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Published February 2007 | public
Journal Article

Haloquadratum walsbyi gen. nov., sp. nov., the square haloarchaeon of Walsby, isolated from saltern crystallizers in Australia and Spain

Abstract

Strains C23^T and HBSQ001 were isolated from solar salterns and are novel square-shaped, aerobic, extremely halophilic members of the domain Archaea and family Halobacteriaceae. Cells stained Gram-negative and grew optimally in media containing 18 % salts at around neutral pH. Mg^(2+) is not required. The DNA G+C content of both isolates was 46.9 mol% and DNA–DNA cross-hybridization showed a relatedness of 80 %. Their 16S rRNA gene sequences showed only 2 nucleotide differences (99.9 % identity) and phylogenetic tree reconstructions with other recognized members of the Halobacteriaceae indicated that they formed a distinct clade, with the closest relative being Halogeometricum borinquense PR 3^T (91.2 % sequence identity). The major polar glycolipid of both isolates was the sulfated diglycosyl diether lipid S-DGD-1. Electron cryomicrosopy of whole cells revealed similar internal structures, such as gas vesicles and polyhydroxyalkanoate granules, but the cell wall of isolate HBSQ001 displayed a more complex S-layer compared with that of isolate C23^T. The phenotypic characterization and phylogenetic data support the placement of isolates C23^T and HBSQ001 in a novel species in a new genus within the Halobacteriaceae, for which we propose the name Haloquadratum walsbyi gen. nov., sp. nov. The type strain of Haloquadratum walsbyi is C23^T (=JCM 12705^T=DSM 16854^T).

Additional Information

Copyright © 2007 International Union of Microbiological Societies. The authors thank Professor Dr Hans G. Trüper for his advice regarding nomenclature. We thank Dr Jane Ding for her help in writing a module of measuring the distance between membrane layers. D. G. B. was supported by an Australian Post-graduate Award. M. L. D.-S. was supported by a University of Melbourne MRGS award in 2005 and by the Department of Microbiology and Immunology. G. J. was supported by NIH grant R01 AI067548. H. B. was supported by a grant from the Netherlands Organization of Science NWO/ALW/NPP-851.20.023. The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of isolates C23^T and HBSQ001 are respectively AY676200 and AM180088.

Additional details

Created:
August 19, 2023
Modified:
October 23, 2023