The foodborne pathogen Bacillus (B.) cereus is a common contaminant in spices and herbs. To further characterise B. cereus and its closely related group members present in spices and herbs, we ...analysed presumptive B. cereus strains isolated from six different condiments with view to B. cereus group species, phylogenetic affiliation and toxinogenic potential.
Of a total of 59 isolates 44 were identified as B. cereus sensu stricto (s.s.), four as B. toyonensis-like, five as B. thuringiensis, one as B. weihenstephanensis, two as B. pseudomycoides/B. mycoides and three as undefined B. cereus group species. A maximum of three different species occurred simultaneously in the same spice sample. The isolates comprised 33 multilocus (ML) sequence types (STs), which can be assigned to three different phylogenetic groups. Except two B. pseudomycoides/B. mycoides strains, all isolates were able to produce enterotoxins and one strain the emetic toxin cereulide as detected by an immunoassay and LC-MS, respectively. The prevalence of toxin genes was 96.6% for nheA, 94.9% for hblD, 50.8% for cytK-2 and 1.7% for ces. The emetic strain was characterised by ST 869, which for the first time was assigned to an emetic B. cereus (s.s.) strain and is not part of the previously known two emetic MLST clusters.
Our results demonstrate that not only B. cereus (s.s.) but also toxin producing B. thuringiensis, B. weihenstephanensis and B. toyonensis-like strains could be detected in condiments. For some isolates MLST revealed disagreements between phylogenetic relationship and the classification as B. weihenstephanensis and B. mycoides based on previously described species markers.
•Different B. cereus group species occur simultaneously in condiments.•Prevalence of toxin genes was 96.6% nheA, 94.9% hblD, 50.8% cytK-2 and 1.7% ces.•ST 869 was for the first time assigned to an emetic B. cereus (s.s.) strain.•MLST revealed disagreements between phylogenetic relationships and species markers.
Numerous studies examined the antimicrobial effects of spice and herb extracts, whereas little is known about the effects of dry condiments on the survival of microorganisms. This study investigated ...the impact of dried condiments on the survival of Bacillus cereus and B. thuringiensis spores as well as Staphylococcus aureus cells. In addition, the survival variability between different strains was evaluated. Condiments (allspice, basil, cinnamon, nutmeg, oregano, paprika, parsley and pepper) were artificially contaminated by a dry spiking method using sand as carrier matrix and as control. The results show that counts of B. cereus and B. thuringiensis spores (initial spore count 5.6 ± 0.2 log10 cfu/g and 6.7 ± 0.1 log10 cfu/g, respectively) did not decline significantly in all condiments over a period of 50 weeks. In contrast, in some of the spiked test materials, cell counts of S. aureus (initial cell count 8.1 ± 0.5 log10 cfu/g) were reduced below the detection limit of 10 cfu/g within 10 weeks of storage. D values for S. aureus ranged between 5 and 31 days depending on the strain, condiment and initial contamination level. In conclusion, dried condiments may not affect the survival of spores but can significantly affect the survival of non-spore forming bacteria. As strain variability can occur, tenacity studies should be conducted including a variety of strains.
•B. cereus spore counts did not decline significantly over 50 weeks in condiments.•S. aureus counts declined below the detection limit after 5 to more than 20 weeks.•Matrix effects could be found for S. aureus, but not for Bacillus strains.•Some differences between the four tested S. aureus strains could be detected.
Cadmium (Cd) and lead (Pb) have become serious soil contaminants in China. In this work, we immobilized B. thuringiensis HM-311 (a heavy metal resistant strain) using vinegar residue biochar and ...hydroxyapatite (HAP) to form BtHM-311@HAP@biochar calcium alginate beads. In aqueous solution, the beads respectively reduced 1000 mg/L Pb2+ to 14.59 mg/L and 200 mg/L Cd2+ to 5.40 mg/L within 20 h. Furthermore, the results of pot experiment showed that the BtHM-311@HAP@biochar beads reduced the bioavailability of Pb and Cd in soil. The accumulation of Pb2+ in rice decreased by 39.97% in shoots and 46.40% in roots, while that of Cd2+ decreased by 34.59 and 44.9%, respectively. Similarly, the accumulation of Pb2+ in corn decreased by 40.86% in shoots and 51.34% in roots, while that of Cd2+ decreased by 41.28 and 42.91%, respectively. The beads also increased the microbial community diversity in the rhizosphere soil. These findings indicate that BtHM-311@HAP@biochar beads may be applicable for the bioremediation of Cd- and Pb-contaminated farmland soil.
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•A heavy metal resistant BtHM-311 strain was used to form BtHM-311@HAP@biochar beads.•The beads reduced the bioavailability of Pb and Cd in soil and promoted crop growth.•The beads increased the microbial community diversity in the rhizosphere soil.
A novel alkaline thermostable phosphatidylcholine-specific phospholipase C (PC-PLCBt) was expressed in E. coli system. Recombinant PC-PLCBt (rPC-PLCBt) activity and thermostability were shown to be ...significantly dependent on the Zn2+. The maximum rPC-PLCBt catalytic activity was found to be 1372 U mg-1 in the presence of 0.1 mM Zn2+ and at 60 °C using an Egg PC as substrate. The interfacial kinetic data show that nPC-PLCBt and rPC-PLCBt display similar substrate specificity on various phospholipid monolayers. The maximal rPC-PLCBt activities were recorded, at decreasing order, on 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dilauroyl-sn-glycero-3-phosphoethanolamine (DLPE), 1,2-diacyl-sn-phosphoglycerol (PG), and 1,2-diacyl-sn-phosphoserine (PS) monolayers at interfacial surface pressures of 15, 25, 20, and 25 mN m-1, respectively. Such important penetrating power could be exploited for pharmacological purposes. The highest activities were recorded on the DLPC monolayer and shown to be 121.61 and 40.13 mmol cm-2 min-1 M-1 for native and recombinant PC-PLCBt, respectively. Interestingly, compared to all known Bacillus PLCs, both PC-PLCBt forms showed an exclusive capacity to hydrolyze the PG film with a more pronounced rate of hydrolysis for the native form with a specific activity of 58.29 mmol cm-2 min-1 M-1. Therefore, the high enzyme level production of about 14 mg L-1, the thermostability as well as the broad phospholipid specificity of PC-PLCBt represent great potential in the crude oil refining industry.
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B. thuringiensis is a naturally occurring insect pathogen, genetically closely related to the human pathogen B. cereus. Commercial B. thuringiensis biopesticides have a long track record of safe use. ...Still, concerns are raised on the potential for enterotoxin production by biopesticide strains, especially since B. thuringiensis found in salad was a hypothesized cause of a foodborne outbreak in the EU.
This review uses the basic steps of a risk assessment to collect available knowledge relevant to B. thuringiensis biopesticides and their impact on food safety of fresh produce. Subsequently, some directions for effective risk management strategies are provided, reflecting on various aspects that might impact decision-making on the use of B. thuringiensis as a biopesticide.
Phylogenetic studies show that B. thuringiensis biopesticide strains are part of another clade compared to highly pathogenic B. cereus group strains. Although they contain enterotoxin genes, their ability to produce these toxins in the human gastrointestinal tract may be more limited. Furthermore, surveys show that it is unlikely to find elevated levels of B. thuringiensis on ready-to-eat fresh produce, higher than the established action limit of 105 CFU/g for presumptive B. cereus on foods. Finally, the B. cereus diarrheal syndrome is generally mild and self-limiting. Therefore, the use of B. thuringiensis biopesticides is expected to pose a low food safety risk.
The focus of this article is the comprehensive study of the Colorado potato beetle population within potato agro-biocenosis. The research delves into the intricate processes that contribute to the ...formation and bioecological characteristics of this beetle population. The article also delves into a specific strain known as
Beauveria bassiana
VTq-28, which was isolated from the Colorado potato beetle. This strain was subjected to testing both in laboratory settings and in the field, targeting various developmental stages of the Colorado potato beetle. The objective was to evaluate the effectiveness of
Beauveria bassiana
VTq-28 as a biocontrol agent against the beetle. Additionally, the research assessed the insecticidal activity of locally sourced strains of B. thuringiensis against the Colorado potato beetle. This analysis provides insights into the potential of
B. thuringiensis
strains as another avenue for biocontrol. By thoroughly examining the population dynamics, bioecological characteristics, and the potential of specific microbial agents for controlling the Colorado potato beetle, this study contributes to the understanding of pest management strategies within potato agro-biocenosis. The findings have implications for sustainable agricultural practices and the effective control of this economically significant pest.
Spices are widely used all over the world in food preparation to give taste, smell and color as well as to preserve food products. Bacillus cereus is a common contaminant in spices which can cause ...food poisoning due to its toxins. This study focused on determining the presence of B. cereus as well as the toxin profiles of the strains. A total of 203 packaged and unpackaged spice samples were collected during the study. B. cereus prevalence was determined as 31.5%. Also, B. thuringiensis was identified in five samples (2.5%). The prevalence of B. cereus in non-irradiated spices (41.5%) was found significantly higher than the irradiated ones (20.7%) (p < 0.05). Moreover, the isolates were examined for nine toxin genes, and entFM (94%) was found as the most abundant gene, followed by cytK (60%) and hblD (60%) genes. No cesB gene was found in isolates. Among the strains only a B. thurgiensis isolate was found to have eight toxin genes. The results show that B. cereus is a potential public health risk in spices. Considering the possibility of contamination of foods by B. cereus via spices, effective decontamination methods should be applied and precautions should be taken to control growing of B. cereus and forming toxins during food preparation and pre-serving stages.
•Prevalence of B. cereus in spices was 31.5%.•B. thuringiensis was identified in 5 of 203 (2.5%) spice samples.•EntFM (94%), cytK (60%) and hblD (60%) were the most abundant toxin genes.•No cesB gene was found in isolates (0/89).•The contamination in non-irradiated spices was significantly higher (p < 0.05).
•Endophytic strain B. subtilis 26DCryChS produced surfactin, Cry1Ia and proteases.•26DCryChS showed antagonistic activity against aphids and S. nodorum in vitro.•Inoculation by 26DCryChS induced JA- ...and SA- signaling pathways in wheat plants.•26DCryChS promoted defense of plant against S. nodorum and S. graminum.•26DCryChS can be used as the biocontrol agent for plant defense.
The novel recombinant Bacillus subtilis 26DCryChS line that contains the Bacillus thuringiensis B-5351 strain gene Btcry1Ia encoding Cry1Ia toxin is described. B. subtilis 26DCryChS line kept endophytic properties and ability to synthesize lipopeptide surfactin of B. subtilis 26D strain and acquired the capability to produce Cry1Ia protein from B. thuringiensis strain B-5351. Insecticidal activity of lipopeptide-rich fraction of cultural filtrate of B. subtilis 26D strain and B. subtilis 26DCryChS line, which was identical to commercial surfactin, against greenbug Schizaphis graminum Rond was shown for the first time. Furthermore, B. subtilis 26DCryChS as much as original B. subtilis 26D strain inhibited growth of fungal wheat pathogen Stagonospora nodorum Berk. Bas1. Insertion of the gene Btcry1Ia in genome of B. subtilis 26D strain contributed to increase of aphicidal activity of B. subtilis 26DCryChS line against S. graminum as compared with both B. thuringiensis B-5351 and B. subtilis 26D strains.
Bacillus strains under investigation induced transcription of some wheat genes, which participate in systemic resistance (ISR) to S. nodorum and S. graminum. Seed treatment with B. subtilis 26DCryChS line promoted greater resistance of wheat to the pathogen and aphid than B. thuringiensis B-5351 and B. subtilis 26D strains. The recombinant B. subtilis 26DCryChS line stimulated transcriptional activity of wheat genes regulating the SA- and JA-signaling pathways.
Thus, B. subtilis 26DCryChS line kept an ability of the source B. subtilis 26D strain to induce salicylate-dependent genes (Tapr1 and TaPrx) and acquired the capability to stimulate transcription of jasmonate-sensitive genes (TaPI and TaChiI). Recombinant B. subtilis 26DCryChS line could be proposed as a solution for the modern biocontrol agents development.
The efficiency of a novel biomarker (the transcriptional regulator, XRE) was tested and evaluated in differentiating Bacillus thuringiensis from Bacillus cereus group species in environmental and ...spiked samples based on PCR and real-time PCR. Totally 120 strains, representing two bacterial groups, B. cereus group and non-Bacillus sp., were used to evaluate the performance of XRE and crystal protein (cry2, an existing biomarker). Further, three diverse samples (kimbap, lettuce, and spinach) were inoculated with B. thuringiensis and prominent biomarkers XRE and cry2 were used as targets. Direct analysis of the detection results for the pure cultures of B. cereus group wild-types, references and type strains revealed an accuracy rate of 97.5% targeting XRE, and 83.3% targeting cry2. The real-time PCR was constructed with a R2-value of 0.993. For the artificially contaminated samples, a concentration of 103 CFU/g of B. thuringiensis in spiked food samples could be detected using real-time PCR targeting XRE. A good performance was obtained with XRE in discriminating B. thuringiensis from B. cereus groups, as well as detecting B. thuringiensis in spiked food samples with PCR or real-time PCR. Therefore, this real-time PCR targeting XRE can be used as a dependable and promising tool to identify B. thuringiensis in foods.
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