Product Code Database
Bacillus cereus is a Gram-positive Bacillus bacterium commonly found in soil, food, and marine sponges. The specific name, cereus, meaning "waxy" in Latin, refers to the appearance of colonies grown on blood agar. Some strains are harmful to humans and cause foodborne illness due to their spore-forming nature, while other strains can be beneficial as probiotics for animals, and even exhibit mutualism with certain plants. (2025). 9780838585290, McGraw Hill. ISBN 9780838585290 (2025). 9780387790572, Springer Science & Business Media. ISBN 9780387790572 B. cereus bacteria may be Aerobic organism or facultative anaerobes, and like other members of the genus Bacillus, can produce protective . They have a wide range of , including phospholipase C, cereulide, sphingomyelinase, metalloproteases, and cytotoxin K, many of which are regulated via quorum sensing. B. cereus strains exhibit Flagellum motility.
The Bacillus cereus group comprises seven closely related species: B. cereus sensu stricto (referred to herein as B. cereus), B. anthracis, B. thuringiensis, B. mycoides, B. pseudomycoides, and B. cytotoxicus; or as six species in a Bacillus cereus sensu lato: B. weihenstephanensis, B. mycoides, B. pseudomycoides, B. cereus, B. thuringiensis, and B. anthracis. A phylogenomic analysis combined with average nucleotide identity (ANI) analysis revealed that the B. anthracis species also includes strains annotated as B. cereus and B. thuringiensis.
Several new enzymes have been discovered in B. cereus, such as AlkC and AlkD, both of which are involved in DNA repair.
These bacteria are both Bacterial spore and biofilm-forming, presenting a large challenge to the food industry due to their contamination capability. Biofilms of B. cereus most commonly form on air-liquid interfaces or on hard surfaces such as glass. B. cereus display flagellar motility, which has been shown to aid in biofilm formation via an increased ability to reach surfaces suitable for biofilm formation, to spread the biofilm over a larger surface area, and to recruit planktonic, or single, free-living bacteria. Biofilm formation may also occur while in spore form due to varying adhesion ability of spores.
Their flagella are peritrichous, meaning there are many flagella located all around the cell body that can bundle together at a single location on the cell to propel it. This flagellar property also allows the cell to change directions of movement depending on where on the cell the flagellum filaments come together to generate movement.
Some studies and observations have shown that silica particles the size of a few nanometers have been deposited in a spore coat layer in the extracytoplasmic region of the Bacillus cereus spore. The layer was first discovered by the use of scanning transmission electron microscopy (STEM), however the images taken did not have resolution high enough to determine the precise location of the silica. Some investigators hypothesize that the layer helps different spores from sticking together. It has also been shown to provide some resistance to acidic environments. The silica coat is related to the permeability of the spore's inner membrane. Strong mineral acids are able to break down spore permeability barriers and kill the spore. However, when the spore has a silica coating, it may reduce the permeability of the membrane and provide resistance to many acids.
The Embden-Meyerhof pathway is the predominant pathway used by Bacillus cereus to catabolize glucose at every stage of the cell's development, according to estimates of a radiorespirometric method of glucose catabolism. This is true at times of germinative phases, as well as sporogenic phases. At the filamentous, granular, forespore, and transitional stages, the Embden-Meyerhof pathway was responsible for the catabolism of 98% of the cell's glucose. The remainder of the glucose was catabolized by the hexose monophosphate oxidative pathway.
Analysis of the core genome of B. cereus reveals a limited presence of enzymes meant for breakdown of and a prevalence of and amino acid degradation and transport pathways, indicating that their preferred diet consists of proteins and their breakdown products.
An isolate of a bacterium found to produce PHBs was identified as B. cereus through analysis of 16S rRNA sequences as well as similarity of morphological and biochemical characteristics. PHBs may be produced when there is excess carbon or limited essential nutrients present in the environment, and they are later broken down by the microbe as a fuel source under starvation conditions. This indicates the potential role of B. cereus in producing biodegradable plastic substitutes. PHB production was highest when provided with glucose as a carbon source.
Following exposure to non-lethal acid shock at pH 5.4-5.5, the arginine deiminase gene in B. cereus, arcA, shows substantial up-regulation. This gene is part of the arcABC operon which is induced by low-pH environments in Listeria monocytogenes, and is associated with growth and survival in acidic environments. This suggests that this gene is also important for survival of B. cereus in acidic environments.
The activation of virulence factors has been shown to be transcriptionally regulated via Quorum sensing in B. cereus. The activation of many virulence factors secreted is dependent on the activity of the Phospholipase C regulator (PlcR), a transcriptional regulator which is most active at the beginning of the stationary phase of growth. A small peptide called PapR acts as the effector in the quorum-sensing pathway, and when reimported into the cell, it interacts with PlcR to activate transcription of these virulence genes. When point mutations were introduced into the plcR gene using the CRISPR/Cas9 system, it was observed that the mutated bacteria lost their hemolytic and phospholipase activity.
The flagella of B. cereus are encoded by 2 to 5 fla genes, depending on the strain.
Below is a list of differential techniques and results that can help to identify B. cereus from other bacteria and Bacillus species. (1989). 9781489935021, Springer Science. ISBN 9781489935021
The Central Public Health Laboratory in the United Kingdom tests for motility, hemolysis, rhizoid growth, susceptibility to γ-phage, and fermentation of ammonium salt-based glucose but no mannitol, arabinose, or xylose.
In a study measuring the ability of B. cereus to degrade keratin in chicken feathers, bacteria were found to sufficiently biodegrade keratin via hydrolytic mechanisms. These results indicate its potential to degrade keratinous waste from the poultry industry for potential recycling of the byproducts.
B. cereus competes with Gram-negative bacteria species such as Salmonella and Campylobacter in the gut; its presence reduces the number of Gram-negative bacteria, specifically via antibiotic activity via enzymes such as that impede their quorum sensing ability and exhibit Bactericide activity. In food animals such as chickens, and , some harmless strains of B. cereus are used as a probiotic feed additive to reduce Salmonella in the animals' and cecum. This improves the animals' growth, as well as food safety for humans who eat them. In addition, B. cereus create and release enzymes that aid in the digestion of materials that are typically difficult to digest, such as woody plant matter, in the guts of other organisms.
The strain is a biofungicide.
The diarrhetic syndromes observed in patients are thought to stem from the three toxins: hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe), and cytotoxin K (CytK). The nhe/ hbl/ cytK genes are located on the chromosome of the bacteria. Transcription of these genes is controlled by PlcR. These genes occur in the taxonomically related B. thuringiensis and B. anthracis, as well. These enterotoxins are all produced in the small intestine of the host, thus thwarting digestion by host endogenous enzymes. The Hbl and Nhe toxins are pore-forming toxins closely related to ClyA of Escherichia coli. The proteins exhibit a conformation known as a "beta-barrel" that can insert into cellular membranes due to a hydrophobic exterior, thus creating pores with hydrophilic interiors. The effect is loss of cellular membrane potential and eventually cell death.
Previously, it was thought that the timing of the toxin production was responsible for the two different courses of disease, but it has since been found that the emetic syndrome is caused by the toxin cereulide, which is found only in emetic strains and is not part of the "standard toolbox" of B. cereus. Cereulide is a cyclic polypeptide containing three repeats of four amino acids: -oxy-—-—-oxy-—- (similar to valinomycin produced by Streptomyces griseus) produced by nonribosomal peptide synthesis. Cereulide is believed to bind to 5-hydroxytryptamine 3 (5-HT3) serotonin receptors, activating them and leading to increased afferent vagus nerve stimulation. It was shown independently by two research groups to be encoded on multiple : pCERE01 or pBCE4810. Plasmid pBCE4810 shares homology with the B. anthracis virulence plasmid pXO1, which encodes the anthrax toxin. Periodontal isolates of B. cereus also possess distinct pXO1-like plasmids. Like most of cyclic peptides containing nonproteogenic amino acids, cereulide is resistant to heat, proteolysis, and acid conditions.
B. cereus is also known to cause difficult-to-eradicate chronic skin infections, though less aggressive than necrotizing fasciitis. B. cereus can also cause keratitis.
While often associated with gastrointestinal illness, B. cereus is also associated with illnesses such as fulminant bacterial infection, central nervous system involvement, respiratory tract infection, and endophthalmitis. Endophthalmitis is the most common form of extra-gastrointestinal pathogenesis, which is an infection of the eye that may cause permanent vision loss. Infections typically cause a corneal ring abscess, followed by other symptoms such as pain, proptosis, and retinal hemorrhage. While different from B. anthracis, B. cereus contains some toxin genes originally found in B. anthracis that are attributed to anthrax-like respiratory tract infections.
A case study was published in 2019 of a catheter-related bloodstream infection of B. cereus in a 91-year-old male previously being treated with hemodialysis via PermCath for end-stage renal disease. He presented with chills, tachypnea, and high-grade fever, his white blood cell count and high-sensitivity C-reactive protein (CRP) were significantly elevated, and CT imaging revealed a thoracic aortic aneurysm. He was successfully treated for the aneurysm with intravenous vancomycin, oral , and PermCath removal. Another case study of B. cereus infection was published in 2021 of a 30-year-old woman with lupus who was diagnosed with infective endocarditis after receiving a catheter. The blood samples were positive for B. cereus and the patient was subsequently treated with vancomycin. PCR was also used to verify toxins that the isolate produces.
B. cereus and other members of Bacillus are not easily killed by alcohol; they have been known to colonize distilled liquors and alcohol-soaked swabs and pads in numbers sufficient to cause infection.
A study of an isolate of Bacillus cereus that was isolated from the stomach of a sheep was shown to be able to break down β-cypermethrin (β-CY) which has been known to be an antimicrobial agent. This strain, known as GW-01, can break down β-CY at a significant rate when the bacterial cells are in high concentrations relative to the antimicrobial agent. It has also been noted that the ability to break down β-CY is inducible. However, as the concentration of β-CY increases, the rate of β-CY degradation decreases. This suggests that the agent also functions as a toxin against the GW-01 strain. This is significant as it shows that in the right concentrations, β-CY can be used as an antimicrobial agent against Bacillus cereus.
|
|
