Role of cAMP receptor protein in phenotype and stress tolerance in Salmonella enterica serovar Typhimurium

Abstract

Salmonella enterica serovar Typhimurium (S. Typhimurium) is exposed to biotic and abiotic stresses. The survival of Salmonella in nature depends on the global regulators like cAMP receptor protein (CRP). The role of CRP in the phenotypic characteristics and stress tolerance was elucidated in S. Typhimurium using a crp gene null mutant (Δcrp). A 1.6-fold decrease in the cell size, a two-fold reduction in the colony size, and a 3.5-fold decrease in motility were observed in the Δcrp compared with the S. Typhimurium wild-type (WT). H₂ S production on selective media was affected in the Δcrp. The utilisation of d-mannose, d-glycerol and d-mannitol was completely affected, whereas that of d-galactose and d-fructose was partially affected. The utilisation of d-arabinose was induced in the Δcrp. The growth rate of the Δcrp in Luria Bertani medium was unaffected. However, in the glucose-containing minimal medium, the growth rate of the Δcrp was reduced by 1.5-fold compared with the WT. The Δcrp was able to utilise ethanolamine as the sole carbon source similar to the WT. The Δcrp was more tolerant to heat and oxidative stress. Overexpression of heat and oxidative stress-related genes was observed in the Δcrp in the stationary phase. The Δcrp was less tolerant to radiation stress compared with the WT. The current findings decisively establish the CRP protein as a global regulator. The CRP affects multiple phenotypes, carbon metabolism and stress physiology of S. Typhimurium.

Keywords: Salmonella Typhimurium; cAMP receptor protein; carbohydrate utilisation; phenotype; stress tolerance; thiosulphate reduction.