Xylella fastidiosa subspecies: X. fastidiosa subsp. [correction] fastidiosa [correction] subsp. nov., X. fastidiosa subsp. multiplex subsp. nov., and X. fastidiosa subsp. pauca subsp. nov

Syst Appl Microbiol. 2004 May;27(3):290-300. doi: 10.1078/0723-2020-00263.


Xylella fastidiosa, a fastidious bacterium causing disease in over 100 plant species, is classified as a single species, although genetic studies support multiple taxons. To determine the taxonomic relatedness among strains of X. fastidiosa, we conducted DNA-DNA relatedness assays and sequenced the 16S-23S intergenic spacer (ITS) region using 26 strains from 10 hosts. Under stringent conditions (Tm -15 degrees C), the DNA relatedness for most X. fastidiosa strains was *70%. However, at high stringency (Tm -8 degrees C), three distinct genotypes (A, B, and C) were revealed. Taxon A included strains from cultivated grape, alfalfa, almond (two), and maple, interrelated by 85% (mean); taxon B included strains from peach, elm, plum, pigeon grape, sycamore, and almond (one), interrelated by 84%; and taxon C included only strains from citrus, interrelated by 87%. The mean reciprocal relatedness between taxons A and B, A and C, and B and C, were 58, 41, and 45%, respectively. ITS results also indicated the same grouping; taxons A and B, A and C, and B and C had identities of 98.7, 97.9, and 99.2%, respectively. Previous and present phenotypic data supports the molecular data. Taxon A strains grow faster on Pierce's disease agar medium whereas B and C strains grow more slowly. Taxon B and C strains are susceptible to penicillin and resistant to carbenicillin whereas A strains are opposite. Each taxon can be differentiated serologically as well as by structural proteins. We propose taxons A, B, and C be named X. fastidiosa subsp. fastidiosa [correction] subsp. nov, subsp. multiplex, subsp. nov., and subsp. pauca, subsp. nov., respectively. The type strains of the subspecies are subsp. fastidiosa [correction] ICPB 50025 (= ATTC 35879T and ICMP 15197), subsp. multiplex ICPB 50039 (= ATTC 35871 and ICMP 15199), and subsp. pauca ICPB 50031 (= ICMP 15198).

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Bacterial Proteins / analysis
  • Base Sequence
  • Carbenicillin / pharmacology
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / isolation & purification
  • DNA, Ribosomal Spacer / chemistry
  • DNA, Ribosomal Spacer / isolation & purification
  • Genotype
  • Molecular Sequence Data
  • Penicillins / pharmacology
  • Plants / microbiology*
  • Sequence Alignment
  • Sequence Analysis, DNA
  • Sequence Homology, Nucleic Acid
  • Serotyping
  • Transition Temperature
  • Xylella / classification*
  • Xylella / genetics*
  • Xylella / growth & development
  • Xylella / isolation & purification
  • Xylella / metabolism


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • DNA, Bacterial
  • DNA, Ribosomal Spacer
  • Penicillins
  • Carbenicillin