Recurrent aphthous stomatitis (RAS) is a common oral mucosal disorder for which no curative treatment is available. We previously reported that decreased Streptococcus salivarius and increased Acinetobacter johnsonii on the oral mucosa are associated with RAS risk. The purpose of this study was to identify antibiotics that selectively inhibit A. johnsonii but minimally inhibit oral mucosal commensals. S. salivarius KCTC 5512, S. salivarius KCTC 3960, A. johnsonii KCTC 12405, Rothia mucilaginosa KCTC 19862, and Veillonella dispar KCOM 1864 were subjected to antibiotic susceptibility test using amoxicillin, cefotaxime, gentamicin, clindamycin, and metronidazole in liquid culture. The minimal inhibitory concentration (MIC) was defined as the concentration that inhibits 90% of growth. Only gentamicin presented a higher MIC for A. johnsonii than MICs for S. salivarius and several oral mucosal commensals. Interestingly, the growth of S. salivarius increased 10~200% in the presence of sub-MIC concentrations of gentamicin, which was independent of development of resistance to gentamicin. In conclusion, gentamicin may be useful to restore RAS associated imbalance in oral microbiota by selectively inhibiting the growth of A. johnsonii but enhancing the growth of S. salivarius.

영남육괴 북동부에 위치하는 춘양화강암은 비알칼리계열 중 칼크-알칼리계열에 해당하는 I-type의 화강암류이며, 고알루미나질이다. 주성분원소 및 미량원소의 함량변화는 체계적인 연속성을 보이며, 일반적인 남한의 쥐라기 화강암류 의 분화경향과 유사하다. 미량원소 중 유동성을 가지는 LILE (Sr, K, Rb, Ba)는 부화되어 있는 반면, 비유동성을 나타 내는 HFSE 중 Ta, Nb, P, Ti의 함량은 상대적으로 결핍되어 있다. HREE에 대한 LREE의 강한 부화((La/Lu)CN=41.8-73.2)와 Eu 부(-)이상[(Eu/Eu*)CN=0.89-1.10]은 남한에 분포하는 쥐라기 화강암류의 패턴과 매우 유사하다. 이러한 춘양 화강암을 암체의 서쪽에 위치하며 영주저반의 대부분을 차지하는 부석심성암체와 비교하면 주성분원소 및 미량원소의 Harker 성분변화도에서 SiO2 함량에 따른 상관관계를 인지할 수 없어 두 암체는 성인적으로 무관한 별개의 암체로 사 료된다. 춘양화강암은 지구조 판별도에서 화산호 환경에 도시되고 따라서 춘양화강암의 지화학적 특성을 종합해보면 쥐 라기 고태평양판이 섭입하는 활동성 대륙주변부 환경에서 생성되었을 것으로 사료된다.

This study was carried out to compare the toxicity of nano and micrometer particles with Cu and Zn on soil microbial community and metal uptake of buck wheat. In microcosm system, soil was incubated for 14 days after soil aliquots were artificially contaminated with 1,000 mg/kg Cu, Zn nano and micro particles, respectively. After then, buck wheat was planted in incubating soils and non incubating soils. After 14 days, we compared bioaccumulation of metal, and microbial carbon substrate utilization patterns between incubating soils and non-incubating soils. The enrichment factor (EF) values of incubating samples were greater than non-incubating soils. Dehydrogenase activity had been inhibited by Cu and Zn nanoparticles in non-incubating soil, as well as it had been inhibited by Zn micro particles in incubating soils. Results of biolog test, it was not significant different between nano particles and micro particles. It cannot be generalized that nanoparticles of metal are always more toxic to soil microbial activity and diversity than micrometer-sized particles and the toxicity needs to be assessed on a case-by-case basis.