Molecular analysis of microbial communities in mobile deltaic muds of Southeastern Papua New Guinea

A culture-independent examination of microbial diversity in mobile deltaic sediments from the Gulf of Papua, Papua New Guinea, was conducted by sequence analysis of 16S rDNA clone library. Universal small subunit primers were used to amplify DNA extracted from the sediment. Of 91 clones randomly selected from the library, 33 contained unique non-chimeric sequences. Analysis of these unique sequences showed that the majority of them belonged to bacteria (94.5%), with proteobacteria being the dominant division (74.8%). One sequence belonging to Crenarchaeota and another to Euryarchaeota were found as well. Bacterial sequences belonging to the following major divisions were identified: Cytophaga-Flexibacter-Bacteroides (5.5%), low GC Gram-positives (1.1%), Nitrospira group (3.3%), OP8 candidate division (2.2%), OS-K candidate division (2.2%), Planctomyces (1.1%), alpha, delta, gamma and epsilon-subdivisions of Proteobacteria (4.4, 20.9, 19.8 and 23.1%, respectively) and Spirochaetales (4.4%). The composition of 16S rDNA library of the Gulf of Papua sediments is similar to those for deepwater sediments from around the Japanese Islands, indicating a possible cosmopolitan nature of microbial communities in suboxic and anoxic sediments of the Pacific. It appears that many Papua/New Guinea sequences are loosely affiliated with bacteria involved in sulfur cycling, thus supporting the hypothesis that the sulfur cycle may be important in early diagenesis of suboxic sediments.