Conserved Role for Biofilm Matrix Polysaccharides in Candida auris Drug Resistance.

Candida auris has emerged as an outbreak pathogen associated with high mortality. Biofilm formation and linked drug resistance are common among Candida species. Drug sequestration by the biofilm matrix accounts for much of the antifungal tolerance. In this study, we examine the biofilm matrix composition and function for a diverse set of C. auris isolates. We show that matrix sequesters nearly 70% of the available triazole antifungal. Like the biofilms formed by other Candida spp., we find that the matrix of C. auris is rich in mannan-glucan polysaccharides and demonstrate that their hydrolysis reduces drug tolerance. This biofilm matrix resistance mechanism appears conserved among Candida species, including C. aurisIMPORTANCECandida auris is an emerging fungal threat linked to poor patient outcomes. The factors responsible for this apparent increase in pathogenicity remain largely unknown. Biofilm formation has been suggested as an important factor for persistence of this organism in patients and the environment. Our findings reveal one mechanism utilized by C. auris to evade the effect of triazole antifungal therapy during biofilm growth. The conservation of the protective biofilm matrix among Candida spp. suggests that is a promising pan-fungal Candida biofilm drug target.

Morphological transitions governed by density dependence and lipoxygenase activity in Aspergillus flavus.

Aspergillus flavus differentiates to produce asexual dispersing spores (conidia) or overwintering survival structures called sclerotia. Results described here show that these two processes are oppositely regulated by density-dependent mechanisms and that increasing the cell density (from 10(1) to 10(7) cells/plate) results in the lowest numbers of sclerotial and the highest numbers of conidial. Extract from spent medium of low-cell-density cultures induced a high-sclerotium-number phenotype, whereas high-cell-density extract increased conidiation. Density-dependent development is also modified by changes in lipid availability. Exogenous linoleic acid increased sclerotial production at intermediate cell densities (10(4) and 10(5) cells/plate), whereas oleic and linolenic acids inhibited sclerotium formation. Deletion of Aflox encoding a lipoxygenase (LOX) greatly diminished density-dependent development of both sclerotia and conidia, resulting in an overall increase in the number of sclerotia and a decrease in the number of conidia at high cell densities (>10(5) cells/plate). Aflox mutants showed decreased linoleic acid LOX activity. Taken together, these results suggest that there is a quorum-sensing mechanism in which a factor(s) produced in dense cultures, perhaps a LOX-derived metabolite, activates conidium formation, while a factor(s) produced in low-density cultures stimulates sclerotium formation.

A Methylobacterium-like organism from algal crusts covering silicone rubber electric insulators in Africa.

AIMS: The primary goals of this study were to isolate, identify and characterize culturable bacteria living in a close association with microalgae within green crusts covering silicone rubber electric insulators in Tanzania. METHODS AND RESULTS: Twenty-four bacterial colonies were isolated from an Apatococcus crust. Characterization by statistical analyses of total cellular protein profiles demonstrated that they were highly similar to one another. Final identification was achieved using 16S rDNA sequencing and fatty acid methyl ester profiling. These analyses revealed the presence of microbes with high similarity to Methylobacterium radiotolerans. The selected isolate, A1, displayed strong inhibitory activity against Rhizoctonia solani and was found to be resistant to relatively high concentrations of zinc in the growth medium. CONCLUSIONS: This study revealed the presence of M. radiotolerans bacteria in a novel environment--within algal crusts formed on electrical insulators in Africa. Moreover, this bacterium was found to be a predominant culturable species within those complex algal-microbial associations. The isolate also shared some traits of biotechnological importance with other members of the Methylobacterium genus. SIGNIFICANCE AND IMPACT OF THE STUDY: The data presented provide a valuable contribution concerning the formation and function of associations between green microalgae and bacteria. This study also provides some information about the utility of bacteria from the genus Methylobacterium in biotechnological applications, such as biocontrol of rhizoctoniosis and bioremediation of heavy metal-contaminated soils.

Protein fingerprinting as a complementary tool for the classification of Pseudomonas bacteria.

A collection of total 42 bacterial strains belonging to the genus Pseudomonas were characterised based on protein fingerprinting using sodium dodecyl sulphate polyacrylamide gel electrophoregrams of cell-free extracts. Densitometrical analysis revealed unique and distinct profiles characteristic of the studied species. This comparison differentiated the isolates into four main clusters and twelve subclusters. The obtained protein patterns have proved to be an effective and reliable method both for the classification of bacteria and for showing similarities and variability among them.

Variability of the fatty acid composition during development of the green microalga Apatococcus constipatus.

The green microalga Apatococcus constipatus was investigated for its fatty acid composition using GC and MS techniques. Considerable variations were found in individual fatty acid contents according to the stage of culture development. A set of saturated fatty acid homologues was distinguished as the main component regardless of the culture age. The occurrence of some uncommon fatty acids in minor amounts, such as hydroxylated ones, was found to be characteristic of the studied species. Depending on the development stage, those compounds were detected either only during initial growth phases or throughout the cultivation time.

Production and secretion of 5-n-alkylresorcinols by Fusarium culmorum.

Fusarium culmorum F1 was found to produce and secrete into the culture medium several of 5-n-alkylresorcinols. The amount of resorcinolic lipids was 5.3 microg/g and 0.9 microg/l in mycelium and in post-culture liquid, respectively. First of all F. culmorum F1 produces saturated homologues with C15 to C25 side chains. The extract from the medium contained only homologues with shorter carbon chains (C13 to C17).

Alkylresorcinols in fruit pulp and leaves of Ginkgo biloba L.

These studies were undertaken to characterise resorcinolic lipids (5-n-alk(en)ylresorcinols) composition and to determine their seasonal fluctuations in fruit pulp and leaves of Ginkgo biloba L. Resorcinolic lipid concentrations were consistently higher in fruit pulp than in leaves. In pulp, several mono- and di-unsaturated homologs of alkylresorcinols were the predominant group of analysed lipids. Contrary to the fruit pulp, only 5-n-pentadecylresorcinol was demonstrated in leaves. Initially, the alkylresorcinol's content both in pulp and leaves increased until June-July and decreased following seeds ripening. This trend continued until senescence of leaves in late September and October.

5-n-Alkylresorcinols from the green microalga Apatococcus constipatus.

Mixtures of six 5-n-alkylresorcinol (ARs) homologues were isolated from acetone extracts of four isolates of the unicellular green microalga Apataococcus constipatus. The pattern of homologues in different algal isolates was diverse. The predominant compounds were 1,3-dihydroxy-5-n-heneicosylbenzene (AR C(21:0)) and 1,3-dihydroxy-5-n-tricosylbenzene (AR C(23:0)) or 1,3-dihydroxy-nonadecylbenzene (AR C(19:0)), depending on the strain. ARs were identified by chromatographic and spectroscopic means.