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Rhinophycomycosis entomophthorae is a variant type of subcutaneous phycomycosis of the face that is caused by Entomophthora coronata. The case we describe was the first patient reported in the world literature, to our knowledge. His infection reappeared after an extended dormant period. Although his condition exhibited an early partial response to surgical and medical management, the condition became refractory to treatment.
Sphingomyelin was isolated from a strain of Entomophthora coronata, a fungus pathogenic for humans. After hydrolysis, the long chain bases were converted to their dinitrophenyl (N2pH) derivatives and the aldehydes prepared by oxidizing these compounds with periodic acid. The aldehydes were studied by gas chromatography. Twelve different aldehydes were identified, the chain distributiion ranging from C14 to C17. The prominent chains were unsaturated. Straight and branched chains were found. The most abundant parent base which formed 52% of the total aldehyde was a 1,3-dihydroxy-2-aminohexadecene.
The fine structure of conidia and immature resting spores of the entomogenous fungus Entomophthora apiculata is described. The two cell types contain comparable organelles and quantities of lipid, and possess a similar cell wall structure. The large quantity of stored lipid and numerous mitochondria in each cell type indicate a capacity for great metabolic activity. Numerous dense, microbody-like organelles were observed in conidia and resting spores, and their possible functions are discussed. Third instar larvae of the cabbage looper Trichopulsia ni were exposed to conidia of E. apiculata. Fungal germ tube formation and penetration of the host integument were observed. The germ tubes did not form appressoria and appeared to penetrate the epicuticle by enzymatic and physical means. After penetration of the epicuticle the germ tube often bifurcates, and expands as two or more digit-like projections parallel to the lamellae of the exocuticle. The hyphae gradually extend inward, cleaving the lamellae of cuticle, and eventually enter the host's body cavity.
Aspects of the fine structure as well as electron cytochemical localization studies of certain hydrolytic enzymes were examined by electron microscopy of ultrathin sections of the vegatative hyphae and conidia of the phycomycetous fungus, Entomophthora coronata. This entomogenous fungal organism is of interest since it has been increasingly implicated as the etiologic agent of phycomycosis of man and animals. On thin section, hyphal cells were frequently observed with septa while the cytoplasm was multinucleate. The conidium was bound by a multilayered cell wall. The cytoplasm of ungerminated conidia characteristically contained large numbers of a class of cytoplasmic organelle found in loose aggregates with lipid storage bodies. Similar organelles were observed in the cytoplasm of hyphal cells from 7-day old cultures. This round to oval to slightly reniform structure was bound by a single limiting membrane and composed of an electron dense, slightly granular matrix without evidence of crystalloid formation. The limiting membrane of the lipid storage bodies was observed to be intimately associated with that of one or more of these microbody-like organelles. This intimate association of the two cytoplasmic organelles suggests that the microbody-like organelle may be involved in some manner with lipid metabolism during the life cycle of the fungus. Cautious interpretations of electron cytochemical localization studies suggested that lipase, nonspecific esterase, and possibly aryl sulfatase were associated with the microbody-like organelles. Neither peroxidatic nor acid phosphatase activity could be demonstrated with these organelles of the conidial cytoplasm.
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.
The results obtained in 15 years of research on the Entomophthorales pathogen of aphids showed the importance of the action of these fungi in the regulation of natural aphid populations and their possible use in agriculture as a biological control agent. Recent ecological studies on natural populations of aphids established the seasonal variation of the different fungal species and the diverse degrees of specificity between the species or groups of species of aphid and the various species of Entomophthora. The study of populations dynamics of an aphid species on a cultivated plant permitted the determination of the way a certain number of biotic and abiotic factors, such as temperature, humidity, thresholds of the insect population and of the infecting fungus lead to an epizootic development. If the air propagation of the disease by conidia is understood for a long time, the role of the soil as a reservoir for the infecting fungus has been demonstrated recently. Under favourable climatic conditions, the use of industrially produced resistant resting spores would allow the regulation of aphid populations in nature.
A set of slides and strains designated as Entomophthora thaxteriana Petch, E. obscura Hall et Dunn and E. ignobilis Hall et Dunn were compared on morphological, physiological, pathological and biochemical bases. It is concluded that E. thaxteriana (name invalidated by Humber, 1978) must be replaced by E. obscura and not by E. ignobilis, this species being considered as nomen dubium. Some intraspecific variations within the species E. obscura were found particularly with regard to the ability to produce resting spores and cystidia.
Changes in the relative abundance of cell constituents of Entomophthora virulenta Hall & Dunn were studied during the various differentiation phases leading to the formation of zygospores. The highest total protein (43%) and nucleic acid (5.2% RNA and 0.2% DNA) concentrations were found in the exponential growth phase; these concentrations decreased regularly as the mycelium aged. The amount of lipids was four times larger at the prespore and spore stage (about 25%) than at the exponential mycelial stage. The zygospore contained a very high concentration of chitin (about 17%), three times more than the mycelial concentrations. However, the percentage of polysaccharides without chitin, but including glycogen, was higher in the deceleration phase mycelium (34%) than in the spore (25%). A physiological model of the sexual sporulation of E. virulenta based on these data has been presented.
Specific activities of 14 enzymes of the Embden-Meyerhof-Parnas and pentose phosphate pathways were determined in extracts of resting spores and vegetative mycelia of Entomophthora pyriformis. All these enzymes were detected in mycelial extracts, whereas only nine were detectable in resting spore extracts. Activities of detectable spore enzymes were much lower than those of the corresponding mycelial enzymes with the exception of triosephosphate dehydrogenase, which had higher activity in spore extracts. The enzyme deficiencies noted point to the inability of either pathway to function in dormant spores.
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Mycelial fragments of E. coronata have been observed in the pus of abscesses of the neck and the shoulder of mice inoculated per os, far from the point of inoculation. However, the subcultures were negative; a positive subculture was obtained in only one instance from a lung taken off ten days after the inoculation by the fungus.
A comparative study was made of the production of extracellular proteolytic enzymes, which were originated from two different strains, one pathogenic and one saprophytic, of E. coronata in stable culture at 30 degrees C. Quantitative differences were found: the maximal activity of the three enzymes (collagenase, esterase, elastase) produced by the strain isolated from soil was always lower than that observed with the human strain.
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