Bacillus cereus is an important foodborne pathogen, which can cause severe food poisoning. The aim of this study was (i) to evaluate the quantitative prevalence of B. cereus in retail prepackaged ...infant formula and ready-to-eat rice flour in China and (ii) to gain the basic information on pheno- and genotypic characteristics of B. cereus isolates. We found that 40 out of the 587 samples were positive for B. cereus. B. cereus in 3.5% of infant formula samples and 1.0% of rice flour samples outnumbered 100 Colony-Forming Units (CFU)/g. B. cereus level even attained 10
-10
CFU/g in four infant formula samples and one rice flour sample. Furthermore, we identified the distribution patterns of toxin genes in B. cereus isolates. The results showed that 97.5% of B. cereus isolates harbored at least one enterotoxin gene. Antibiotic susceptibility tests revealed that all isolated B. cereus strains were resistant to penicillin and 50% of them were multidrug resistant. Thirteen new sequence types (STs) and four new alleles were identified via multilocus sequence typing. Clonal Complex (CC) ST-205 and CC ST-142 were predominant clonal complexes. Interestingly, we revealed the special relationship between STs of B. cereus isolates and the geographical distributions of infant food manufacturers for the first time. The data implied that B. cereus of different STs might have a distinct ecological niche in China. In view of relatively high contamination level of enterotoxin- producing B. cereus in a proportion of infant foods, especially in those suitable for the ≤6-month-old infant group, appropriate safety criteria and hygienic control measures for infant foods should be drafted in China to prevent B. cereus infection.
A newly acquired polyhydroxyalkanoate (PHA) producing
Bacillus spp. was identified to be a strain of
Bacillus cereus using a range of microbiological and molecular techniques. This strain, named
B. ...cereus SPV, was found to be capable of using a wide range of carbon sources including glucose, fructose, sucrose, various fatty acids and gluconate for the production of PHAs, an advantage for the commercial production of the polymers. The media used for the polymer production was novel in the context of the genus
Bacillus. The PHA, once produced, was found to remain at a constant maximal concentration, without any degradation, a great advantage for the commercial production of the PHAs. This particular strain of
Bacillus spp. was able to synthesize various PHAs with 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV) and 4-hydroxybutyrate (4HB)-like monomer units from structurally unrelated carbon sources such as fructose, sucrose and gluconate. This is the first report of the incorporation of a 4HB related monomer containing PHA by the genus
Bacillus and from structurally unrelated carbon sources. The PHAs isolated had molecular weights ranging between (0.4 and 0.8)
×
10
6 and low polydispersity index values (
M
W/
M
N) ranging from 2.6 to 3.4.
The nucleotide sequence reported in this paper will appear in the GenBank nucleotide sequence database under accession numbers
DQ177461
and
DQ177462
.
Chitosan hydrolysis by chitosanase is one of the most effective methods to produce chitosan oligosaccharides. One of the prerequisites of enzyme fermentation production is to select and breed ...enzyme-producing cells with good performance. So in the process of fermentation production, the low yield of chitosanase cannot meet the current requirement. In this paper, a strain producing chitosanase was screened and identified, and a novel mutagenesis system (Atmospheric and Room Temperature Plasma (ARTP)) was selected to increase the yield of chitosanase. Then, the fermentation medium was optimized to further improve the enzyme activity of the strain. A strain of Bacillus cereus capable of producing chitosanase was screened and identified from soil samples. A mutant strain of B.cereus was obtained by Atmospheric and Room Temperature Plasma mutagenesis and bioscreening method, and chitosanase activity was 2.49 folds that of the original bacterium. After an optimized fermentation medium, the enzyme activity of the mutant strain was 1.47 folds that of the original bacterium. Combined with all the above optimization experiments, the enzyme activity of mutant strain increased by 3.66 times. The results showed that the Atmospheric and Room Temperature Plasma mutagenesis and bioscreening method could significantly increase the yield of chitosanase in B.cereus, and had little effect on the properties of the enzyme. These findings have potential applications in the mutagenesis of other enzyme-producing microorganisms.
Psychrotrophic strains of the foodborne pathogen Bacillus cereus can multiply during the refrigerated storage of food products. The aim of this study was to determine the impact of anaerobiosis on ...the growth of two psychrotrophic B. cereus strains exposed to acidic pH at a cold temperature in a laboratory medium. At 10 °C, growth occurred at pH values equal to or higher than 5.7 during anaerobiosis, whereas aerobic growth was observed from pH 5.4. Growth rates during aerobiosis were similar at pH 5.4 and pH 7. No growth was observed for the two tested strains at 8 °C without oxygen regardless of the pH; however, both strains grew at this temperature from pH 5.4 in the presence of oxygen. These pH growth limits in aerobiosis are consistent with those reported for different strains and different foods or media, but no other studies have described anaerobic growth at acidic pH values. The maximal B. cereus concentration was approximately 6.0 log10 CFU/ml for cultures in the absence of oxygen and approximately 8.0 log10 CFU/ml for cultures in the presence of oxygen. In conclusion, we found that the combination of anaerobiosis, pH < 5.7 at 10 °C, or anaerobiosis and temperatures ≤8 °C prevent psychrotrophic B. cereus growth.
•Bacillus cereus did not grow at or below 8 °C in anaerobiosis.•B. cereus did not grow below pH 5.7 at 10 °C in anaerobiosis.•B. cereus grew at 8 °C from pH 5.4 in aerobiosis.•B. cereus Nmax in anaerobiosis were approx. 2 log10 below those with oxygen.•Combination of anaerobiosis, low pH and low temperature reduces B. cereus growth.
An endophytic bacterium was isolated from the Chinese medicinal plant Artemisia annua L. The phylogenetic and physiological characterization indicated that the isolate, strain SZ-1, was Bacillus ...cereus. The endophyte could produce an exopolysaccharide (EPS) at 46 mg/L. The 1,1-diphenyl-2-picrylhydracyl (DPPH) radical scavenging activity of the EPS reached more than 50% at 3-5 mg/mL. The EPS was also effective in scavenging superoxide radical in a concentration dependent fashion with an EC50 value of 2.6 mg/mL. The corresponding EC50 for scavenging hydroxyl radical was 3.1 mg/mL. Moreover, phenanthroline-copper complex-mediated chemiluminescent emission of DNA damage was both inhibited and delayed by EPS. The EPS at 0.7-1.7 mg/mL also protected supercoiled DNA strands in plasmid pBR322 against scission induced by Fenton-mediated hydroxyl radical. The preincubation of PC12 cells with the EPS prior to H₂O₂ exposure increased the cell survival and glutathione (GSH) level and catalase (CAT) activities, and decreased the level of malondialdehyde (MDA) and lactate dehydrogenase (LDH) activity in a dose-dependent manner, suggesting a pronounced protective effect against H₂O₂-induced cytotoxicity. Our study indicated that the EPS could be useful for preventing oxidative DNA damage and cellular oxidation in pharmaceutical and food industries.
Purpose
Electroplating industries are the main sources of heavy metals, chromium, nickel, lead, zinc, cadmium and copper. The highest concentrations of chromium (VI) in the effluent cause a direct ...hazards to human and animals. Therefore, there is a need of an effective and affordable biotechnological solution for removal of chromium from electroplating effluent.
Methods
Bacterial strains were isolated from electroplating effluent to find out higher tolerant isolate against chromate. The isolate was identified by 16S rDNA sequence analysis. Absorbed chromium level of bacterium was determined by inductively coupled plasma-atomic emission spectrometer (ICP-AES), atomic absorption spectrophotometer (AAS), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive X-ray analysis (EDX). Removal of metals by bacterium from the electroplating effluent eventually led to the detoxification of effluent confirmed by MTT assay. Conformational changes of functional groups of bacterial cell surface were studied through Fourier transform infrared spectroscopy.
Results
The chromate tolerant isolate was identified as
Bacillus cereus
. Bacterium has potency to remove more than 75% of chromium as measured by ICP-AES and AAS. The study indicated the accumulation of chromium (VI) on bacterial cell surface which was confirmed by the SEM-EDX and TEM analysis. The biosorption of metals from the electroplating effluent eventually led to the detoxification of effluent. The increased survivability of Huh7 cells cultured with treated effluent also confirmed the detoxification as examined by MTT assay.
Conclusion
Isolated strain
B
.
cereus
was able to remove and detoxify chromium (VI). It would be an efficient tool of the biotechnological approach in mitigating the heavy metal pollutants.
Eight new pairs of PCR primers were designed and efficiently detect eight toxin genes (
hblC,
hblD,
hblA,
nheA,
nheB,
nheC,
cytK, and
entFM) in 411
B. cereus strains (121 food- and 290 soil isolates) ...and 205
B. thuringiensis strains (43 serovars, 10 food- and 152 soil isolates). According to the presence of these eight toxin genes, they were divided into four groups among the total 616 isolates. In Group I, all eight genes occurred simultaneously in 403 (65.42%) isolates, while Group II (134 isolates or 21.75%) and Group III (46 isolates or 7.47%) were devoid of
hblCDA and
cytK, respectively. In Group IV, there were thirty-three isolates which lacked both
hblCDA and
cytK. The presence of
hblCDA in
B. thuringiensis strains (86.80%) was significantly higher (
P
<
0.05) than in
B. cereus strains (66.18%) whereas no significant difference in
nheABC,
cytK and
entFM occurrence was detected between both bacterial groups. Both
nheABC and
entFM genes were found in all
B. cereus and
B. thuringiensis strains (616 strains in total), while the
cytK gene could be detected in 365 (88.80%) of the
B. cereus and 172 (83.90%) of the
B. thuringiensis strains. None of the 616 tested strains showed the presence of only a single or two genes in either the
hbl or
nhe operons. The eight primer pairs designed for this multiplex PCR allowed rapid detection of eight toxin genes from boiled cells with high sensitivity, gave 100% reproducibility, and did not cross-react to 32 other bacterial strains.
A new strain SWH-15 was successfully isolated after initial electrokinetic remediation experiment using the same saline soil sampled from Shengli Oilfield, China. Four methods (morphological and ...biochemical characteristics, whole-cell fatty acid methyl esters (FAMEs) analysis, 16S rRNA sequence analysis and DNA G + C content and DNA–DNA hybridization analysis) were used to identify the taxonomic status of SWH-15 and confirmed that SWH-15 was a novel species of the
Bacillus (B.) cereus
group. Then, we assessed the degrading ability of the novel strain SWH-15 to crude oil through a microcosm experiment with four treatments, including control (CK), bioremediation using SWH-15 (Bio), electrokinetic remediation (EK), and combined bioremediation and electrokinetic remediation (Bio + EK). The results showed that the Bio + EK combined remediation treatment was more effective than the CK, Bio, and EK treatments in degrading crude oil contaminants. Bioaugmentation, by addition of the strain SWH-15 had synergistic effect with EK in Bio + EK treatment. Bacterial community analysis showed that electrokinetic remediation alone significantly altered the bacterial community of the saline soil. The addition of the strain SWH-15 alone had a weak effect on the bacterial community. However, the strain SWH-15 boosted the growth of other bacterial species in the metabolic network and weakened the impact of electrical field on the whole bacterial community structure in the Bio + EK treatment.
Bacillus cereus strain CPT56D‐587‐MTF (CPTF) was isolated from the highly contaminated Oak Ridge Reservation (ORR) subsurface. This site is contaminated with high levels of nitric acid and multiple ...heavy metals. Amplicon sequencing of the 16S rRNA genes (V4 region) in sediment from this area revealed an amplicon sequence variant (ASV) with 100% identity to the CPTF 16S rRNA sequence. Notably, this CPTF‐matching ASV had the highest relative abundance in this community survey, with a median relative abundance of 3.77% and comprised 20%–40% of reads in some samples. Pangenomic analysis revealed that strain CPTF has expanded genomic content compared to other B. cereus species—largely due to plasmid acquisition and expansion of transposable elements. This suggests that these features are important for rapid adaptation to native environmental stressors. We connected genotype to phenotype in the context of the unique geochemistry of the site. These analyses revealed that certain genes (e.g. nitrate reductase, heavy metal efflux pumps) that allow this strain to successfully occupy the geochemically heterogenous microniches of its native site are characteristic of the B. cereus species while others such as acid tolerance are mobile genetic element associated and are generally unique to strain CPTF.
In this study, a halotolerant strain was isolated from high salinity leachate and identified as Bacillus cereus NT‐3. It can produce a high concentration of polyhydroxyalkanoates (PHAs) with no ...significant changes when NaCl concentration is up to 50 g/L. FTIR and NMR spectra of PHAs synthesized by Bacillus cereus NT‐3 were similar to the standard or previous results. Effluent from acidogenic fermentation of food waste and pure volatile fatty acids (VFAs) mixture was used as carbon source to check the effect of non‐VFAs compounds of the effluent on PHAs production. The maximum PHAs production was 0.42 g/L for effluent fermentation, whereas it was 0.34 g/L for pure VFAs fermentation, indicating that bacteria could use actual effluent in a better way. Furthermore, a mathematical model was established for describing kinetic behavior of bacteria using different carbon sources. These results provided a promising approach for PHAs biosynthesis with a low‐cost carbon source.
A halotolerant strain (Bacillus cereus NT‐3) isolated from high salinity leachate could produce high concentration of polyhydroxyalkanoates (PHAs) with NaCl concentration below 50 g/L. The CDW and PHAs production were a little higher in the substrate with actual VFAs effluent as carbon source compared with that in simulated VFAs medium.
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