| Summary: | 碩士 === 國立東華大學 === 海洋生物研究所 === 106 === Denitrifying bacteria of the genus Pseudovibrio (Alphaproteobacteria: Rhodobacterales: Rhodobacteraceae) are widely distributed in the in the marine environment, especially within sponges. They were first isolated and described in 2004 from seawater of Nanwan Bay, Kenting National Park, Taiwan. These facultatively anaerobic marine bacteria were repeatedly isolated from marine invertebrates such as ascidians, tunicates, algae, tube worms, corals and sponges. Pseudovibrio is in fact believed to play an important role in symbiotic relationships with their hosts. Moreover, antimicrobial activities within Pseudovibrio sp. toward broad-spectrum of pathogens has been described many times, suggesting they could be used as a novel source of bioactive compounds. In the present study, 9 sponge samples were used to screen for Pseudovibrio strains by using a culture-based method. Sponge samples were collected from either the husbandry center, National Museum of Marine Biology and Aquarium (NMMBA) or Nanwan Bay, Taiwan. A total of 867 bacterial strains were isolated from three different selective media, among which 301 strains displayed denitrifying activity and within which 188 strains were confirmed to be Pseudovibrio based on 16s rRNA gene sequences. Phylogenetic analysis of these strains based on 16S rDNA fragments indicated that most of the isolates belong to Pseudovibrio denitrificans (157 isolates, 83.51%). However, many isolates are difficult to resolve to species suggesting some of them might be new Pseudovibrio species. All the Pseudovibrio isolates were screened for their antimicrobial activity against five test bacteria and a fungus. Fifty-two (27.96%) of the isolates showed activity against at least one test microbes. Our results demonstrate that marine sponge could be a source of Pseudovibrio strains which have a great potential in discovery of usefully medical molecules.
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