• Biotechnology and Bioprocess Engineering:BBE
• /
• 제5권2호
• /
• pp.141-145
• /
• 2000

Entomopathogenic nematodes are being used for insect control. We purified a toxin secreted by the insect-pathogenic bacterium, Xenorhadbus nematophilus, which lives in the gut of entomopathogenic nematodes. Culture broth of X. nematophilus was separated by centrifugation and concentrated by ultration. The concentrated culture broth was applied to a DEAE Sephadex A-50 column, and proteins were eluted stepwise with increasing concentrations of KCI. Fractions column. The molecty weight of purified toxin was39 kDa on SDS-PAGE, and Fourier tranformed infrared (FTIR) spectroscopy indicated that this toxin could be a new protein exhiting the charactristics of C=O stretching peak near 1650cm-1.

• Biotechnology and Bioprocess Engineering:BBE
• /
• 제9권5호
• /
• pp.379-382
• /
• 2004

Entomopathogenic nematodes are used for insect control. Herein, an extracellular protease was partially purified from a culture supernatant of Xenorhabdus nematophilus, a symbiotic bacterium of an entomopathogenic nematode, Steinernema glaseri: using precipitation with $80\%$ v/v isopropyl alcohol followed by gel permeation chromatography with a packed Sephacryl S-300 HR media. The partially purified protease exhibited maximal activity at pH 7 in the presence of 1 mM $CaCl_2$. The protease was identified as a metallo-protease based on the inhibition of its activity by the metal chelating agent, EDTA.

• 한국미생물·생명공학회지
• /
• 제38권2호
• /
• pp.117-123
• /
• 2010

BT toxin is produced by a soil bacterium Bacillus thuringiensis and has long been used as a biological insecticide without any competition. Recently, Photorhabdus, a symbiotic bacterium from entomopathogenic nematodes, family Heterorhabditae, has been researched and discussed as alternatives to B. thuringiensis. Photorhabdus, which lives in the gut of entomopathogenic nematodes, is a highly virulent pathogen of a wide range of insect larvae. When an insect is infected by the nematodes, the bacteria are released into the cadaver, and produce a number of insecticidal toxins. The biological role of the different Photorhabdus toxins in the infection process is still unclear. Photorhabdus toxin complex (Tc) is highly secreted gut-active toxin and has been characterized as a potent three-component (A, B and C) insecticidal protein complex. These components are necessary for full oral activity against insect larvae. The Photorhabdus PirAB binary toxins exhibit a potent injectable activity for Galleria mellonella larvae, and have oral toxicity against mosquitoes and caterpillar pest Plutella xylostella. Other toxin, 'makes caterpillars floppy' (Mcf) showed injectable activity on caterpillars. Recombinant Mcf triggers apoptosis in both insect hemocytes and the midgut epithelium and carries a BH3 domain. In this review, the relationship between the Photorhabdus and the nematode is discussed and recent important insecticidal toxins from Photorhabdus are described.

• Biotechnology and Bioprocess Engineering:BBE
• /
• 제4권1호
• /
• pp.12-16
• /
• 1999

Xenorhabdus nematophilus sp., an insect-pathogenic bacterium, was newly isolated from Korean entomopathogenic nematode of Steinernema carpocapsae, which can be used as a useful bioinsecticide. Primary and secondary form variants of Xenorhabdus nematophilus were observed when cultured in vitro. Primary form variants adsorbed bromothymol blue, while secondary form did not. However, many other characters of two variants were very similar. The variants were all rod-shaped and cell size was highly variable ranging from 0.5 by 2.0 ${\mu}$m to 1.0 by 5.0 ${\mu}$m. Both produced highly toxic substances and killed the insect larva within 20∼38 hr, indicating that insect pathogenicity of Xenorhabdus is not directly associated with its phase variation. In addition, cell-free culture supernatant of Xenorhabdus was sufficient to kill the insect larva by injecting it ito insect hemolymph; however, cell-harboring culture broth was more effective for killing the insect. The use of Xenorhabdus nematophilus may provide a potential alternative to Bacillus thuringiensis (Bt) toxins.

• KSBB Journal
• /
• 제14권3호
• /
• pp.303-308
• /
• 1999

본 연구에서는 환경친화적인 무공해생물농약 재발을 위하여 곤충병원성 선충의 in vitro 배양방법을 개별하였다. 곤충병원선 층연 Steinernem$\alpha$ glasen 종으로부터 공생박테리아를 분리하여 동정한 결과 Xenorhabdus nem$\alpha$tophllus 종임을 확인하였으며, X enorhabdus nematophilus는 감염단계 선충의 장내에서와 in vitro 배양 동안에 그 생화학적 특성이에서 차이를 보이는 동 질형화 헨상을 나타냄을 확인하였다. 균주의 최적바지 조성은 5% yeast extract, 0.5% NaCl, $K_2HPO_4$, $0.02% MgSO_4$.$7H_2O$이였으며, $28^{\circ}C$가 최적배양 온도였다, 초기 pH 6-7에 관계 없이 성장이 진행됨에 따라서 약 90까지 층가하였다. Flask 배양에 비해서 fennentortor양에서 균주의 성장속도가 1.4배 빠르게 나타났으나, 그에 따른 상변회도 빠르게 진행되었다. 한편 Steinem$\xi$ma glaseri익 in vitro 배양을 위 힌 인공배지원으로 chIcken offal, dog food, peanut 퉁이 사용될 수 있으며 최적의 배지는 농축펀 bovine liver로 조사되었으며, 그 농도논 80%일 때 가장 높은 증식을 보였다. 또한 곤충병원선충으로부터 분리된 공생박테리아를 이용한 혼합배양방법은 공생박테리아를 사용­하지 않는 경우보다 선충의 in vitro 증식속도가 2 배 가량 빨랐으며, 15일만에 약 $5.5\times10^4$/mL 의 선충이 수확되였다.

• Journal of Microbiology and Biotechnology
• /
• 제17권3호
• /
• pp.420-427
• /
• 2007

We investigated the temperature effects on the virulence, development, reproduction, and otility of two Korean isolates of entomopathogenic nematodes, Steinernema glaseri Dongrae strain and S. longicaudum Nonsan strain. In addition, we studied the growth and virulence of their respective symbiotic bacterium, Xenorhabdus poinarii for S. glaseri and Xenorhabdus sp. for S. longicaudum, in an insect host at different temperatures. Insects infected with the nematode-bacterium complex or the symbiotic bacterium was placed at $13^{\circ}C,\;18^{\circ}C,\;24^{\circ}C,\;30^{\circ}C,\;or\;35^{\circ}C$ in the dark and the various parameters were monitored. Both nematode species caused mortality at all temperatures tested, with higher mortalities occurring at temperatures between $24^{\circ}C\;and\;30^{\circ}C$. However, S. longicaudum was better adapted to cold temperatures and caused higher mortality at $18^{\circ}C$ than S. glaseri. Both nematode species developed to adult at all temperatures, but no progeny production occurred at $13^{\circ}C\;or\;35^{\circ}C$. For S. glaseri, nematode progeny production was best at inocula levels above 20 infective juveniles/host at $24^{\circ}C\;and\;30^{\circ}C$, but for S. longicaudum, progeny production was generally better at $24^{\circ}C$. Steinernema glaseri showed the greatest motility at $30^{\circ}C$, whereas S. longicaudum showed good motility at $24^{\circ}C\;and\;30^{\circ}C$. Both bacterial species grew at all tested temperatures, but Xenorhabdus sp. was more virulent at low temperatures $(13^{\circ}C\;and\;18^{\circ}C)$ than X. poinarii.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2001년도 추계학술발표회
• /
• pp.107-110
• /
• 2001

The biological control potential of entomopathogenic nematodes (EPN) can be enhanced by improved culture efficiency. Optimization of media is a key factor for improving in vitro mass production of entomopathogenic nematodes. EPN yield was dependant of complex medium concentration, of which mixture is carbohydrates, lipids, proteins, salts, and growth factors, on the growth of Heterorhabditis bacteriophora and its symbiotic bacterium Photorhabdus luminescensLipids.

• Journal of Microbiology and Biotechnology
• /
• 제11권4호
• /
• pp.644-648
• /
• 2001

The biological control potential of entomopathogenic nematodes (EPN) can be enhanced by improved culture efficiency. Optimization of the media is a key factor for improving in vitro mass production of entomopathogenic nematodes. This study reports the effect of medium concentration. The medium is a combination of carbohydrates, lipids, proteins, sats, and growth factors, on the growth of Heterorhabditis bacteriophora and its symbiotic bacterium Photorhabdus liminescens. The overall optimal medium concentration for nematode recovery, hermaphrodite size, bacterial mass, infective juveniles (IJs) yield, and doubling time was 84 g/l. At this concentration rate, the doubling time of IJs production and the biomass of symbiotic bacteria was 1.6 days and 12.8 g/l, respectively. The maximum yield of $2.4{\times}{10^5}IJs/ml$ was attained within a one-generation cycle (eight days). The yield coefficient was $2.8{\times}{10^6}$ IJs/g medium, and the maximum productivity was $3.1{\times}{10^7}$ IJs per day. Medium concentration affected two independent factors, recovery and hermaphrodite size, which in turn influenced the final yield.

• 한국응용곤충학회지
• /
• 제51권1호
• /
• pp.39-45
• /
• 2012

곤충병원세균인 제노랍두스($Xenorhabdus$ sp.)는 곤충병원선충인 $Steinernema$ $monticolum$으로부터 분리되었다. 이 세균 배양액을 배추좀나방($Plutella$ $xylostella$) 혈강에 주입할 경우 높은 병원력을 나타내지만, 섭식 처리할 경우 낮은 병원력을 보였다. 본 연구는 이 제노랍두스 세균 배양액이 $Bacillus$ $thuringiensis$(비티)와 혼합하여 배추좀나방 종령충에 처리할 경우 비티의 병원력을 뚜렷하게 증가시키는 것을 보였다. 또한 제노랍두스 배양액과 비티의 혼합비율을 달리할 경우 병원력이 크게 차이를 보였다. 최적의 두 세균 혼합비율을 이용하여 야외에 발생한 배추좀나방에 처리하였으며, 비티 단독처리에 비해 뚜렷이 상승된 방제 효과를 확인할 수 있었다. 이러한 결과는 제노랍두스 배양액을 비티와 혼합하여 새로운 미생물 살충제로 개발할 수 있는 가능성을 제시했다.

• KSBB Journal
• /
• 제14권2호
• /
• pp.198-204
• /
• 1999

Asymbiotic bacterium with highly effective toxins was isolated from entomopathogenic nematode Steinernema glaseri which has been widely used against various soil-inhabiting pests. The symbiont of S. glaseri was identified as Xenorhabdus nematophilus sp. by using several biochemical and physiological tests. When this strain was released into the hemolymph of insect larva, it produced highly toxic substances and killed the larva within 2 days. Two colony forms that differed n some biochemical characteristics were observed when cultures in vitro. Phase l colonies were mucid and difficult to be dispersed in liquid. Phase II was not mucoid and was easily dispersed in liquid. It did not adsorb neutral red or bromothymol blue. Rod-shaped cell size was highly variable between two phases, ranging 2-10 ${\mu}{\textrm}{m}$. It was also found that only infective-stage nematodes can carry only primary-phase Xenorhabdus in their intestine.