Nitrogen partitioning in Heterorhabditis bacteriophora-infected hosts and the effects of nitrogen on attraction/repulsion

Entomopathogenic nematode behavior is affected by the condition of their in fected hosts. We hypothesized that nitrogen compounds released from infecte d hosts may be one factor affecting entomopathogenic nematode host-finding and infection behaviors. Our objectives were to (1) investigate the partiti oning of nitrogen in Galleria mellonella (L,) infected by Heterorhabditis b acteriophora Poinar and (2) determine attraction and repulsion of H. bacter iophora to various quantities of nitrogen (ammonia). Volatile (ammonia), or ganic, and inorganic nitrogen forms were monitored during the course of inf ection. Approximately 0.052 mg of nitrogen was released from a single infec ted host as volatile ammonia, Most of the ammonia release was detected with in the first 3 days postinoculation. Organic nitrogen increased during the course of infection, whereas inorganic nitrogen decreased. The net nitrogen change in the infected host consisted of a loss of approximately 47 mg, mo st of which was lost within the Ist meek of infection, Accelerated loss of nitrogen early in the infection process was likely correlated with activity and growth of bacterial symbionts, Increased organic nitrogen was likely a ssociated with nematode reproduction within the host. Attraction or repulsi on of H. bacteriophora to nitrogen (ammonium hydroxide) was measured on aga r quadrant plates, Nematodes were attracted to 16 and 160 mu g of nitrogen and repelled by concentrations of 1600 and 8000 mu g. Our data indicate tha t nitrogen released from H. bacteriophora-infected hosts attracts nematodes at lower levels (early in the infection) and repels them at higher concent rations (later in the infection process). (C) 2000 Academic Press.