The exploration of biodiversity (“bioprospecting”) provides mankind with an immense pool of novel organisms, molecules and information, which can be exploited for the development of innovative biotechnological processes and new ways to treat diseases. In the past decades, the marine environment emerged as an untapped source of biodiversity, and this study investigated the marine bacterial family Vibrionaceae (“vibrios”) for its potential as reservoir of novel biodiversity and of species relevant for the ecology of the marine environment. The characterization of a novel species, Vibrio galatheae, contributed to the understanding of the phylogeny and diversity of Vibrionaceae, while the use of growth conditions mimicking the niche of isolation showed that substrates that are abundant in the marine environment significantly influence the metabolism of vibrios. Indeed, during a screening of approximately three hundred strains, the number of vibrios capable to inhibit the growth of a fish pathogen was nearly doubled when isolates were grown on chitin, the most abundant polymer in the marine environment, as compared to when they were grown on mannose or glucose. This observation led to investigate at the transcriptome level the effects of chitin on the two vibrios Vibrio coralliilyticus and Photobacterium galatheae. It was shown that the dynamics of chitin colonization and utilization in these two species are similar to those reported for the well-characterized chitin colonizer Vibrio cholerae. Bacteria reach chitinous surfaces by chemotaxis before adhering to it and completing their chitin degradation/utilization program. The complementation of this information with the metabolomic profiles of the strains suggested a possible role of secondary metabolites in chitin colonization, although further work is required to elucidate whether they are produced to antagonize competitors or to communicate with other colonizers and/or a potential host. In conclusion, this PhD study adds to the knowledge of Vibrionaceae as an untapped reservoir of biodiversity and important players in the ecology of the marine environment. Studying microbial eco-physiology is important not only for the development of ecological models, but also as foundation for bioprospecting studies, where this knowledge may be used, for example, to elicit silent biosynthetic gene clusters during natural product discovery.