Bioprospecting the bacterial diversity of marine sponges by culture-dependent and culture-independent approaches

Author(s)

Danilo Tosta Souza

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2016-11-08

Examining board members

Itamar Soares de Melo; Fernando Dini Andreote; Eduardo José Crevelin; Vania Maria Maciel Melo

• Advisor: Itamar Soares de Melo

Abstract

This study describes the diversity of associated bacterial communities to five marine sponges, and the potential of these microorganisms as producers of bioactive substances with fungicidal properties. Sponges live in symbiosis with microorganisms that have a high ecological interest, evolutionary and biotechnological. However, this microbial system remains poorly understood. To fully understand sponge biology, it is necessary to describe the ecological and evolutionary factors that influence the structure and dynamics of their microbial communities. In this work, it is supported the hypothesis that the taxonomic composition and structure of bacterial communities correlate with phylogenetic relatedness of their corresponding hosts. Bacterial communities associated with the sponges Aplysina fulva, Aiolochroia crassa, Chondrosia collectrix, Didiscus oxeata and Scopalina ruetzleri were examined using the Ion Torrent platform for partial sequencing of the 16S rRNA gene. Seawater surrounding specimens were collected for comparisons. The analysis detected a complex and specific microbial system living in sponges, with the operational taxonomic units dominant classified in the phyla: Acidobacteria, Actinobacteria, Chloroflexi, Proteobacteria and Gemmatimonadetes. Despite sympatric occurrence of the specimens, the studied sponges presented different bacterial compositions that differed from those observed in seawater. However, lower dissimilarities in bacterial communities were clearly observed within sponges from the same phylogenetic group (A. fulva and A. crassa). Isolation of bacteria was done from the sponges D. oxeata and S. ruetzleri. Fifty-six strains were isolated and classified into three phyla: Actinobacteria, Proteobacteria and Firmicutes. Phylogenetic analysis indicated five possible novel bacterial species. Based in a polyphasic taxonomy approach, one of the isolates denominated ASPSP 40 was identified as belonging to a novel species of the genus Saccharopolyspora for which the name, Saccharopolyspora spongiae sp. nov. has been proposed. All bacterial isolates were evaluated by their antagonisms against Pythium species. Two of them, Terrabacter sp. ASPSP 140 and Bacillus sp. ASPSP 434 demonstrated strong potential in inhibiting the following species P. aphanidermatum, P. ultimum and P. graminicola. The bioactive secondary metabolites of both, characterized by LC-MS/MS, were identified as a mixture of cyclic dipepitides belonging to the class of diketopiperazine (DKP). This is the first report of fungicidal activity, and thus the detection of DKP of the genus Terrabacter. (AU)

• FAPESP's process: 13/25505-8 - MICROBIAL DIVERSITY: THE IMPORTANCE OF EXPLORATION ABOUT NEW SOURCES OF BIODIVERSITY
• Grantee: Danilo Tosta Souza
• Support Opportunities: Scholarships in Brazil - Doctorate