Culturable heterotrophic bacteria in seawater and Mytilus galloprovincialis from a Mediterranean area (Northern Ionian Sea - Italy)

Although Mar Piccolo of Taranto (Ionian Sea, Italy) is one of the most important Mytilus galloprovincialis farming areas, data concerning the natural bacterial microbiota of these mussels and their surrounding environment are still scant. This study was carried out seasonally, throughout a year, to determine culturable heterotrophic bacteria both in the water and mussels samples collected at three sampling sites in the Northern Ionian Sea: S. Vito, Lido Gandoli and Lido Silvana. Culturable heterotrophic bacteria abundance was determined by spread plate on Marine Agar. Heterotrophic bacteria were identified by several morphological, culture and biochemical methods. Bacterial concentrations were higher in the mussel samples compared to the corresponding seawater throughout the year. Among Gram negative heterotrophic bacteria, Aeromonas prevailed both in the water (18%) and mussel samples (40%). Other genera such as Moraxella, Pseudomonas, Alcaligenes, Acinetobacter, Flavobacterium, Chromobacterium, Photobacterium and Flexibacter were present with different percentages of isolation. Bacilli were predominant among Gram positive bacteria. Some genera (Lucibacterium and Vibrio) were present only in mussel samples. The results obtained contribute to improve the knowledge on both the bacterial abundance and diversity in mussels and the surrounding seawater in the Northern Ionian Sea.