The extracellular bioactive substances of Arthrobotrys oligospora during the nematode-trapping process

• Arthrobotrys oligospora prey nematode larvae on livestock.
• The extracellular polymeric substances of A. oligospora play the key role in the process of capturing nematodes.
• Proteases are required for A. oligospora to catch and feed on nematodes.

To investigate the role of the extracellular polymers present on the traps of the predatory fungus Arthrobotrys oligospora in the nematode-trapping process, five solutions with different chemical properties, two enzymes, and seven protease inhibitors were used to treat the extracellular polymers. The effects of these treatments on mycelial growth and on the ability of the fungus to trap and kill nematodes were subsequently observed. The results demonstrate that 5 mol L−1 LiCl and pronase E can significantly reduce the trapping of the fungus to nematodes, while 0.1 mol L−1 NaOH, SDS–mercaptoethanol–urea PBS solution and 1.5% SDS can completely prohibit the trapping and mycelial growth. Enzyme inhibitors (except phenanthroline) had no significant impacts on the adhesion to the nematodes, while serine protease inhibitors can inhibit the killing of the fungi to the nematodes. It had no effect on the adhesion when treated nematodes with the inhibitors. Taken together, the extracellular polymers on A. oligospora traps that are critical for adhering to and capturing nematodes are proteins or protein-containing substances. Moreover, it was indirectly confirmed that although proteases are not essential for the adhesion and capture stages of nematode trapping, they play an important role in the subsequent killing of nematodes.

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