Proposed Minimal Standards for Description of New Taxa in the Order Halobacteriales

Abstract

In accordance with Recommendation 30b of the International Code of Nomenclature of Bacteria, which calls for the development of minimal standards for describing new species, we propose minimal standards for description of new taxa in the order Hulobucteriules. The minimal standards include information on the following characteristics: cell morphology; motility; pigmentation; the requirement for salt to prevent cell lysis; optimum NaCl and MgCl, concentrations for growth and range of salt concentrations enabling growth; temperature and pH ranges for growth; anaerobic growth in the presence of nitrate or arginine; acid production from a range of carbohydrates; ability to grow on single carbon sources; catalase and oxidase tests; hydrolysis of starch, casein, and Tween 80; sensitivity to different antibiotics; and polar lipids. The placement of a new taxon should be consistent with phylogeny, which is usually based on 16s rRNA nucleotide sequence information, and with DNA-DNA hybridization data in the case of descriptions of new species. This proposal has been endorsed by the members of the Subcommittee on the Taxonomy of Hulobucteriuceue of the International Committee on Systematic Bacteriology.In accordance with Recommendation 30b of the International Code of Nomenclature of Bacteria (21), which calls for the development of minimal standards for describing new species, we propose minimal standards for descriptions of new taxa of aerobic halophilic archaea (order Halobacteriales).General principles. The purpose of this article is to provide microbiologists involved in the taxonomy of the aerobic halophilic archaea (order Halobacteriales, family Halobacteriaceae; also called halobacteria below) a framework for studying them. Adherence to the suggested minimum standards below should help stabilize the taxonomy of the Halobacteriales. With the consent and support of the Subcommittee on the Taxonomy of Halobacteriaceae we have adopted a polyphasic view of halophile taxonomy as suggested by Murray et al. (26). We recommend that all future taxonomic publications on the Halobacteriales should contain data on phenetic, chemical, and molecular properties. We thus recognize that modern natural classification requires as complete a data set as possible, including phenotypic and genotypic information. Table 1 provides a list of the presently recognized genera and species in the Halobacteriales. The current classification is based on the following three kinds of data: (i) phenotypic data, such as cell morphology, growth properties, etc. (34); (ii) chemical data, especially the patterns of polar lipids present in the membranes (34, 36) (differences in polar lipid patterns have been particularly important at the genus level); and (iii) 16s rRNA sequence information and DNA-DNA hybridization data. During the last few years a fairly complete database of 16s rRNA sequences of the type strains of the species in the Halobacteriales has become available and has enabled the con-*

Natrialba hulunbeirensis sp. nov. and Natrialba chahannaoensis sp. nov., novel haloalkaliphilic archaea from soda lakes in Inner Mongolia Autonomous Region, China.

“…As shown in Table 2, there are two subgroups in the genus Natrialba ; members of one subgroup (Natrialba asiatica JCM 9576 T and JCM 9577) contain a glycolipid (2,6-HSO $ -Manp-α(1 2)-Glcp-α(1 1)-sn-glyceroldiether ; S # -DGD-1) in addition to phospholipids (PG and PGP-Me), and members of the other subgroup (Natrialba magadii NCIMB 2190 T and our two isolates) contain only PG and PGP-Me. This feature would imply that the genus Natrialba constitutes a heterogeneous group and it is not in accordance with the principles of polyphasic taxonomy (Grant & Larsen, 1989 ;Oren et al, 1997). Future studies should clarify the classification of the entire group.…”

“…Phenotypic tests on strains X21 T and C112 T were carried out in accordance with the recommended standard methods for halobacteria (Oren et al, 1997). Cell motility and shape were examined by phasecontrast microscopy without fixation and by Gram staining with acetic acid fixation.…”

“…Therefore, in combination with other phenotypic features such as morphology, physiology and biochemistry, the phylogenetic inference of 16S rRNA sequences and DNA-DNA hybridization play important roles in the classification of haloalkaliphilic archaea. In 1997, the ICSB Subcommittee on the Taxonomy of Halobacteria proposed minimum standards for the classification of halobacterial archaea and suggested that the classification of halobacteria should be polyphasic and consistent with the phylogenetic analysis of 16S rRNA 01718 # 2001 IUMS gene sequences (Oren et al, 1997). Recently, great progress has been made in the classification of haloalkaliphilic archaea : Kamekura et al (1997) classified some species previously included in the genus Natronobacterium into three different genera : Natronomonas, Natrialba and Halorubrum.…”

Haloterrigena thermotolerans sp. nov., a halophilic archaeon from Puerto Rico.

“…Biochemical tests. Unless specified otherwise, tests for phenotypic properties were carried out as indicated in the proposed minimal standards for the description of new taxa in the order Halobacteriales (Oren et al, 1997). Nitrate reduction was tested in liquid SG medium supplemented with 0n5 % NaNO $ .…”

Isolation, Identification and Extracellular Enzymatic Activity of Culturable Extremely Halophilic Archaea and Bacteria of IncheBoroun Wetland

“…The development of red color in saline environments is a phenomenon which was observed thousand of years ago. Studies in the early 20 th century identified the cause and described several archaeal isolates [6]. Halophilic archaea can accumulate potassium ions intracellularly in order to balance the high salt content of saline environments.…”