Microbial epibionts of the colonial ascidians Didemnum galacteum and Cystodytes sp.

作者：da Silva Oliveira Francisca Andrea; Colares Georgia B; Hissa Denise C; Angelim Alysson L; Melo Vania M M; Lotufo Tito M C^*

来源：Symbiosis, 2013, 59(1): 57-63.

DOI：10.1007/s13199-012-0210-2

• Symbiosis
• Ascidiacea
• Microbiota
• Brazil

Symbiosis with microorganisms has been well documented for many marine invertebrate taxa. However, knowledge of the diversity of microorganisms associated with ascidians is still limited. This study assessed the microbial epibionts of Didemnum galacteum and Cystodytes sp., two ascidian species collected from the western coast of Ceara state (Brazil), at Dois Coqueiros beach and the port of Pec,m, respectively. The microbiota were examined using optical microscopy, followed by subsequent analysis of fingerprinting profiles obtained by denaturing gradient gel electrophoresis (DGGE) and 16S rRNA clone libraries. The microscopy analysis showed for both ascidians a community comprising cyanobacteria, mainly Prochloron-like species, and diatoms. The DGGE results indicated that D. galacteum hosts a more diverse microbiota when compared to Cystodytes sp. The same analysis also suggested that the diversity of the seawater microbiota was higher than the diversity of the ascidian-associated microbiota. The analysis of the 16S rRNA clone libraries revealed the dominance of Proteobacteria symbionts associated with both ascidians, with Alphaproteobacteria as the major component in D. galacteum and Gammaproteobacteria the major component in Cystodytes sp. The analysis of the clone libraries also revealed the presence of other taxa such as Bacteroidetes, Planctomycetes, Actinobacteria, Cyanobacteria, and uncultured bacteria in D. galacteum, but not in Cystodytes sp. Among the bacteria found to be exclusively associated with the ascidians, none were shared by the two studied hosts. The combined results point to a diverse microbiota associated with the external surface of the ascidians, with a mixed composition including organisms typically found in the surrounding seawater, but also a more specific set of taxa.

• 出版日期2013-1