Thermostable enzymes and thermophilic cell factories may afford economic advantages in the production of many chemicals and biomass-based fuels. Here we describe and compare the genomes of two thermophilic fungi, Myceliophthora thermophila and Thielavia terrestris. To our knowledge, these genomes are the first described for thermophilic eukaryotes and the first complete telomere-to-telomere genomes for filamentous fungi. Genome analyses and experimental data suggest that both thermophiles are capable of hydrolyzing all major polysaccharides found in biomass. Examination of transcriptome data and secreted proteins suggests that the two fungi use shared approaches in the hydrolysis of cellulose and xylan but distinct mechanisms in pectin degradation. Characterization of the biomass-hydrolyzing activity of recombinant enzymes suggests that these organisms are highly efficient in biomass decomposition at both moderate and high temperatures. Furthermore, we present evidence suggesting that aside from representing a potential reservoir of thermostable enzymes, thermophilic fungi are amenable to manipulation using classical and molecular genetics.

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Comparative genomic analysis of the thermophilic biomass-degrading fungi Myceliophthora thermophila and Thielavia terrestris

The existing literature on the role of fatty acids in microbial temperature adaptation is reviewed. Several modes of change of cellular fatty acids at varying environmental temperatures are shown t...

Microbial Fatty Acids and Thermal Adaptation

Occurrence and Characteristics of Oils and Fats

Microbial community dynamics during composting of straw material studied using phospholipid fatty acid analysis

Gamma linolenic acid--occurrence and physical and chemical properties.

The lipid composition of nine thermophilic and nine mesophilic species of seven genera of fungi were compared. The total lipids varied between 8.0% and 54.1% with most fungi possessing between 8.0% and 18.3% lipids. The predominant fatty acids were found to be palmitic, oleic and linolenic. Lesser amounts of arachidic, linolenic, palmitoleic, pentadecanoic, myristic and lauric acids were found. The mesophiles varied between 0% and 18.5% linolenic acid, while the thermophiles did not contain any appreciable linolenic acid (<0.5%). The mesophile,Mucor globosus, and the thermophile,Mucor pusillus, contain γ linolenic acid. The fatty acids of the thermophilic fungi were more saturated than the corresponding mesophilic species.

The lipids of thermophilic fungi: Lipid composition comparisons between thermophilic and mesophilic fungi

The relative per cents of polar and neutral lipids and the fatty acid profile of the polar and neutral lipids of nine thermophilic and nine mesophilic fungi were examined and compared. The polar lipids of the thermophiles contained an average of 0.89 double bonds per mole fatty acid (unsaturation index, USI) and were considerably more saturated than the corresponding lipids of the mesophiles (average 1.32 USI). Within the thermophilic species the polar lipids were generally more saturated than the neutral lipids (average 0.95 USI) and in the mesophilic species the polar lipids were usually more saturated than the neutral lipids (average 1.14 USI). The mesophiles produced higher levels of 16∶1, 18∶2 and 18∶3 fatty acids than the thermophiles and preferentially incorporated 16∶1 and 16∶2 into their polar lipids. The thermophiles produce higher levels of saturated fatty acids and 18∶1 than the mesophiles and preferentially incorporated the saturated fatty acids into their polar lipids.

Thermophilic fungi: II. Fatty acid composition of polar and neutral lipids of thermophilic and mesophilic fungi.

The lipids of the thermophilic fungusHumicola grisea var.thermoidea were qualitatively and quantitatively determined. The polar lipids consisted of 38.4–42.3% of the total lipids. The relative per cent phospholipids based upon the total phospholipids were as follows: phosphatidyl choline, 32.3–33.7%; phosphatidic acid, 24.5–31.7%; phosphatidyl ethanolamine, 15.8–20.9%; phosphatidyl inositol, 12.5–13.0%; phosphatidyl serine, 2.3–5.4%; and diphosphatidyl glycerol, 3.9–4.0%. The relatively high concentration of phosphatidic acid may be characteristic of fungi grown at elevated temperatures. Several sterol glycosides (3.1–6.0%) were present in the polar lipids. The neutral lipids consist of triglycerides, 28.6–36.0%; free fatty acids, 5.3–13.5%; sterols, 11.4–13.9%; sterol esters, 1.8–3.0%; and diglycerides, 2.2–3.4%. The sterols and derivatives comprise an unusually large fraction of the total lipids (16.3–22.9%) suggesting a role in thermostability.

R. D. Sekura

Papers

The lipids of thermophilic fungi: Lipid composition comparisons between thermophilic and mesophilic fungi

Thermophilic fungi: II. Fatty acid composition of polar and neutral lipids of thermophilic and mesophilic fungi.

Thermophilic fungi: III. The lipids ofHumicola grisea var.thermoidea.