The rgg0182 gene encodes a transcriptional regulator required for the full Streptococcus thermophilus LMG18311 thermal adaptation

In this study, we demonstrated that Streptococcus thermophilus thermal stress adaptation required the rgg0182 gene which transcription depends on the culture medium and the growth temperature. This gene encoded a protein showing similarity with members of the Rgg family transcriptional regulator. Our data confirmed that Rgg0182 is a transcriptional regulator controlling the expression of its neighboring genes as well as chaperones and proteases encoding genes. Therefore, analysis of a Δrgg0182 mutant revealed that this protein played a role in the heat shock adaptation of Streptococcus thermophilus LMG18311.These data showed the importance of the Rgg0182 transcriptional regulator on the survival of S. thermophilus during dairy processes and more specifically during changes in temperature.The species Streptococcus thermophilus is a Lactic Acid Bacterium (LAB) used as a starter of fermentation in yogurt and cheese production. In nature and during dairy fermentation processes, S. thermophilus is subjected to sudden changes in its environment and its industrial performance is conditioned by its ability to successfully adapt to harsh conditions. To survive, like many other bacteria, this species must develop appropriate physiological responses by modifying gene expression appropriately.One of the stresses, that S. thermophilus commonly encounters, is the modification of the temperature. For instance, during the production of dairy products, temperature shifts are applied to regulate the bacterial growth and, thus, control the lactic acid production [1]. S. thermophilus survival against thermal stress is conditioned by its ability to sense and quickly adapt its physiology mainly by the synthesis of adequate proteins at the right moment. For example, adaptation of S. thermophilus to a lowering of temperature required the synthesis of a set of chaperones called cold shock proteins (Csp) that is strongly induced in response to a rapid decrease in growth temperature [2,3]. As