The family spiroplasmataceae

The family Spiroplasmataceae is one of two in the order Entomoplasmatales. The family contains a single genus, Spiroplasma, whose members are regularly associated with arthropod or plant hosts. Spiroplasma species can be traced to a common ancestor; however, this lineage also includes the nonhelical Entomoplasma, Mesoplasma, and mycoides group (Mycoplasma) descendants. Spiroplasma cells are characterized by their helical shape, which is most common during exponential growth, and by their lack of a cell wall. They are motile due to a unique linear motor that allows for rotatory, flexional, and translational motility. Genome sizes range from 780 to 2,220 kbp in these AT-rich organisms (24-31 mol% G+C) that commonly harbor viral sequences in large areas of repetitive sequence. Spiroplasmas are chemo-organotrophic, generally fermenting glucose through the phosphoenolpyruvate-dependent sugar transferase system. Most strains require rich media for initial isolation and/or maintenance, and all spiroplasmas are resistant to penicillin. Temperature ranges (5-41 °C), growth optima, and doubling times are species specific. Due to motility, colonies are diffuse and range in size from 0.1 to 4.0 mm. Historically, Spiroplasma classification relied on surface serology as a surrogate for DNA-DNA hybridization assays, resulting in 49 reported serogroups and 15 subgroups. There are a total of 38 described Spiroplasma species, as not all serogroup/subgroup type strains have been fully characterized. Most host relationships are commensal, but cases of mutualism and pathogenicity have been reported. For example, spiroplasma infections cause citrus stubborn disease, corn stunt disease, sex ratio disorders, and honey bee mortality; spiroplasmas are pathogenic for suckling rodents and/or chicken embryos under experimental conditions. This chapter is a modified and updated version of previous family descriptions (Williamson DL, Gasparich GE, Regassa LB, Saillard C, Renaudin J, Bové JM, Whitcomb RF (2010) Family II. Spiroplasmataceae. In: Krieg NR, Ludwig W, Whitman WB, Hedlund BP, Paster BJ, Staley JT, Ward N, Brown D, Parte A (eds) Bergey's Manual of Systematic Bacteriology, vol 4. Springer, New York, pp 654-686; Brown DR, Bradbury JM, Whitcomb RF (2010) Order II. Entomoplasmatales. In: Krieg NR, Ludwig W, Whitman WB, Hedlund BP, Paster BJ, Staley JT, Ward N, Brown D, Parte A (eds) Bergey's Manual of Systematic Bacteriology, vol 4. Springer, New York, pp 644-645).