Domain dependent orchestrated regulation of bacterial growth, persistence and chemotaxis by an essential GTPase, CgtA, in Vibrio cholerae

Abstract

CgtA, an evolutionarily conserved GTPase, associated with the 50S ribosome controls a broad spectrum of physiological processes in bacteria. It has three structural domains, viz., N-terminal domain (NTD), GTPase domain and C-terminal domain (CTD). CgtA regulates expression of several of genes during nutritional stress in Vibrio cholerae. The mechanism of transcriptional regulation by CgtA is unknown, though the NTD concomitantly with the GTPase domain participates in the process. Here, we show that the in vivo deletion of the 57 amino acids long CTD of CgtA GTPase of V. cholerae is dispensable for viability, contrary to the complete knockdown of cgtA gene. Slower growth was observed in cgtA knockdown strain with intermittent diauxic lags in minimal media than the CTD deleted strain. Irreversible defect in colony morphology was observed in the cells with CTD deletion. Resuscitation of persister cells occurred when nutritionally deprived complete cgtA knockdown cells after growing for longer periods were transferred to nutritionally enriched media. The motility of the cgtA knockdown strain was significantly reduced than the wild type cells. Furthermore, CTD deleted cells were also found to be defective in motility, but comparatively lower than cgtA knockdown cells. Elongated and slender V. cholerae cells were observed by SEM imaging upon cgtA depletion, whereas, upon CTD deletion cellular elongation did not occur. Based on our study here, we propose that the CTD of CgtA perceives the nutritional stress response, to which the NTD and GTPase responds.