**3. Taxonomy**

The most identifications of environmental isolates are done by 16S rRNA sequence analysis, in a first common identification step, diagnostic taxonomic properties are: (1) yellow, "fried egg" shaped colonies with several amounts of slime production under cultivation media specific conditions; (2) rods, some species have strong polymorphic, branched, twisted cell morphology growing on nutrient agar with larger amounts of polyphosphate granula, can lead to the false impression of a Gram-positive staining reaction; however all *Xanthobacter* stain are truly Gram negative when is using a counterstain in polyphosphate-free cells of *X. autotrophicus* [2, 22, 24].
