Glutamate dehydrogenase (GdhA) of S. pneumoniae is required for high temperature adaptation

ABSTRACT: During its progression from nasopharynx to other sterile and non-sterile niches of its human host, Streptococcus pneumoniae must cope with changes in temperature. We hypothesized that the pneumococcal temperature adaptation is an important facet of pneumococcal in host survival. Here we evaluate the effect of temperature on the phenotype of pneumococcus and the role of glutamate dehydrogenase (GdhA) during thermal stress adaptation associated with virulence and survival. Microarray analysis revealed a significant transcriptional response to temperature changes, affecting the expression of 132 and 119 genes at 34°C and 40°C, respectively, at mid-exponential growth phase relative to at 37ºC. One of the differentially regulated genes was gdhA, which is upregulated at 40°C while downregulated at 34°C relative to 37°C. Mutation of gdhA attenuated the growth, cell size, biofilm formation, pH survival, and virulence factor generation in a temperature dependent manner. Moreover, we identify that both D39 and ΔgdhA strains showed homo-lactic fermentation in glucose, however, ΔgdhA had higher formate production than D39 at all temperatures, which raised the hypothesis that gdhA involves in the regulation of pyruvate formate lyase (pflB) which is activated by catabolite control protein A (CcpA). In silico analysis pointed that a putative CcpA binding site (cre) was found in two proximal regions of -gdhA-coding sequence. The CcpA binding to the putative promoter region of gdhA was confirmed by EMSA. Furthermore, the transcriptional regulation of gdhA by CcpA, was temperature dependent. Finally, ΔgdhA grown at 34°C or 40°C was less virulent in Galleria mellonella infection model, suggesting that GdhA is required for pneumococcal virulence in fluctuating temperatures. These data demonstrated that temperature is an important parameter that affects physiology of S. pneumoniae and GdhA plays a significant role in temperature adaptation.

ORGANISM(S): Streptococcus pneumoniae D39

PROVIDER: GSE154888 | GEO | 2021/11/24

REPOSITORIES: GEO