Diversity and community structure within anoxic sediment from marine salinity meromictic lakes and a coastal meromictic marine basin, Vestfold Hills,Eastern Antarctica

16S rDNA clone library analysis was used to examine the biodiversity and co mmunity structure within anoxic sediments of several marine-type salinity m eromictic lakes and a coastal marine basin located in the Vestfolds Hills a rea of Eastern Antarctica. From 69 to 130 (555 total) 16S rDNA clones were analysed from each sediment sample, and restriction fragment length polymor phism (RFLP) and sequence analysis grouped the clones into 202 distinct phy lotypes (a clone group with sequence similarity of > 0,98), A number of phy lotypes and phylotype groups predominated in all libraries, with a group of 10 phylotypes (31% of clones) forming a novel deep branch within the low G + C Gram-positive division. Other abundant phylotypes detected in several different clone libraries grouped with Prochlorococcus cyanobacteria, diato m chloroplasts, delta proteobacteria (Desulfosarcina group, Syntrophus and Geobacter/Pelobacter/Desulphuromonas group), order Chlamydiales (Parachlamy diaceae) and Spirochaetales (wall-less Antarctic spirochaetes). Most archae al clones detected (3.1% of clones) belonged to a highly diverged group of Euryarchaeota clustering with clones previously detected in rice soil, aqui fer sediments and hydrothermal vent material. Little similarity existed bet ween the phylotypes detected in this study and other clone libraries based on marine sediment, suggesting that an enormous prokaryotic diversity occur s within marine and marine-derived sediments.