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“Three soil bacterial strains were identified as Chryseobacterium sp. TFB on the basis of their 16S rRNA gene sequences. Conidia of Arthrobotrys oligospora produced a few mycelial traps (MT) and conidial traps (CT) when cultured with bacterial cells that they

did not produce when cultured with a bacterial cell-free culture filtrate. However, co-culture of A. oligospora with bacterial cells and bacteria-free filtrate simultaneously induced MT and CT in large amounts. With the increased concentration of bacteria-free filtrate, the number of typical CT increased, but conidial germination was progressively inhibited. Scanning electron GSK-3 inhibitor microscopy of A. oligospora co-cultured with bacteria revealed that bacterial attachment to hyphae was a prerequisite to trap formation and that bacteria-free filtrate facilitated bacterial attachments to hyphae. The results that the addition of nutrients in co-culture medium decreased the number

of traps suggest that this type of trap formation may be favoured at a low nutrient status. Eight fungi tested were able to form MT and CT when co-cultured with bacterial cells and bacteria-free culture filtrate, check details but the abilities varied among species. This study provides novel evidence that under laboratory conditions, soil bacteria attaching to hyphae could induce traps in nematode-trapping fungi. Over 200 species of predacious fungi develop specific morphological structures called traps that adhere to, penetrate, kill and digest free-living nematodes in the soil (Li et al., 2000). Among the nematode-trapping fungi, differentiated structures such as adhesive nets, branches and knobs as well as mechanical traps called constricting or nonconstricting rings are well known and typical of particular species (Nordbring-Hertz et al., 2002). The formation of traps is very important for these fungi. These

fungi thus enter the parasitic phase see more and capture nematodes on the surface of these structures. The traps can develop from hyphal branches and these are termed mycelial traps (MT). Alternatively, they can also form directly upon spore germination without an intermediate mycelial phase or on the germination hyphae, forming conidial traps (CT). MT can be formed either spontaneously or be induced in response to signals from the environment, including certain amino acids, valyl peptides and nemin that were secreted by host nematodes (Dijksterhuis et al., 1994). CTs were formed when conidia were allowed to germinate in cow dung (Dackman & Nordbring-Hertz, 1992), fungistatic soil (Mankau, 1962), rhizosphere soil or soil extracts (Persmark & Nordbring-Hertz, 1997), and the formation of CT was believed to be a response to nutrient deprivation due to strong nutrient competition between soil microorganisms. Fungi and bacteria coexist in a myriad of different environments.