Inducible bacteriophages from ruminal bacteria.

The incidence of temperate bacteriophage in a wide range of ruminal bacteria was investigated by means of induction with mitomycin C. Supernatant liquid from treated cultures was examined for phagelike particles by using transmission electron microscopy. Of 38 ruminal bacteria studied, nine organisms (23.7%) representing five genera (Eubacteria, Bacteroides, Butyrivibrio, Ruminococcus, and Streptococcus) produced phagelike particles. Filamentous particles from Butyrivibrio fibrisolvens are the first of this morphological type reported from ruminal bacteria. All of the other particles obtained possessed polyhedral heads and long, noncontractile tails (group B-type phage). The limited range of morphological types produced by mitomycin C induction cannot yet account for the much wider range of types found in ruminal contents by direct examination. The presence of viral genetic material in a significant percentage of the bacteria tested, as well as in a range of different genera, indicates that viral genetic material may be a normal constituent of the genome of appreciable numbers of ruminal bacteria.     

Isolation of an endoglucanase gene from Bacteroides ruminicola subsp. brevis

A gene coding for endo-1, 4-beta-glucanase activity has been isolated from Bacteroides ruminicola subsp. brevis by cloning in Escherichia coli. After restriction mapping of a 6.4 kb insert, a 2.2 kb DNA fragment was sub-cloned in pUC19 to produce the enzymically active clone pJW3. Recloning of the gene fragment in the reverse orientation in pUC18 (clone pJW4) indicated that a gene promoter was present in the cloned fragment and was able to function in E. coli. The clone pJW4 displayed increased activity which was attributed to expression from the lac promoter of pUC18. The enzyme encoded by pJW4 was optimally active at pH 5.5-6.0, and in the temperature range 37-42 degrees C. The preferred substrate was carboxymethylcellulose, but the enzyme displayed 50-60% of maximal activity on both acid-swollen cellulose and soluble xylan. No significant activity was detected on ball-milled filter paper or particulate xylan. Deletion experiments confirmed that both cellulase and xylanase activities were altered to a similar extent by deletion of DNA from the 3' end of the gene, suggesting that both are a function of the same polypeptide product.