Heat shock response as a cue for phenotypic variability: a study of psychrotrophic and mesophilic strains of Cellulosimicrobium cellulans

Abstract

We report the expression pattern of heat shock proteins (HSPs) in an Antarctic psychrotrophic strain of Cellulosimicrobium cellulans (DSM 22151) by comparing with its mesophilic counterpart (DSM 43879T) at different temperatures. In both strains, the synthesis of HSPs declined with growth phase. The Antarctic isolate could upregulate 60 kDa, 52 kDa and 41.6 kDa HSPs at 60°C while for its mesophilic counterpart, regulation was restricted to a 64 kDa fraction. The highly unstable nature of this fraction could have led to the impaired thermotolerance exhibited by the mesophilic strain. The downshift of thermal shock from 60°C to 45°C resulted in further upregulation of HSPs in the psychrotrophic strain, while there was no marked variation in the mesophilic strain. This work highlights the significance of a 60 kDa protein in the Antarctic strain of C. cellulans and also indicates the role of a 52 kDa protein in the previously reported heat shock response. Contrary to expectations, the psychrotrophic strain was found to have better mechanisms to tolerate higher temperatures—a property that could give valuable insights into the evolution and adaptation of cold-adapted bacteria.