Vibrio sp. ArtGut-C1, a polyhydroxybutyrate producer isolated from the gut of the aquaculture live diet Artemia (Crustacea)

BACKGROUND: Vibrio species display variable and plastic fitness strategies to survive and interact with multiple hosts, including marine aquaculture species that are severely affected by pathogenic Vibrios. The culturable Vibrio sp. strain ArtGut-C1, the focus of this study, provides new evidence of such phenotypic plasticity as it accumulates polyhydroxybutyrate (PHB), a biodegradable polymer with anti-pathogen activity, particularly in the marine larviculture phase. The strain was isolated from the gut of laboratory-reared Artemia individuals, the live diet and PHB carrier used in larviculture. Its main phenotypic properties, taxonomic status and genomic properties are reported based on the whole-genome sequencing. RESULTS: Vibrio sp. ArtGut-C1 yielded 72.6% PHB of cells' dry weight at 25 C. The genomic average nucleotide identity (ANI) shows it is closely related to V. diabolicus (ANI: 88.6%). Its genome contains 5,236,997- bp with 44.8% GC content, 3,710 protein-coding sequences, 96 RNA, 9 PHB genes functionally related to PHB metabolic pathways, and several genes linked to competing and colonizing abilities. CONCLUSIONS: This culturable PHB-accumulating Vibrio strain shows high genomic and phenotypic variability. It may be used as a natural pathogen biocontrol in the marine hatchery and as a potential cell factory for PHB production.

Enhancement of chitosanase production by cell immobilization of Gongronella sp. JG

Chitosanase production of Gongronella sp. JG cells immobilized in calcium alginate gel and polyurethane foam was compared with that of the free cells, there was a 60% increase in the enzyme yield (2429 U/L) compared to the highest yield obtained from free cells (1513 U/L). The optimal immobilization parameters (concentrations of sodium alginate, calcium chloride, bead inoculums, bead diameter, etc) for the enhanced production of chitosanase were determined as: sodium alginate 2% (w/v), 0.1 M calcium chloride, inoculum 10 mL beads to 100 mL production media and 2.7 mm bead diameter. Maximum chitosanase production was achieved with initial pH of 5.5 and temperature of 30 ºC. The alginate beads had well stability, retained 85% ability of enzyme production even after 7 cycles of repeated batch fermentation. These results showed the immobilization technique was a feasible and economical method for chitosansase production by Gongronella sp. JG.

Ocorrência de Salmonella spp. e Staphylococcus coagulase positiva em pescado no nordeste, Brasil / Occurrence of Salmonella spp. and coagulse positive Staphylococcus in fish and crustaceans in the northeast of Brazil

O presente estudo foi conduzido com o objetivo de verificar a ocorrência de Salmonella spp. e Staphylococcus coagulase positiva em pescados e crustáceos provenientes da região nordeste no período de fevereiro de 2004 a dezembro de 2005. Das 143 amostras de peixes e crustáceos (camarão congelado e cauda de lagosta), 5 (3,5%) apresentaram-se positivas para Salmonella spp. Enquanto nas amostras de peixe e cauda de lagosta a contagem de Staphylococcus coagulase positiva foi < 1,0 x 102UFC/g estimado, nas amostras de camarão congelado, em duas a contagem foi 1,0 x 101UFC/g estimado e em uma 2,6 x 101UFC/g estimado, as demais <1,0 x 101UFC/g estimado. Com base nos resultados obtidos conclui-se que as amostras analisadas apresentaram baixos níveis de ocorrência de Salmonella spp. e Staphylococcus coagulase positiva e que, mesmo com estes baixos índices, constantemente deve-se buscar uma melhora na qualidade dos produtos da pesca, melhora esta que passa pelo treinamento constante em boas práticas de fabricação, procedimentos padrões de higienização e análise de perigos e pontos críticos de controle do pessoal que trabalha na pesca ou em fazendas de criação de camarão, bem como dos funcionários das indústrias.

The present study was carried out to evaluate the occurrence of Salmonella spp. and coagulase-positive Staphylococcus in fish and crustaceans from the Brazilian Northeast. Five out of the 143 samples (3.5%) were positive for Salmonella spp. While none of the fish and lobster tail samples were positive for coagulase positive Staphylococcus, two shrimp samples presented an estimated count of 1.0 x 101colony forming units per gram (cfu/g), and one presented 2.6 x 101 cfu/g. The results showed a low level of Salmonella and coagulase positive Staphylococcus occurrence. However, even with these low levels of bacterial numbers in fish and crustaceans we should search look for an improvement in their quality. This improvement should be associated to constant training for good manufacturing practice, a standard procedure of hygiene and analysis of hazards and critical control points related to employees that work as fishers or on shrimp farms, as well as those working in the industry as a whole.

Susceptibilidade"in vitro" a antimicrobianos de estirpes de Vibrio spp isoladas de camarões (Litopenaeus vannamei) e de água de criação destes animais provenientes de uma fazenda de camarões no Ceará - Nota prévia / In vitro antimicrobial susceptibility of Vibrio spp isolated from shrimp (Litopenaeus vannamei) and water from ponds of a shrimp farm in Ceará

Foram feitos ensaios de susceptibilidade a antibióticos em 48 cepas de Vibrio isoladas do cultivo do Litopenaeus vannamei no Ceará. Para os testes de difusão foram utilizados 11 antibióticos. A espécie que apresentou maior percentagem de resistência aos antimicrobianos foi V. cholerae, onde 33,33% das 12 cepas testadas mostraram-se resistentes a sulfazotrim, 25% a ampicilina e 33,33% a ceftriaxona.

Suscetibility assays were performed for 48 Vibrio strains isolated from pond-reared Litopenaeus vannamei in Ceará, Brazil. The diffusion assays tested 11 antibiotics. The most resistant species was V. cholerae: of 12 strains tested, one third was resistant to sulfamethoxazole-trimethoprim, one fourth to ampicillin and one third to ceftriaxone.

Recombinant expression of marine shrimp lysozyme in Escherichia coli

Shrimp Lysozyme (Lyz) is a key component of the antibacterial response as part of the innate defense in Crustacea; however, it has not been possible to purify this protein because of the very low amount present in the shrimp blood cells (hemocytes). In an effort to produce enough protein to study its function and biochemical properties we have overexpressed Lysozyme from marine shrimp (Penaeus vannamei) in E. coli. A bacterial protein expression system based on the T7 polymerase promoter was used. Although Lyz was produced as insoluble protein in inclusion bodies, its refolding led to an active protein with a yield of ~10 percent. Details of the protein recombinant expression techniques applied to this shrimp protein are presented.