Fungal artillery of zombie flies: infectious spore dispersal using a soft water cannon.

Dead sporulating female fly cadavers infected by the house fly-pathogenic fungus Entomophthora muscae are attractive to healthy male flies, which by their physical inspection may mechanically trigger spore release and by their movement create whirlwind airflows that covers them in infectious conidia. The fungal artillery of E. muscae protrudes outward from the fly cadaver, and consists of a plethora of micrometric stalks that each uses a liquid-based turgor pressure build-up to eject a jet of protoplasm and the initially attached spore. The biophysical processes that regulate the release and range of spores, however, are unknown. To study the physics of ejection, we design a biomimetic 'soft cannon' that consists of a millimetric elastomeric barrel filled with fluid and plugged with a projectile. We precisely control the maximum pressure leading up to the ejection, and study the cannon efficiency as a function of its geometry and wall elasticity. In particular, we predict that ejection velocity decreases with spore size. The calculated flight trajectories under aerodynamic drag predict that the minimum spore size required to traverse a quiescent layer of a few millimetres around the fly cadaver is approximately 10 µm. This corroborates with the natural size of E. muscae conidia (approx. 27 µm) being large enough to traverse the boundary layer but small enough (less than 40 µm) to be lifted by air currents. Based on this understanding, we show how the fungal spores are able to reach a new host.

Regulation of hyphal growth and sporulation of the insect pathogenic fungus Entomophthora thripidum in vitro.

Entomophthora thripidum is an obligate biotrophic insect pathogenic fungus that grows as protoplasts within the hemocoel of thrips. Prior to penetration through the insect cuticle and spore formation at the insect surface the protoplasts switch to hyphal growth. In vitro, the differentiation to hyphal growth was a prerequisite for the subsequent formation of infectious spores and was detected 10-20 days after inoculation. E. thripidum secreted a factor that autoinduced the differentiation to hyphal growth. The discovery of this activity inducing hyphal growth made possible the reliable production of spores, the infection of host insects and the consecutive re-isolation of the fungus from the infected insects.

[Biologic activity and tolerance of a preparation of polyunsaturated fatty acids, obtained by a microbiological route ["biopolyene"]]. / Biologicheskaia aktivnost' i perenosimost' preparata polinenasyshchennykh zhirnykh kislot, poluchaemykh mikrobiologicheskim putem ["biopoliena"].

Biopolyene is a mixture of ethyl ethers of polyunsaturated fatty acids isolated from biomass of Entomophthora virulenta, a mycelial fungus. Its acute and chronic toxicity was studied on rats and guinea pigs. After oral administration of the preparation in single doses exceeding 50 g/kg there were no disorders in the general state of the rats. In chronic experiments with oral biopolyene in doses of 100 and 500 mg/kg and its local application to the intact skin of the animals in a dose of 1 g/kg there were no significant changes in the functional state of the liver and kidneys as well as the peripheral blood count. Insignificant changes in the serum levels of liver enzymes and coagulation were transient. The preparation showed no allergenic or immunomodulating effects. It had neither embryotoxic, teratogenic nor mutagenic action.

[Nutritional requirements of Entomophthorales (author's transl)]. / Comparison des exigences nutritionnelles de Entomophthorales.

Twenty-six species of Entomophthorales were classified considering their ability to utilize mineral or organic nitrogen, metabolize oxydized or reduced form of S and synthetize vitamins. Intergeneric, interspecific but also intraspecific variations were found concerning the nutritional requirements of the 73 strains studied.

[Growth and sporulation of Entomophthora virulenta Hall and Dunn in discontinuous liquid culture]. / Croissance et sporulation d'Entomophthora virulenta Hall et Dunn en culture liquide discontinue.

Fermented cultures of Entomophthora virulenta showed an exponential phase with a specific growth rate of 0,14 h-1. The deceleration phase was 4 times longer than the exponential phase. Sexual sporulation occurred at the end of the deceleration phase. A technique of medium replacement demonstrated that any lack of nutritive balance induced the sporulation.

[Sporulation of Entomophthora obscura Hall and Dunn in liquid culture]. / Sporulation de Entomophthora obscura Hall & Dunn en culture liquide.

Growth and production of azygospores of Entomophthora obscura were studied through batch cultures in media containing glucose, or vegetable oil, and yeast extract. In media containing 3% glucose and 1% yeast extract, an 8-h lag phase occurred and sporulation began only at the 40th hour of culture; spore maturation lasted 4 days in average. Young mycelial stages were characterized by high nucleic acid and protein but low lipid concentrations. During sporogenesis stages, the quantity of lipids and chitin increased and the concentration of total polyosides (chitin excluded) was lower in comparison with the mycelial stages. Sporulation was induced by means of medium starvation in carbon and (or) nitrogen. The only sporulation inhibitor which allowed considerable growth was sodium fluoroacetate.

[Age changes in the lipid fatty acid makeup of cultures of the family Entomophthoraceae]. / Bozrastnye izmeneniia zhirnokislotnogo sostava lipidov u nekotorykh kul'tur semeistva Entomophthoraceae.

The rate of biosynthesis of lipids and their fatty acid composition were studied in four cultures of microscopic fungi belonging to the family Entomophthoraceae in the course of their growth. The cultures synthesized from 23% to 43% of lipids. The lipids comprised fatty acids containing from 9 to 24 carbon atoms in the chain. The lipids differed in their fatty acid composition and the degree of saturation: unsaturated fatty acids (50-60%) prevailed in the lipids of Ent. conica 1716, Ent. thaxteriana 1711 and 1931, while saturated fatty acids (70%) predominated in the lipids of Ent. coronata 1710. Isomers with different position of double bonds were found among C18-unsaturated fatty acids (two octadecenic, three octadecadienic and two octadecatrienic acids). Branched fatty acids were detected in low amounts in the lipids. The character of changes in the fatty acid composition of lipids was different in the process of the cultural growth.

[Growth and sporulation of 6 species of Entomophthorales. II. Effect of various nitrogen sources]. / Croissance et sporulation de 6 espèces d'Entomophthorales II. Influence of diverses sources d'azote

Growth and sporulation of Entomophthora near obscura, E. destruens, E. near thaxteriana, E. virulenta, Basidiobolus ranarum and Conidiobolus osmodes were studied in solid synthetic media containing various nitrogen sources at 0,33 g N/liter. Thirty two nitrogen sources representing nitrates, ammonium salts, amino acids and protein hydrolysates were tested. E. near obscura did not grow on any medium. Protein hydrolysates, ammonium salts and ten of the sixteen amino acids tested were the best nitrogen sources for growth and resting spores production of the five other species.