Microbiological quality and bacterial diversity of the tropical oyster Crassostrea rhizophorae in a monitored farming system and from natural stocks

Abstract

ABSTRACT. Microbiological evaluation is one of the most important parameters for analyzing the viability of an oyster farming system, which addresses public health and ecological concerns. Here, the microbiological quality of the oyster Crassostrea rhizophorae cultivated in a monitored environment and from natural beds in Bahia, northeastern Brazil, was determined. Bacterial diversity in oysters was measured by polymerase chain reaction-denaturing gradient gel electrophoresis. Sequence analysis revealed that most bacterial species showed similarity with uncultured or unidentified bacteria from environmental samples, and were clustered into the phylum Proteobacteria. Diverse bacteria from cultivated (monitored) oyster samples were grouped in the same cluster with a high similarity (2015) index (above 79%). Microbiological analyses revealed that these oysters did not contain pathogens. These results reflect the natural balance of the microbial communities essential to the maintenance of health and in inhibiting pathogen colonization in the oyster. On the other hand, bacterial diversity of samples from native stocks in extractive areas displayed a similarity index varying between 55 and 77%, and all samples were clustered separately from each other and from the cluster of samples derived from the cultivation area. Microbiological analyses showed that oysters from the extractive area were not fit for human consumption. This reflected a different composition of the microbial community in this area, probably resulting from anthropic impact. Our study also demonstrated that low temperatures and high rainfall limits the bacterial concentration in tropical oysters. This is the first study analyzing the total bacterial community profiles of the oyster C. rhizophorae.

Effect of freshwater mussels on the vertical distribution of anaerobic ammonia oxidizers and other nitrogen-transforming microorganisms in upper Mississippi river sediment

“…Numerous studies have found Proteobacteria to be the most abundant phylum in freshwater sediments (Bucci et al, 2014; Dai et al, 2016; Wakelin, Colloff & Kookana, 2008; Zeng et al, 2008; Zhang et al, 2015), sediments with mollusks (Fernandez et al, 2014; Lee et al, 2015), and also mollusk microbiomes (Frischer et al, 2000; Neta et al, 2015; Ngangbam et al, 2015; Trabal et al, 2012). Although our results showed Proteobacteria were the most abundant phylum, we observed a decrease in Proteobacteria by 6% and an increase in Nitrospirae by 10% in the presence of mussels.…”

“…Mussel tissue and fecal material has been shown to contain less diverse microbiomes than the surrounding water and sediment for the zebra mussel (Frischer et al, 2000), tropical oyster ( Crassostrea rhizophorae ) (Neta et al, 2015), and marine mussel, Mytilus californianus (Frischer et al, 2000; Pfister, Gilbert & Gibbons, 2014). Some studies have attributed immediate increased sediment microbial activity to the mussel intestinal microbiome (Grenz et al, 1990).…”

BACTERIAL COMMUNITIES OF THE OYSTERS Crassostrea corteziensis AND C. sikamea OF COSPITA BAY, SINALOA, MEXICO

“…The cultivable Vibrio flora harbored in healthy oysters is a bivalve-specific community with densities ranging from 10 2 to 10 4 colony forming units (CFU)/ mg of tissues, and higher loads may be expected at higher temperatures (Saulnier et al 2010). However, if bacterial concentrations are too high, they may induce negative stress, with consequent high mortalities and low condition indices (Harekrishna et al 2014).…”

Identification of 15 novel polymorphic microsatellite loci in pearl oyster (Pinctada fucata)

“…Because of their co-dominance, high polymorphism, and genome-wide abundance, microsatellites (simple sequence repeats, SSRs) are effective molecular markers used in molecular marker-assisted selection and to maintain genetic variance in shellfish (Li et al, 2003;Sato et al, 2005;Evans et al, 2006;Andrea et al, 2014;Silva Neta et al, 2015). Although some polymorphic microsatellite loci have been isolated for P. fucata (Kuang et al, 2009;Fan et al, 2014), more SSRs are needed for genetic research.…”