of polymerization (DP) = 3-60] of β-2,1-linked fructose monomers with a terminal glucose residue, whereas FOS have the same backbone but a maximal chain length of 8 monomeric units. The increasing use of prebiotics to enhance gut health is driving research into their mode of action. Many studies have shown that both inulin and FOS selectively stimulate the growth of potentially beneficial gut bacteria such as bifidobacteria and lactobacilli (reviewed in ref.2). However, only a few studies have considered the potential for stimulation of other bacterial groups that may also be beneficial (3-6).The bifidogenic dose of inulin has been defined as 5-8 g/d (7), yet the effect of such supplementation on other beneficial groups of gut bacteria and the differences relating to different compositions of inulin...

3T3 fibroblasts were treated sequentially with 25 mM-KCl/0.05% Nonidet P40, 130 mM-KCl/0.05% Nonidet P40 and finally with 1% Nonidet P40/1% deoxycholate in order to release free, cytoskeletal-bound and membrane-bound polysomes respectively. The membrane-bound fraction was enriched in the mRNA for the membrane protein beta 2-microglobulin, whereas the cytoskeletal-bound polysomes were enriched in c-myc mRNA. Actin mRNA was present in both free and cytoskeletal-bound polysomes. The results suggest that cytoskeletal-bound polysomes are involved in the translation of specific mRNA species.

When incubated in axenic culture, strains of anaerobic rumen fungi were more active than cellulolytic bacteria in solubilizing barley straw stem fragments 5 to 10 mm in length. Pretreatment with ammonia had little effect on microbial attack. Of three species of methanogens tested, Methanobrevibacter smithii strain PS formed the most stable and reproducible co‐cultures with the fungi and with Ruminococcus albus, and the presence of this organism enhanced the extent of degradation of straw, although this effect was less marked than that previously observed when pure cellulose was used as substrate.