Immuno-crossreactivity of an anti-Pichia anomala killer toxin monoclonal antibody with a Williopsis saturnus var. mrakii killer toxin.

A monoclonal antibody (mAbKT4), produced against the Pichia anomala ATCC 96603 killer toxin (PaKT) was used to detect the toxin (WmKT) produced by Williopsis saturnus var. mrakii MUCL 41968 which inhibits the growth of a PaKT-sensitive P. anomala strain MUCL 41969. Immunofluorescence studies revealed that mAbKT4 specifically labels the surface of P. anomala and W. saturnus var. mrakii, suggesting that both taxa secrete a killer toxin bearing a common epitope. Immunoblot analyses of concentrated supernatants from P. anomala and W. saturnus var. mrakii cultures showed that in both taxa mAbKT4 reacts with high molecular weight secreted proteins ranging 85-200 kDa. However, immunoblot experiments showed that the molecular weights of PaKT and WmKT are quite different, indicating that the two toxins are related but not identical molecules.