A new and simple technique for the isolation of symbiotic bacteria associated with entomopathogenic nematodes (Heterorhabditidae and Steinernematidae) (original) (raw)

2015, TURKISH JOURNAL OF ZOOLOGY

The entomopathogenic nematode species (EPNs) of 2 genera, Heterorhabditis and Steinernema, are effective biological control agents against major insect pests (Kaya and Gaugler, 1993). These nematodes each contain symbiotic bacteria, with Photorhabdus spp. for Heterorhabditis and Xenorhabdus spp. for Steinernema (Akhurst, 1980; Boemare et al., 1993). The symbiotic bacteria reside in the nematode intestine (for Heterorhabditis) or in a bacterial vesicle (for Steinernema) and are released into the insect hemocoel when the nematode enters the target insect host (Dowds and Peters, 2002). The bacteria multiply, producing septicemia, and kill the insect host within 24 to 48 h, allowing the colonizing nematodes to feed on both the bacteria and the digested insect tissues (Dunphy and Webster, 1988; Park and Kim, 2000). Once developed, infective juveniles (IJs) emerge from the cadaver and search for another host. These bacteria are of interest not only for the mutualistic association with EPNs, but also for their production of toxins, antibiotics, and enzymes (Webster et al., 2002; Park and Forst, 2006; Proschak et al., 2011). As there are currently no selective media for these bacteria and freeliving forms of these bacteria have not yet been discovered, to carry out research on these bacteria, they must first be isolated from their nematode hosts. Three methods have been used for isolating symbiotic bacteria from entomopathogenic nematodes. The "hanging drop" method uses a sterile drop of insect hemolymph,