Thesis (M.Sc.)--Chulalongkorn University, 2013

Thailand is surrounded by Andaman Sea and Gulf of Thailand. As Thailand is located around an equator with hot and rainy climate, Thai marine comprise abundant microbial biodiversity. Yet, conventional or standard method cultural procedures could reveal < 1% of all microbiota due to limited capacity of the microorganismal growth under laboratory condition. Presently, the other > 99% of the microbiota could be revealed by culture-independent approach known metagenomics. This research utilized culture-dependent and culture-independent methods (metagenomics combined with pyrotagged 16S rDNA sequencing) to attain a complete picture of the true prokaryotic diversity of this environment, and better understand the ecosystem of bacteria and archaea in the southeast Andaman Sea off the west coast of Thailand. The seawater samples of two different distances from the Andaman coast: 08º56.004'N 98º05.857'E (PT) at 30-meter depth and 08º51.096'N 97º31.207'E (TC) on the surface and at 30, 100, 150-meter depth were investigated. The PT and TC sites had the seafloor depths of approximately 35 meters and 155 meters, respectively. The latter represents the farther seashore distance sample. The culture-dependent and culture-independent data demonstrated that the culture-dependent method provided far fewer number of isolates than by the culture-independent method, which could detect species that were missed by plating and also highlighted several uncultured bacteria. Subsequently, this thesis helped better understand the aquatic bacterial and archaeal population structures, and their metabolic potentials at PT and TC.