Antimicrobial activity of the Nisin Z producer Lactococcus lactis subsp. lactis Lc08 against Listeria monocytogenes in skim milk / Atividade antimicrobiana de Lactococcus lactis subsp. lactics Lc08 produtor de Nisina Z contra Listeria monocytogenes em leite desnatado

The presented study aimed to verify the effect of different pH values, enzyme solutions and heat treatments on the antimicrobial activity of the bacteriocinogenic strain Lactococcus lactis subsp. lactis Lc08 and to test their antimicrobial activity against Listeria monocytogenes in reconstituted skim milk at refrigeration temperatures. This strain was previously described as a nisin Z producer and capable of inhibiting L. monocytogenes growth in in vitro tests. The antimicrobial activity of the bacteriocin cell-free supernatant of Lc08 was sensitive to enzyme treatments (except papain). The pH values and heating (65ºC for 30min, 75ºC for 15s) had no apparent effect on the antimicrobial activity of the bacteriocin produced by Lc08. Only treatment at autoclave conditions result in loss of their antimicrobial activity. Lc08 presented antimicrobial activity against L. monocytogenes in the milk system after 12h at 25ºC. No effect was found at 7ºC. The results show the application viability of the Lc08 in food systems as a biopreservative against L. monocytogenes.

O presente estudo teve como objetivo verificar o efeito de diferentes valores de pH, soluções enzimáticas e tratamentos térmicos na atividade antimicrobiana da cepa bacteriocinogênica Lactococcus lactis subsp. lactis Lc08 e testar sua atividade antagonista contra Listeria monocytogenes em leite desnatado reconstituído em diferentes temperaturas de estocagem. Essa cepa já foi descrita como produtora de nisina Z e capaz de inibir o desenvolvimento de L. monocytogenes em testes in vitro. A atividade antimicrobiana do sobrenadante de Lc08 contendo a bacteriocina produzida e livre de células foi sensível ao tratamento pelas enzimas testadas (exceto papaína). A aplicação de diferentes valores de pH e o tratamento térmico (65ºC por 30 min, 75ºC por 15s) não influenciaram na atividade antimicrobiana da bacteriocina produzida por Lc08. Apenas o tratamento em autoclave resultou em perda da sua capacidade em inibir o desenvolvimento de L. monocytogenes. A cepa Lc08 apresentou atividade antagonista contra L. monocytogenes em leite após período de estocagem de 12h a 25ºC. Não foi observado efeito a 7ºC. Os resultados mostram a viabilidade de aplicação da cultura Lc08 ou de sua bacteriocina em produtos lácteos como bioconservador contra L. monocytogenes.

Antimicrobial activity of the Nisin Z producer Lactococcus lactis subsp. lactis Lc08 against Listeria monocytogenes in skim milk / Atividade antimicrobiana de Lactococcus lactis subsp. lactics Lc08 produtor de Nisina Z contra Listeria monocytogenes em leite desnatado

The presented study aimed to verify the effect of different pH values, enzyme solutions and heat treatments on the antimicrobial activity of the bacteriocinogenic strain Lactococcus lactis subsp. lactis Lc08 and to test their antimicrobial activity against Listeria monocytogenes in reconstituted skim milk at refrigeration temperatures. This strain was previously described as a nisin Z producer and capable of inhibiting L. monocytogenes growth in in vitro tests. The antimicrobial activity of the bacteriocin cell-free supernatant of Lc08 was sensitive to enzyme treatments (except papain). The pH values and heating (65ºC for 30min, 75ºC for 15s) had no apparent effect on the antimicrobial activity of the bacteriocin produced by Lc08. Only treatment at autoclave conditions result in loss of their antimicrobial activity. Lc08 presented antimicrobial activity against L. monocytogenes in the milk system after 12h at 25ºC. No effect was found at 7ºC. The results show the application viability of the Lc08 in food systems as a biopreservative against L. monocytogenes.(AU)

O presente estudo teve como objetivo verificar o efeito de diferentes valores de pH, soluções enzimáticas e tratamentos térmicos na atividade antimicrobiana da cepa bacteriocinogênica Lactococcus lactis subsp. lactis Lc08 e testar sua atividade antagonista contra Listeria monocytogenes em leite desnatado reconstituído em diferentes temperaturas de estocagem. Essa cepa já foi descrita como produtora de nisina Z e capaz de inibir o desenvolvimento de L. monocytogenes em testes in vitro. A atividade antimicrobiana do sobrenadante de Lc08 contendo a bacteriocina produzida e livre de células foi sensível ao tratamento pelas enzimas testadas (exceto papaína). A aplicação de diferentes valores de pH e o tratamento térmico (65ºC por 30 min, 75ºC por 15s) não influenciaram na atividade antimicrobiana da bacteriocina produzida por Lc08. Apenas o tratamento em autoclave resultou em perda da sua capacidade em inibir o desenvolvimento de L. monocytogenes. A cepa Lc08 apresentou atividade antagonista contra L. monocytogenes em leite após período de estocagem de 12h a 25ºC. Não foi observado efeito a 7ºC. Os resultados mostram a viabilidade de aplicação da cultura Lc08 ou de sua bacteriocina em produtos lácteos como bioconservador contra L. monocytogenes.(AU)

First report of austrodiplostomum compactum and ithyoclinostomum dimorphum in trahira (hoplias malabaricus) from the middle course of the Rio Doce, Minas Gerais, Brazil / Primeiro relato de austrodiplostomum compactum e ithyoclinostomum dimorphum em traíras (hoplias malabaricus) provenientes do médio curso do rio doce, Minas Gerais, Brasil

Austrodiplostomum compactum and Ithyoclinostomum dimorphum are two trematodes commonly found in trahira, but these parasites were never reported in trahiras from Rio Doce. Thus, the aim of this study is to describe the occurrence of A. compactum and I. dimorphum metacercariae in trahira from the middle course of the Rio Doce and to record the presence of eggs in I. dimorphum metacercariae. The parasites were identified and analyzed using methods described previously. There were found 10 A. compactum metacercariae in the aqueous humor of eyes in four of the trahiras and 12 I. dimorphum metacercariae encysted in the peritoneal cavity in five of the trahiras. Maceration of the I. dimorphum metacercariae revealed the presence of eggs. These results demonstrate the broad distribution of these parasites and the first report of these parasites in trahira from Rio Doce.

Austrodiplostomum compactum e Ithyoclinostomum dimorphum são dois trematódeos comumente encontrados em traíras, contudo, esses parasitas nunca foram relatados em traíras do Rio Doce. O objetivo do estudo é descrever a ocorrência de metacercárias de A. compactum e I. dimorphum, e presença de ovos em metacercárias de I. dimorphum em traíras provenientes do médio curso do Rio Doce. Os parasitas foram analisados e identificados utilizando métodos descritos anteriormente. Foram encontradas 10 metacercárias de A. compactum no humor aquoso dos olhos em quatro traíras e 12 metacercárias de I. dimorphum encistadas na cavidade peritoneal de cinco traíras. A maceração de metacercárias de I. dimorphum revelou a presença de ovos nestes parasitos. Esses resultados demonstram a ampla distribuição desses trematódeos e este é o primeiro relato destes parasitos em traíra do Rio Doce.

First report of austrodiplostomum compactum and ithyoclinostomum dimorphum in trahira (hoplias malabaricus) from the middle course of the Rio Doce, Minas Gerais, Brazil / Primeiro relato de austrodiplostomum compactum e ithyoclinostomum dimorphum em traíras (hoplias malabaricus) provenientes do médio curso do rio doce, Minas Gerais, Brasil

Austrodiplostomum compactum and Ithyoclinostomum dimorphum are two trematodes commonly found in trahira, but these parasites were never reported in trahiras from Rio Doce. Thus, the aim of this study is to describe the occurrence of A. compactum and I. dimorphum metacercariae in trahira from the middle course of the Rio Doce and to record the presence of eggs in I. dimorphum metacercariae. The parasites were identified and analyzed using methods described previously. There were found 10 A. compactum metacercariae in the aqueous humor of eyes in four of the trahiras and 12 I. dimorphum metacercariae encysted in the peritoneal cavity in five of the trahiras. Maceration of the I. dimorphum metacercariae revealed the presence of eggs. These results demonstrate the broad distribution of these parasites and the first report of these parasites in trahira from Rio Doce.(AU)

Austrodiplostomum compactum e Ithyoclinostomum dimorphum são dois trematódeos comumente encontrados em traíras, contudo, esses parasitas nunca foram relatados em traíras do Rio Doce. O objetivo do estudo é descrever a ocorrência de metacercárias de A. compactum e I. dimorphum, e presença de ovos em metacercárias de I. dimorphum em traíras provenientes do médio curso do Rio Doce. Os parasitas foram analisados e identificados utilizando métodos descritos anteriormente. Foram encontradas 10 metacercárias de A. compactum no humor aquoso dos olhos em quatro traíras e 12 metacercárias de I. dimorphum encistadas na cavidade peritoneal de cinco traíras. A maceração de metacercárias de I. dimorphum revelou a presença de ovos nestes parasitos. Esses resultados demonstram a ampla distribuição desses trematódeos e este é o primeiro relato destes parasitos em traíra do Rio Doce.(AU)

Bacteriocinogenic and virulence potential of Enterococcus isolates obtained from raw milk and cheese.

AIMS: To provide molecular and phenotypical characterization of Enterococcus isolates obtained from raw milk and cheese, regarding their bacteriocinogenic and virulence activity. METHODS AND RESULTS: Forty-three bacteriocinogenic enterococci isolates were identified by 16s rDNA, fingerprinted by RAPD-PCR analysis and tested by PCR for the presence of genes for lantibiotics (lanM, lanB and lanC) and enterocins (entA, entB, entP, entL50AB and entAS48) and by phenotypical methods for bacteriocin production and inhibitory spectrum. Also, the virulence of the isolates was evaluated by PCR for genes gelE, hyl, asa1, esp, cylA, efaA, ace, vanA, vanB, hdc1, hdc2, tdc and odc and by phenotypical tests for gelatinase, lipase, DNAse and α- and ß-haemolysis. Most isolates (93·0%) harboured at least one lantibiotic or enterocin gene and were positive for several tested virulence genes, mainly asa1 (100%), gelE (93·0%) and efaA (83.7%). 53.5% of the isolates presented ß-haemolysis [corrected]. CONCLUSIONS: Enterococcus spp. isolates presented an interesting potential application for food preservation because of bacteriocin production; however, virulence-related genes were identified in all RAPD profiles. SIGNIFICANCE AND IMPACT OF THE STUDY: The study demonstrated the contradictory characteristics of the tested Enterococcus isolates: they presented a good potential for application in food biopreservation but contained several virulence factors.

Molecular identification of naturally occurring bacteriocinogenic and bacteriocinogenic-like lactic acid bacteria in raw milk and soft cheese.

Lactic acid bacteria (LAB) are currently used by food industries because of their ability to produce metabolites with antimicrobial activity against gram-positive pathogens and spoilage microorganisms. The objectives of this study were to identify naturally occurring bacteriocinogenic or bacteriocinogenic-like LAB in raw milk and soft cheese and to detect the presence of nisin-coding genes in cultures identified as Lactococcus lactis. Lactic acid bacteria cultures were isolated from 389 raw milk and soft cheese samples and were later characterized for the production of antimicrobial substances against Listeria monocytogenes. Of these, 58 (14.9%) LAB cultures were identified as antagonistic; the nature of this antagonistic activity was then characterized via enzymatic tests to confirm the proteinaceous nature of the antimicrobial substances. In addition, 20 of these antagonistic cultures were selected and submitted to genetic sequencing; they were identified as Lactobacillus plantarum (n=2) and Lactococcus lactis ssp. lactis (n=18). Nisin genes were identified by polymerase chain reaction in 7 of these cultures. The identified bacteriocinogenic and bacteriocinogenic-like cultures were highly variable concerning the production and activity of antimicrobial substances, even when they were genetically similar. The obtained results indicated the need for molecular and phenotypic methodologies to properly characterize bacteriocinogenic LAB, as well as the potential use of these cultures as tools to provide food safety.

Burkholderia silvatlantica sp. nov., a diazotrophic bacterium associated with sugar cane and maize.

In a previous study, nitrogen-fixing isolates were recovered from the rhizosphere of maize and from surface-sterilized leaves of sugar cane cultivated in Rio de Janeiro, Brazil. On the basis of 16S rRNA gene sequence similarities, these isolates were identified as belonging to the genus Burkholderia, and whole-cell-protein profiles demonstrated that they are closely related to each other. In the present study, novel isolates were recovered from the roots of different sugar-cane varieties cultivated in diverse geographical regions of Brazil. Twenty-one nitrogen-fixing isolates were analysed using polyphasic taxonomy criteria, including DNA-DNA relatedness, 16S rRNA gene sequence similarities, fatty acid profiles, whole-cell-protein patterns and multilocus enzyme electrophoresis profiles, as well as morphological, physiological and biochemical characterization. The analysis confirmed that these isolates belong to a novel species within the genus Burkholderia, for which the name Burkholderia silvatlantica sp. nov. is proposed. The type strain, SRMrh-20(T) (=LMG 23149(T)=ATCC BAA-1244(T)), was isolated from the rhizosphere of maize var. Avantis A2345 cultivated in Seropédica, Rio de Janeiro.

Diazotrophic burkholderia species associated with field-grown maize and sugarcane.

Until recently, diazotrophy was known in only one of the 30 formally described species of Burkholderia. Novel N(2)-fixing plant-associated Burkholderia species such as B. unamae, B. tropica, and B. xenovorans have been described, but their environmental distribution is scarcely known. In the present study, the occurrence of N(2)-fixing Burkholderia species associated with different varieties of sugarcane and maize growing in regions of Mexico and Brazil was analyzed. Only 111 out of more than 900 isolates recovered had N(2)-fixing ability as demonstrated by the acetylene reduction assay. All 111 isolates also yielded a PCR product with primers targeting the nifH gene, which encodes a key enzyme in the process of nitrogen fixation. These 111 isolates were confirmed as belonging to the genus Burkholderia by using a new 16S rRNA-specific primer pair for diazotrophic species (except B. vietnamiensis) and closely related nondiazotrophic Burkholderia. In Mexico, many isolates of B. unamae (predominantly associated with sugarcane) and B. tropica (more often associated with maize) were recovered. However, in Brazil B. tropica was not identified among the isolates analyzed, and only a few B. unamae isolates were recovered from one sugarcane variety. Most Brazilian diazotrophic Burkholderia isolates (associated with both sugarcane and maize plants) belonged to a novel species, as revealed by amplified 16S rRNA gene restriction profiles, 16S rRNA gene sequencing, and protein electrophoresis. In addition, transmissibility factors such as the cblA and esmR genes, identified among clinical and environmental isolates of opportunistic pathogens of B. cenocepacia and other species of the B. cepacia complex, were not detected in any of the plant-associated diazotrophic Burkholderia isolates analyzed.