[Advances in classification and biodiversity of spiroplasmas--a review]

Spiroplasma spp. are helical, motile bacteria that lack cell wall and flagellum, and are enclosed within a single membrane with their genomes ranging from approximately 0.78-2.20 Mb in size, the smallest among known self-replicating prokaryotes. So they have been used as model organisms for studying movement, metabolisms and sex ratio. Currently, 34 serological groups are recognized; three of these groups encompass 15 subgroups of inter-related strains. To date, 37 species among all serogroups and subgroups have been given binomial names. Complete characterization of a new species involves numerous phenotypic and genotypic tests as outlined in the minimal standards document, including phylogenetic data and a reevaluated set of required phenotypic and genotypic tests. Spiroplasma spp. are most often found in association with insects and plants flowers, and the interactions of Spiroplasma/host can be classified as commensal, pathogenic or mutualistic. Investigation of spiroplasma resources in China and research on their biodiversity will undoubtedly improve our understanding of these important microbial resources.