Genetic and functional analysis of the cytK family of genes in Bacillus cereus

Fagerlund, Annette; Ween, Ola; Lund, T.; Hardy, Simon P.; Granum, Per Einar

doi:10.1099/mic.0.26975-0

Cited by 182 publications

(138 citation statements)

References 30 publications

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“…This is consistent with a study by Fagerlund et al (19) in which hlyII was detected in 6 of the 29 (21%) B. cereus strains tested. We further show that hlyII is found only in pathogenic strains isolated from food-poisoning outbreaks or clinical infections.…”

Section: Discussionsupporting

confidence: 82%

InhA1, NprA, and HlyII as Candidates for Markers To Differentiate Pathogenic from NonpathogenicBacillus cereusStrains

Cadot

Tran

Vignaud³

et al. 2010

J Clin Microbiol

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Bacillus cereus is found in food, soil, and plants, and the ability to cause food-borne diseases and opportunistic infection presumably varies among strains. Therefore, measuring harmful toxin production, in addition to the detection of the bacterium itself, may be key for food and hospital safety purposes. All previous studies have focused on the main known virulence factors, cereulide, Hbl, Nhe, and CytK. We examined whether other virulence factors may be specific to pathogenic strains. InhA1, NprA, and HlyII have been described as possibly contributing to B. cereus pathogenicity. We report the prevalence and expression profiles of these three new virulence factor genes among 57 B. cereus strains isolated from various sources, including isolates associated with gastrointestinal and nongastrointestinal diseases. Using PCR, quantitative reverse transcriptase PCR, and virulence in vivo assays, we unraveled these factors as potential markers to differentiate pathogenic from nonpathogenic strains. We show that the hlyII gene is carried only by strains with a pathogenic potential and that the expression levels of inhA1 and nprA are higher in the pathogenic than in the nonpathogenic group of strains studied. These data deliver useful information about the pathogenicity of various B. cereus strains.

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Section: Discussionsupporting

confidence: 82%

InhA1, NprA, and HlyII as Candidates for Markers To Differentiate Pathogenic from NonpathogenicBacillus cereusStrains

Cadot

Tran

Vignaud³

et al. 2010

J Clin Microbiol

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“…The resulting vegetative cells produce three enterotoxins responsible for diarrheal symptoms (2,8,18). These enterotoxins are hemolysin BL (Hbl) (4), nonhemolytic enterotoxin (Nhe) (27), and the single cytotoxin protein Cyt K (11,28). Hbl is composed of three proteins L2, L1, and B encoded by genes clustered into an operon with the transcriptional order hblC, hblD, and hblA (42).…”

mentioning

confidence: 99%

Control of Enterotoxin Gene Expression in Bacillus cereus F4430/73 Involves the Redox-Sensitive ResDE Signal Transduction System

et al. 2006

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In contrast to Bacillus subtilis, the role of the two-component regulatory system ResDE has not yet been investigated in the facultative anaerobe Bacillus cereus. We examined the role of ResDE in the food-borne pathogen B. cereus F4430/73 by constructing resDE and resE mutants. Growth performances, glucose metabolism, and expression of hemolysin BL (Hbl) and nonhemolytic enterotoxin (Nhe) were analyzed in the three strains under distinct oxygenation and extracellular oxidoreduction potential (ORP) conditions. We show that growth and glucose metabolism were only moderately perturbed in both resDE and resE mutants under aerobiosis, microaerobiosis, and anaerobiosis generated under N 2 atmosphere (initial ORP ‫؍‬ ؉45 mV). The major effects of resDE and resE mutations were observed under low-ORP anaerobic conditions generated under hydrogen atmosphere (iORP ‫؍‬ ؊148 mV). These conditions normally favor enterotoxin production in the wild type. The resE mutation was more deleterious to the cells than the resDE mutation, causing growth limitation and strong deregulation of key catabolic genes. More importantly, the resE mutation abolished the production of enterotoxins under all of the conditions examined. The resDE mutation only decreased enterotoxin expression under anaerobiosis, with a more pronounced effect under low-ORP conditions. Thus, the ResDE system was found to exert major control on both fermentative growth and enterotoxin expression, and it is concluded that the ResDE system of B. cereus should be considered an anaerobic redox regulator. The data presented also provide evidence that the ResDE-dependent regulation of enterotoxins might function at least partially independently of the pleiotropic virulence gene regulator PlcR.The facultative anaerobic, spore-forming Bacillus cereus has gained notoriety as an opportunistic human pathogen capable of causing a wide variety of diseases ranging from periodontitis, endophthalmitis, and meningitis in immunocompromised patients to the more frequent gastrointestinal infections (24,44). B. cereus is associated with two types of gastrointestinal infection, both causing diarrhea and vomiting after the ingestion of a contaminated food. Recent evidence suggests that B. cereus cells are primarily ingested as spores and that the spores are able to adhere to the mucosal epithelium of the small intestine, where they can then germinate (52). The resulting vegetative cells produce three enterotoxins responsible for diarrheal symptoms (2,8,18). These enterotoxins are hemolysin BL (Hbl) (4), nonhemolytic enterotoxin (Nhe) (27), and the single cytotoxin protein Cyt K (11, 28). Hbl is composed of three proteins L2, L1, and B encoded by genes clustered into an operon with the transcriptional order hblC, hblD, and hblA (42). All three components need to be excreted to induce biological effects, which include enterotoxic activity and hemolytic and dermonecrotic activities (5, 6). Nhe is also a threecomponent enterotoxin. It was first isolated from an Hbl-negative strain of B. cereus i...

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“…The toxicoinfection referred to as diarrheal disease occurs after consumption of B. cereus spores or vegetative cells, most likely due to the action of heat-labile enterotoxins, which are produced by cells multiplying in the small intestine (4,22,30,39). Contrarily, the emetic type of food-borne illness is caused by intoxication with the heat-stable peptide cereulide, which is preformed in foods and elicits vomiting a few hours after ingestion (18,51,58).…”

mentioning

confidence: 99%

Identification of the Main Promoter Directing Cereulide Biosynthesis in Emetic Bacillus cereus and Its Application for Real-Time Monitoring of ces Gene Expression in Foods

Dommel

Frenzel

Strasser

et al. 2010

Appl Environ Microbiol

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Cereulide, the emetic Bacillus cereus toxin, is synthesized by cereulide synthetase via a nonribosomal peptide synthetase (NRPS) mechanism. Previous studies focused on the identification, structural organization, and biochemical characterization of the ces gene locus encoding cereulide synthetase; however, detailed information about the transcriptional organization of the ces genes was lacking. The present study shows that the ces-PTABCD genes are transcribed as a 23-kb polycistronic transcript, while cesH, encoding a putative hydrolase, is transcribed from its own promoter. Transcription initiation was mapped by primer extension and rapid amplification of cDNA ends (RACE). Deletion analysis of promoter elements revealed a main promoter located upstream of the cesP coding sequence, encoding a 4-phosphopantetheinyl transferase. This promoter drives transcription of cesPTABCD. In addition, intracistronic promoter regions in proximity to the translational start sites of cesB and cesT were identified but were only weakly active under the chosen assay conditions. The identified main promoter was amplified from the emetic reference strain B. cereus F4810/72 and fused to luciferase genes in order to study promoter activity in complex environments and to establish a biomonitoring system to assess cereulide production in different types of foods. ces promoter activity was strongly influenced by the food matrix and varied by 5 orders of magnitude. The amount of cereulide toxin extracted from spiked foods correlated well with the bioluminescence data, thus illustrating the potential of the established reporter system for monitoring of ces gene expression in complex matrices.Bacillus cereus is the causative agent of two types of food poisoning: diarrhea and emesis. The toxicoinfection referred to as diarrheal disease occurs after consumption of B. cereus spores or vegetative cells, most likely due to the action of heat-labile enterotoxins, which are produced by cells multiplying in the small intestine (4,22,30,39). Contrarily, the emetic type of food-borne illness is caused by intoxication with the heat-stable peptide cereulide, which is preformed in foods and elicits vomiting a few hours after ingestion (18,51,58).Regulation of enterotoxin expression of B. cereus has been studied in some detail (e.g., references 16, 29, and 46; for a review, see reference 58), revealing a major role of the pleiotropic transcription regulator PlcR in activation of enterotoxin genes and other virulence factors (1,29,45). Cereulide synthesis in emetic B. cereus, in contrast to synthesis of B. cereus enterotoxins, is not controlled by PlcR but by the Spo0A phosphorelay. The global transition state factor AbrB was identified as one factor repressing cereulide production in early exponential phase (38). Although B. cereus enterotoxins and the emetic toxin cereulide seem to belong to completely different regulatory networks, production of both types of toxins depends substantially on nutritional and environmental factors (3,46,55), and it is expe...

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Genetic and functional analysis of the cytK family of genes in Bacillus cereus

Cited by 182 publications

References 30 publications

InhA1, NprA, and HlyII as Candidates for Markers To Differentiate Pathogenic from NonpathogenicBacillus cereusStrains

InhA1, NprA, and HlyII as Candidates for Markers To Differentiate Pathogenic from NonpathogenicBacillus cereusStrains

Control of Enterotoxin Gene Expression in Bacillus cereus F4430/73 Involves the Redox-Sensitive ResDE Signal Transduction System

Identification of the Main Promoter Directing Cereulide Biosynthesis in Emetic Bacillus cereus and Its Application for Real-Time Monitoring of ces Gene Expression in Foods

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