Isolamento e identificação de bactérias do trato digestório do camarão marinho (Litopenaeus vannamei) cultivado em sistema de bioflocos

Abstract

Litopenaeus vannamei is the main commercially produced shrimp species in the world. The system of marine shrimp farming in bioflocs is an alternative to conventional systems by developing a heterotrophic microbial community capable of maintaining water quality and providing microbial protein as food. In aquatic animals, it is believed that the microbial community of the gastrointestinal tract (GIT) is influenced by the raising environment, but differs from the microbiota from the environment, and can be modified by other factors, such as the development stage of the animal. In this study, the microbiota of the gut of the L. vannamei shrimp was evaluated in five stages during a production cycle: ten days post-larvae (PL10) and four ages in the biofloc system, after adaptation to the different rations of each phase (CR1, CR2, CR3 and CR4). The bacterial water counts of the raising system and of the contents of different portions of the GIT of the shrimps were compared. Culture-dependent methodology was carried out using different culture media for enumeration and isolation of the microorganisms, followed by identification by mass spectrometry (MALDI-TOF). The GIT microbiota had higher counts of microorganisms than the water samples. Proteobacteria phylum was dominant in the water of the raising system and in the samples obtained from the digestive system of the prawns, being Vibrio the predominant genus. The mean counts of heterotrophic bacteria and Vibrio spp. differed (p<0.05) between CR1 and CR4, suggesting an increase in microbial density in GIT with increasing age of the animal. There was no change in the microbiota richness of the shrimp gut in the different raising phases, but the composition of the microbiota was modified: some genera occurred exclusively at a given stage (Enterobacter was verified only in CR1 and CR2). Acinetobacter and Kocuria were exclusively identified in the PL10 microbiota associated to another raising environment, demonstrating that it influences the shrimp GIT microbiota. The bacterial communities of the different portions of the GIT of the shrimp were similar in relation to the composition of genders, with lower (p<0.05) mean counts of microorganisms in the anterior portion, compared to the medium intestine. The results demonstrate that the bacterial community of the L. vannamei GIT is dynamic, and is influenced by the stage of development of the animal, the portion of the digestive system and the environment in which the animal is raised.