Project description:Rumen bacterial species belonging to the genera Butyrivibrio are important degraders of plant polysaccharides, particularly hemicelluloses (arabinoxylans) and pectin. Currently, four distinct species are recognized which have very similar substrate utilization profiles, but little is known about how these microorganisms are able to co-exist in the rumen. To investigate this question, Butyrivibrio hungatei MB2003 and Butyrivibrio proteoclasticus B316T were grown alone or in co-culture on the insoluble substrates, xylan or pectin, and their growth, release of sugars, fermentation end products and transcriptomes were examined. In single cultures, B316T was able to degrade and grow well on xylan and pectin, while MB2003 was unable to utilize either of these insoluble substrates to support significant growth. Co-cultures of B316T grown with MB2003 revealed that MB2003 showed almost equivalent growth to B316T when either xylan or pectin were supplied as substrates. The effect of co-culture on the transcriptomes of B316T and MB2003 was very marked; B316T transcription was largely unaffected by the presence MB2003, but MB2003 expressed a wide range of genes encoding carbohydrate degradation/metabolism and oligosaccharide transport/assimilation in order to compete with B316T for the released sugars. These results suggest that B316T has a role as an initiator of the primary solubilization of xylan and pectin, while MB2003 competes effectively as a scavenger for the released soluble sugars to enable its growth and maintenance in the rumen.
Project description:This study was undertaken with two major goals in mind: i) To investigate the potential for interspecies hydrogen transfer between a hemicellulytic rumen bacterium (B. proteoclasticus) and a methanogenic achaea (M. ruminantium) Microscopic examination had previously shown B. proteoclasticus in co-culture with M. ruminantium rapidly formed cell to cell co-aggregates. ii) To examine the expression of genes involved in methanogenesis under more rumen-like conditions.
Project description:This study was undertaken with two major goals in mind: i) To investigate the potential for interspecies hydrogen transfer between a hemicellulytic rumen bacterium (B. proteoclasticus) and a methanogenic achaea (M. ruminantium) Microscopic examination had previously shown B. proteoclasticus in co-culture with M. ruminantium rapidly formed cell to cell co-aggregates. ii) To examine the expression of genes involved in methanogenesis under more rumen-like conditions. Cells of M.ruminantium and B. proteoclasticus were grown in triplicate as mono- or co-cultures until a mid-exponential growth phase was reached. RNAs were extracted and purified. The relative quantities of RNAs contributed by each organism to the co-culture samples were determined by rt qPCR using genes previously shown to be constitutively expressed. The mono-culture RNAs were then combined in the determined proportions to normalise mRNA abundance with their co-culture replicates. cDNAs were synthesized and labelled and hybridised to the arrays. 3 biological replicates were used and the cDNA from each was divided in two to allow each to undergo a dyeswap (total of six arrays) giving technical replicates. Each gene was probed in triplicate adding further technical replication. Blanks and negative controls were also included. The log ratios for each probes replicates (biological and technical) were averaged prior to further analysis.