Ten strains of anaerobic, gram negative, monotrichous, butyric acid-producing curved rods have been isolated from ingesta of the bovine rumen. These 10 strains of butyrivibrio represented 1/5 of all isolates at 1 x 10⁻⁸ dilutions. Morphological and physiological characteristics of the 10 strains and a strain isolated by gill and king (1958) have also been studied. No two of the isolates were identical in all reactions. Most of the organisms produced a large amount of butyric and some lactic, formic, propionic and succinic acids with the utilization of acetic acid in a rumen fluid glucose medium. The fermentation carried on by these organisms was sensitive to most tested environmental changes. Studies with buffered rumen fluid-glucose media demonstrated a shift of the fermentation products with pH. Addition of fatty acids to this medium indicated that these organisms were active in the conversion of acetate and possibly propionate to butyrate. Two strains apparently had the ability to produce propionate at the expense of lactate. The results of the fermentation tests in 98 per cent rumen fluid medium showed that the tested strains used acetic (plus formic) or lactic (plus succinic) to produce butyric or propionic acid, and produced higher concentrations of fatty acids under a carbon dioxide atmosphere than under nitrogen. When rumen fluid and acetic acid were absent all strains had the ability to produce either formic or acetic acid. / Master of Science

One or more factors which occur in bovine rumen fluid stimulate the growth of a strain of Butyrivibrio. The stimulating material is heat stable, organic in nature and non-dialyzable. It cannot be extracted from rumen fluid with lipid solvents and is retained in part on anion and cation exchange resins. It can be eluted from the resins with strong acid. It is stable to enzymatic hydrolysis by trypsin. Granular mucin or bovine saliva will partially replace the stimulatory activity. The part of the material which was not replaced by mucin did not appear to be any compound that is commonly used to stimulate bacterial growth. The presence of a possible inhibitor for the growth of a strain of Butyrivibrio was demonstrated. / Master of Science

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

Butyrivibrio proteoclasticus B316T is the most recently described species of the Butyrivibrio / Pseudobutyrivibrio assemblage and now the first to have its genome sequenced. The genome of this organism was found to be spread across four replicons: a 3.5 Mb major chromosome and three additional large replicons: 186, 302 and 361 Kb in size. This thesis describes the sequencing, analysis, annotation and initial characterisation of all three B. proteoclasticus auxiliary replicons. Most significantly, these analyses revealed that the 302-Kb replicon is a second chromosome. This small chromosome, named BPc2, encodes essential systems for the uptake and/or biosynthesis of biotin and nicotinamide adenine mononucleotide, as well as the enzymes required for utilisation of fumarate as the terminal electron acceptor during anaerobic respiration, none of which are found on the main chromosome. In addition, BPc2 contains two complete rRNA operons, a large number of enzymes involved in the metabolism of carbohydrates, nitrogen and fatty acids. In contrast to BPc2, both megaplasmids appear largely cryptic, collectively encoding 421 genes not previously described in public databases. Nevertheless, only the 186-Kb, but not 361-Kb megaplasmid, could be cured from Butyrivibrio proteoclasticus B316T. The largest megaplasmid has a copy number of 5, while all other replicons are present at a copy number of 1. %GC content and codon usage analyses strongly suggests that all three auxiliary replicons have co-resided with the major chromosome for a significant evolutionary period. Moreover, the replication machineries of these three replicons are conserved. Interestingly, a survey of a number of Butyrivibrio / Pseudobutyrivibrio species revealed that the megaplasmids are widespread in this assemblage, however these other large plasmids do not show concordance with their 16S rRNA phylogeny and appear distinct to those of B. proteoclasticus B316T. A microarray analysis of gene expression in a co-culture experiment between B. proteoclasticus and the important ruminal methanogen, Methanobrevibacter ruminantium M1, revealed a potentially mutualistic interspecies interaction. In this relationship M. ruminantium appears to provide B. proteoclasticus with glutamate, essential to the final step of NAD+ biosynthesis, while B. proteoclasticus appears to provide M. ruminantium with formate, hydrogen and carbon dioxide, each important substrate for methanogenesis.