Background:Bacillus cereus is an important pathogen that causes human food poisoning,specifically diarrhea and vomiting.B.cereus can also induce mastitis in dairy cows and has a strong survival ability in milk,as it c...Background:Bacillus cereus is an important pathogen that causes human food poisoning,specifically diarrhea and vomiting.B.cereus can also induce mastitis in dairy cows and has a strong survival ability in milk,as it cannot be inactivated by high-temperature short-time pasteurization.Therefore,B.cereus can enter the market through pasteurized milk and other dairy products,imposing enormous hidden dangers on food safety and human health.Results:In this study,B.cereus 2101(BC)was isolated from milk samples of cows with mastitis.BC grew rapidly with strong hemolysis,making it difficult to prevent mastitis and ensure food security.MAC-T cells were treated with BC and/or Lactobacillus rhamnosus GR-1(LGR-1).Pretreatment with LGR-1 protected the integrity of tight junctions and the expression of zonula occludens-1(ZO-1)and occludin destroyed by BC.Furthermore,LGR-1 pretreatment reduced the expression of NOD-like receptor family member pyrin domain-containing protein 3(NLRP3),caspase recruitment and activation domain(ASC),Caspase-1 p20,gasdermin D(GSDMD)p30,inflammatory factors(interleukin(IL)-1βand IL-18),and cell death induced by BC.Moreover,LGR-1 pretreatment reduced NLRP3 inflammasome activity and increased expressions of ZO-1 and occludin induced by lipopolysaccharides(LPS)+ATP stimulation.MAC-T cells were transfected with NLRP3 si RNA or MCC950 and/or treated with BC and/or LGR-1.NLRP3-si RNA transfection and MCC950 attenuated BC-induced NLRP3 inflammasome activity.Expression of inflammatory cytokines and cell death suggested that the inflammatory pathway might play an important role in the induction of the NLRP3 inflammasome by BC and the protection of LGR-1.Conclusions:These results suggest that LGR-1 might be a probiotic alternative to antibiotics and could be administered to prevent mastitis in dairy cows,thus ensuring food security.展开更多
Although biofilm formation may promote growth,biofilms are not always beneficial to their hosts.The biofilm formation characteristics of Bacillus cereus WPySW2 and its changes at different temperatures were studied.Re...Although biofilm formation may promote growth,biofilms are not always beneficial to their hosts.The biofilm formation characteristics of Bacillus cereus WPySW2 and its changes at different temperatures were studied.Results show that B.cereus WPySW2 promoted the growth of Neoporphyra haitanensis(an economically cultivated seaweed)at 20℃ but accelerated algal rot at 28℃.Thicker B.cereus WPySW2 biofilms covered the surface of N.haitanensis thalli at 28℃,which hindered material exchange between the algae and surrounding environment,inhibited algal photosynthesis and respiration,and accelerated algal decay.Compared with planktonic bacteria,mature biofilm cells had lower energy consumption and metabolic levels.The biofilm metabolic characteristics of B.cereus WPySW2 changed significantly with temperature.High temperature accelerated biofilm maturation,which made it thicker and more stable,allowing the bacteria to easily adapt to environmental changes and obtain greater benefits from their host.High temperature did not affect the production or increased the abundance of toxic metabolites,indicating that the negative effects of B.cereus WPySW2 on algae were not caused by toxins.This study shows that increased temperature can transform a harmless bacterium into a detrimental one,demonstrating that temperature may change the ecological function of phycospheric bacteria by affecting their morphology and metabolism.展开更多
Objective:To synthesize the ecofriendly nanoparticles,which is viewed as an alternative to the chemical method which initiated the use of microbes like bacteria and fungi in their synthesis.Methods:The current study u...Objective:To synthesize the ecofriendly nanoparticles,which is viewed as an alternative to the chemical method which initiated the use of microbes like bacteria and fungi in their synthesis.Methods:The current study uses the endophytic bacterium Bacillus cereus isolated from the Garcinia xanthochymus to synthesize the silver nanoparticles(AgNPs).The AgNPs were synthesized by reduction of silver nitrate solution by the endophytic bacterium after incubation for 3-5 d at room temperature.The synthesis was initially observed by colour change from pale white to brown which was confirmed by UV-Vis spectroscopy.The AgNPs were further characterized using FTIR,SEM-EDX and TEM analyses.Results:The synthesized nanoparticles were found to he spherical with the size in the range of 20-40 nm which showed a slight aggregation.The energy-dispersive spectra of the nanoparticle dispersion confirmed the presence of elemental silver.The AgNPs were found to have antibacterial activity against a few pathogenic bacteria like Escherichia coli,Pseudomonas aeruginosa,Staphylococcus aureus,Salmonella typhi and Klebsiella pneumoniae.Conclusions:The endophytic bacteria identified as Bacillus cereus was able to synthesize silver nanoparticles with potential antibacterial activity.展开更多
As a unique ecological system with low temperature and low nutrient levels, glaciers are considered a "living fossil" for the research of evolution. In this work, a lytic cold-active bacteriophage designated...As a unique ecological system with low temperature and low nutrient levels, glaciers are considered a "living fossil" for the research of evolution. In this work, a lytic cold-active bacteriophage designated VMY22 against Bacillus cereus MYB41-22 was isolated from Mingyong Glacier in China, and its characteristics were studied. Electron microscopy revealed that VMY22 has an icosahedral head(59.2 nm in length, 31.9 nm in width) and a tail(43.2 nm in length). Bacteriophage VMY22 was classified as a Podoviridae with an approximate genome size of 18 to 20 kb. A one-step growth curve revealed that the latent and the burst periods were 70 and 70 min, respectively, with an average burst size of 78 bacteriophage particles per infected cell. The pH and thermal stability of bacteriophage VMY22 were also investigated. The maximum stability of the bacteriophage was observed to be at pH 8.0 and it was comparatively stable at p H 5.0–9.0. As VMY22 is a cold-active bacteriophage with low production temperature, its characterization and the relationship between MYB41-22 and Bacillus cereus bacteriophage deserve further study.展开更多
Objective:To investigate the detection and sequencing of plasmid encoded tetracycline resistance genes(tet A and tet B) from food-borne and standard strains of Bacillus cereus(B. cereus).Methods:PCR was carried out to...Objective:To investigate the detection and sequencing of plasmid encoded tetracycline resistance genes(tet A and tet B) from food-borne and standard strains of Bacillus cereus(B. cereus).Methods:PCR was carried out to detect the tetracycline resistance genes(tet A and tet B) in food-borne B.cereus strains and the amplified products were sequenced.Results:The phenotypic resistance against tetracycline was observed in 39 of the 118 food-borne isolates and two reference strains(MTCC 430 and MTCC 1307) of B.cereus.Among the phenotypically resistant isolates,tet A was detected in 36 food-borne isolates and two reference strains(MTCC 430 and MTCC 1307).whereas,tel B was detected in 12 food-bome isolates and MTCC 1307 strain. Conclusions:A close association was therefore found between phenotypic resistance against tetracycline and presence of tetracycline resistance genes.The tet A and tet B gene fragments were amplified,purified and sequenced.The gene sequences of the isolates studied herein were found similar to tetA and tetB gene sequences of other bacteria available in NCBI.The occurrence of tetA and tetB genes in B.cereus indicate the horizontal transfer of antibiotic resistance determinants from other bacteria into B.cereus.The transfer of these resistant determinants to other potentially pathogenic bacteria may be a matter of great concern.展开更多
Bacillus cereus NJSZ-13,an endophytic bacterium with nematicidal activity,was isolated from stems of healthy Pinus elliottii Engelm.Colonization of P.massoniana Lamb.by endophytic B.cereus was studied using scanning e...Bacillus cereus NJSZ-13,an endophytic bacterium with nematicidal activity,was isolated from stems of healthy Pinus elliottii Engelm.Colonization of P.massoniana Lamb.by endophytic B.cereus was studied using scanning electron microscopy and confocal laser scanning microscopy.After the plasmid p GFP78 containing the green fluorescent protein(GFP)gene was transformed into the NJSZ-13 strain,the NJSZ-13:gfp showed the same nematicidal activity and growth curve as the wild-type strain,and the plasmid p GFP78 was stably maintained in strain NJSZ-13 for at least 96 h of bacterial cultivation on medium without antibiotics.After inoculation into Masson pine roots,colonization of the NJSZ-13:gfp strain in plant roots and stems was visualized using confocal laser scanning and the strain was enumerated in inoculated roots and stems.These results suggest that NJSZ-13:gfp is an efficient colonizer of Masson pine and can transfer vertically from roots to stems.展开更多
Objective:To screen the bacteriocinogenic isolate from buffalo milk and to characterize it on physical,chemical and biological aspects for the application in biopreservation.Methods:Bacillus cereus(B.cereus)was isolat...Objective:To screen the bacteriocinogenic isolate from buffalo milk and to characterize it on physical,chemical and biological aspects for the application in biopreservation.Methods:Bacillus cereus(B.cereus)was isolated and assessed for its baceteriocinogenic activity.Bacteriocin was produced and purified by ammonium sulphate precipitation,dialysis and gel filtration chromatography.Purified bacteriocin was used to clieck its antimicrobial activity against food borne bacteria.Effect and stability of bacteripcin was determined with the respect to temperature,pH,enzymes,organic solvents and chemicals.Bacteriocin was also subjected to SDS PAGE analysis to determine its molecular weight.In addition,functional groups exist in the bacteriocin was determined by FTIR analysis.Results:B.cereus was identified by 16S rRNA sequence analysis.Bacteriocin showed increased activity against all the bacteria used and its activity unit was found to be 51,200 AU/mL.It was stable to high temperature(100℃)and wide range of pH(3-10),sensitive to proteolytic enzymes and resistant to nonprotcolytic enzymes.It was low molecular weight(3.5-6 kDa)protein and FTIR study revealed the presence of amide group and NH stretching,Conclusions:Bacteriocin produced in this study possesses the highest antimicrobial activity against both gram positive and gram negative bacteria thereby it has immense application as biopreservative agent.FTIR proved its peptide nature.展开更多
Objective:To isolate marine bacteria,statistically optimize them for maximum asparaginase production.Methods:In the present study,statistically based experimental designs were applied to maximize the production of L-a...Objective:To isolate marine bacteria,statistically optimize them for maximum asparaginase production.Methods:In the present study,statistically based experimental designs were applied to maximize the production of L-asparaginase from bacterial strain of Bacillus cereus（B.cereus） MAB5（HQ675025） isolated and identified by 16S rDNA sequencing from mangroves rhizosphere sediment.Results:Plackett-Barman design was used to identify the interactive effect of the eight variables viz.yeast extract,soyabean meal,glucose,magnesium sulphate,KH<sub>2</sub>PO<sub>4</sub>,wood chips,aspargine and sodium chloride.All the variables are denoted as numerical factors and investigated at two widely spaced intervals designated as -1（low level） and +1（high level）. The effect of individual parameters on L-asparaginase production was calculated.Soyabean meal,aspargine,wood chips and sodium chloride were found to be the significant among eight variables.The maximum amount of L-asparaginase produced（51.54 IU/mL） from the optimized medium containing soyabean meal（6.282 8 g/L）,aspargine（5.5 g/L）,wood chips（1.383 8 g/L） and NaCl（4.535 4 g/L）.Conclusions:The study revealed that,it is useful to produce the maximum amount of L-asparaginase from B.cereus MAB5 for the treatment of various infections and diseases.展开更多
16S rDNA and ERIC(Enterobacteia Repetitive Intergenic Consensus Sequences) based on PCR method were tested for the effectiveness of the differentiation of B.thuringiensis and B.cereus.16S rDNA-PCR primers were designe...16S rDNA and ERIC(Enterobacteia Repetitive Intergenic Consensus Sequences) based on PCR method were tested for the effectiveness of the differentiation of B.thuringiensis and B.cereus.16S rDNA-PCR primers were designed based on the sequence difference in variable regions of B.cereus 16S rDNA and B.thuringiensis 16S rDNA.16S rDNA-PCR showed no obvious difference between B.cereus and B.thuringiensis.The only difference was that one 1600-bp amplificon could be obtained from all the three B.Cereus strains,and none amplificon from any B.thuringiensis strains.ERIC was optimized based on previous reports.The genomic DNA was used for the template of ERIC-PCR,and the following DNA fingerprints were analyzed by the agarose gel electrophoresis.The results showed that DNA fingerprint of three B.thuringiensis strains had a unique amplicon less than 100-bp,while DNA fingerprint of three B.cereus strains had none.Moreover,DNA fingerprint of B.cereus showed a 700-bp amplicon,but didn't have any DNA fingerprints of B.thuringiensis genome.Therefore,ERIC-PCR technique should be able to be used for the differentiation of B.thuringiensis and B.cereus.展开更多
Objective:To study characteristics of phospholipases C(PLCs),their importance for producing microorganisms us well us the potential of their use for industrial purposes.Methods:PLC from Bacillus cereus(B.cereus) D101 ...Objective:To study characteristics of phospholipases C(PLCs),their importance for producing microorganisms us well us the potential of their use for industrial purposes.Methods:PLC from Bacillus cereus(B.cereus) D101 was selected as an example of Gram-positive PLCs and PLC from Pseudomanas aeruginosa(P.aeruginosa) D183 of Gram-negative ones.Enzymes were partially purified by ammonium sulfate precipitation followed by membrane dialysis.Partially purified preparations were used to study effect of different factors on activities as well as in substrate specificity tests which were conducted using a turbidimetric assay method.Results:Maximum activity was at pH 7 and 8 and 40 ℃ for P.aeruginosa PLC,and pH 8-10 and 37 ℃ for B.cereus PLC.Both PLCs were inhibited by Pi at 5 mM or higher,whereas,PLC from B.cereus only was inhibited by EDTA.Activity of P.aeruginosa PLC was not affected by removing Zn^(2+) ions from reaction mixture or their replacement with Ca^(2+),Ba^(2+),Mg^(2+) or Mn^(2+)ions.Vis-a-vis,activity of B.cereus PLC was found to be metal ion dependent PLCs from both isolates were relatively thermostable and showed maximum affinity toward phosphatidylcholine.Sphingomyelin and phosphatidylethanolamine were not good substrates and phosphatidylinositol,phosphatidylserine,phosphatidylglycerol and cardiolipin could be considered nonsubstrates.Conclusions:Human body physiological conditions could favor activity of P.aeruginosa and B.cereus PLCs.These enzymes may participate in phosphate scavenging and virulence of producing isolates but not in autolysis.PLCs from both isolates are potential candidates for industrial use.展开更多
Objective: To investigate the true incidence of Bacillus cereus(B. cereus) in food and children diarrhea cases. Methods: A total of 110 samples of various dairy products such as raw milk, long life pasteurized milk, y...Objective: To investigate the true incidence of Bacillus cereus(B. cereus) in food and children diarrhea cases. Methods: A total of 110 samples of various dairy products such as raw milk, long life pasteurized milk, yoghurt and infant powdered milk formulas, raw rice, and feces were examined for the presence of B. cereus by selective plating on mannitol-egg-yolk-polymyxin agar. Confirmation of B. cereus was carried out by biochemical tests and PCR. Identification of non-B. cereus isolates was carried out by 16 S r DNA sequencing. Antimicrobial susceptibility was done by disk diffusion method.Results: Overall 35 samples(31.8%, n = 110) yielded Bacillus-like growth. Of which 19 samples(54.28%) were positive for B. cereus. All isolates were positive for enterotoxin production. No psychrotolerant B. cereus strains were detected in all samples. All B. cereus isolates were resistant to penicillin G, but susceptible to vancomycin, erythromycin and clindamycin. Conclusions: The results of this study confirm the importance of including B. cereus in disease control and prevention programs, as well as in routine clinical and food quality control laboratories in both Saudi Arabia and Egypt.展开更多
基金the following funds:the National Key R&D Program of China(Project No.2017YFD0502200)the National Natural Science Foundation of China(Project No.31960721)the National Natural Science Foundation of China(Project No.31873034)。
文摘Background:Bacillus cereus is an important pathogen that causes human food poisoning,specifically diarrhea and vomiting.B.cereus can also induce mastitis in dairy cows and has a strong survival ability in milk,as it cannot be inactivated by high-temperature short-time pasteurization.Therefore,B.cereus can enter the market through pasteurized milk and other dairy products,imposing enormous hidden dangers on food safety and human health.Results:In this study,B.cereus 2101(BC)was isolated from milk samples of cows with mastitis.BC grew rapidly with strong hemolysis,making it difficult to prevent mastitis and ensure food security.MAC-T cells were treated with BC and/or Lactobacillus rhamnosus GR-1(LGR-1).Pretreatment with LGR-1 protected the integrity of tight junctions and the expression of zonula occludens-1(ZO-1)and occludin destroyed by BC.Furthermore,LGR-1 pretreatment reduced the expression of NOD-like receptor family member pyrin domain-containing protein 3(NLRP3),caspase recruitment and activation domain(ASC),Caspase-1 p20,gasdermin D(GSDMD)p30,inflammatory factors(interleukin(IL)-1βand IL-18),and cell death induced by BC.Moreover,LGR-1 pretreatment reduced NLRP3 inflammasome activity and increased expressions of ZO-1 and occludin induced by lipopolysaccharides(LPS)+ATP stimulation.MAC-T cells were transfected with NLRP3 si RNA or MCC950 and/or treated with BC and/or LGR-1.NLRP3-si RNA transfection and MCC950 attenuated BC-induced NLRP3 inflammasome activity.Expression of inflammatory cytokines and cell death suggested that the inflammatory pathway might play an important role in the induction of the NLRP3 inflammasome by BC and the protection of LGR-1.Conclusions:These results suggest that LGR-1 might be a probiotic alternative to antibiotics and could be administered to prevent mastitis in dairy cows,thus ensuring food security.
基金Supported by the Zhejiang Province Nature Science Foundation of China(No.LY22C190002)the National Natural Science Foundation of China(Nos.31772871,31872540)+4 种基金the Major Scientific and Technological Project of Zhejiang Province(No.2021C02069-9)the Major Scientific and Technological Project of Ningbo(Nos.2021Z004,2021Z103)the Scientific and Technological Project of Ningbo(No.2021S063)the China Agriculture Research System of MOF and MARAthe K.C.Wong Magna Fund of Ningbo University。
文摘Although biofilm formation may promote growth,biofilms are not always beneficial to their hosts.The biofilm formation characteristics of Bacillus cereus WPySW2 and its changes at different temperatures were studied.Results show that B.cereus WPySW2 promoted the growth of Neoporphyra haitanensis(an economically cultivated seaweed)at 20℃ but accelerated algal rot at 28℃.Thicker B.cereus WPySW2 biofilms covered the surface of N.haitanensis thalli at 28℃,which hindered material exchange between the algae and surrounding environment,inhibited algal photosynthesis and respiration,and accelerated algal decay.Compared with planktonic bacteria,mature biofilm cells had lower energy consumption and metabolic levels.The biofilm metabolic characteristics of B.cereus WPySW2 changed significantly with temperature.High temperature accelerated biofilm maturation,which made it thicker and more stable,allowing the bacteria to easily adapt to environmental changes and obtain greater benefits from their host.High temperature did not affect the production or increased the abundance of toxic metabolites,indicating that the negative effects of B.cereus WPySW2 on algae were not caused by toxins.This study shows that increased temperature can transform a harmless bacterium into a detrimental one,demonstrating that temperature may change the ecological function of phycospheric bacteria by affecting their morphology and metabolism.
文摘Objective:To synthesize the ecofriendly nanoparticles,which is viewed as an alternative to the chemical method which initiated the use of microbes like bacteria and fungi in their synthesis.Methods:The current study uses the endophytic bacterium Bacillus cereus isolated from the Garcinia xanthochymus to synthesize the silver nanoparticles(AgNPs).The AgNPs were synthesized by reduction of silver nitrate solution by the endophytic bacterium after incubation for 3-5 d at room temperature.The synthesis was initially observed by colour change from pale white to brown which was confirmed by UV-Vis spectroscopy.The AgNPs were further characterized using FTIR,SEM-EDX and TEM analyses.Results:The synthesized nanoparticles were found to he spherical with the size in the range of 20-40 nm which showed a slight aggregation.The energy-dispersive spectra of the nanoparticle dispersion confirmed the presence of elemental silver.The AgNPs were found to have antibacterial activity against a few pathogenic bacteria like Escherichia coli,Pseudomonas aeruginosa,Staphylococcus aureus,Salmonella typhi and Klebsiella pneumoniae.Conclusions:The endophytic bacteria identified as Bacillus cereus was able to synthesize silver nanoparticles with potential antibacterial activity.
基金supported by the National Natural Science Foundation of China (31160121)the Yunnan Provincial Education Fund project (2013Z138)funded by the Open Research Fund Program of the State Key Laboratory of Virology of China (2013002)
文摘As a unique ecological system with low temperature and low nutrient levels, glaciers are considered a "living fossil" for the research of evolution. In this work, a lytic cold-active bacteriophage designated VMY22 against Bacillus cereus MYB41-22 was isolated from Mingyong Glacier in China, and its characteristics were studied. Electron microscopy revealed that VMY22 has an icosahedral head(59.2 nm in length, 31.9 nm in width) and a tail(43.2 nm in length). Bacteriophage VMY22 was classified as a Podoviridae with an approximate genome size of 18 to 20 kb. A one-step growth curve revealed that the latent and the burst periods were 70 and 70 min, respectively, with an average burst size of 78 bacteriophage particles per infected cell. The pH and thermal stability of bacteriophage VMY22 were also investigated. The maximum stability of the bacteriophage was observed to be at pH 8.0 and it was comparatively stable at p H 5.0–9.0. As VMY22 is a cold-active bacteriophage with low production temperature, its characterization and the relationship between MYB41-22 and Bacillus cereus bacteriophage deserve further study.
基金Head of Departments of Veterinary Public Health and Animal Biotechology of Guru Angad Dev Veterinary and Animal Sciences University,Ludhiana(India) for providing all the necessary facilities and funds to make this research successfulHead of Departments of Veterinary Public Health (SKUSAT-K) for providing the reference strain of B.cereus(NCTC11143)
文摘Objective:To investigate the detection and sequencing of plasmid encoded tetracycline resistance genes(tet A and tet B) from food-borne and standard strains of Bacillus cereus(B. cereus).Methods:PCR was carried out to detect the tetracycline resistance genes(tet A and tet B) in food-borne B.cereus strains and the amplified products were sequenced.Results:The phenotypic resistance against tetracycline was observed in 39 of the 118 food-borne isolates and two reference strains(MTCC 430 and MTCC 1307) of B.cereus.Among the phenotypically resistant isolates,tet A was detected in 36 food-borne isolates and two reference strains(MTCC 430 and MTCC 1307).whereas,tel B was detected in 12 food-bome isolates and MTCC 1307 strain. Conclusions:A close association was therefore found between phenotypic resistance against tetracycline and presence of tetracycline resistance genes.The tet A and tet B gene fragments were amplified,purified and sequenced.The gene sequences of the isolates studied herein were found similar to tetA and tetB gene sequences of other bacteria available in NCBI.The occurrence of tetA and tetB genes in B.cereus indicate the horizontal transfer of antibiotic resistance determinants from other bacteria into B.cereus.The transfer of these resistant determinants to other potentially pathogenic bacteria may be a matter of great concern.
基金supported by the National Key R&D Program of China[2018YFC1200400]the Nature Science Foundation of the Jiangsu Higher Education Institutions of China[14KJA220002]+1 种基金the Postgraduate Scientific Research and Innovation Program of Jiangsu Province[KYLX16_0859]the National Natural Science Foundation of China[31370643]。
文摘Bacillus cereus NJSZ-13,an endophytic bacterium with nematicidal activity,was isolated from stems of healthy Pinus elliottii Engelm.Colonization of P.massoniana Lamb.by endophytic B.cereus was studied using scanning electron microscopy and confocal laser scanning microscopy.After the plasmid p GFP78 containing the green fluorescent protein(GFP)gene was transformed into the NJSZ-13 strain,the NJSZ-13:gfp showed the same nematicidal activity and growth curve as the wild-type strain,and the plasmid p GFP78 was stably maintained in strain NJSZ-13 for at least 96 h of bacterial cultivation on medium without antibiotics.After inoculation into Masson pine roots,colonization of the NJSZ-13:gfp strain in plant roots and stems was visualized using confocal laser scanning and the strain was enumerated in inoculated roots and stems.These results suggest that NJSZ-13:gfp is an efficient colonizer of Masson pine and can transfer vertically from roots to stems.
基金Managemtent of Vivekananda Educational Inslitulions Tiruchengode, India for their support throughout the project
文摘Objective:To screen the bacteriocinogenic isolate from buffalo milk and to characterize it on physical,chemical and biological aspects for the application in biopreservation.Methods:Bacillus cereus(B.cereus)was isolated and assessed for its baceteriocinogenic activity.Bacteriocin was produced and purified by ammonium sulphate precipitation,dialysis and gel filtration chromatography.Purified bacteriocin was used to clieck its antimicrobial activity against food borne bacteria.Effect and stability of bacteripcin was determined with the respect to temperature,pH,enzymes,organic solvents and chemicals.Bacteriocin was also subjected to SDS PAGE analysis to determine its molecular weight.In addition,functional groups exist in the bacteriocin was determined by FTIR analysis.Results:B.cereus was identified by 16S rRNA sequence analysis.Bacteriocin showed increased activity against all the bacteria used and its activity unit was found to be 51,200 AU/mL.It was stable to high temperature(100℃)and wide range of pH(3-10),sensitive to proteolytic enzymes and resistant to nonprotcolytic enzymes.It was low molecular weight(3.5-6 kDa)protein and FTIR study revealed the presence of amide group and NH stretching,Conclusions:Bacteriocin produced in this study possesses the highest antimicrobial activity against both gram positive and gram negative bacteria thereby it has immense application as biopreservative agent.FTIR proved its peptide nature.
文摘Objective:To isolate marine bacteria,statistically optimize them for maximum asparaginase production.Methods:In the present study,statistically based experimental designs were applied to maximize the production of L-asparaginase from bacterial strain of Bacillus cereus（B.cereus） MAB5（HQ675025） isolated and identified by 16S rDNA sequencing from mangroves rhizosphere sediment.Results:Plackett-Barman design was used to identify the interactive effect of the eight variables viz.yeast extract,soyabean meal,glucose,magnesium sulphate,KH<sub>2</sub>PO<sub>4</sub>,wood chips,aspargine and sodium chloride.All the variables are denoted as numerical factors and investigated at two widely spaced intervals designated as -1（low level） and +1（high level）. The effect of individual parameters on L-asparaginase production was calculated.Soyabean meal,aspargine,wood chips and sodium chloride were found to be the significant among eight variables.The maximum amount of L-asparaginase produced（51.54 IU/mL） from the optimized medium containing soyabean meal（6.282 8 g/L）,aspargine（5.5 g/L）,wood chips（1.383 8 g/L） and NaCl（4.535 4 g/L）.Conclusions:The study revealed that,it is useful to produce the maximum amount of L-asparaginase from B.cereus MAB5 for the treatment of various infections and diseases.
基金Supported by Genetically Modified Organisms Breeding Major Projects (2009ZX08009-031B)State Key Laboratory for Biology of Plant Diseases and Insect Pests Open Fund (DKL2010OP13)
文摘16S rDNA and ERIC(Enterobacteia Repetitive Intergenic Consensus Sequences) based on PCR method were tested for the effectiveness of the differentiation of B.thuringiensis and B.cereus.16S rDNA-PCR primers were designed based on the sequence difference in variable regions of B.cereus 16S rDNA and B.thuringiensis 16S rDNA.16S rDNA-PCR showed no obvious difference between B.cereus and B.thuringiensis.The only difference was that one 1600-bp amplificon could be obtained from all the three B.Cereus strains,and none amplificon from any B.thuringiensis strains.ERIC was optimized based on previous reports.The genomic DNA was used for the template of ERIC-PCR,and the following DNA fingerprints were analyzed by the agarose gel electrophoresis.The results showed that DNA fingerprint of three B.thuringiensis strains had a unique amplicon less than 100-bp,while DNA fingerprint of three B.cereus strains had none.Moreover,DNA fingerprint of B.cereus showed a 700-bp amplicon,but didn't have any DNA fingerprints of B.thuringiensis genome.Therefore,ERIC-PCR technique should be able to be used for the differentiation of B.thuringiensis and B.cereus.
文摘Objective:To study characteristics of phospholipases C(PLCs),their importance for producing microorganisms us well us the potential of their use for industrial purposes.Methods:PLC from Bacillus cereus(B.cereus) D101 was selected as an example of Gram-positive PLCs and PLC from Pseudomanas aeruginosa(P.aeruginosa) D183 of Gram-negative ones.Enzymes were partially purified by ammonium sulfate precipitation followed by membrane dialysis.Partially purified preparations were used to study effect of different factors on activities as well as in substrate specificity tests which were conducted using a turbidimetric assay method.Results:Maximum activity was at pH 7 and 8 and 40 ℃ for P.aeruginosa PLC,and pH 8-10 and 37 ℃ for B.cereus PLC.Both PLCs were inhibited by Pi at 5 mM or higher,whereas,PLC from B.cereus only was inhibited by EDTA.Activity of P.aeruginosa PLC was not affected by removing Zn^(2+) ions from reaction mixture or their replacement with Ca^(2+),Ba^(2+),Mg^(2+) or Mn^(2+)ions.Vis-a-vis,activity of B.cereus PLC was found to be metal ion dependent PLCs from both isolates were relatively thermostable and showed maximum affinity toward phosphatidylcholine.Sphingomyelin and phosphatidylethanolamine were not good substrates and phosphatidylinositol,phosphatidylserine,phosphatidylglycerol and cardiolipin could be considered nonsubstrates.Conclusions:Human body physiological conditions could favor activity of P.aeruginosa and B.cereus PLCs.These enzymes may participate in phosphate scavenging and virulence of producing isolates but not in autolysis.PLCs from both isolates are potential candidates for industrial use.
文摘Objective: To investigate the true incidence of Bacillus cereus(B. cereus) in food and children diarrhea cases. Methods: A total of 110 samples of various dairy products such as raw milk, long life pasteurized milk, yoghurt and infant powdered milk formulas, raw rice, and feces were examined for the presence of B. cereus by selective plating on mannitol-egg-yolk-polymyxin agar. Confirmation of B. cereus was carried out by biochemical tests and PCR. Identification of non-B. cereus isolates was carried out by 16 S r DNA sequencing. Antimicrobial susceptibility was done by disk diffusion method.Results: Overall 35 samples(31.8%, n = 110) yielded Bacillus-like growth. Of which 19 samples(54.28%) were positive for B. cereus. All isolates were positive for enterotoxin production. No psychrotolerant B. cereus strains were detected in all samples. All B. cereus isolates were resistant to penicillin G, but susceptible to vancomycin, erythromycin and clindamycin. Conclusions: The results of this study confirm the importance of including B. cereus in disease control and prevention programs, as well as in routine clinical and food quality control laboratories in both Saudi Arabia and Egypt.
