A detailed phenotypic characterisation of the type strains of Halomonas species

We have made a detailed phenotypic characterisation of the type strains of 21 species within the genus Halomonas and have also studied any possible intraspecific variation of strains within H. eurihalina, H. halophila, H. maura and H. salina. We used 234 morphological, physiological, biochemical, nutritional and antimicrobial susceptibility tests. Nutritional assays were carried out using both classical and miniaturized (BIOLOG system) identification methods. Two different numerical analyses were made using the TAXAN program; the first included the differential data from all the tests carried out whilst the second used only the 57 tests with the highest diagnostic scores ( ! 0.5). The results of both analyses were quite similar and demonstrated the phenotypic heterogeneity of the Halomonas species in question. At a 62% similarity level the type species were grouped into three phena, the main difference between them being the capacity of those included within phenon A (H. aquamarina, H. meridiana, H. cupida, H. pantelleriensis and H. halmophila) to produce acids from sugars. The species grouped in phenon C (H. campisalis, H. desiderata and H. subglasciescola) used fewer organic substrates than the others. The remaining strains were included in phenon B. H. marisflavi was clearly distinct and thus was not included in any of the three phena. High phenotypic similarity (more than 88%) was found between Halomonas campisalis and Halomonas desiderata. The results of our work should allow researchers to minimise the tests required to arrive at a reliable phenotypic characterisation of Halomonas isolates and to select those of most use to differentiate Halomonas species from each other.