Mycophagous mites and their internal associated bacteria cooperate to digest chitin in soil

The greater bulk of soil nitrogen is immobilized in chitinous cell walls of fungi. Mycophagous soil mites participate in chitin decomposition and, hence, in the subsequent mobilization of nitrogen. The source of the chitinolytic enzymes was searched in this study. A multimethodical approach was designed for these studies. Histology, plating and identification of bacteria from mite homogenate and, finally, homogenate and bacterial treatment of the soil fungi were applied. Here the presence and activity of chitinolytic bacteria inside mycophagous mites are reported. These bacteria form an extraintestinal group within the mite’s body and pass their enzymes into the mite’s gut. Our results demonstrate that true mycophagous mites, defined by their ability to digest chitin (i.e. the fungal cell wall), achieve this through internal “cooperation” with chitinolytic bacteria that provide the necessary chitinolytic enzymes. The nitrogen from chitin is thus made available to other soil organisms and plants.