Antibacterial activity of phytopathogenic Streptomyces strains against bacteria associated to clinical diseases / Atividade antimicrobiana de Streptomyces fitopatogênicas contra bactérias associadas a doenças de importância clínica

The genus Streptomyces is associated with the ability to produce and excrete a variety of bioactive compounds, such as antibiotic, antifungal and antiviral. Biological active polyketide and peptide compounds with applications in medicine, agriculture and biochemical research are synthesized by PKS-I and NRPS genes. The evaluation of the presence of these genes associated with the biosynthesis of secondary metabolites in different phytopathogenic Streptomyces strains were performed using degenerated primers. The positive signal was observed in 58/63 Streptomyces strains for NRPS gene, 43/63 for PKS-I, and for PKS-II all the 63 strains showed positive signal of amplification. These strains also were tested with double layer agar-well technique against bacterial with clinical importance, and it was possible to observe the Streptomyces spp. strains were able to inhibit the growth of 14, 20, 13 and 3 isolates Gram-positive and Gram-negative bacteria, Staphylococcus aureus (ATCC 25923), Bacillus cereus (ATCC 14579), Pseudomonas aeruginosa (ATCC 27853) and Escherichia coli (ATCC 11775) respectively. The Streptomyces sp. strains IBSBF 2019 and IBSBF 2397 showed antibacterial activity against all four bacteria-target tested.(AU)

O gênero Streptomyces apresenta alta capacidade de produzir e excretar uma grande variedade de compostos biologicamente ativos, como antibióticos, antifúngicos e antivirais. Compostos biologicamente ativos de policetídeos e peptídeos com aplicações na medicina, agricultura e pesquisas bioquímicas são sintetizados pelos genes PKS-I e NRPS. A avaliação da presença desses genes associados à biossíntese de metabólitos secundários em diferentes linhagens de Streptomyces fitopatogênicas foi realizada através do uso de primers degenerados. O sinal positivo foi observado em 58/63 linhagens de Streptomyces para o gene NRPS, 43/63 para o gene PKS-I e, para o gene PKS-II, todas as 63 linhagens apesentaram o sinal positivo de amplificação. Essas linhagens também foram testadas através da técnica de dupla camada contra bactérias de importância clínica e foi possível observar que as linhagens de Streptomyces spp. foram capazes de inibir o crescimento de 14, 20, 13 e 3 isolados de bactérias Gram-positivas e Gram-negativas, Staphylococcus aureus (ATCC 25923), Bacillus cereus (ATCC 14579), Pseudomonas aeruginosa (ATCC 27853) e Escherichia coli (ATCC 11775), respectivamente. As linhagens de Streptomyces sp. ISBSF 2019 e 2397 apresentaram atividade antibacteriana contra todas as bactérias-alvo testadas.(AU)

Improved Cultural Conditions for Methionine Accumulation in Submerged Cultivation of Bacillus cereus S8.

Aims: To improve the cultural conditions for enhanced methionine production by Bacillus cereus S8 Study design: Study of the fermentation process in shake flask culture. Place and Duration of Study: Department of Applied Microbiology and Brewing, Nnamdi Azikwe University, Awka, Nigeria between 2011 to 2012. Methodology: The effects of medium/fermenter volume ratio, carbon and nitrogen sources, growth stimulators, vitamins and amino acid on methionine accumulation in the broth culture of Bacillus cereus S8 were investigated. The time course for methionine production was also studied. Results: A 20% medium/fermenter volume ratio improved methionine yield. Glucose and ammonium sulphate at 6.0 and 1.0% respectively stimulated methionine accumulation by Bacillus cereus S8. Yeast extract, peptone, DL-leucine and all vitamins studied enhanced methionine production. A methionine yield of 3.23mg/ml was produced after 96h fermentation and at a pH of 6.90. Conclusion: Improving the cultural conditions of Bacillus cereus S8 in submerged medium stimulated methionine increase.

Growth of enterotoxin producing Bacillus cereus in meat substrate at 10 ºC and 30 ºC

The behaviour of enterotoxin-producing Bacillus cereus in meat was investigated by inoculating spore suspensions of five cultures into meat substrate (pH 5.8) and incubating at 10ºC and 30ºC. The bacterial populations were evaluated after different times by plate counts in nutrient agar. All the cultures presented growth at 30ºC with the generation time varying from 28.8 to 36.0 minutes. Three cultures also presented growth at 10ºC with generation times between 10.16 and 28.38 h. Considering the results, it was concluded that meat kept at abusive temperatures would be subject to development of this microorganism.

Microrganismos heterotróficos mesófilos e bactérias do grupo do Bacillus cereus em leite integral submetido a ultra alta temperatura / Mesophilic heterotrophic microorganisms and spore forming bacteria from Bacillus cereus group in ultra high temperature milk

Cento e dez amostras de 11 diferentes marcas de leite ultra alta temperatura (UAT), comercializadas em São José do Rio Preto - SP, foram submetidas à contagem de microrganismos heterotróficos mesófilos viáveis e à pesquisa de bactérias do grupo do Bacillus cereus. A população de microrganismos mesófilos variou de <1,0 10² UFC/ml a >1,0 10(6) UFC/ml. Bactérias do grupo do Bacillus cereus foram verificadas em 13 (11,8 por cento) amostras. Os resultados evidenciaram elevada população de microrganismos indicadores mesófilos.

Efecto de las microondas sobre la sobrevivencia de bacterias esporuladas inoculadas en carne molida / Microwave effect on the survival of sporulated bacteria inoculated in minced meat

Debido a la creciente tendencia de cocinar y recalentar en horno de microondas platillos a base de carne y a la posibilidad de que estos transmitan enfermedades de origen bacteriano, se evaluó la capacidad de sobrevivencia de esporas de bacterias inoculadas en carne molida y tratadas en horno de microonda. Las tortas de carne fueron inoculadas con un número conocido de esporas de Bacillus cereus o Clostridium perfringens y posteriormente cocinadas en horno de microondas Amana de 2450 Hz. Se utilizó la técnica descrita por Vanderzant y Splittstoesser para determinar la tase de sobrevivencia y la actividad de la enxima fosfatasa ácida como parámetro de conocimiento. Las esporas de B. cereus mostraron una tendencia a disminuir en número, conforme aumenta el tiempo de exposición a la radiación, pero si llegar a desaparecer totalmente. Las esporas de C. perfringens disminuyen en número al aumentar el tiempo de exposición, pero presentan un segundo aumento asociado a la germinación de esporas sobrevivientes.

Inhibition of fooborne pathogens by bacteriocin-producing leuconostocs and lactobacillus sake isolated from "lingüiça frescal"

Two strains of lactic acid bacteria, isolated from "lingüiça" (a typical Brazilian meat product) stored under refrigeration, produced antagonistic substances active against selected foodborne pathogens. The proteinaceous nature of the inhibitors was demonstrated and so they were classified as bacteriocins. The inhibition due to acid production and phages was ruled out. The bacteriocin produced by Leuconostoc sp was active against Bacillus cereus, Listeria monocytogenes and Staphylococcus aureus. The bacteriocin produced by Lactobacillus sake was active against Listeria monocytogenes and Staphylococcus aureus. Gram negative were bacteria not inhibited by the bacteriocins produced.

Multiplicacion del Bacillus Cereus inoculado en Leche en Polvo reconstituida / Multiplication of Bacillus cereus inoculated into reconstituted powder milk

Se estudio el crecimiento del Bacillus cereus en muestras de leche en polvo reconstituida, inoculadas experimentalmente. Las muestras se incubaron a diversas temperaturas y los conteos se hicieron a diferentes intervalos de tiempo. La leche refrigerada a 7 C durante 24 h mantiene el mismo nivel de concentracion de B. cereus que presentaba al inicio; la multiplicacion del germen se retarda mas a 25 C que a 31 C. La ingestion de la leche despues de 6 h a 31 C o despues de 12 h a 25 C puede ser nociva para la salud