The halophilic melanized yeast-like fungi Hortaea werneckii, Phaeotheca triangularis, and the halotolerant Aureobasidium pullulans, isolated from salterns as their natural environment, were grown at different NaCl concentrations and their membrane lipid composition and fluidity were examined. Among sterols, besides ergosterol, which was the predominant one, 23 additional sterols were identified. Their total content did not change consistently or significantly in response to raised NaCl concentrations in studied melanized fungi. The major phospholipid classes were phosphatidylcholine and phosphatidylethanolamine, followed by anionic phospholipids. The most abundant fatty acids in phospholipids contained C16 and C18 chain lengths with a high percentage of C18:2Δ9,12. Salt stress caused an increase in the fatty acid unsaturation in the halophilic H. werneckii and halotolerant A. pullulans but a slight decrease in halophilic P. triangularis. All the halophilic fungi maintained their sterol-to-phospholipid ratio at a significantly lower level than did the salt-sensitive Saccharomyces cerevisiae and halotolerant A. pullulans. Electron paramagnetic resonance (EPR) spectroscopy measurements showed that the membranes of all halophilic fungi were more fluid than those of the halotolerant A. pullulans and salt-sensitive S. cerevisiae, which is in good agreement with the lipid composition observed in this study.

Salt-induced changes in lipid composition and membrane fluidity of halophilic yeast-like melanized fungi.

This article reviews the comparative diversity of psychrophilic and psychrotrophic fungi, their adaptability mechanisms for survival and potential applications in biotechnology and pharmaceuticals. Fungi are able to grow and survive at low temperature and exist widely in polar and non-polar habitats. These cold regions are known for very low temperature, high ultra violet-B radiation, frequent freeze and thaw cycles and low water and nutrient availability. Most of the fungi adapt to such harsh conditions by evolving various strategies in their metabolism and physiology. Psychrophilic and psychrotrophic fungi are of importance in biotechnological and pharmaceutical fields due to their diverse characteristics developed or evolved due to their adaptation and survival in extreme environments, like; production of cold-active enzymes, pharmaceutical or bioactive metabolites and exo-polysaccharides, have potential for bioremediation and can also be used as biofertilizer.

Psychrophilic and psychrotrophic fungi: a comprehensive review

In this paper, we report the results of a systematic attempt to relate the intrinsic plasma membrane fluidity of three different cell lines to their electroporation behaviour, which consists of reversible and irreversible electroporation. Apart from electroporation behaviour of given cell lines the time course required for membrane resealing was determined in order to distinguish the effect of resealing time from the cell’s ability to survive given electric pulse parameters. Reversible, irreversible electroporation and membrane resealing were then related to cell membrane fluidity as determined by electron paramagnetic resonance spectroscopy and computer characterization of membrane domains. We found that cell membrane fluidity does not have significant effect on reversible electroporation although there is a tendency for the voltage required for reversible electroporation to increase with increased membrane fluidity. Cell membrane fluidity, however, may affect irreversible electroporation. Nevertheless, this effect, if present, is masked with different time courses of membrane resealing found for the different cell lines studied. The time course of cell membrane resealing itself could be related to the cell’s ability to survive.

Cell membrane fluidity related to electroporation and resealing

http://lbk.fe.uni-lj.si/pdfs/bb2008mk.pdf

The temperature effect during pulse application on cell membrane fluidity and permeabilization.

Following the widely spread EPR spin-label applications for biosystem characterization, a novel approach is proposed for EPR-based characterization of biosystem complexity. Hereto a computational method based on a hybrid evolutionary optimization (HEO) is introduced. The enormous volume of information obtained from multiple HEO runs is reduced with a novel so-called GHOST condensation method for automatic detection of the degree of system complexity through the construction of two-dimensional solution distributions. The GHOST method shows the ability of automatic quantitative characterization of groups of solutions, e.g. the determination of average spectral parameters and group contributions. The application of the GHOST condensation algorithm is demonstrated on four synthetic examples of different complexity and applied to two physiologically relevant examples − the determination of domains in biomembranes (lateral heterogeneity) and the study of the low-resolution structure of membrane proteins.

M Schara

Papers

Fast and Accurate Characterization of Biological Membranes by EPR Spectral Simulations of Nitroxides