The cold‐shock stress response in Mycobacterium smegmatis induces the expression of a histone‐like protein

Abstract

SummaryThe response of Mycobacterium smegmatis to a cold shock was investigated by monitoring changes in both growth and cellular protein composition of the organism. The nature of the cellular response was influenced by the magnitude of the temperature reduction, with the shock from 378C to 108C having the most widespread effect on growth, metabolism and protein composition. This 278C temperature reduction was associated with a lag period of 21± 24 h before increases were seen in all the measured cellular activities. The response to cold shock was adaptive, with growth resuming after this period, albeit at a 50-fold slower rate. The synthesis of at least 15 proteins was induced during the lag period. Two distinct patterns of cold-induced synthesis were apparent, namely transient and continuous, indicating the production of both cold-induced and cold-acclimation proteins. One of these cold-shock proteins, CipMa, was identified as the histone-like protein, Hlp, of M. smegmatis, which is also induced during anaerobic-induced dormancy. The corresponding gene demonstrated transient, cold-inducible expression with a five-to sevenfold increase in mRNA occurring 9±12 h after temperature shift. Although bacterial survival was unaffected, CipMa/Hlp knockout mutants were unable to adapt metabolically to the cold shock and resume growth, thus indicating a key role for CipMa in the cold-shock response.

σ Factors and Global Gene Regulation inMycobacterium tuberculosis

“…Several of these regulators have been characterized; some of them respond to environmental stresses such as cold shock (60), heat shock (41, 63), hypoxia (18,51,59), iron starvation (56), surface stress (41), and oxidative stress (42, 55), while others respond to still unknown environmental conditions (28,52,72). The resulting picture is still incomplete, but it suggests very complex regulatory systems with overlapping functions and redundancies.…”

One of the Two Genes Encoding Nucleoid-Associated HU Proteins in Streptomyces coelicolor Is Developmentally Regulated and Specifically Involved in Spore Maturation

“…Hlp could also promote DNA end joining in the presence of DNA ligase and could repress transcription by T7 RNA polymerase (38). The low abundance and the fact that mutants lacking Hlp grew normally and were not affected in survival of cold shock or anaerobiosis show that additional proteins must be involved in organizing the chromatin structure in mycobacteria, e.g., homologs of IHF, H-NS and Dps, and the newly described DNA-bridging protein Lsr2 (10,31,49). Hlp was instead suggested to be involved in repair or recombination processes, like nonhomologous end joining, and in regulating gene activity in response to stressful conditions (38).…”

Coping with the cold: the cold shock response in the Gram-positive soil bacterium Bacillus subtilis

“…Interestingly, although in B. subtilis none of these proteins has been examined with respect to a function during the cold shock response, it was shown that in E. coli gyrase and HU proteins (HBsu homologues) function in concert (Mizushima et al 1997). In fact, HU proteins are essential during cold shock adaptation of E. coli (Wada et al 1988) and in Mycobacterium smegmatis a histone-like protein is one of the major cold-induced proteins (Shires & Steyn 2001). Since SspF is currently the only SASP to which no specific function has been assigned during sporulation (Loshon et al 1997), it might be interesting to investigate whether it is of relevance to the cold shock response-especially in conjunction with HBsu which was shown to modulate the effects of SASPs, at least in vitro (Ross & Setlow 2000).…”