Uso de perifíton na dinâmica microbiológica, na qualidade da água e no crescimento de tilápia-do-nilo em tanques de cultivo

The objective of this work was to evaluate the effect of the use of an artificial substrate for periphytic biofilm growth on the microbiological composition of the biofilm, water quality, and zootechnical performance of Nile tilapia (Oreochromis niloticus) in rearing tanks. The experiment consisted of two treatments: presence and absence of artificial substrate for the growth of periphyton, with five replicates. Water quality parameters were evaluated throughout the entire experimental period. Every two weeks, samples of the periphyton were collected for the analysis of its microbiological composition and biometric measurements of the fish were performed. The number of heterotrophic bacteria in the biofilm increased during the experimental period, but that of Aeromonas decreased with the use of the artificial substrate. The total ammonia nitrogen in the tanks with periphyton reduced in 30% compared with that of the control. Tilapia reared with the biofilm showed a final weight 2.4 times greater than that of those subjected to the control, as well as an increase of 59.19% in their productivity. The use of an artificial substrate for periphytic biofilm in Nile tilapia rearing tanks favors the maintenance of the quality of the culture water, the protection of the fish against pathogens, and the improvement of the zootechnical performance of the fish.O objetivo deste trabalho foi avaliar o efeito do uso de substrato artificial para o crescimento de biofilme perifítico sobre a composição microbiológica do biofilme, a qualidade da água e o desempenho zootécnico de tilápia-do-nilo (Oreochromis niloticus), em tanques de cultivo. O experimento consistiu de dois tratamentos: presença e ausência de substrato artificial para o crescimento de perifíton, com cinco repetições. Os parâmetros de qualidade de água foram avaliados durante todo o período experimental. A cada duas semanas, foram coletadas amostras do perifíton para análise da sua composição microbiológica e realizadas medidas biométricas dos peixes. A quantidade de bactérias heterotróficas no biofilme aumentou durante o período experimental, mas a de Aeromonas reduziu com o uso do substrato artificial. O nitrogênio amoniacal total dos tanques com perifíton reduziu 30% em relação ao do controle. As tilápias criadas com o biofilme apresentaram peso final 2,4 vezes maior que às submetidas ao controle, além de aumento de 59,19% na sua produtividade. O uso de substrato artificial para a formação de biofilme perifítico em cultivo de tilápia em tanques favorece a manutenção da qualidade da água de cultivo, a proteção dos peixes contra patógenos e a melhora do desempenho zootécnico dos peixes

Avaliação quantitativa e bioatividade de um biofilme perifítico oriundo de piscicultura

The objective of this work was to quantitatively analyze the cultivable microbiota in isolated periphyton of tilapia cultivation tanks with later prospecting for bioactive substances produced in the biofilm and resistance to the action of antibiotics. The standard plate counting method using the pour plate technique was used to quantify the cultivable heterotrophic bacteria (CHB) and the spread plate technique for fungi. The production of antimicrobial substances by the community and the susceptibility to broad-spectrum antibiotics were investigated, both through the agar diffusion technique. The periphyton sample showed 1.73x106 CFU/mL in relation to the count of total cultivable heterotrophic bacteria and 1.45x102 CFU/mL relative to the density of fungi. The periphytic biofilm showed antibacterial action against Gram-positive bacteria. The antibiotics chloramphenicol, tetracycline, and cephalothin were effective against the biofilm components. However, the community showed a profile of resistance to imipenem. Bacteria are the dominant components in periphytic biofilm compared to fungi, contributing to nutrient cycling and influencing the quality of cultivated water. Periphyton has biotechnological potential for antimicrobial action.Um biofilme perifítico formado em um cultivo de tilápias-do-nilo foi analisado para determinação quantitativa de bactérias e fungos, detecção de substâncias com ação antibacteriana e avaliação de perfis de resistência frente a antibióticos comerciais.  Foi empregado o método de contagem padrão em placas por meio da técnica inoculação em profundidade para a quantificação das bactérias heterotróficas cultiváveis (BHC) e a técnica de espalhamento sobre meio de cultura para a de fungos. Investigou-se a produção de substâncias antibacterianas pela comunidade e a susceptibilidade a antibióticos de amplo espectro, ambos por meio da técnica de difusão em ágar. As concentrações de bactérias e fungos cultiváveis na comunidade de perifíton foram, respectivamente, 1,73×106 UFC/mL e 1,45×102 UFC/mL. O biofilme perifítico mostrou ação antibacteriana contra bactéria indicadora Gram positiva. Os antibióticos Cloranfenicol, Tetraciclina e Cefalotina foram eficientes contra os componentes do biofilme. Entretanto, a comunidade apresentou perfil de resistência ao Imipinem. As bactérias são os componentes dominantes no biofilme perifítico em comparação com os fungos contribuindo com a ciclagem de nutrientes e influenciando a qualidade da água de cultivo. O perifíton possui potencial biotecnológico de ação antimicrobiana

Evaluación de estirpes bacterianas para la formación de consorcio probiótico para uso en el cultivo de camarones marinos: Litopenaeus vannamei / Evaluation of bacterial strains for the formation of a probiotic consortium for use in the cultivation of marine shrimps: Litopenaeus vannamei

El objetivo del presente trabajo fue evaluar estirpes bacterianas con características probióticas, aisladas del tracto intestinal de camarones marinos (Litopenaeus vannamei). Ciento noventa y una (191) estirpes fueron evaluadas para su selección basada en pruebas fenotípicas y genotípicas incluyendo: factores de virulencia (elastasa, gelatinasa, caseinasa, lípasa e fosfolipasa), tolerancia a diferentes temperaturas (4°C e 40°C) y pHs (5 e 9), prueba de susceptibilidad a antimicrobianos, prueba de agregación, antagonismo y prueba de identificación molecular  (secuenciamiento-gen 16S rRNA). Las estirpes identificadas fueron agrupadas en diferentes géneros: Bacillus, Vibrios, Staphylococcus y un grupo con representantes de diferentes géneros bacterianos. Fueron formados tres grupos bacterianos prioritarios atendiendo a la respuesta de las estirpes frente a las diferentes pruebas analizadas. La mayoría de las estirpes (66,45%) presentó resistência frente a la oxitetraciclina. Todas las estirpes presentaron susceptibilidad frente al cloranfenicol y la tetraciclina. Ninguna estirpe presentó antagonismo frente al patógeno Vibrio parahaemolyticus. De las 70 estirpes que formaron parte de los tres grupos prioritarios, 16 estirpes (22,85%) resultaron antagónicas frente a Vibrio harvey. Doce estirpes bacterianas mostraron resultados satisfactorios en la técnica de antagonismo cruzado. Fueron formados tres consorcios bacterianos con aquellas estirpes que cumplieron los requisitos como probiótico potencial

Influência de fatores ambientais na dinâmica do perifíton na aquicultura

With the growth of aquaculture activity and the increase in the entry of organic wastes from the cultivation environments into natural water bodies, the development of techniques that minimize the impacts of the activity is necessary. One strategy that has shown promising results in mitigating the negative impacts of the activity is the manipulation of the natural microbial communities of aquatic ecosystems. These communities use high nutrient loads for their development and their growth in the medium is regulated by several natural factors. In this review, the main environmental factors that can modify the dynamics and function of biofilms in cultivation environments were carefully analyzed. Several factors categorized as biotic: parasitism, predation and grazing and abiotic: nutrient concentration, temperature, pH, substrates, light, water velocity and hydrological regime were identified as determinants for the colonization and establishment of the biofilm. However, some of these were more active in the dynamics of the periphytic community, being possible to distinguish those that present greater interference in the development and dynamics of the community.  RESUMO | Com o crescimento da atividade aquícola e o aumento da entrada de resíduos orgânicos oriundos dos ambientes de cultivo em corpos de águas naturais, o desenvolvimento de técnicas que minimizem os impactos da aquicultura se faz necessário. Uma estratégia que vem mostrando resultados promissores na mitigação dos impactos negativos da aquicultura é a manipulação das comunidades microbianas naturais dos ecossistemas aquáticos. Essas comunidades utilizam as altas cargas de nutrientes para o seu desenvolvimento e o seu crescimento no meio é regulado por vários fatores naturais. Nesta revisão, os principais fatores ambientais que podem modificar a dinâmica e função do biofilme nos ambientes de cultivo, foram minunciosamente analisados. Diversos fatores categorizados como bióticos: parasitismo, predação e pastejo e abióticos: concentração de nutrientes, temperatura, pH, substratos, luz, velocidade de água e regime hidrológico foram apontados como determinantes para a colonização e estabelecimento do biofilme. Todavia, alguns fatores se demonstraram mais atuantes na dinâmica da comunidade, sendo possível distinguir aqueles que apresentam maior interferência no desenvolvimento e dinâmica da comunidade.ABSTRACT: With the growth of aquaculture activity and the increase in the entry of organic wastes from the cultivation environments into natural water bodies, the development of techniques that minimize the impacts of the activity is necessary. One strategy that has shown promising results in mitigating the negative impacts of the activity is the manipulation of the natural microbial communities of aquatic ecosystems. These communities use high nutrient loads for their development and their growth in the medium is regulated by several natural factors. In this review, the main environmental factors that can modify the dynamics and function of biofilms in cultivation environments were carefully analyzed. Several factors categorized as biotic: parasitism, predation and grazing and abiotic: nutrient concentration, temperature, pH, substrates, light, water velocity and hydrological regime were identified as determinants for the colonization and establishment of the biofilm. However, some of these were more active in the dynamics of the periphytic community, being possible to distinguish those that present greater interference in the development and dynamics of the community

Imbalances in the hardness/alkalinity ratio of water and Nile tilapia’s growth performance - doi: 10.4025/actascitechnol.v36i1.18995

The present work determined the effects of water with unbalanced calcium hardness/total alkalinity (CH/TA) ratio on Nile tilapia growth performance. Two unbalanced CH/TA ratios were tested for 8 weeks using one indoor system with 30 circular polyethylene 100 L tanks and one outdoor system with 36 circular polyethylene 250 L tanks. The factors and their specific levels tested were the total alkalinity of water (TA; 50 and 100 mg L-1 CaCO3) and the CH/TA ratio of water (CH/TA; 1/2, 1/1 and 5/1). In the indoor system, the 5/1 CH/TA ratio tanks had higher total ammonia nitrogen (TAN) than the 1/2 or 1/1 CH/TA ratio tanks. In the outdoor system, higher concentrations of TAN were found in the 1/2 CH/TA ratio tanks. The soil of the 5/1 CH/TA ratio indoor tanks had higher concentrations of organic carbon than the 1/2 or 1/1 CH/TA ratio tanks. The detrimental effects of the 5/1 CH/TA ratio on fish growth performance were stronger than those associated with the 1/2 CH/TA ratio. A significantly better food conversion ratio was observed in the 1/1 CH/TA ratio outdoor tanks regardless of the TA level of the water.  

Aquatic microbiota diversity in the culture of Nile tilapia (Oreochromis niloticus) using bioflocs or periphyton: virulence factors and biofilm formation

The following research isolated and identified the main bacterial groups present in the culture of juvenile Nile tilapia in the presence of bioflocs and/or periphyton. The strains were also tested for the production of exoenzymes, indicative of potential virulence factors, and ability to form biofilm. The water samples were taken from tilapia cultured in the presence of bioflocs (T1), in the presence of bioflocs and periphyton (T2), from traditional culture (T3) and from culture in the presence of periphyton (T4). In the growth and selection of the bacterial groups, pour plate method was used, along with the following media: Plate Count Agar (PCA - DIFCO), Aero Pseudo Selective Agar (GSP - Himedia) and Nutrient Agar (AN - Merck). 46 strains were isolated in the following distribution: T1 (n = 12); T2 (n = 10); T3 (n = 14) and T4 (n = 10). Among the isolates, the most frequent genera were: Pseudomonas spp., Aeromonas spp., Staphylococcus spp., Bacillus spp., Mycobacterium spp., Micrococcus spp., and Corybacterium spp. Bacterial isolates in treatments T1 and T3 tested positive for five virulence profiles each, while those isolated from T2 and T4 for two and three virulence profiles, respectively. Treatments in bioflocs and periphyton (T2) or only periphyton (T4) yielded bacteria of less pathogenic potentials. In relation to the fish growth, T1 and T4 resulted in a higher final weight.