Amino acids other than glutamate affect the expression of the GAD system in Listeria monocytogenes enhancing acid resistance.

Amino acids other than glutamate affect the expression of the GAD system in Listeria monocytogenes enhancing acid resistance. Food Microbiol. 2020 Sep;90:103481 Authors: Paudyal R, O'Byrne CP, Karatzas KA Abstract The Glutamate Decarboxylase (GAD) system is important for survival of L. monocytogenes and other microorganisms under acidic conditions. Environmental conditions influence the function of the GAD system. Until now, the only conditions known to lead to increased transcription of the GAD system are the stationary phase in rich media and anoxic conditions. Previously, we showed that transcription of the GAD system requires unidentified compounds other than glutamate present in rich media. Following a test looking at various compounds we identified for first time that peptone, tryptone and casamino acids activate the GAD system under oxic conditions suggesting that amino acid(s) other than glutamate and/or peptides are important for the above process. The defined medium, where the GAD system is inactive, once it is supplemented with the above compounds results in an active intracellular and extracellular GAD system and increased acid resistance. Through functional genomics we show that these compounds are required for GadD2 activity and although we previously showed that GadD3 is active part of the intracellular GAD system, the supplementation did not activate this gene. The above is explained by the fact that only gadD2 transc...
Source: Food Microbiology - Category: Food Science Authors: Tags: Food Microbiol Source Type: research