title: Genetic variation in sialidase and linkage to N-acetylneuraminate catabolism in Mycoplasma synoviae.
abstract: We explored the genetic basis for intraspecific variation in mycoplasmal sialidase activity that correlates with virulence, and its potentially advantageous linkage to nutrient catabolism. Polymorphism in N-acetylneuraminate scavenging and degradation genes (sialidase, N-acetylneuraminate lyase, N-acetylmannosamine kinase, N-acetylmannosamine-6-phosphate epimerase, N-acetylglucosamine-6-phosphate deacetylase, and glucosamine-6-phosphate deaminase) was evident among eight strains of the avian pathogen Mycoplasma synoviae. Most differences were single nucleotide polymorphisms, ranging from 0.34+/-0.04 substitutions per 100 bp for N-acetylmannosamine kinase to 0.65+/-0.03 for the single-copy sialidase gene nanI. Missense mutations were twice as common as silent mutations in nanI; 26% resulted in amino acids dissimilar to consensus; and there was a 12-base deletion near the nanI promoter in strain WVU1853(T), supporting a complex genetic basis for differences in sialidase activity. Two strains had identical frameshifts in the N-acetylneuraminate lyase gene nanA, resulting in nonsense mutations, and both had downstream deletions in nanA. Such genetic lesions uncouple extracellular liberation of sialic acid from generation of fructose-6-phosphate and pyruvate via intracellular N-acetylneuraminate degradation. Retention of nanI by such strains, but not others in the M. synoviae phylogenetic cluster, is evidence that sialidase has an important non-nutritional role in the ecology of M. synoviae and certain other mycoplasmas.
authors.affiliation: Department of Infectious Diseases and Pathology, College of Veterinary Medicine, University of Florida, Gainesville, FL 32611-0880, USA. mmay@ufl.edu
authors.forename: Meghan
authors.initials: M
authors.lastname: May
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Brown
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001482:Base Composition; D001715:Bird Diseases / Q000382:microbiology*; D002645:Chickens; D014644:Genetic Variation; D008969:Molecular Sequence Data; D009154:Mutation; D009175:Mycoplasma Infections / Q000382:microbiology / Q000662:veterinary*; D045805:Mycoplasma synoviae / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D019158:N-Acetylneuraminic Acid / Q000235:genetics / Q000378:metabolism; D009439:Neuraminidase / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D009439:Neuraminidase; D019158:N-Acetylneuraminic Acid; D000117:Acetylglucosamine