Abstract
Photorhabdus and Xenorhabdus are symbiotic with entomopathogenic nematodes (EPNs) of the genera Heterorhabditis and Steinernema, respectively. These bacteria produce several secondary metabolites including antimicrobial compounds. The objectives of this study were to isolate and identify EPNs and their symbiotic bacteria from Mae Wong National Park, Thailand and to evaluate the antibacterial activities of symbiont extracts against drug resistant bacteria. A total of 550 soil samples from 110 sites were collected between August 2014 and July 2015. A total of EPN isolates were obtained through baiting and White trap methods, which yielded 21 Heterorhabditis and 3 Steinernema isolates. Based on molecular identification and phylogenetic analysis, the most common species found in the present study was P. luminescens subsp. akhurstii associated with H. indica. Notably, two species of EPNs, H. zealandica and S. kushidai, and two species of symbiotic bacteria, X. japonica and P. temperata subsp. temperata represented new recorded organisms in Thailand. Furthermore, the association between P. temperata subsp. temperata and H. zealandica has not previously been reported worldwide. Disk diffusion, minimal inhibitory concentration, and minimal bactericidal concentration analyses demonstrated that the crude compound extracted by ethyl acetate from P. temperata subsp. temperata could inhibit the growth of up to 10 strains of drug resistant bacteria. Based on HPLC-MS analysis, compound classes in bacterial extracts were identified as GameXPeptide, xenoamicin, xenocoumacin, mevalagmapeptide phurealipids derivatives, and isopropylstilbene. Together, the results of this study provide evidence for the diversity of EPNs and their symbiotic bacteria in Mae Wong National Park, Thailand and demonstrate their novel associations. These findings also provide an important foundation for further research regarding the antimicrobial activity of Photorhabdus bacteria.
Highlights
Photorhabdus and Xenorhabdus are symbiotic with entomopathogenic nematodes (EPNs) of the genera Heterorhabditis and Steinernema, respectively (Hominick, 2002)
We evaluated the antibacterial activities of identified Xenorhabdus and Photorhabdus extracts against drug resistant bacteria using the disk diffusion method as well as minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) analyses
Genomic DNA could not be obtained from the remaining eight isolates owing to contamination by protozoa and fungi.We identified 13 Heterorhabditis isolates as H. indica, H. baujardi (Five isolates with 99% identity), and H. zealandica
Summary
Photorhabdus and Xenorhabdus are symbiotic with entomopathogenic nematodes (EPNs) of the genera Heterorhabditis and Steinernema, respectively (Hominick, 2002). Photorhabdus and Xenorhabdus belong to Family Enterobacteriaceae, which are Gram negative, rod shaped, and motile via peritrichous flagella. These bacteria are carried in the intestines of IJs that invade into the hemocoel of an insect host through the mouth, spiracles, and anus whereupon they are released from the IJ intestines into the hemolymph (Wang and Gaugler, 1998). The EPNs develop through one to three generations in the host cadaver by feeding on the bacteria and dead insect tissue. Upon depletion of the food resources, the IJs emerge from the host cadaver to search for a new host (Wang and Gaugler, 1998)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
