ASSOCIATION OF MARINE ARCHAEA WITH THE DIGESTIVE TRACTS OF 2 MARINE FISH SPECIES

Recent studies have shown that archaea which were always thought to li ve under strict anoxic or extreme environmental conditions are also pr esent in cold, oxygenated seawater, soils, the digestive tract of a ho lothurian deep-sea-deposit feeder, and a marine sponge, In this study we show, by using PCR-mediated screening in other marine eukaryotes, t hat marine archaea are also present in the digestive tracts of Bounder and grey muller, two fish species common in the North Sea, in fecal s amples of flounder, and in suspended particulate matter of the North S ea water column. No marine archaea could be detected in the digestive tracts of mussels or the fecal pellets of a copepod species. The archa eal 16S ribosomal DNA clone libraries of feces of Rounder and the cont ents of the digestive tracts of grey mullet and Bounder were dominated by group II marine archaea, The marine archaeal clones derived from R ounder and grey mullet digestive tracts and feces formed a distinct cl uster within the group II marine archaea, with 76.7 to 89.8% similarit y to previously described group TH clones, Fingerprinting of the archa eal community of flounder digestive tract contents and feces by termin al restriction fragment length polymorphism of archaeal 16S rRNA genes after restriction with HhaI showed a dominant fragment at 249 hp, whi ch is likely to be derived from group II marine archaea, Clones of mar ine archaea that were closely related to the fish-associated marine ar chaea clones were obtained from suspended particulate matter of the wa ter column at two stations in the North Sea, Terminal restriction frag ment length polymorphism fingerprinting of the archaeal community pres ent in suspended particulate matter showed the same fragment pattern a s was found for the archaeal community of the Bounder digestive tract contents and feces. These data demonstrate that marine archaea are pre sent in the digestive tracts and feces of very common marine fish. It is possible that the marine archaea associated with the digestive trac ts of marine fish are liberated into the water column through the fece s and subsequently contribute to the marine archaeal community of susp ended particulate matter.