RESUMO
Bacillus cereus is considered the most potent bacterial strain in terms of the increment in induced proteins during thermal treatment at 52 °C for 90 min. Protein production in food-born microorganism (Bacillus cereus) recovered from contaminated food was investigated in response to heat shock treatment. Bacterial tolerance towards pH, salinity, and temperature at various levels was also investigated. Heat-shock proteins (HSPs) produced when exposed to 52 °C for up to 60 minutes led to significant differences (30%) above the untreated control (37 °C), and the maximum difference was recorded at 52°C at 90 minutes. ISSR detected a higher number of bands/primer than RAPD (13.7 vs. 12.7, respectively), and more polymorphic bands (10.7 vs. 8.4 bands/primer, respectively). The untreated bacterial strain did not grow at pH levels lower than 3, whereas the thermally treated strain grew significantly at pH two. A consistent increase in HSPs was observed, with a gradual increase in salinity of less than 16%. Surprisingly, the gradual increase in temperature did not induce tolerance against higher temperatures. However, a significant growth rate was noticed in response to heat-shocked treatments. The untreated Bacillus cereus demonstrated antibiotic resistance to gentamycin and clindamycin (1.54 and 1.65 cm, respectively), much lower than the corresponding inhibition areas with preheat-treated test pathogen which were recorded (2.37 and 2.49 cm, respectively).
Assuntos
Bacillus cereus , Temperatura Alta , Bacillus cereus/genética , Técnica de Amplificação ao Acaso de DNA Polimórfico , Temperatura , Estresse Fisiológico , Genômica , Concentração de Íons de HidrogênioRESUMO
Bacillus cereus is considered the most potent bacterial strain in terms of the increment in induced proteins during thermal treatment at 52 °C for 90 min. Protein production in food-born microorganism (Bacillus cereus) recovered from contaminated food was investigated in response to heat shock treatment. Bacterial tolerance towards pH, salinity, and temperature at various levels was also investigated. Heat-shock proteins (HSPs) produced when exposed to 52 °C for up to 60 minutes led to significant differences (30%) above the untreated control (37 °C), and the maximum difference was recorded at 52°C at 90 minutes. ISSR detected a higher number of bands/primer than RAPD (13.7 vs. 12.7, respectively), and more polymorphic bands (10.7 vs. 8.4 bands/primer, respectively). The untreated bacterial strain did not grow at pH levels lower than 3, whereas the thermally treated strain grew significantly at pH two. A consistent increase in HSPs was observed, with a gradual increase in salinity of less than 16%. Surprisingly, the gradual increase in temperature did not induce tolerance against higher temperatures. However, a significant growth rate was noticed in response to heat-shocked treatments. The untreated Bacillus cereus demonstrated antibiotic resistance to gentamycin and clindamycin (1.54 and 1.65 cm, respectively), much lower than the corresponding inhibition areas with preheat-treated test pathogen which were recorded (2.37 and 2.49 cm, respectively).
Bacillus cereus é considerada a cepa bacteriana mais potente em termos de incremento de proteínas induzidas durante o tratamento térmico a 52 °C por 90 min. A produção de proteínas em microorganismos de origem alimentar (Bacillus cereus) recuperados de alimentos contaminados foi investigada em resposta ao tratamento de choque térmico. A tolerância bacteriana ao pH, salinidade e temperatura em vários níveis também foram investigadas. Proteínas de choque térmico (HSPs) produzidas quando expostas a 52 °C por até 60 minutos levaram a diferenças significativas (30%) acima do controle não tratado (37 °C), e a diferença máxima foi registrada a 52 °C em 90 minutos . O ISSR detectou um maior número de bandas/iniciador do que o RAPD (13,7 vs. 12,7, respectivamente) e mais bandas polimórficas (10,7 vs. 8,4 bandas/iniciador, respectivamente). A cepa bacteriana não tratada não cresceu em níveis de pH abaixo de 3, enquanto a cepa tratada termicamente cresceu significativamente em pH dois. Observou-se aumento consistente de HSPs, com aumento gradual da salinidade inferior a 16%. Surpreendentemente, o aumento gradual da temperatura não induziu tolerância a temperaturas mais altas. No entanto, uma taxa de crescimento significativa foi observada em resposta aos tratamentos de choque térmico. O Bacillus cereus não tratado demonstrou resistência antibiótica à gentamicina e clindamicina (1,54 e 1,65 cm, respectivamente), muito menor do que as áreas de inibição correspondentes com patógeno de teste pré-tratado que foram registradas (2,37 e 2,49 cm, respectivamente).