The Product of arcR, the sixth gene of the arc operon of Lactobacillus sakei, is essential for expression of the arginine deiminase pathway.

Lactobacillus sakei is a lactic acid bacterium commonly used as a starter culture for dry sausage production and can utilize arginine via the arginine deiminase pathway. The arcABCTD cluster of L. sakei has been characterized, and transcriptional studies have shown that its expression is subject to carbon catabolite repression and induction by arginine. Downstream of arcD an additional gene has been found; this gene, arcR, codes for a putative regulatory protein of the Crp/Fnr family. Transcriptional studies have shown that arcR is coordinately transcribed with the remaining arc genes, and therefore, these genes constitute the arcABCTDR operon. Northern analysis also showed a complex pattern of transcripts, suggesting that processing and partial termination may play a role in regulation of the expression of individual genes of the operon. Inactivation of arcR led to arrest of transcription of the operon, indicating that the ArcR protein is essential for expression of the arc genes. The availability of this mutant made it possible to study whether the ability to utilize arginine affects the growth of L. sakei in meat fermentations. Under our experimental conditions, expression of arginine deiminase does not confer an obvious advantage to L. sakei, since the wild type and an arcR mutant strain displayed similar dynamics of growth.