title: Phenotypic switching in Mycoplasma gallisepticum hemadsorption is governed by a high-frequency, reversible point mutation.
abstract: Mycoplasma gallisepticum is a flask-shaped organism that commonly induces chronic respiratory disease in chickens and infectious sinusitis in turkeys. Phenotypic switching in M. gallisepticum hemadsorption (HA) was found to correlate with phase variation of the GapA cytadhesin concurrently with that of the CrmA protein, which exhibits cytadhesin-related features and is encoded by a gene located downstream of the gapA gene as part of the same transcription unit. In clones derived from strain R(low), detailed genetic analyses further revealed that on-off switching in GapA expression is governed by a reversible base substitution occurring at the beginning of the gapA structural gene. In HA(-) variants, this event generates a stop codon that results in the premature termination of GapA translation and consequently affects the expression of CrmA. Sequences flanking the mutation spot do not feature any repeated motifs that could account for error-prone mutation via DNA slippage and the exact mechanism underlying this high-frequency mutational event remains to be elucidated. An HA(-) mutant deficient in producing CrmA, mHAD3, was obtained by disrupting the crmA gene by using transposition mutagenesis. Despite a fully functional gapA gene, the amount of GapA detected in this mutant was considerably lower than in HA(+) clonal variants, suggesting that, in absence of CrmA, GapA might be subjected to a higher turnover.
authors.affiliation: Institute of Bacteriology, Mycology and Hygiene, University of Veterinary Medicine Vienna, A-1210 Vienna, Austria.
authors.forename: Florian
authors.initials: F
authors.lastname: Winner
authors.forename: Ivana
authors.initials: I
authors.lastname: Markovà
authors.forename: Peter
authors.initials: P
authors.lastname: Much
authors.forename: Albin
authors.initials: A
authors.lastname: Lugmair
authors.forename: Karin
authors.initials: K
authors.lastname: Siebert-Gulle
authors.forename: Gunther
authors.initials: G
authors.lastname: Vogl
authors.forename: Renate
authors.initials: R
authors.lastname: Rosengarten
authors.forename: Christine
authors.initials: C
authors.lastname: Citti
mesh_terms: D018829:Adhesins, Bacterial / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D000595:Amino Acid Sequence; D001483:Base Sequence; D004912:Erythrocytes / Q000378:metabolism; D006382:Hemadsorption; D008969:Molecular Sequence Data; D009174:Mycoplasma / Q000502:physiology*; D010641:Phenotype; D017354:Point Mutation; D015843:Serpins / Q000032:analysis / Q000235:genetics / Q000502:physiology; D014158:Transcription, Genetic; D014764:Viral Proteins
chemical_list: D018829:Adhesins, Bacterial; C117938:GapA cytadhesin; D015843:Serpins; D014764:Viral Proteins; C074641:interleukin-1beta-converting enzyme inhibitor