Investigation of structure and antigenic capacities of Thermococcales cellenvelopes and reclassification of "Caldococcus litoralis" Z-1301 as Thermococcus litoralis Z-1301

Fourteen strains of hyperthermophilic organotrophic anaerobic marine Archae a were isolated from shallow water and deep-sea hot vents, and four of them were characterized. These isolates, eight previously published strains, an d six type strains of species of the order Thermococcales were selected for the study of cell wall components by means of thin sectioning or freeze-et ching electron microscopy. The cell envelopes of most isolates were shown t o consist of regularly arrayed surface protein layers, either single or dou ble, with hexagonal lattice (p6) symmetry, as the exclusive constituents ou tside the cytoplasmic membrane. The S-layers studied differed in center-to- center spacing and molecular mass of the constituent protein subunits. Poly clonal antisera raised against the cells of 10 species were found to be spe cies-specific and allowed 12 new isolates from shallow water hot vents to b e identified as representatives of the species Thermococcus litoralis. Ther mococcus stetteri, Thermococcus chitonophagus, and Thermococcus pacificus. Of the 7 deep-sea isolates, only 1 was identified as a T. litoralis strain. Thus, hyperthermophilic marine organotrophic isolates obtained from deep-s ea hot vents showed greater diversity with regard to their S-layer proteins than shallow water isolates.