Effect of bacteriocins on the adhesion and protein expression profiling of Staphylococcus aureus

• Autor(a) principal: Pimentel Filho, Natan de Jesus
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1566
• topic: Alimentos - Microbiologia; Biofilme; Proteômica; Bacteriocinas; Staphylococcus aureus; Food - Microbiology; Biofilm; Proteomics; Bacteriocins; Staphylococcus aureus; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::MICROBIOLOGIA AGRICOLA

Staphylococcus aureus is a human opportunistic pathogen responsible for a broad spectrum of infections ranging from food poisoning and superficial skin infections to more serious diseases such as endocarditis, pneumonia, meningitis, sepsis, and toxic shock syndrome. S. aureus is able to adhere to surfaces and form biofilms and, in the food industry, these biofilms may lead to cross-contamination causing risks for food safety. This study aims to evaluate the effect of subinhibitory concentrations of the bacteriocins bovicin HC5 and nisin on the adhesion of S. aureus to polystyrene surface, and by using proteomic approach, the stress response of this pathogen to bovicin HC5. Subinhibitory dosages of the bacteriocins, which did not prevent bacterial growth, reduced cell adhesion probably due to changes in the hydrophobicity of the bacterial cell and polystyrene surfaces. Both surfaces became more hydrophilic and the free energy of adhesion between bacteria and polystyrene surface was thermodynamically unfavorable after treatment with bovicin HC5 and nisin. The transcript levels of genes related to adhesion and quorum sensing mechanism were assessed by RT-qPCR approach, revealing that both bacteriocins affected the expression of icaD, fnbA, and clfB, biofilm associated genes, and also rnaIII, involved in quorum sensing system. Expression of icaD and fnbA was up-regulated by bovicin HC5 and nisin. While clfb expression decreased in the presence of bovicin HC5, the transcript levels of rnaIII enhanced in the presence of nisin. The synthesis profile of cytoplasmatic proteins of S. aureus COL changed in the presence of subinhibitory concentration of bovicin HC5. Synthesis of several proteins involved in amino acids biosynthesis, mainly products of ilv-leu operon, and DNA metabolism, such as DNA polymerase I (PolA), decreased following bovicin HC5 treatment while proteins involved in catabolism (TCA cycle) and chaperones (DnaK, GrpE, GroEL, ClpP, and ClpB) were over-expressed. The synthesis of important regulators (CodY and CcpA) also increased in the presence of the bacteriocin. These results indicate that bovicin HC5 and nisin can reduce bacterial adhesion in polymeric surface, and consequently biofilm establishment, by reducing hydrophobic characteristics of the cell surface and also polystyrene surface. Stress caused by bovicin HC5 in the cell membrane disturbs cell homeostasis leading S. aureus to stop growth, reduce protein synthesis and, at the same time, enhance synthesis of chaperones and enzymes involved in energy-efficient catabolism in attempt to restore its energy and maintain cell homeostasis. These are important information to understand the action of bacteriocins on bacterial adhesion inhibition and also to understand response mechanisms in attempt to reveal new potential targets for pathogen control.