The beet armyworm, Spodoptera exigua, is one of the worldwide distributed agricultural pest insects and has been known to show high resistance to conventional chemical insecticides. Since it has been reported that secondary metabolites from actinomycetes show insecticidal activities against various insect pests, actinomycetes could be a potential source of insecticidal compounds. In this study, culture extracts of Streptomyces strains were tested for their insecticidal activity against Spodoptera exigua. Among them, culture extracts of IMBL-0003 strain which was identified as Streptomyces celluloflavus showed a high insecticidal activity (more than 90% mortality). These results suggested that secondary metabolites of this isolate could have potentials to be a efficient eco-friendly pesticide for controling Spodoptera exigua.

Mosquitoes are medically important insect pests that act as vectors of various diseases when they feed on humans. Insect growth regulators (IGRs) could become an effective alternative to control mosquitoes because of their high specificity and relatively low toxicity to environment. Recently, we have developed high-throughput juvenile hormone antagonist (JHAN) screening system based on yeast-two hybrid assay. Actinomycetes have been reported to produce various bioactive compounds including insect growth regulators (IGRs). In this study, culture filtrates and mycelia extracts of 2,875 actinomycetes isolates screened for their IGR activities and mosquitocidal activities. Among 75 culture filtrates and 17 mycelia extracts with JHAN activities, 19 culture filtrate and 3 mycelia extracts showed high level of mosquitocidal activities against 3rd instar larvae of Aedes albopictus. These results suggested that secondary metabolites of actinomycetes could be used as environmentally benign mosquitocidal agents.

Chlorhexidine has long been used in mouth washes for the control of dental caries, gingivitis and dental plaque. Minimal inhibitory concentration (MIC) is the lowest concentration of an antimicrobial substance to inhibit the growth of bacteria. Concentrations lower than the MIC are called sub minimal inhibitory concentrations (sub-MICs). Many studies have reported that sub-MICs of antimicrobial substances can affect the virulence of bacteria. The aim of this study was to investigate the effect of sub-MIC chlorhexidine on biofilm formation and coaggregation of oral early colonizers, such as Streptococcus gordonii, Actinomyces naeslundii and Actinomyces odontolyticus. The biofilm formation of S. gordonii, A. naeslundii and A. odontolyticus was not affected by sub-MIC chlorhexidine. However, the biofilm formation of S. mutans increased after incubation with sub-MIC chlorhexidine. In addition, cell surface hydrophobicity of S. mutans treated with sub-MIC of chlorhexidine, decreased when compared with the group not treated with chlorhexidine. However, significant differences were seen with other bacteria. Coaggregation of A. naeslundii with A. odontolyticus reduced by sub-MIC chlorhexidine, whereas the coaggreagation of A. naeslundii with S. gordonii remained unaffected. These results indicate that sub-MIC chlorhexidine could influence the binding properties, such as biofilm formation, hydrophobicity and coaggregation, in early colonizing streptococci and actinomycetes.

Minimal inhibitory concentration (MIC) is the lowest antibiotic concentration that inhibits the visible growth of bacteria. Sub-minimal inhibitory concentration (Sub-MIC) is defined as the concentration of an antimicrobial agent that does not have an effect on bacterial growth but can alter bacterial biochemistry, thus reducing bacterial virulence. Many studies have confirmed that sub-MICs of antibiotics can inhibit bacterial virulence factors. However, most studies were focused on Gram-negative bacteria, while few studies on the effect of sub-MICs of antibiotics on Gram-positive bacteria. In this study, we examined the influence of sub-MICs of doxycycline, tetracycline, penicillin and amoxicillin on biofilm formation and coaggregation of Streptococcus gordonii, Streptococcus mutans, Actinomyces naeslundii, and Actinomyces odontolyticus. In this study, incubation with sub-MIC of antibiotics had no effect on the biofilm formation of S. gordonii and A. naeslundii. However, S. mutans showed increased biofilm formation after incubation with sub-MIC amoxicillin and penicillin. Also, the biofilm formation of A. odontolyticus was increased after incubating with sub-MIC penicillin. Coaggregation of A. naeslundii with S. gordonii and A. odontolyticus was diminished by sub-MIC amoxicillin. These observations indicated that sub-MICs of antibiotics could affect variable virulence properties such as biofilm formation and coaggregation in Gram-positive oral bacteria.

The BIG11003 strain was isolated as protein-degrading actinomycetes from cucumber farm. The effect of plant natural resources (Azadirachta indica L and Sophora angustifolia) of juveniles and the hatching of eggs of Meloidogyne sp. were examined the laboratory. The nematicides (fosthiazate), actinomycetes protease and S. angustifolia extract resulted in 45.6, 46.6 and 51.23% mortality of J2 of M. incognita. The nematicides (fosthiazate), A. indica L and S. angustifolia extract resulted in 2.06, 3.96 and 6.22% hatch of egg of M. incognita. Antinematode activity test had done after the formulation of liquid (Nemastar) with mixture of additives and inerts into selected highly active natural material and actinomycetes protease. In pot and field experiments, the nemastar had good control efficacy against plant root-knot nematodes. Anti-nematode activity of strain BIG11003 from phylogentic analysis based on 16S rDNA sequences, it is suggested the Streptomyces koyangensis.

제주도 연안해역 4개 지역(한림, 애월, 신촌, 함덕) 해수의 온도, 염분농도, 용존산소량(DO), 화학적 산소요구량(COD), 부유물질(SS), 암모니아성 질소(NH3-N), 질산성 질소(NO3-N) 및 아질산성 질소(NO2-N)와 같이 다양한 이화학적 특성을 확인하였다. 해수의 평균 온도는 26.23~28.6℃, 염분농도는 31.4~32.88‰, pH는 8.15~8.35, COD는 0.48~0.91 mg

경상북도내의 금속광산, 공장 및 공업지역의 토양의 오염도를 조사하고 중금속 오염토양 중에 분포하는 미생물 flora의 정량적 평가를 위하여 청정지역인 독도토양과 비교한 결과, 일반세균의 경우 10~100배 낮은 분포율을 나타내었으며, 6가크롬 오염토양 중 곰팡이는 거의 검출되지 많았다. 방선균은 수은 오염토양의 경우 6.7X105~7.5X107 cfu g-1, 6가크롬 오염토양 내 방선균 수는 4.8X104~5.0