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Glycoinositolphosphoceramides (GIPCs) are complex sphingolipids present at the plasma membrane of various eukaryotes with the important exception of mammals. In fungi, these glycosphingolipids commonly contain an a-mannose residue (Man) linked at position 2 of the inositol. However, several pathogenic fungi additionally synthesize zwitterionic GIPCs carrying an a-glucosamine residue (GlcN) at this position. In the human pathogen Aspergillus fumigatus, the GlcNα1,2IPC core (where IPC is inositolphosphoceramide) is elongated to Manα1,3Manα1,6GlαNα1,2IPC, which is the most abundant GIPC synthesized by this fungus. In this study, we identified an A. fumigatus Nacetylglucosaminyltransferase, named GntA, and demonstrate its involvement in the initiation of zwitterionic GIPC biosynthesis. Targeted deletion of the gene encoding GntA in A. fumigatus resulted in complete absence of zwitterionic GIPC; a phenotype that could be reverted by episomal expression of GntA in themutant. The N-acetylhexosaminyltransferase activity of GntAwas substantiated by production of N-acetylhexosamine-IPC in the yeast Saccharomyces cerevisiae upon GntA expression. Using an in vitro assay, GntAwas furthermore shown to use UDP-N-acetylglucosamine as donor substrate to generate a glycolipid product resistant to saponification and to digestion by phosphatidylinositol- phospholipase C as expected for GlcNAca1,2IPC. Finally, as the enzymes involved in mannosylation of IPC, GntA was localized to the Golgi apparatus, the site of IPC synthesis. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate the incidence of fungal and bacterial contaminations of in-use eye drop products in the teaching department of ophthalmology, Imam Khomeini Hospital, Ahvaz. Two hundred and eighty seven eye drop bottles were randomly collected at the end of day 1, day 2, day 3, day 4 and day 7 of use. The eye drop residues, swabs from internal caps and droppers were inoculated onto MacConkey agar, blood agar and Sabouraud's dextrose agar. The identification of the recovered organisms was accomplished using standard microbial identification techniques. The incidence of microbial contamination of in-use eye drop products was 17.8%, with the highest rate (24.6%) and the lowest rate (9.0%) noted with day 1 and day 3 samples, respectively. The most contaminated part of the eye drop products was the caps (45.9%) followed by droppers (41.0%) and residual contents (13.1%). Considering mendicants contents, those with pilocarpine (41.7%) had the highest rate of contamination followed by atropine (31.8%), tropicamide (28.6%) and betamethasone (23.3%). Our study revealed the potential risk of contamination of in-use eye drop products in hospitals, but we did not find a direct relationship between usage duration and contamination rate. [ABSTRACT FROM AUTHOR]

Filamentous fungi are ubiquitous and ecologically important organisms with rich and varied life histories, however, there is no consensus on how to identify or measure their fitness. In the first part of this study we adapt a general epidemiological model to identify the appropriate fitness metric for a saprophytic filamentous fungus. We find that fungal fitness is inversely proportional to the equilibrium density of uncolonized fungal resource patches which, in turn, is a function of the expected spore production of a fungus. In the second part of this study we use a simple life history model of the same fungus within a resource patch to show that a bang-bang resource allocation strategy maximizes the expected spore production, a critical fitness component. Unlike bang-bang strategies identified in other fife-history studies, we find that the optimal allocation strategy for saprophytes does not entail the use of all of the resources within a patch. [ABSTRACT FROM AUTHOR]

Abstract: Sclerotinia sclerotiorum is unusual among necrotrophic pathogens in its requirement for senescent tissues to establish an infection and to complete the life cycle. A model for the infection process has emerged whereby the pathogenic phase is bounded by saprophytic phases; the distinction being that the dead tissues in the latter are generated by the actions of the pathogen. Initial colonization of dead tissue provides nutrients for pathogen establishment and resources to infect healthy plant tissue. The early pathogenicity stage involves production of oxalic acid and the expression of cell wall degrading enzymes, such as specific isoforms of polygalacturonase (SSPG1) and protease (ASPS), at the expanding edge of the lesion. Such activities release small molecules (oligo-galacturonides and peptides) that serve to induce the expression of a second wave of degradative enzymes that collectively bring about the total dissolution of the plant tissue. Oxalic acid and other metabolites and enzymes suppress host defences during the pathogenic phase, while other components initiate host cell death responses leading to the formation of necrotic tissue. The pathogenic phase is followed by a second saprophytic phase, the transition to which is effected by declining cAMP levels as glucose becomes available and further hydrolytic enzyme synthesis is repressed. Low cAMP levels and an acidic environment generated by the secretion of oxalic acid promote sclerotial development and completion of the life cycle. This review brings together histological, biochemical and molecular information gathered over the past several decades to develop this tri-phasic model for infection. In several instances, studies with Botrytis species are drawn upon for supplemental and supportive evidence for this model. In this process, we attempt to outline how the interplay between glucose levels, cAMP and ambient pH serves to coordinate the transition between these phases and dictate the biochemical and developmental events that define them. [Copyright &y& Elsevier]