Moléculas sinalizadoras de quorum sensing em biofilmes formados por bactérias psicrotróficas isoladas de leite

• Autor(a) principal: Viana, Eliseth de Souza
• Data de Publicação: 2006
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1555
• topic: Bactérias psicrotróficas; Biofilme; Quorum sensing; Leite; Psychrotrophic bacteria; Biofilm; Quorum sensing; Milk; CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::CIENCIA DE ALIMENTOS::MICROBIOLOGIA DE ALIMENTOS

This study aimed to evaluate the effect of different culture media on biofilm formation and proteolytic activity of sessile and planktonic cells of psychrotrophic bacteria isolated from cooled milk; to detect the presence of quorum sensing signaling molecules produced by these isolates and to evaluate the effects of furanones and acyl homoserines lactones (AHLs) on biofilm formation. The growth of Pseudomonas fluorescens was evaluated in polystyrene microplates containg different culture media. The proteolytic activity was determined using azocasein as substrate. The monitor strains Chromobacterium violaceum CV026, Agrobacterium tumefaciens A136, WCF47 and KYC55 and Escherichia coli pSB403 were used to study the production of quorum sensing signaling molecules produced by sessile and planktonic cells in agar diffusion assays and in thin layer chromatography (TLC). The effects of furanones and AHLs in biofilm formation were evaluated by spectrophotometry and scanning electronic microscopy. It was verified that complex media favored growth, but not biofilm formation by P. fluorescens strains. The salts minimal media MMS containing glycerol as carbon source enhanced biofilm formation by P. fluorescens in microplates and in stainless steel coupons and the strains 097, 0109, 0137 had higher numbers of sessile cells. Hafnia alvei 067, 071 and Aeromonas hydrophila 099 also adhered to coupons of stainless steel immersed in MMS, indicating the potential for these isolates to form biofilms. In MMS, the proteolytic activity of P. fluorescens 097 increased with the increase in viable cell number. The proteolytic activity was favored in tryptone yeast extract and phosphate media TYEP added with CaCl2. The evidence for quorum sensing signaling molecules production in P. fluorescens 097 was obtained by reduction of violacein production by C. violaceum and β-gal production by A. tumefaciens WCF47 in the presence of sessile cells and extracts from these cells. However, the presence of signaling molecules was not confirmed by TLC. The production of AHL was detected in biofims of H. alvei 059, 067, 071 and A. hydrophila 099, being A. tumefaciens WCF47 the monitor strain most sensible to AHLs. The extracts obtained from planktonic cells supernatants of H. alvei 071 induced positive responses in the monitors E. coli pSB403 and A. tumefaciens WCF47 in agar diffusion assays and in TLC. A significant difference was verified in the inhibition of biofilm formation by H. alvei 071 in the presence of furanones and scanning electronic microscopy images confirmed this result. The addition of AHLs did not affect the biofilm formation in the strains evaluated. The detection of signaling molecules produced by sessile cells of H. alvei strains and the inhibitory effect of furanones suggest that quorum sensing influences the regulation of these structures. These results contributed to better understand the mechanisms involved in the regulation of biofilm formation by bacteria isolated from milk and it can also contribute to propose new strategies to prevent and control biofilm formation.