Submitted to: Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/1999
Publication Date: N/A
Interpretive Summary: In ruminant animals, feedstuffs are fermented in the rumen prior to intestinal digestion, and microbial protein is an important source of amino acids for cattle. Labeling studies indicated that 30% of the rumen bacteria lysed (burst) before they had a chance to leave the rumen. Lysis decreases microbial protein and amino acid availability. The following experiments described the lysis of the rumen bacterium, Streptococcus bovis, and results indicated that this process was controlled by two factors proteolytic activation and inactivation by a component of the cell wall. Research on rumen bacterial lysis has the potential to improve the efficiency of cattle production.
Technical Abstract: Streptococcus bovis JB1 does not normally lyse, but stationary phase lysis can be induced by including 2-deoxyglucose (2DG) in the growth medium. It was possible to select mutants resistant to 2DG-induced lysis (Lys-), as well as mutants that were deficient in glucose/2DG phosphotransferase activity (PTS-). Because mutants could be Lys-PTS+ or Lys-PTS-, the ability to phosphorylate 2DG via the PTS was not an obligate requirement for 2DG-induced lysis. A lipoteichoic acid (LTA) extraction procedure (hot aqueous phenol) yielded a product from glucose-grown cells that could inhibit the lysis of 2DG-treated cultures, but a similar extract prepared from 2DG-grown cells was without effect. Thin-layer chromatography and differential staining procedures (anisaldehyde versus anthrone based reagents) were utilized to monitor the incorporation of glucose and 2DG into LTA-containing extracts from S. bovis cultures. Wild-type cells and the Lys+PTS- mutant incorporated 2DG into LTA, but the lysis-resistant mutants (Lys-PTS+, Lys-PTS-) did not. In all cases, glucose-, but not 2DG-containing LTA was able to prevent 2DG-dependent lysis in the wild-type. Group D streptococci (including S. bovis) normally have an a-1, 2 linked glucose disaccharide (kojibiose) in their LTA, but kojibiose cannot be synthesized from 2DG. This observation suggested that the kojibiose moiety of LTA was involved in autolysin inactivation. Wild-type S. bovis had ATP- as well as PEP-dependent mechanisms of 2DG phosphorylation, and one lysis-resistant (Lys-PTS-) had reduced levels of both activities. However, the Lys-PTS+ mutant was still able to phosphorylate 2DG via ATP and PEP, and this result indicated that some other step of 2DG incorporation into LTA was being inhibited.