Genetic diversity analysis of Rhodothermus reflects geographical origin ofthe isolates

The genetic diversity and relationships of 81 Rhodothermus isolates from di fferent geothermal environments in Iceland were examined by analysis of ele ctrophoretically demonstrable allelic variation of 13 genes encoding enzyme s. All the enzymes were polymorphic. A total of 71 distinctive multilocus g enotypes (electrophoretic types, ETs) were identified. The mean genetic div ersity per locus (H-t) was 0.586. The relatively high genetic variance obse rved within Rhodothermus isolates from different locations is most likely t he result of genetic changes occurring independently in the locations studi ed. A high G(st) value (0.284) indicates that a considerable part of the va riance observed is due to differences between locations, Cluster analysis r evealed two major groups of ET clusters diverging at a genetic distance of 0.75, reflecting strongly the geographic origin of isolates. Estimation of the association index (I-A) indicates that Rhodothermus marinus is a clonal species in which recombination events occur rarely. Partial or whole seque ncing of the 16S rRNA genes of Rhodothermus isolates grouping at genetic di stance of 0.40 confirmed that all the isolates belonged to the species Rhod othermus marinus. The results of this study confirm that, despite phylogene tic and phenotypic similarity, genetic diversity within Rhodothermus marinu s is quite high.