A novel hybrid kinase is essential for regulating the σ B ‐mediated stress response of Bacillus cereus

The mechanisms involved in the ability of Bacillus cereus to multiply at low temperatures were investigated. It was assumed that many genes involved in cold acclimation would be upregulated at low temperatures. Recombinase-based in vivo expression technology (IVET) was adapted to the detection of the transient activation of B. cereus promoters during growth at 10°C. Four independent screenings of a promoter library from type strain ATCC 14579 were performed, and 17 clones were isolated. They corresponded to 17 promoter regions that displayed reproducibly elevated expression at 10°C relative to expression at 30°C. This analysis revealed several genes that may be important for B. cereus to grow successfully under the restrictive conditions of cold habitats. Among them, a locus corresponding to open reading frames BC5402 to BC5398, harboring a lipase-encoding gene and a putative transcriptional regulator, was identified three times. While a mutation in the putative regulator-encoding gene did not cause any particular phenotype, a mutant deficient in the lipase-encoding gene showed reduced growth abilities at low temperatures compared with the parental strain. The mutant did not change its fatty acid profiles in the same way as the wild type when grown at 12°C instead of 37°C. This study demonstrates the feasibility of a promoter trap strategy for identifying cold-induced genes. It outlines a first picture of the different processes involved in B. cereus cold acclimation.The food-borne disease agent Bacillus cereus is an endospore-forming bacterium belonging to the B. cereus group (B. cereus sensu lato). B. cereus sensu lato has recently been divided into seven major phylogenetic groups (I to VII) with clear-cut differences in growth temperature ranges, suggesting that the genetic structure corresponds to "thermotypes" and showing the emergence of multiple psychrotrophic groups within B. cereus sensu lato (26). Temperature adaptation has thus presumably played a major role in B. cereus evolution. B. cereus is also a human pathogen, causing local and systemic infections. Most outbreaks of food-borne poisoning have been caused by mesophilic strains (26) that can grow at temperatures as low as 10°C. This characteristic enables initially relatively low levels of B. cereus in foods to increase greatly under commonly reported suboptimal refrigeration conditions (20). Understanding the ability of B. cereus to grow at low temperatures will help to control multiplication in refrigerated food and prevent outbreaks of food-borne poisoning.At low temperatures, bacteria undergo various modifications in cellular physiology, with effects such as decreased membrane fluidity and inefficient folding of proteins and secondary structures of RNA and DNA (43). Bacterial responses can be divided into low-temperature responses (or acclimation, also called low-temperature adaptation) and cold shock responses (43). Both types of responses include a vast array of structural and physiological adjustments to cope with the reduction in biochemic...

Section: Discussionsupporting

confidence: 82%

Identification of Bacillus cereus Genes Specifically Expressed during Growth at Low Temperatures

Brillard

Jéhanno

Dargaignaratz

et al. 2010

“…This finding suggested a role for B during disinfectant exposure in B. cereus, corroborated by the previously described induction following different stress responses in many bacteria (11,60), as well as in the resistance of Listeria monocytogenes to detergents such as QAC (48). However, in the current study, the deletion of the rsbY and rsbK genes, encoding proteins involved in the activation of B (17,61), did not sensitize B. cereus ATCC 14579 to disinfectant stresses. This result suggests that B , even though induced, has no direct role in protecting B. cereus cells against disinfectant treatments.…”

Section: Discussioncontrasting

confidence: 45%

Comparative Transcriptomic and Phenotypic Analysis of the Responses ofBacillus cereusto Various Disinfectant Treatments

Ceragioli

Mols

Moezelaar

et al. 2010

Self Cite

Antimicrobial chemicals are widely applied to clean and disinfect food-contacting surfaces. However, the cellular response of bacteria to various disinfectants is unclear. In this study, the physiological and genome-wide transcriptional responses of Bacillus cereus ATCC 14579 exposed to four different disinfectants (benzalkonium chloride, sodium hypochlorite, hydrogen peroxide, and peracetic acid) were analyzed. For each disinfectant, concentrations leading to the attenuation of growth, growth arrest, and cell death were determined. The transcriptome analysis revealed that B. cereus, upon exposure to the selected concentrations of disinfectants, induced common and specific responses. Notably, the common response included genes involved in the general and oxidative stress responses. Exposure to benzalkonium chloride, a disinfectant known to induce membrane damage, specifically induced genes involved in fatty acid metabolism. Membrane damage induced by benzalkonium chloride was confirmed by fluorescence microscopy, and fatty acid analysis revealed modulation of the fatty acid composition of the cell membrane. Exposure to sodium hypochlorite induced genes involved in metabolism of sulfur and sulfur-containing amino acids, which correlated with the excessive oxidation of sulfhydryl groups observed in sodium hypochlorite-stressed cells. Exposures to hydrogen peroxide and peracetic acid induced highly similar responses, including the upregulation of genes involved in DNA damage repair and SOS response. Notably, hydrogen peroxide-and peracetic acid-treated cells exhibited high mutation rates correlating with the induced SOS response.

“…Recent research has revealed how a 2CS contributes to the high adaptability of B. cereus strains that enables these bacteria to persist in processed foods (25). Some 2CSs were shown to play diverse roles in B. cereus adaptation (26)(27)(28)(29)(30), but most of the 2CSs found among B. cereus sensu lato strains have an unknown function (31), and none has yet been shown to be involved in low-temperature adaptation.…”

mentioning

confidence: 99%

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

Diomandé

Chamot

Antolinos

et al. 2014

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.