RESUMO
Aureocin A70 is a four-component bacteriocin produced by Staphylococcus aureus A70. Its locus encompasses three transcriptional units coding for: (i) structural peptides (aurABCD), (ii) an ABC transporter (aurT) and (iii) the dedicated immunity protein and a putative transcriptional regulator (aurRI). The data provided here showed that AurR is an HTH-containing protein that reduces aureocin A70 production on solid medium, but not in broth. AurR seems to work similarly to LtnR and CylR2, repressors of lantibiotics lacticin 3147 and cytolysin, respectively. At least two other factors play a role in aureocin A70 production: (i) the alternative σ(B) factor, as σ(B)-defective cells produce more bacteriocin than the restored σ(B+) cells, and (ii) the Ï11 regulator cI, since a lysogenic strain for Ï11 exhibited a significant reduction in aureocin A70 production on solid medium when compared with the non-lysogenic isogenic strain. Full aeration and ROS generation abolished the effect of the phage regulators on aureocin A70 production. Interestingly, the Ï11 regulator cI seems to cooperate with AurR to abolish aureocin A70 production. This study therefore represents the first report showing that phage regulators may play a role in regulation of bacteriocin production.
Assuntos
Bacteriocinas/biossíntese , Regulação Bacteriana da Expressão Gênica , Staphylococcus aureus/metabolismo , Fatores de Transcrição/metabolismo , Proteínas Virais/metabolismo , Lisogenia , Fagos de StaphylococcusRESUMO
Aureocin A53 is an antimicrobial peptide produced by Staphylococcus aureus A53. The genetic determinants involved in aureocin A53 production and immunity to its action are organized in at least four transcriptional units encoded by the 10.4-kb plasmid pRJ9. One transcriptional unit carries only the bacteriocin structural gene, aucA. No immunity gene is found downstream of aucA, as part of the same transcriptional unit. Further downstream of aucA is found an operon which contains the three genes aucEFG, whose products seem to associate to form a dedicated ABC transporter. When aucEFG were expressed in RN4220, an aureocin A53-sensitive S. aureus strain, this strain became partially resistant to the bacteriocin. A gene disruption mutant in aucE was defective in aureocin A53 externalization and more sensitive to aureocin A53 than the wild-type strain, showing that aucEFG are involved in immunity to aureocin A53 by active extrusion of the bacteriocin. Full resistance to aureocin A53 was exhibited by transformants carrying, besides aucEFG, the operon formed by two genes, aucIB and aucIA, located between aucA and aucEFG and carried in the opposite strand. AucIA and AucIB share similarities with hypothetical proteins not found in the gene clusters of other bacteriocins. A gene disruption mutant in orf8, located upstream of aucA and whose product exhibits about 50% similarity to a number of hypothetical membrane proteins found in many Gram-positive bacteria, was strongly affected in aureocin A53 externalization but resistant to aureocin A53, suggesting that Orf8 is also involved in aureocin A53 secretion.
Assuntos
Bacteriocinas/genética , Bacteriocinas/metabolismo , Genes Bacterianos , Peptídeos/genética , Peptídeos/metabolismo , Staphylococcus aureus/genética , Transportadores de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/metabolismo , Peptídeos Catiônicos Antimicrobianos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Bacteriocinas/química , Bacteriocinas/farmacologia , Sequência de Bases , Escherichia coli/efeitos dos fármacos , Expressão Gênica , Mutação , Fases de Leitura Aberta , Óperon , Peptídeos/imunologia , Peptídeos/farmacologia , Análise de Sequência de DNA , Staphylococcus aureus/metabolismoRESUMO
O objetivo deste trabalho consistiu na investigação da produção de substâncias antimicrobianas por estirpes de Bacillus, isoladas de frutas, e verificar o potencial dessas substâncias na inibição de patógenos, associados à deterioração ou à transmissão de doenças por alimentos, como fungos e bactérias Gram-negativas ou Gram-positivas. Dez estirpes submetidas à coloração de Gram que mostraram ser bacilos foram testadas quanto à produção de substâncias antimicrobianas, utilizando-se como indicadoras diferentes bactérias Gram-positivas e Gram-negativas. Três estirpes, denominadas de Ame3, Mam1 e Pes1 apresentaram os maiores espectros de ação contra bactérias Gram-positivas, sugerindo que as substâncias produzidas por essas estirpes possam apresentar potencial de aplicação como biopreservativo de alimentos.Dez estirpes submetidas à coloração de Gram que mostraram ser bacilos foram testadas quanto à produção de substâncias antimicrobianas, utilizando-se como indicadoras diferentes bactérias Gram-positivas e Gram-negativas. Três estirpes, denominadas de Ame3, Mam1 e Pes1 apresentaram os maiores espectros de ação contra bactérias Gram-positivas, sugerindo que as substâncias produzidas por essas estirpes possam apresentar potencial de aplicação como biopreservativo de alimentos. Dez estirpes submetidas à coloração de Gram que mostraram ser bacilos foram testadas quanto à produção de substâncias antimicrobianas, utilizando-se como indicadoras diferentes bactérias Gram-positivas e Gram-negativas. Três estirpes, denominadas de Ame3, Mam1 e Pes1 apresentaram os maiores espectros de ação contra bactérias Gram-positivas, sugerindo que as substâncias produzidas por essas estirpes possam apresentar potencial de aplicação como biopreservativo de alimentos.
Assuntos
Antibacterianos , Microbiologia de Alimentos , Conservação de Alimentos , Tecnologia de Alimentos , FrutasRESUMO
In the present study, 31 coliform strains were isolated from salad, cheese, and meat products sold in commercial establishments in Rio de Janeiro city, and were tested for antibiotic resistance and antimicrobial substance production. Thirteen strains (41.9%) were resistant to at least one antibiotic tested, among which one presented resistance to nine different antibiotics. Two strains (6.4%) exhibited inhibitory activity against the indicator strains, Escherichia coli LMIFRJ and Salmonella enterica I. The antimicrobial substances that they produced were sensitive to proteolytic enzymes, suggesting that they might be bacteriocins. The producer strains were identified as Klebsiella ozaenae and Raoultella terrigena. Although they had similar spectrums of action, the bacteriocins were shown to be different. Both of them were able to inhibit E. coli, Klebsiella, Enterobacter, and Salmonella strains, including antibiotic-resistant ones. Our results suggest that these bacteriocins, named klebicin K and raoultellin L, could have potential use against some foodborne pathogens.
