THE TRIANGULAR HALOPHILIC ARCHAEBACTERIUM HALOARCULA-JAPONICA STRAIN TR-1

We have isolated a predominantly triangular disc-shaped halophilic archaebacterium, strain TR-1, from a Japanese saltern soil. The taxonomical characteristics of this strain led us to propose a new species Haloarcula japonica. The cell division of Ha. japonica strain TR-1 was analyzed by time lapse microscopic cinematography. Cell plates were laid down asymmetrically, generating triangular or rhombic daughter cells which then separated. We have demonstrated the occurrence of a glycoprotein with an apparent molecular mass of 170 kDa on the cell surface of Ha. japonica. The release of this cell surface glycoprotein (CSG), accompanied by a morphological change (triangular to spherical), was observed after lowering the magnesium concentration in the medium. Thus, it is likely that the CSG plays an important role in maintaining the characteristic shape of Ha. japonica.