The CasKR Two-Component System Is Required for the Growth of Mesophilic and Psychrotolerant Bacillus cereus Strains at Low Temperatures

Abstract

eThe different strains of Bacillus cereus can grow at temperatures covering a very diverse range. Some B. cereus strains can grow in chilled food and consequently cause food poisoning. We have identified a new sensor/regulator mechanism involved in lowtemperature B. cereus growth. Construction of a mutant of this two-component system enabled us to show that this system, called CasKR, is required for growth at the minimal temperature (T min ). CasKR was also involved in optimal cold growth above T min and in cell survival below T min . Microscopic observation showed that CasKR plays a key role in cell shape during cold growth. Introducing the casKR genes in a ⌬casKR mutant restored its ability to grow at T min . Although it was first identified in the ATCC 14579 model strain, this mechanism has been conserved in most strains of the B. cereus group. We show that the role of CasKR in cold growth is similar in other B. cereus sensu lato strains with different growth temperature ranges, including psychrotolerant strains.

Involvement of the CasK/R two-component system in optimal unsaturation of the Bacillus cereus fatty acids during low-temperature growth

“…We previously identified a TCS named CasK/R, widespread among B. cereus sensu lato (B. cereus sl), including B. anthracis, B. thuringiensis and B. weihenstephanensis (Diomandé et al, 2014). The isogenic casK/R mutants constructed in several mesophilic and cold-tolerant strains of B. cereus sl showed impaired growth and survival abilities in addition to morphological changes at low temperatures, revealing a major role of this TCS for B. cereus sl cold adaptation (Diomandé et al, 2014).…”

“…The isogenic casK/R mutants constructed in several mesophilic and cold-tolerant strains of B. cereus sl showed impaired growth and survival abilities in addition to morphological changes at low temperatures, revealing a major role of this TCS for B. cereus sl cold adaptation (Diomandé et al, 2014). The aim of the present study was to identify the regulon of CasK/R and the mechanism involving CasK/R during B. cereus low temperature adaptation.…”

“…Several studies describing the way B. cereus adapts to low temperature Broussolle et al, 2010;de Sarrau et al, 2013a;Diomandé et al, 2014) have shown that cold adaptation by B. cereus is multifactorial (translational factors, membrane modifications, etc. ).…”

The adaptive response of bacterial food-borne pathogens in the environment, host and food: Implications for food safety

“…A two component, sensor-regulator system, CasKR, which deletion prevented growth at low temperature of B. cereus, was recently identified (Diomande et al, 2014). At low temperature, deletion of CasKR caused a reduction in the expression of the desaturase gene desA and a concomitant reduction in the synthesis of fatty acids unsaturated in position 5 (Diomandé et al, 2015-in this issue).…”

“…The most thermophilic phylogenetic group (group VII corresponding to B. cytotoxicus), unable to grow below 20°C (Guinebretiere et al, 2008) lacks the genes of the two components sensor-regulator system CasKR, necessary for growth at low temperatures in B. cereus strains from other phylogenetic groups (Diomande et al, 2014). Phylogenetic group VII is also characterized by a particularly low amount of iso-C 13 and high amount of iso-C 15 (Guinebretiere et al, 2013).…”