Growth dynamics and biotechnological potential of bacterial isolates from Raspaciona aculeata

Marine sponges are a reservoir of microbial diversity and host many species-specific bacterial symbionts that may be of great biotechnological interest. This research concerns the first characterization of the growth dynamics of the bacterial community associated with the marine sponge Raspaciona aculeata, to evaluate the effects of incubation temperature on its biotechnological potential. Fifty-two strains were isolated from R. aculeata homogenate and, based on the different morphology of the colonies (shape, color, margins and size), five potential morphological clusters were identified (confirmed by rRNA analysis). 16S rDNA sequencing revealed that all bacterial isolates belonged to the Pseudomonadaceae and Pseudoalteromonadaceae families. The bacterial strains were grown in Marine Broth medium at different growth temperatures (4, 15, 25 and 37±1 °C) for up to 50 days. Changes occurring in cell hydrophobicity (polystyrene adhesion assay) and surfactant production (emulsion activity, %, E24) were correlated with growth measurements (optical density, OD600nm). The results highlighted that although temperature represents an important natural factor in the adhesion processes, this did not generally influence the growth dynamics. The highest emulsification activity values were recorded with average values of ~ 29% (%, E24) among all strains under study at the temperature of 15 °C and values of~ 30% (%, E24) at the temperature of 25±1°C. The ability of the bacterial strains to degrade crude oil, tetradecane and phenanthrene at the different temperatures under study was also analyzed, with the average values among all the strains under study being higher (by ~49%, ~46% and ~50% respectively) at the temperature of 25±1°C. These findings suggest that the sponge-associated bacterial strains isolated in this study show potential for surfactant production and hydrocarbon degradation, and could be further investigated for their possible application in bioremediation processes.