Diversity of Extremely Halophilic Bacteria
Masahiro KAMEKURA*
Noda Institute for Scientific Research, 399 Noda, Noda-shi 278, Japan
The extremely halophilic, aerobic Archaea are classified within the single family Halobacteriaceae of the order Halobacteriales, which currently contains ten valid genera: Halobacterium, Halococcus, Haloarcula, Haloferax, Halorubrum, Halobaculum, Natrialba, Natronobacterium, Natronomonas, and Natronococcus. These divisions are based largely on chemotaxonomic criteria, particularly composition of membrane polar lipids, and phylogenetic analyses of 16S rRNA gene sequences.
Recent phylogenetic analysis of the four species of alkaliphilic halobacteria has shown that they belong to four different genera. Though there had been a tacit consensus that extreme halophiles of the same genus contained the same membrane glycolipid until mid 1995, the genus Halorubrum now comprises species containing different glycolipids, including a haloalkaliphile H. vacuolatum (1).
More recently, analysis of 16S rRNA gene sequences of three strains possessing different glycolipid patterns ("Halobacterium trapanicum" JCM 9743, strain GSL-11, and Halococcus turkmenicus) has shown that they constitute a new species of a new genus "Haloterrigens turkmenicus"(2).
The PCR amplification of 16S rRNA genes with DNA extracted from environmental samples has promised the expansion of the diversity of halobacteria in nature, e.g., clones HAC 1 and HAC4 isolated by Rodriguez-Valera et al. from Spanish salt ponds (3), and clones FFSB 12 and FFSB9 of halophile DNA obtained from Finnish forest soil (4,5). The HAC1 and HAC4 sequences clearly suggest that they are from candidates of a novel family of the order Halobacteriales.
1. Kamekura, M., Dyall-Smith, M.L., Upasani, V., Ventosa, A., and Kates, M. (1997) Int. J. Syst. Bacteriol., 47, 853-857.
2. Ventosa, A., Gutierrez, M.C., Kamekura, M., and Dyall-Smith, M.L. (1997) Int. J. Syst. Bacteriol., submitted.
3. Benlloch, S., Martinez-Murcia, A.J., and Rodriguez-Valera, F. (1995) Syst. Appl. Microbiol., 18, 574-581.
4. Schleper, C., Holben, W.,and Klenk, P.-H. (1997) Appl. Environ. Microbiol., 63, 321-323.
5. Jurgens, G., Personal communication.
