Growth Changes of ccpA-deficient Lacticaseibacillus rhamnosus

Abstract:

The gene encoding the carbon metabolism control protein, ccpA, plays a critical role in the utilization of carbon sources and environmental adaptation of lactic acid bacteria. The ccpA gene of Lacticaseibacillus rhamnosus hsryfm 1301 was completely deleted using an in-frame, marker-free method. The growth status of L. rhamnosus hsryfm 1301 and its ccpA deficient strain were compared under different conditions. The use of glucose, fructose, mannose, galactose, or lactose as the sole carbon source resulted in the wild-type strain reaching the stationary phase 4~5 h faster than the ccpA mutant. At low mass fraction of mixed carbon sources (0.2%) and the presence of non-preferred carbon sources, the wild-type strain exhibited a secondary growth phase. In contrast, the mutant strain did not exhibit the secondary growth phase but entered the stationary phase earlier than the wild-type strain. Under low-carbon source conditions, the biomass of the ccpA mutant was greater (approximately 0.3 of OD600) than that of the wild-type strain. The ccpA gene enhanced the growth rate of L. rhamnosus, but it inhibited growth under low carbon source conditions. The effects of the ccpA gene on the growth of L. rhamnosus varied across different environments, conferring a growth advantage to the strain under conditions with ample carbon sources.