Influence of Tween 80 on Lipid Metabolism of an Aspergillus niger Strain

Nemec, Tamara; Jernejc, Katarina

doi:10.1385/abab:101:3:229

Cited by 17 publications

(16 citation statements)

References 24 publications

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“…We are presently developing a small-scale MIC test using the NCCLS M38-A format, and the preliminary data are consistent with results described here. Our findings, together with the recognition that pathogenic microorganisms differ markedly in their ability to import cholesterol (3,39), have immediate biomedical implications and should foster the development of improved antifungal agents.…”

Section: Discussionmentioning

confidence: 78%

“…Another possible factor is exogenous sterol uptake. Although uptake of abiotic cholesterol by filamentous fungi is known (3,39), effects of sterol import on antifungal therapy have never been studied. Our results demonstrate that the fungal pathogen A. fumigatus imports cholesterol from medium, a process that is associated with enhanced growth.…”

Section: Discussionmentioning

confidence: 99%

“…1C). We did not attempt to solubilize the cholesterol with cyclodextrins or detergents like Tween-80, because the former can sequester cholesterol and the latter is known to affect sterol metabolism in A. niger (39). Lipoprotein cholesterol and liposome preparations that would introduce an additional carbon source for growth were also avoided.…”

Section: Serum Enhances Growth Of a Fumigatusmentioning

confidence: 99%

“…Cholesterol import also occurs in the budding yeast Saccharomyces cerevisiae but only under anaerobic conditions (5). Unlike yeast, filamentous fungi, such as Aspergillus niger (10,39) and Chrysosporium keratinophilum (3), can import cholesterol under aerobic conditions. Recently, A. fumigatus was reported to thrive in the presence of high concentrations of human serum (21).…”

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confidence: 99%

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Cholesterol Import by Aspergillus fumigatus and Its Influence on Antifungal Potency of Sterol Biosynthesis Inhibitors

Xiong¹,

Hassan

Wilson³

et al. 2005

Antimicrob Agents Chemother

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High mortality rates from invasive aspergillosis in immunocompromised patients are prompting research toward improved antifungal therapy and better understanding of fungal physiology. Herein we show that Aspergillus fumigatus, the major pathogen in aspergillosis, imports exogenous cholesterol under aerobic conditions and thus compromises the antifungal potency of sterol biosynthesis inhibitors. Adding serum to RPMI medium led to enhanced growth of A. fumigatus and extensive import of cholesterol, most of which was stored as ester. Growth enhancement and sterol import also occurred when the medium was supplemented with purified cholesterol instead of serum. Cells cultured in RPMI medium with the sterol biosynthesis inhibitors itraconazole or voriconazole showed retarded growth, a dose-dependent decrease in ergosterol levels, and accumulation of aberrant sterol intermediates. Adding serum or cholesterol to the medium partially rescued the cells from the drug-induced growth inhibition. We conclude that cholesterol import attenuates the potency of sterol biosynthesis inhibitors, perhaps in part by providing a substitute for membrane ergosterol. Our findings establish significant differences in sterol homeostasis between filamentous fungi and yeast. These differences indicate the potential value of screening aspergillosis antifungal agents in serum or other cholesterol-containing medium. Our results also suggest an explanation for the antagonism between itraconazole and amphotericin B, the potential use of Aspergillus as a model for sterol trafficking, and new insights for antifungal drug development.

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Section: Discussionmentioning

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Section: Serum Enhances Growth Of a Fumigatusmentioning

confidence: 99%

mentioning

confidence: 99%

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Cholesterol Import by Aspergillus fumigatus and Its Influence on Antifungal Potency of Sterol Biosynthesis Inhibitors

Xiong¹,

Hassan

Wilson³

et al. 2005

Antimicrob Agents Chemother

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“…This number was in good agreement with the number obtained for cells eluted with triton X100-supplemented buffer (see above). Since triton X-100 is not a likely carbon/ energy substrate (Zeng et al, 2007), the sharp increase in the number of RSG-stained cells is most probably not due to metabolic activation but due to the surfactant properties of triton X-100, affecting the permeability of the cell membrane (Helenius and Simons, 1975;Nemec and Jernejc, 2002) and facilitating cell penetration by RSG. These results indicated that to use this approach to obtain cells for downstream analysis, including cultivation, a modification of the extraction buffer omitting triton X-100 was necessary to avoid the risk of cell membrane disruption.…”

Section: Resultsmentioning

confidence: 99%

Real-time detection of actively metabolizing microbes by redox sensing as applied to methylotroph populations in Lake Washington

2008

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Redox sensor green (RSG), a novel fluorescent dye from Invitrogen was employed as a tool for realtime detection of microbes metabolically active in situ, in combination with flow cytometry and cell sorting. Lake Washington sediment, an environment known for high rates of methane oxidation, was used as a model, and methylotrophs were targeted as a functional group. We first tested and optimized the performance of the dye with pure methylotroph cultures. Most cells in actively growing cultures were positive for staining, whereas in starved cultures, few cells fluoresced. However, starved cells could be activated by addition of substrate. High numbers of fluorescing cells were observed in a Lake Washington sediment sample, and activation of subpopulations of cells was demonstrated in response to methane, methanol, methylamine and formaldehyde. The fraction of the population activated by methane was investigated in more detail, by phylogenetic profiling. This approach showed that the major responding species were the Methylomonas species, previously isolated from the site, and Methylobacter species that have not yet been cultivated from Lake Washington. In addition, from the methane-stimulated fraction, uncultivated bacterial sequences were obtained that belonged to unclassified Deltaproteobacteria, unclassified Verrucomicrobiles and unclassified Acidobacteria, suggesting that these microbes may also be involved in methane metabolism. The approach was further tested for its utility in facilitating enrichment for functional types that possess specific metabolic activities but resist cultivation. It was demonstrated that in enrichment cultures inoculated with cells that were sorted after stimulation with methane, Methylobacter sequences could be detected, whereas in enrichment cultures inoculated by randomly sorted cells, Methylomonas species quickly outcompeted all other types.

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Industrial antifoam agents impair ethanol fermentation and induce stress responses in yeast cells

Nielsen

Lino²,

Rasmussen³

et al. 2017

Appl Microbiol Biotechnol

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The Brazilian sugarcane industry constitutes one of the biggest and most efficient ethanol production processes in the world. Brazilian ethanol production utilizes a unique process, which includes cell recycling, acid wash, and non-aseptic conditions. Process characteristics, such as extensive CO2 generation, poor quality of raw materials, and frequent contaminations, all lead to excessive foam formation during fermentations, which is treated with antifoam agents (AFA). In this study, we have investigated the impact of industrial AFA treatments on the physiology and transcriptome of the industrial ethanol strain Saccharomyces cerevisiae CAT-1. The investigated AFA included industrially used AFA acquired from Brazilian ethanol plants and commercially available AFA commonly used in the fermentation literature. In batch fermentations, it was shown that industrial AFA compromised growth rates and glucose uptake rates, while commercial AFA had no effect in concentrations relevant for defoaming purposes. Industrial AFA were further tested in laboratory scale simulations of the Brazilian ethanol production process and proved to decrease cell viability compared to the control, and the effects were intensified with increasing AFA concentrations and exposure time. Transcriptome analysis showed that AFA treatments induced additional stress responses in yeast cells compared to the control, shown by an up-regulation of stress-specific genes and a down-regulation of lipid biosynthesis, especially ergosterol. By documenting the detrimental effects associated with chemical AFA, we highlight the importance of developing innocuous systems for foam control in industrial fermentation processes.Electronic supplementary materialThe online version of this article (10.1007/s00253-017-8548-2) contains supplementary material, which is available to authorized users.

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Influence of Tween 80 on Lipid Metabolism of an Aspergillus niger Strain

Cited by 17 publications

References 24 publications

Cholesterol Import by Aspergillus fumigatus and Its Influence on Antifungal Potency of Sterol Biosynthesis Inhibitors

Cholesterol Import by Aspergillus fumigatus and Its Influence on Antifungal Potency of Sterol Biosynthesis Inhibitors

Real-time detection of actively metabolizing microbes by redox sensing as applied to methylotroph populations in Lake Washington

Industrial antifoam agents impair ethanol fermentation and induce stress responses in yeast cells

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