In the presence of calcofluor white, budding scars and dividing cross-walls of Saccharomyces cereuisiae exhibited fluorescence, indicating that the brightener was a specific marker of fungal chitin. In addition, incubation of cells in the presence of the brightener did not stop protein and wall-polymer formation, but abnormal deposition of chitin occurred. Chitin synthesis was normal in regenerating protoplasts of Candida albicans in the presence of calcofluor, but formation of the crystalline lattice was blocked. These results suggest that crystallization of nascent subunits may occur by a self-assembly mechanism that was blocked by the stain.

The Candida albicans MKCl gene encodes a mitogen-activated protein (MAP) kinase, which has been cloned by complementation of the lytic phenotype associated with Saccharomyces cerevisiae slt2 (mpkl) mutants. In this work, the physiological role of this MAP kinase in the pathogenic fungus C. albicans was characterized and a role for MKC7 in the biogenesis of the cell wall suggested based on the following criteria. First, C. albicans m k c l hlmkcl A strains displayed alterations in their cell surfaces under specific conditions as evidenced by scanning electron microscopy. Second, an increase in specific cell wall epitopes (0-glycosylated mannoprotein) was shown by confocal microscopy in mkc7 hlmkcl A mutants. Third, the sensitivity to antifungals which inhibit (1,3)+glucan and chitin synthesis was increased in these mutants. In addition, evidence for a role for the MKCl gene in morphological transitions in C. albicans is presented based on the impairment of pseudohyphal formation of m k c l hlmkcl A strains on Spider medium and on the effect of its overexpression on Sacch. cerevisiae colony morphology on SLADH medium. Using the two-hybrid system, it was also demonstrated that MKCl is able to interact specifically with Sacch. cerevisiae Mkklp and MkkZp, the MAPkinase kinases of the PKC1-mediated route of Sacch. cerevisiae, and to activate transcription in Sacch. cerevisiae when bound to a DNA-binding element. These results suggest a role for this MAP kinase in the construction of the cell wall of C, albicans and indicate its potential relevance for the development of novel antif ungals.

No abstract

Different techniques released from the wall of Candida albicans mycelial cells high molecular weight mannoprotein materials with different levels of complexity. SDS solubilized among others one protein of 180 kDa which reacted with a monoclonal antibody (MAb) specific of a O-glycosylated protein secreted by regenerating mycelial protoplasts [Elorza et al. (1989) Biochem Biophys Res Commun 162:1118-1125]. Zymolyase, chitinase and beta-mercaptoethanol, released different types of high molecular highly polydisperse mannoprotein materials (greater than 180 kDa) that also reacted with the same MAb. These materials had N-glycosidically linked sugar chains, in addition to the O-glycosidically bonded sugars, as their molecular masses were significantly reduced by Endo H digestion. Besides, the specific materials released by either zymolyase or chitinase seemed to be the same throughout the process of germ tube formation. Transmission electron microscopy of thin sections of cells and walls showed that mannoproteins and chitin are evenly distributed throughout the entire cell wall structure.

From September 1999 to March 2000, meat (pork, beef, and chicken), fish (salmon, hake, and sole), vegetable (lettuce and spinach), and Spanish potato omelette samples obtained at restaurants were collected and tested for the occurrence of Listeria spp. Listeria monocytogenes was isolated from 3 (2.9%) out of 103 studied samples. Other species isolated were Listeria grayi (13.6%), Listeria innocua (1.9%), Listeria ivanovii (5.8%), Listeria seeligeri (3.9%), and Listeria welshimeri (1.9%). Listeria was neither isolated from beef nor any type of fish.