Bacillus cereus spores and toxins – The potential role of biofilms
Section snippets
Bacillus cereus: spores, toxins and biofilms
Bacillus cereus sensu lato group comprise several closely related species including Bacillus cereus sensu stricto (B. cereus s.s. referred as B. cereus below), Bacillus thuringiensis, Bacillus anthracis, Bacillus weihenstephanensis, Bacillus mycoides, Bacillus pseudomycoides and Bacillus cytotoxicus (Jensen et al., 2003; Lechner et al., 1998; Guinebretière et al., 2010). B. cereus is a recognized foodborne pathogen widely distributed environmentally in spores and/or vegetative cells, causing
Genetic links for spore, toxin and biofilm production
Table 1 and Fig. 2 below summarise the current knowledge of genetic determinants and related pathways involved in spore, toxin and biofilm formation of B. cereus and/or Bacillus subtilis (B.subtilis) based on literature review.
Intertwined regulatory pathways between biofilm formation and sporulation have been proposed for B. subtilis (Vlamakis et al., 2013). These could also be similar in B. cereus but this needs to be confirmed. A Spo0A deletion mutant of B. subtilis shows a defect in biofilm
Biofilm: a supportive reservoir for sporulation?
B. cereus biofilms are mainly comprised of vegetative cells, however during maturation and aging, B. cereus is able to form spores within the established biofilms (Ryu and Beuchat, 2005; Wijman et al., 2007; Faille et al., 2014). The biofilms on manufacturing plant surfaces could become a reservoir for spores, as has been shown previously for thermophilic spore-formers Geobacillus stearothermophilus (Burgess et al., 2014). Those spores formed in the biofilm may provide a source of contamination
Biofilm: a microbial community that favors toxin production?
The expression of toxin genes and toxin production can be influenced by environmental factors and can vary from strain to strain of B. cereus (Jeβberger et al., 2015), making studies difficult. However, there is little knowledge about toxin production within biofilms cells compared to planktonic grown cells. It is commonly accepted that B. cereus-induced diarrhoea is caused by enterotoxin produced in the intestine (Ceuppens et al., 2012), therefore, biofilm formed in the intestine should be
Spores and toxins
Spores and toxins of B. cereus combine to provide a food safety concern, however, the link between spores and toxin production is unknown. It is known that spores of B. cereus survive gastric passage to attach to the small intestine, germinate and produce enterotoxins during outgrowth causing diarrhoea, however, these toxins hardly withstand the gastrointestinal conditions (Ceuppens et al., 2012). The cytotoxicity of B. cereus group members (B. cereus, B. subtilis and B. thuringiensis) could be
Future perspectives
The sporulation of B. cereus within biofilms has been demonstrated, although further study is needed to investigate if biofilms play a role in sporulation and the direct link between biofilm formation and sporulation of B. cereus. There is little evidence of the link between toxin production and biofilm formation in B. cereus. There is also a little evidence of the role of sporulation in the toxin production of B. cereus. As a foodborne pathogen, toxin production is important and any
Declaration of competing interest
This manuscript is original, and no part of the manuscript has been published before. There are no conflicts of interest to disclose.
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