Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/1999
Publication Date: 2/15/2000
Citation: Chen, J., Banks, D., Jarret, R.L., Chung, C.J., Smith, B.J. 2000. Using 16s + DNA sequences as signature characters to identify Xylella fastidiosa. Current Microbiology. 40:29-33
Interpretive Summary: Xylella fastidiosa is a Gram negative bacterial pathogen that causes many economically important plant diseases; however, identification of this pathogen is difficult due to its nutritional fastidiousness. Serology has been the most frequently utilized method to identify Xyl. fastidiosa at the species level; but, the taxonomic roles of the targeted antigens are not well defined. The 16S rDNA, which codes for the small subunit of ribosomal RNA, is now the most widely used informational macromolecule for bacterial systematic studies at the family, genus, species, and subspecies levels. The 16S rDNA contains conserved sequences that can be used to infer natural relationships between distantly related species and variable regions that can be used to separate closely related ones. Such a 16S rDNA sequence-based identification technique will substantially facilitate the ecological study and the control of difficult to culture microorganisms. In this study we determined that the 6S rDNA of Xyl. fastidiosa strains are highly homologous and characteristically different from other bacteria including the most closely related Xanthomonas. 16S rDNA sequences can be used as signature characters to identify this bacterium. These results will be utilized by research scientists studying diseases caused by this pathogen and ultimately by growers and extension agents for identification of this pathogen.
Technical Abstract: The nucleotide sequences of 16S rDNAs (coding for the small sub- unit ribosomal RNAs) were used to identify Xylella fastidiosa, a nutritionally fastidious plant pathogenic bacterium. The near- complete 16S rDNAs from nine strains of Xyl. fastidiosa including seven pathotypes and one strain of Xanthomonas campestris pv. campestris, were amplified through PCR using two conserved primers (forward primer 5'- AGA GTT TGA TCC TGG CTC AG-3' and reverse primer 5' -AAG GAG GTG ATC CAG CC-3') and sequenced. The 16S sequences were compared with all eukaryote and prokaryote DNA entries in GenBank database. A Xyl. fastidiosa 16S rDNA sequence, M26601, was determined to be the most similar one to all the near- complete (1,537 bp) and partial 5' end sequences from Xyl. fastidiosa but not those from the Xanthomonas strain. A 20 bp oligonucleotide (5'-TTG GTA GTA ATA CCA TGG GT-3') was found to be highly characteristic of Xyl. fastidiosa. Since the 16S rDNA of Xyl. fastidiosa strains are highly homologous and characteristically different from other bacteria including the most closely related Xanthomonas, 16S rDNA sequences can be used as signature characters to identify this bacterium.