Relationship of arginine and lactose utilization by Lactococcus lactis ssp. lactis ML3

The arginine deiminase (ADI) pathway exists in many microorganisms and is one of the main characteristics that distinguish between Lactococcus lactis ssp. lactis and ssp. cremoris. The ADI pathway converts arginine to produce ammonia, carbon dioxide, and ATP. Induction of this pathway in relation to energy production is not well characterized. The presence of arginine changed the metabolism of strain ML3 in the media containing different levels of lactose. The interaction between lactose and arginine utilization changed the pH of the growth medium in a cyclic pattern. Transcriptional analysis showed that the first enzyme in the ADI pathway (arginine deiminase, arcA) was induced by pH rather than arginine addition. Analysis of the ratio arginine to lactose led to a statistical model that linked lactose, arginine, external pH, and the ADI pathway.