Identification and regulation of cold-inducible factors of Bordetella bronchiseptica

Abstract

The expression of bacterial cold-shock proteins (CSPs) is highly induced in response to cold shock, and some CSPs are essential for cells to resume growth at low temperature.Bordetella bronchisepticaencodes five CSPs (named CspA to CspE) with significant amino acid homology to CspA ofEscherichia coli. In contrast toE. coli, the insertional knock-out of a singlecspgene (cspB) strongly affected growth ofB. bronchisepticaindependent of temperature. In the case of three of thecspgenes (cspA,cspB,cspC) more than one specific transcript could be detected. The net amount ofcspA,cspBandcspCtranscripts increased strongly after cold shock, while no such effect could be observed forcspDandcspE. The exposure to other stress conditions, including translation inhibitors, heat shock, osmotic stress and nutrient deprivation in the stationary phase, indicated that thecspgenes are also responsive to these conditions. The coding regions of all of the cold-shock genes are preceded by a long non-translated upstream region (5′-UTR). In the case of thecspBgene, a deletion of parts of this region led to a significant reduction of translation of the resulting truncated transcript, indicating a role of the 5′-UTR in translational control. The cold-shock stimulon was investigated by 2D-PAGE and mass spectrometric characterization, leading to the identification of additional cold-inducible proteins (CIPs). Interestingly, two cold-shock genes (cspCandcspD) were found to be under the negative control of the BvgAS system, the main transcriptional regulator ofBordetellavirulence genes. Moreover, a negative effect of slight overexpression of CspB, but not of the other CSPs, on the transcription of the adenylate cyclase toxin CyaA ofBordetella pertussiswas observed, suggesting cross-talk between the CSP-mediated stress response stimulon and theBordetellavirulence regulon.