Bacterial consortium associated with the“black disease＂of reef-building corals

• Main Authors: Ming-Hui Liao, 廖敏惠
• Other Authors: 陳昭倫
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/28062313077787256522

碩士 === 國立臺灣大學 === 海洋研究所 === 96 === Coral diseases are one of the major natural disturbances that threat the survival of coral reefs worldwide. However, the characterization and mechanism of infection have been difficult in understanding the outbreak of coral diseases due to the limitation of applying classical microbiological assays. In this thesis, the bacteria consortium of the “black disease” caused by a black mat-like sponge, Terpios hoshinota, was characterized by electronic microscopy, denaturing gradient gel electrophoresis (DGGE), and 16S ribosomal DNA library construction. In order to understand the possible pathogenic bacteria in “black disease”, the specificity of T. hoshinota associated bacterial community and the variation between sponge-infected (SI) and non-sponge-infected (NSI) Porites lutea associated bacterial community were investigated in the fringing reef of the Green Island (Lutao), where outbreak of Terpios sponge was first reported in 2006. Result shows that the bacterial communities from seawater, sponge, and coral were specific. T. hoshinota associated bacterial community was specific and the dominant bacteria group was autotrophic Cyanobacteria. The Cyanobacteria associated with T. hoshinota were supposedly a new Cyanobacteria species as demonstrated by 16S rDNA sequence with a unique morphology. Furthermore, the high abundance of cyanobacteria in T. hoshinota may contribute positively to T. iii hoshinota outbreak. On the other hand, the diversity and composition similarity of bacterial community associated with SI and NSI P. lutea were analyzed using DOTUR and LIBSHUFF. In NSI P. lutea, the dominant bacterial groups were Gammaproteobacteria, Cyanobacteria, and unclassified bacteria; however, in SI P. lutea, Gammaproteobacteria and Alphaproteobacteria were major groups and the abundance of Cyanobacteria and unclassified bacteria were low. In previous studies, there were diverse coral holobiont on a coral. The natural coral holobiont changed to dominant bacteria group with abundance of opportunistic bacteria when corals experience environmental stress; similar situation was observed in SI P. lutea. The increase of the abundance of Gammaproteobacteria is probably related to environmental stress (sponge or seawater pollution). In addition, the unexpected emergence of alphaproteobacteria could be opportunistic bacteria because of disturbance of natural bacterial community. Disturbance of coral holobiont possible loss the normal symbiont function for coral and it directly or indirectly supposed to result in coral disease. Coral associated microbes were variable in different environment and may be a good bioindicator for environmental stress; therefore, building up a bioindicator, a long term investigation is apparently essential.