Phenotypes of M. gallisepticum strains and mutants used as inocula in the experimental infection. Hemadsorption capacity, expression of GapA and CrmA, and the nature of the underlying mutations in HA− mutants Rhigh, RCL2, and mHAD3 are depicted. While Rhigh displays a frameshift mutation in gapA and mHAD3 a disruption of crmA by transposon insertion, RCL2 harbors a nonsense mutation in gapA which is highly reversible.