Arthrobotrys oligospora

Predation of nematodes occurs in low nitrogen environments,[9] as the nematode becomes the main nitrogen source for the fungi.[2] It has been found that the presence of ammonium causes a higher decrease of predation when compared to presence of nitrate or nitrite.[3] Adding green manure or carbohydrates has been found to increase nematode trapping behaviors.[6] A complex 3-dimensional net of hyphae is formed to trap the nematodes under conditions of pH 4.9-8.1 and a temperature less than 37 °C (99 °F).[5][6][8][9] Nematodes, and specifically "nemin" (an extract derived from nematodes) were found to stimulate net formation.[2][6] Nematodes are not as attracted to A. oligospora colonies that have not manifested traps, suggesting that these structures serve an additional attractant role possibly through the expression of pheromones.[9][10]

A full net is not needed to catch nematodes as smaller nematodes can be caught with a single loop.[2] Lectins are used in attaching nematode to fungi[9] The entire surface of net is covered in adhesive material.[2][8] Strong adhesion keeps the nematode trapped and when the nematode struggles, it often results in multiple points of adhesion of the nematode to the net.[8][10] It was even found that the adhesion of the nematode to the fungus remained under washing of agar plate with water.[8] The net is flexible which results in 'hyphal drag' tiring the nematode.[8] Multiple points of adhesion and 'hyphal drag' allow the net to be capable of catching both large and small nematodes easily.[8] In vitro, bait nematodes are consumed often leaving Bunonema nematodes.[8]

A substance found in paralyzed nematodes was found to be capable of paralyzing healthy nematodes,[6][8] and it was later determined that a paralyzing substance, Subtilisin (A serine protease),[11] is excreted into nematodes.[2][8] An unstable toxin was thought to be made by the fungus,[6][8] and it was later found that toxic levels of linoleic acid for nematodes (lethal dose of linoleic acid for C. elegans is 5–10 μg/ml)[12] were found in the fungus.[5][12] Enzymatic hyphal invasion, likely using collagenases which are found in 'Arthrobotrys',[2] of a trapped nematode is followed by the digestion of contents of the nematode.[8][9] Shortly after hyphal invasion, a hyphal bulb appears where hyphae grow outwards from the bulb along the entire body of the nematode.[8]

Not all nematodes are caught by the net as the nematode needs to be in contact with the net for a short period of time in order for adhesion to occur.[8] Nematodes were found to quickly move away from any net followed by curling if instantaneous contact occurs.[8][13] The nematode then proceeds to move forward until out of the area of the net and unless prolonged contact is made the nematode is safe.[8] This means one or several instantaneous contacts are not enough for adhesion between the nematode and net to occur.[8]

No competing fungi or bacteria are found in nematodes which are being consumed by the fungus which means it is possible an antibiotic is released inside the nematode.[8] In 1993, secondary metabolites (oligosporon, oligosporol A, and oligosporal B) which can act as antibiotics were found in the fungus.[2][12] Oligosporon, oligosporol A, oligosporal B have hemolytic effects and are cytotoxic to nematodes, however they are not toxic to the C. elegans.[12] Other oligosporon-type secondary metabolites also found in A. oligospora include (4S,5R,6R)-4′,5′- dihydrooligosporon, (4S,5R,6R)-hydroxyoligosporon, and (4S,5R,6R)-10′11 ′-epoxyoligosporon.[12]

A branch of hyphae grows out of a vegetative hyphae eventually arching back to the parent hyphae and fuses with it to make a loop.[3][7][8] This process repeats from any hyphae along any existing branches or a new parent hyphae.[3][8] The nets are immediately adhesive,[8] and hyphae in the loop have different organelles to trap nematodes which are not found in vegetative cells.[2]