Plant growth promotion effect of Arthrobacter enclensis Yangsong-1 isolated from a button mushroom bed

양송이배지로부터 분리한 Arthrobacter enclensis Yangsong-1의 식물생장촉진효과

Abstract

An auxin-producing bacterium Yangsong-1 was isolated from a button mushroom bed in Chung cheongnam-do. The strain Yangsong-1 was classified as a novel strain of Arthrobacter enclensis based on a chemotaxonomic and phylogenetic analysis. The isolated A. enclensis Yangsong-1 was confirmed to produce indole-3-acetic acid (IAA), which is one of the auxin hormones. When the concentration of IAA was assessed by HPLC quantity analysis, the maximum concentration of IAA, $152.903mg\;L^{-1}$, was detected from the culture broth incubated in R2A medium containing 0.2% L-tryptophan for 48 h at $35^{\circ}C$. A negative relationship between IAA production and pH was estimated to show that the increase in IAA caused pH acidification of the culture. The effect of the supplement on L-tryptophan, a known precursor of IAA production, appeared to be at maximal production at 0.2% concentration and was rather reduced at concentration above 0.4%. To investigate the growth-promoting effects on the crops, the culture broth of A. enclensis Yangsong-1 was placed in water cultures and seed pots of mung beans and lettuce. In consequence, the adventitious root induction and root growth of mung beans and lettuce were 1.5 and 1.9 times higher, respectively, than those of the control.

충청남도 부여군 석성면 양송이 재배 농가에서 양송이 수확 후 배지로부터 토양을 채취하여 auxin(IAA) 생성능이 뛰어난 세균 Yangsong-1 균주를 분리하였다. TLC 및 HPLC 분석을 통해 분리균이 생성한 IAA 농도를 확인한 결과, 0.2% L-tryptophan를 함유한 pH 7.0의 R2A broth 배지에 $35^{\circ}C$, 48시간 배양 시 최대 생성농도는 $126.33mg\;L^{-1}$이었다. 생리적 특성 및 계통학적특성 분석을 통해 분리균은 Gram 음성 간균인 Arthrobacter enclensis Yangsong-1로 동정되었다. 배양조건별 IAA의 생산능 비교 시, IAA 농도의 증가가 배양액의 pH 산성화에 기인함으로서 IAA 생성량과 pH 변화에는 부의 상관성이 있는 것으로 관측되었다. IAA 생성을 위한 전구물질로 알려진 L-tryptophan의 첨가효과는 0.2% 첨가 시 균 생육 및 IAA 생성량이 최대이었으며, 0.4% 이상 고농도 첨가 배지에서는 오히려 IAA의 생성이 저해되었다. 또한 분리균에 의한 식물생육촉진효과를 조사하기 위하여 수경재배 및 pot 재배를 통한 녹두발근 생검법과 상추발근 생검법을 수행한 결과, A. enclensis Yangsong-1의 배양액 접종 시 녹두발근 생검법에서는 대조구에 비해 발근수와 뿌리길이에서 약 1.5배의 뿌리신장효과를 보였고, 상추발근 생검법에서는 대조구에 비해 뿌리길이와 무게에서 약 1.9배의 뿌리신장효과를 보였다.

Fig. 1. Isolation of auxin-producing strains using Salkowski-R2A broth.

Fig. 2. Phylogenetic trees of strain Yangsong-1 estimated from 16S rRNA gene sequence.

Fig. 3. TLC analysis of IAA produced from the selected strains. Concentration of IAA standard:100 mg L^-1

Fig. 4. HPLC chromatogram of auxin extracted from the strains IAA standard 100 mg L^-1(A), Yangsong-1 (B).

Fig. 5. The profile of IAA production of Arthrobacter enclensis Yangsong-1 based on incubation time.

Fig. 6. The profile of viable cells of Arthrobacter enclensis Yangsong-1 based on incubation time.

Fig. 7. The effect of concentration of L-tryptophan(%) on IAA production from Arthrobacter enclensis Yangsong-1.

Fig. 8. The effect of concentration of L-tryptophan(%) on Cell Growth from Arthrobacter enclensis Yangsong-1

Table 1. Estimation of IAA produced from the Isolated strains by HPLC.

Table 2. Growth effect of mung bean infected with producing bacteria in water culture and seed pot culture.

Table 3. Growth effect of lettuce infected with auxinproducing bacterium in seed pot culture