Investigations on the taxonomy and the genetics of caldoactive bacteria

Abstract

The technique of pyrolysis mass spectrometry was used to attempt to obtain taxonomic groupings for a number of extremely thermophilic bacteria isolated from New Zealand hot springs. The New Zealand isolates were compared with a number of appropriate reference strains obtained from culture collections or as gifts from other laboratories. Three groups of bacteria were analysed. The Thermus-like group was found to consist of three species - level groupings with most of the New Zealand isolates belonging to a single species group. The two reference species T. aquaticus and T. thermophilus apparently belong to separate species groups. Bacillus-like strains grown at neutral pH formed three separate species groups which could correspond to the three species of thermophilic Bacilli proposed by Wolf and Sharp (1981). Analysis of a number of archaebacteria confirmed the unique nature of AN1 isolated from a New Zealand hot spring by Morgan and Daniels (1982). The Thermoproteus-type strains isolated from New Zealand seem rather different from the type strain T. tenax which also has some different physiological properties. An interesting feature of these strains was the contribution of sulphur to the mass spectra. Taxonomic groupings did not show a close relationship with source temperature and pH but regional groupings were obtained in some cases. The distribution of AN1-like strains seems to be related to the Na⁺ content of source pools. The majority of New Zealand isolates tended to form rather large clusters, probably at the species level, although sub-species level clusters existed within these. This suggests that although extreme thermophiles may be very variable as reported, this variability is limited. Differences in clustering patterns of different isolates from the same source confirm a considerable level of sub-species level variability does exist. A method for cloning Themrus genes by cosmid packaging was attempted and was apparently successful but gene expression was not demonstrated. A UV inducible temperate phage was isolated from Sulfolobus acidocaldarius strain B-12. It was purified and partially characterised and a method of growing Sulfolobus on solid medium obtained.