Molecular characterization of symbiotic associations between chemoautotrophic sulfur-oxidizing microorganisms and nematodes in shallow marine sediments

Shallow marine sediments are preferred environments for nematodes harboring endo- or ectosymbiotic microorganisms. In most cases, the symbionts are autotrophic, sulfur-oxidizing bacteria. In the present work molecular biological methods such as comparative 16S rRNA and 18S rRNA sequence analysis, fluorescence in situ hybridization (FISH) and slot blot hybridization with group specific rRNA-targeted oligonucleotide probes were used to investigate and characterize these symbiotic associations and their natural habitat. Thus we investigated the specificity of the symbiotic association between ectosymbiotic bacteria and gut-bearing nematodes of the genus Leptonemella from intertidal sandy sediments near the island of Sylt (Wadden Sea) and we determined the identity and phylogeny of the endosymbionts of mouthless nematode, Astomonema sp. from coral reef sediments in the Bahamas. Also the microbial diversity and community structure of the intertidal Sylt sandy sediments, the preferred habitat of the Leptonemella spp. was determined and characterized over depth (0 to 12 cm) and seasons (March, July, October).