Fungi Feeling Their Surroundings

Abstract

Candida albicans , a human fungal pathogen, exhibits contact-dependent behaviors, such as invasive hyphal growth or biofilm formation, in response to host tissues or growth on solid surfaces. Yeast have a cell integrity mitogen-activated protein kinase (MAPK) pathway that is involved in responses to cell-wall damage or membrane deformation, and Kumamoto investigated the possibility that this pathway was activated by contact with a solid surface. The author used Western blot analysis to show that the C. albicans cell integrity kinase, Mkc1p, was phosphorylated not only after treatments that induced cell-wall stress or membrane curvature but also in response to growth on semisolid agar rather than liquid media. Whereas wild-type C. albicans grown on the surface of an agar medium extended invasive filaments into the agar, a strain lacking Mkc1p did not; invasive filamentous growth was restored by introducing wild-type MKC1 into the mutant strain. When grown on a polystyrene surface, cells lacking Mkc1p formed an abnormal biofilm. Although invasive filamentation in cells lacking Mkc1p was restored through ectopic expression of the DNA binding protein Czfp1, Czfp1 antagonized biofilm formation. Thus, the author concluded that the cell integrity pathway is involved in the response of C. albicans to contact with a surface and that the different responses to different types of surface involve the integration of input from multiple signaling pathways. C. A. Kumamoto, A contact-activated kinase signals Candida albicans invasive growth and biofilm development. Proc. Natl. Acad. Sci. U.S.A. 102 , 5576-5581 (2005). [Abstract] [Full Text]