http://scholar.google.de/scholar?q=differentiate+different+species+of+Xanthomonas&hl=de&as_sdt=0&as_vis=1&oi=scholart&sa=X&ei=qWR2U_HeHKPh4QTmmYGoBg&ved=0CC4QgQMwAA

get the sequence of 16s RNA

Devendra, using biochemical methods only you can easily differentiate only 5 species (see Xanthomonas taxonomy before 1995: http://ijs.sgmjournals.org/content/40/4/348.short; http://ijsb.sgmjournals.org/content/40/3/312.short). Other species (over 20) were identified by combination of many tests including DNA:DNA hybridization, MLST, protein analysis, FAME, etc., and species recognized by classic methods were not always supported by new ones (http://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO.2000.90.7.677).

My experience show that only highly pathogenic "typical" isolates of xanthomonads have biochemical properties like type strains of the species. But, isolates from rare or wild host plant, or causing unusual symptoms can be very different despite genetic symilarity to type cultures.

PS: unfortunatelly, 16S rRNA sequence is useless for Xanthomonas species identification except a few ones, that could be in fact not Xanthomonas, but of other genera (like X. albilineans, X. translucens, etc.)

You can do the fatty acid analysis described by this paper

http://link.springer.com/article/10.1023%2FA%3A1008601614221

thank you all for your kind words and support