Abstract
Respiratory quinine compositions were analyzed by a high-performance liquid chromatography to characterize the depth-related changes and site-specific differences of microbial communities in marine sediments. Two deep-sea sediment samples and one coastal sediment sample were investigated from three sites on the coast of Japan, Sagami Bay, Suruga Bay and Tokyo Bay. Although depth-related changes in microbial community structures were observed, site-specific differences appeared to have greater influence on overall community structures. A variety of quinine homologs was commonly identified at all sampling sites and depths examined, but a few minor quinine fractions, mainly derived from Actinobacteria, were detected only at specific sampling sites. Methylmenaquinone-7 (MMK-7) was the major component throughout the examined depths in Sagami Bay and Tokyo Bay. Most abundant quinine homologs changed with each depth in Suruga Bay. Menaquinone-6 (MK-6) predominated in the 0 to 2-cm layer (19%). Below 0-2 cm, the most abundant homolog in each sampling depth was phylloquinone (K sub(1); 13%, 4-6 cm), MK-8 (19%, 8-10 cm) and MK-7 (13%, 16-18 cm). The microbial respiratory quinone profiling method shown here, successfully demonstrates the usefulness of this approach to characterize microbial communities in marine sediments.
