ARS | Publication request: INDUCER EXPULSION IS NOT A DETERMINANT OF DIAUXIC GROWTH IN STREPTOCOCCUS BOVIS

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 7, 1995
Publication Date: N/A

Interpretive Summary: Streptococcus bovis is an opportunistic bacterium that is found in the rumen of ruminant farm animals (cattle, sheep, goats) and in the colon of humans. This species outgrows other ruminal and colonic bacteria when there is an abundance of carbohydrate. This overgrowth causes acute indigestion, ruminal acidosis, and even the death of cattle. In humans, S. bovis has been implicated in the etiology of colon cancer. In previous research, we found that S. bovis had two mechanisms of carbohydrate regulation. These two mechanisms were termed "inducer exclusion" and "inducer expulsion" respectively. In this manuscript we used mutants and found that inducer expulsion alone was unable to inhibition utilization of the carbohydrate, lactose. Information on the regulation of carbohydrate utilization may provide ways of inhibiting S. bovis, thereby alleviating ruminal acidosis, improving the economics of animal production and decreasing colon cancer.

Technical Abstract: When Streptococcus bovis JB1 was repeatedly transferred with the non- metabolizable glucose analog, 2-deoxyglucose, it lost its phosphotransferase system for glucose but was still able to take up glucose via a facilitated diffusion mechanism. The wild type (JB1) had an inducible enzyme II lactose, but the mutant (JB1 2DG) had a constitutive lactose PTS. .JB1 2DG was no longer able to exclude lactose when it was provided with glucose, but it retained its ability to expel the non-metabolizable lactose analog. Because JB1 2DG could utilize glucose and lactose simultaneously and grow in a non-diauxic fashion, it appeared that inducer expulsion was not an important catabolite regulatory mechanism. Based on these results, inducer expulsion may be an artifact of non-metabolizable sugars.