Taxonomy of spirochetes

The taxonomy of spirochetes has improved considerably over the last few years. Even non-cultivable spirochetes have been classified and identified and highly discriminating analytical methods have been used to distinguish these unique organisms. The present article reviews major characteristics and techniques that have been applied in recent molecular taxonomy and chemotaxonomy of spirochetes. These comprise cellular lipids, carbohydrates, peptidoglycan, enzymes, cell proteins, cytoplasmic fibrils, metabolites, genome size, structure and base composition, restriction endonuclease analysis, restriction fragment length polymorphism, multilocus enzyme electrophoresis, pulsed-field gel electrophoresis, DNA-DNA hybridization, arbitrarily primed polymerase chain reaction/randomly amplified polymorphic DNA fingerprinting, ribosomal (r) RNA cataloguing and sequencing, characterization of intergenic spacer regions of rRNA genes, ospA, lipoprotein and flagellin gene sequencing, and rRNA gene organization. Characteristics and techniques such as those listed above have contributed to the recognition of new spirochetal genera and species and have made spirochetal taxonomy polyphasic. Despite these improvements, significant reservoirs of hitherto unrecognized. spirochetal diversity probably still exist. (C) 2000 Academic Press.