Fisiologia de Bacillus subtilis R14 sob condiÃÃes restrita e irrestrita de oxigÃnio: produÃÃo de compostos bioativos e esporulaÃÃo

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

Several strains of Bacillus subtilis produce lipopeptides, which are amphiphilic compounds with surfactant and antimicrobial activities. Production of lipopeptide, sporulation and competence in B. subtilis are interconnected through a complex array of controlling elements. The aims of this study were to evaluate the activity of B. subtilis R14 against several phytopathogens and to identify conditions that favor the synthesis of lipopeptides or sporulation. Antagonism was evaluated through agar diffusion method against eight phytopathogenic bacteria. Acidovorax avenae subsp. Citrulli, the causal agent of watermelon fruit blotch; Agrobacterium tumefaciens, the causal agent of crown gall; Erwinia amylovora, the causal agent of fire blight of fruit-trees; Pectobacterium carotovorum, the causal agent of soft rot; Ralstonia solanacearum, the causal agent of bacterial wilts tomato and potato; Xanthomonas campestris pv. campestris, the causal agent of black rot of crucifers; Xanthomonas campestris pv. viticola, the causal agent of bacterial canker of grapevine. B. subtilis R14 inhibited the growth of all phytopathogens tested. To identify stimuli that favor the synthesis of lipopeptides and sporulation, the physiology of B. subtilis R14 was investigated in synthetic medium, containing glucose as carbon source and NH4SO4 or NaNO3 as nitrogen sources, under unrestricted and restricted oxygen availability. Growth, production of bioactive compounds and sporulation were followed during cultivations in a 4-liter working-volume batch bioreactor, at temperature and pH regulated at 37ÂC and 7, respectively. In excess-oxygen culture, B. subtilis R14 did not produce bioactive compounds in detectable amounts in any growth phase and sporulated after glucose depletion, reaching 108 CFU/mL. In oxygen-limited culture, sporulation did not occur, but increasing concentration of bioactive compounds was observed during the restricted growth phase. No growth was observed under anaerobiosis

ASSUNTO(S)

esporulaÃÃo fisiologia biosurfactantes substÃncias bioativas quimica dos produtos naturais bacillus subtilis r14

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