Scholler M, Rubner A
Institut für Allgemeine und Spezielle Mikrobiologie, Universität Greifswald, Germany.
Microbiol Res. 1994 Jun;149(2):145-9. doi: 10.1016/S0944-5013(11)80110-2.
The nematophagous fungus Arthrobotrys oligospora Fres. can live saprophytically as well as predatorily. As a predator it forms sticky reticulate traps in the presence of living nematodes which enable it to kill and consume the animals. In laboratory experiments the nutrient acquisition of the fungus was tested on agar media with various N- and C-sources in different concentrations. The intensity of predacious response was determined by counting the traps formed on the agar surface after induction by nematodes. Predacious activity (PA) served as a unit of the strength of nematophagous response. PA was defined as the number of traps/100 mm2. In contrast to carnivorous higher plants, which consume insects in order to compensate their N-deficit, the fungus seems to kill nematodes to get both, N as well as C. If the agar substrate contains a certain concentration of N and C, the fungus does not form traps and lives as a saprophyte. The level which determines the switch towards pure saprophytism under laboratory conditions ranges around 0.12 M C at a N-concentration of 0.05 M. If no nitrogen is added to the medium the fungus forms nematode-induced traps even in the most concentrated C-media. On N-media without any carbon source the fungus shows a much stronger PA compared with N-free media. Furthermore, more chlamydospores were formed on N-media.
捕食线虫真菌少孢节丛孢（Arthrobotrys oligospora Fres.）既能腐生生活，也能捕食生活。作为捕食者，它在活线虫存在的情况下形成粘性网状陷阱，使其能够杀死并消耗这些动物。在实验室实验中，在含有不同浓度各种氮源和碳源的琼脂培养基上测试了该真菌的养分获取情况。通过计算线虫诱导后在琼脂表面形成的陷阱数量来确定捕食反应的强度。捕食活性（PA）作为线虫捕食反应强度的一个单位。PA定义为陷阱数量/100平方毫米。与为了补偿氮缺乏而捕食昆虫的食虫高等植物不同，该真菌似乎杀死线虫是为了获取氮和碳。如果琼脂底物含有一定浓度的氮和碳，该真菌不会形成陷阱，而是以腐生菌的形式生活。在实验室条件下，决定转向纯腐生生活的水平在氮浓度为0.05 M时约为0.12 M碳。如果不向培养基中添加氮，即使在碳浓度最高的培养基中，该真菌也会形成线虫诱导的陷阱。与无氮培养基相比，在无碳源的氮培养基上该真菌表现出更强的PA。此外，在氮培养基上形成了更多的厚垣孢子。
