RESUMEN
Certain Bacillus strains are important producers of antimicrobial peptides with great potential for biological control. Antimicrobial peptide production by Bacillus amyloliquefaciens P11 was investigated in the presence of heat-inactivated cells of bacteria and fungi. B. amyloliquefaciens P11 exhibited higher antimicrobial activity in the presence of inactivated cells of Staphylococcus aureus and Aspergillus parasiticus compared to other conditions tested. Expression of essential genes related to biosynthesis of the antimicrobial peptides surfactin (sfp), iturin A (lpa-14 and ituD), subtilosin A (sboA) and fengycin (fenA) was investigated by quantitative real-time PCR (qRT-PCR). The genes lpa-14 and ituD were highly expressed in the presence of S. aureus (inactivated cells), indicating induction of iturin A production by B. amyloliquefaciens P11. The other inducing condition (inactivated cells of A. parasiticus) suppressed expression of lpa-14, but increased expression of ituD. A twofold increase in fenA expression was observed for both conditions, while strong suppression of sboA expression was observed in the presence of inactivated cells of S. aureus. An increase in antimicrobial activity was observed, indicating that synthesis of antimicrobial peptides may be induced by target microorganisms.
Asunto(s)
Péptidos Catiónicos Antimicrobianos/biosíntesis , Aspergillus/química , Bacillus/genética , Bacillus/metabolismo , Proteínas Bacterianas/biosíntesis , Expresión Génica , Staphylococcus aureus/química , Activación TranscripcionalRESUMEN
Temperature and pH are key factors influencing the production of antimicrobial peptides. In this work, qRT-PCR methodology was used to demonstrate the effect of these two variables on sboA (subtilosin A) and ituD (iturin A) expression in Bacillus sp. P11, an isolate from aquatic environment of the Amazon. Bacillus sp. P11 was incubated in BHI broth for 36 h at 30, 37 and 42 °C, and the pH values were 6.0, 7.4 and 8.0. The production of subtilosin A and iturin A was confirmed by mass spectrometry. The sboA expression increased 200-fold when the initial pH was 8.0. In contrast, ituD expression was maximum at pH 6.0. Increased temperature (42 °C) was adverse for both genes, but ituD expression increased at 37 °C. Expression of sboA and ituD was strongly affected by pH and temperature and qRT-PCR proved to be a powerful tool to investigate the potential of Bacillus strains to produce subtilosin A and iturin A.
Asunto(s)
Bacillus/genética , Bacteriocinas/biosíntesis , Regulación Bacteriana de la Expresión Génica/fisiología , Concentración de Iones de Hidrógeno , Péptidos Cíclicos/biosíntesis , Temperatura , Bacillus/crecimiento & desarrollo , Bacillus/metabolismo , Bacteriocinas/genética , Bacteriocinas/aislamiento & purificación , ADN Bacteriano/genética , ADN Complementario/genética , Péptidos Cíclicos/genética , Péptidos Cíclicos/aislamiento & purificación , ARN Bacteriano/biosíntesis , ARN Bacteriano/genética , ARN Mensajero/biosíntesis , ARN Mensajero/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Espectrometría de Masa por Láser de Matriz Asistida de Ionización DesorciónRESUMEN
Com o objetivo de monitorar os resíduos de compostos tóxicos em alimentos, verificou-se a freqüência e os níveis de praguicidas organoclorados (OC) e bifenilas policloradas (PCBs) em amostras de salsichas Hot-Dog, comercializadas na Cidade de Santa Maria, Estado do Rio Grande do Sul (RS) e, compararam-se os valores com aqueles estabelecidos pela Legislação. Para as análises, procedeu-se a extração da gordura das amostras. A partir da purificação desta, obteve-se um extrato do qual se determinaram os resíduos organoclorados por cromatografia gasosa com detector de captura eletrônica (CG - µECD63Ni). Verificou-se que o lindano e o HCB foram os pesticidas que apresentaram as maiores concentrações médias (0,001798ppm e 0,001652ppm, respectivamente). O somatório dos níveis médios dos pesticidas organoclorados detectados foi de 0,015783ppm, sendo que deste total 0,011165ppm pertencia aos metabólitos do DDT. Quanto as bifenilas policloradas, as maiores concentrações médias corresponderam às PCBs 10 (0,001817ppm) e 28 (0,000317ppm). O somatório das PCBs foi de 0,002172ppm. As concentrações de praguicidas organoclorados e PCBs encontradas nas amostras analisadas estavam abaixo dos limites máximos permitidos pela legislação.
