Taxonomic Studies of Red Halophilic Bacteria

Abstract

A total of 95 strains of moderately to extremely halophilic bacteria, either from culture collections or freshly isolated, were subjected to taxonomic analysis by the computer method. The culture collection strains were examined in the initial phase of the study, and the fresh isolates were examined later. Three major groupings of these organisms were evident: a group of rodlike halophiles, a group of halotolerant, rod-shaped bacteria, and a less morphologically homogeneous, but taxonomically distinct, cluster of halophilic cocci. The rodlike halophiles could be further subdivided into one cluster containing strains of Halobacterium cutirubrum, which, on initial isolation, are capable of growth on media containing 8% salt when incubated at elevated temperatures, and another cluster containing strains of Halobacterium salinarium, which have a minimum requirement for 15% salt irrespective of the temperature of incubation. NRC 34002 and NRC 34001 are proposed as the neotype strains of Halobacterium salinarium and Halobacterium cutirubrum, respectively. The group of halophilic cocci appeared to be less homogeneous, i.e., were less uniform in character frequency of occurrence. Halococcus morrhuae is judged to be the correct name for the halophilic cocci. Results of the taxonomic analyses also indicated that at least two, and perhaps three, biovars comprise H. cutirubrum. A comparative study of the halophiles and a sample of 48 strains of halotolerant streptococci, staphylococci, and micrococci did not reveal any significant interrelationships. The moderate halophiles included in this analysis appear to be taxonomically distinct from the extreme halophiles. Results of lipid and pigment analyses accumulated for the halophilic bacteria support the taxonomic conclusions.Bacteria that require high concentrations of salt for growth have been known for nearly a century. The obligately halophilic bacteria, generally regarded as those which require at least 12% sodium chloride for growth, are found in the Dead Sea (B. Elazari-Volcani, Ph.D. thesis, Hebrew University, Jerusalem, Israel), on solar salt (30), on salted codfish (20), and in association with other salted products. The classification of these microorganisms has been rather uncertain, and their nomenclature has progressed from the "Microbe du rouge de morue" (29) through Bacillus (23), Pseudomonas (20), Bacterium (H. F. M. Petter, Ph.D. thesis, University of Utrecht, Utrecht, the Netherlands), Serratia (30), and Flauobacterium (14). In the seventh edition of Bergey's Manual (5), the obligately halophilic, rod-shaped bacteria were collected under the genus Halobacterium. The halophilic cocci, however, remained dispersed in the genera Micrococcus and Sarcina. This arrangement was changed in the eighth edition in which the genera Halo bacterium and Halococcus were placed together in part VII, Family 4: Halobacteriaceae (18).f Deceased, December 1977.In 1967, Larsen (28) suggested that bacteria which demonstrate a requirement for salt for optimal growth be designated as...

Nucleic Acid Studies on Halophilic Archaebacteria

“…cutirubrum C C M 2088 show high D N A homologies with each other (Table 2) and probably should be considered different isolates of the same species. These type strains have at various other times been considered identical (Gibbons, 1974;Colwell et a/., 1979). Most other strains examined and originally described as Hulohucfrrium sp.…”

“…Environmental pressures in the extreme conditions of salt pans and soda lakes may limit variety in biochemical and physiological processes, reflected in relative biochemical inactivity in most strains examined (Colwell et al, 1979;Gibbons, 1974). Some phenotypic differences do exist between the R N A homology groups, as can be seen in Table 1, although the number of biochemical traits is small and a greater divergence may emerge as more biochemical data is accumulated.…”

The Family Halobacteriaceae

“…In view of the ease (for some strains, extreme ease) with which halobacteria spontaneously lose their ability to produce gas vacuoles, the recognition of H. salinarium and H. halobium as different species should be reconsidered. Colwell et al (1979) (Buchanan and Gibbons, 1974), for H. cutirubrum: NRC 34001 (Colwell et aI., 1979).…”

The Halobacteriaceae

“…They were also insensitive to penicillin and related compounds, as would be expected from their lack of peptidoglycan (Kushner, 1978). Since then, tests of other halobacteria with antibiotic disks (Colwell et al, 1979;Soliman and Trüper, 1982;Hilpert et al, 1981) and tube dilutions (Pecher and Bock, 1981) showed that, depending on the strain used and the test employed, chloramphenicol and tetracycline were sometimes inhibitory. Aminoglycosides (e.g., streptomycin) and many inhibitors of protein synthesis that act on 70 S and 80 S ribosomes in other cells were inactive, as was pen icillin.…”