Arthrobotrys Dactyloides Research Articles

Nitratreduktion durch pilze und die verwertbarkeit des merkmals für die systematik

Nearly 200 species of fungi of various orders has been assayed for presence of nitrate reductase by examining the presence of nitrite in the culture medium. This property seems to be useful for identification purposes in the same way as the widely used Bavendamm-test for extracellular oxidases. A literature survey has also been made of fungi assimilating nitrate-nitrogen and those unable to grow with nitrate as sole source of nitrogen. The data in this paper show that there is a good correlation between the ability to reduce nitrate and the assimilation of nitrate-nitrogen. Most of the Deuteromycetes (14 out of 17 investigated) reduce nitrate, whereas the Basidiomycetes (135 species investigated) generally lack this property, except for few taxa like Lepista (Tricholomataceae; Agaricales). A correlation between nitrate reduction and ecological requirements was shown only for Deuteromycetes, where the pathogenic Dermatophytes do not use nitrate-nitrogen and the nematode trapping Arthrobotrys dactyloides is unable to reduce nitrate.

The Predaceous Fungus Arthrobotrys Dactyloides: Induction of Trap Formation

The Predaceous Fungus Arthrobotrys Dactyloides: Induction of Trap Formation

Trapping Effectiveness of Five Species of Nematophagous Fungi Cultured with Mycophagous Nematodes

SUMMARYFour-day cultures of nematophagous fungi that contained mycophagous nematodes exhibited little correlation between increased fungal growth and increased nematode-trapping effectiveness. Increased fungal growth did not appear to be affected by the assimilation of nematode protoplasm. Temperature and nematode presence appeared to be the two factors that affected fungal growth. Cultures that did not contain nematodes responded in a similar fashion to temperature. The presence of nematodes resulted in 5 C increase in optimum growth temperatures over control cultures, increased absolute areas of fast-growing species (Arthrobotrys oligospora, A. musiformis, and Monacrosporium bembicodes), and increased relative areas of slow-growing species (Arthrobotrys dactyloides and Monacrosporium cionopagum).

The formation and closure of the constricting rings in two nematode-catching hyphomycetes

The two fungi studied produce rings of the same type and are affected by the same conditions. Both produce rings on media containing horse serum, or living sterile nematodes. Arthrobotrys dactyloides will produce some rings in contact with a glass surface but many more after the addition of sterile nematode liquid. Dactylella doedycoides will not produce rings on a glass surface but only after the addition of the nematode liquid. After separation of the horse serum by electrophoresis on agar both fungi will produce rings on the β- and γ-globulin fractions and near the negative pole. There was no indication that the albumins were ring-forming stimulants. Ring closure was effected by either hot water or a red-hot needle. Sucrose solutions above 0·5 m inhibited the mechanism of closure and there was no reopening of previously closed rings with these concentrations. Sucrose solutions up to 0·2m had no effect on the mechanism, but solutions between 0·2 and 0·5m showed a gradual increase in the time taken to close. This increase in time showed itself as a lag phase between the stimulation by heat and the beginning of closure, once closure had begun it was always instantaneous. Under dry conditions the rings showed reduced percentage closure. Acetylcholine solutions also had an effect on ring closure, concentrations of 10−7 g/ml being stimulatory and concentrations up to 10−3g/ml being inhibitory. The mechanism of ring closure is discussed briefly.

The Formation of Constricting Rings in Nematode-catching Hyphomycetes Grown in Pure Culture

Constricting rings are normally formed in the presence of nematodes. The fungi can be induced to form rings if treated with certain organic substances such as animal extracts and sera. One of the fungi discussed, Arthrobotrys dactyloides Drechsler, will produce rings without the addition of stimulants. Ring formation is not due to starvation of the fungus. An experiment describing the growth of the fungi on to cover-glasses indicates that the rings may be initiated as a result of the contact with the glass surface.