PHYLOGENETIC DIVERSITY OF BACTERIA AND ARCHAEA IN THE NANSHA MARINE SEDIMENTS, AS DETERMINED BY 16S rDNA ANALYSIS

A 16S ribosomal DNA (rDNA) clone library from Nansha marine sediments was established by PCR using suitable primers. A total of 200 clones were selected by amplified rDNA restriction analysis(ARDRA) using four,fourbase specific restriction enzymes( Afa Ⅰ, Alu Ⅰ, Hae Ⅲ, Msp Ⅰ). 70 restriction fragment length polymorphism(RFLP) types,constituting 35% of the total clone libraries,were detected and sequenced. Examination of 70 16S rDNA clones showed that the marine sediments of Nansha in the South China Sea contained a phylogenetically diverse population of organisms from the bacteria domain covering most of the microbial diversity in the libraries. For 70 clones,only one clone was identical to the known 16S rDNA sequences in the Ribosomal Database Project small subunit RNA database. In our clone library,all sequences had85% similarity to rDNA sequences retrieved from the DNA databases. The sequenced clones fell into four major lineages of the domain bacteria:the alpha,gamma and delta Proteobacteria ,Gram positive bacteria,Green nonsulfur bacteria, Planctomycetes and related organisms. 60% of clones belonged to the delta,alplla and gamma Proteobacteria ,13% belonged to Gram positive bacteria. 10% to Planctomycetes and related organisms and the remaining 6% to Green nonsulfur bacteria(6%). The results suggest that these clones are very diverse in phylogeny. The subclass of the Proteobacteria ,especially delta Proteobacteria predominates in this study. Molecular diversity of archaea was also analyzed by PCR amplification and sequencing of the rDNA clone library using an archaeaspecific primer set. The secondary structure and sequence signatures of the 16S rDNA from the representative clones were analyzed and the results showed that all clones obtained from the archaea clone library were closely related to uncultured bacteria. Therefore, no archaea was found in this library.