Open AccessCharacterization of Caulobacter crescentus response to low temperature and identification of genes involved in freezing resistance
Author(s) -
Mazzon Ricardo R.,
Lang Elza A.S.,
Braz Vânia S.,
Marques Marilis V.
Publication year - 2008
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2008.01337.x
Subject(s) - caulobacter crescentus , biology , mutant , genetics , gene , helicase , bacteria , microbiology and biotechnology , rna , cell cycle
Free‐living bacteria must respond to a wide range of temperature changes, and have developed specific mechanisms to survive in extreme environments. In this work we describe a remarkable resistance of mesophilic bacterium Caulobacter crescentus to several cycles of freezing at −80 °C, which was able to grow at low temperatures. Exponentially growing cells and late stationary‐phase cells presented higher freezing resistance at both −20 and −80 °C than early stationary‐phase cells. Cryotolerance was observed when log‐phase cultures grown at 30 °C were preincubated at 5, 15 or 20 °C before freezing at −20 °C. A transposon library was screened to identify mutants sensitive to freezing at −80 °C and three strains presenting <10% survival were isolated. Identification of genes disrupted in each mutant showed that they encoded an AddA family DNA helicase, a DEAD/DEAH box RNA helicase and a putative RND (resistance, nodulation, cell division) efflux system component. These strains showed longer generation times than wild‐type cells when growing at 15 °C, with the RNA helicase mutant presenting a severe growth defect. These analyses suggest that the singular intrinsic resistance to freezing of C. crescentus is in fact a consequence of several independent traits, especially the maintenance of a proper degree of supercoiling of nucleic acids.