• 미생물학회지
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• 제47권2호
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• pp.163-166
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• 2011

항 진균제의 인체에 대한 부작용을 완화시키는 방법은 부작용이 적은 새로운 항 진균제 개발이나 기존 항 진균제와 혼용하여 상승효과를 나타내는 물질이 필요하다. 이를 위해 Rahnella aquatilis AY2000가 생산하는 항 효모물질은 일종의 단백질성 고분자 물질이란 점에서 기존 항 진균제와 차이가 있다. 이 항 효모물질은 유도기나 대수증식 기에 있는 효모 생육을 억제시켰으며, cell cycle 분석에서 sub-G1기에 속하는 세포수의 증가 없이 세포를 arrest시켰다. 따라서 항 효모물질은 Candida albicans에 정균작용을 나타내었다. 또한 in vitro 실험에서 이 항 효모물질과 itraconazole이나 fluconazole을 병용한 후 fractional inhibitory concentration index 분석을 행한 결과 항 효모활성이 더욱 상승되었다. 결론적으로 이 항 효모물질은 정균 작용을 가질 뿐만 아니라 azole계의 항 진균제와 혼용하면 상승효과를 가짐으로 부작용이 적은 새로운 개념의 항 진균제로 개발할 가치가 있을 것이라고 생각된다.

• 한국미생물·생명공학회지
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• 제36권4호
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• pp.285-290
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• 2008

Rahnella aquatilis AY2000 균주는 항효모성 물질(AYS)을 생산하지만, AYS가 저장 중에 활성이 감소되는 경향이 있었다. 따라서 본 연구에서는 AYS활성이 저하되는 원인을 알아보기 위하여 AYS에 다양한 이화학적인 처리를 행하였다. 그 결과 열처리가 AYS의 활성을 감소시키는 하나의 인자이며, AYS를 침전시키는 유기용매인 methanol의 사용 또한 AYS의 활성을 감소시키는 원인이었다. 또한 $\beta$-mercaptoethanol 과 dithiothreitol 등 thiol화합물 역시 AYS의 활성을 감소시키는 인자로 작용하였으나, pH, EDTA나 NaCl은 AYS의 활성저하를 가져오지 않았다. 한편, 정제과정에서 AYS의 조성분 중 다당류와 미지의 물질(230 nm)을 DEAE-cellulose 이온교환수지로 분리시키면 AYS의 활성이 완전히 소실되지만, AYS를 Sephacryl S-400 gel 여과를 행하여 이들 성분이 분리되지 않은 상태에서는 그 활성이 잘 유지되었다. 본 실험에 사용된 AYS의 MIC는 S. cerevisiae 대해 $7.8-15.6{\mu}g/mL$ 범위로 측정된다.

• Journal of Microbiology and Biotechnology
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• 제16권10호
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• pp.1597-1604
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• 2006

To screen for an anti-yeast substance (AYS), many bacteria were isolated from soil and a strain AY2000 was selected. The strain AY2000 was identified as Rahnella aquatilis by morphology, biochemical properties, and 16S r-RNA nucleotide sequence analyses. The strain AY2000 showed anti-yeast activity against Candida albicans and Saccharomyces cerevisiae, whereas R. aquatilis ATCC33071 as a type strain did not show the activity against the yeasts under the same condition. The growth of yeast cell was significantly inhibited by AYS produced by the strain AY2000, as shown by optical density and MTT assay. The minimum inhibitory concentration (MIC) of the AYS against S. cerevisiae and C. albicans at $28^{\circ}C\;was\;20{\mu}g/ml\;and\;60{\mu}g/ml$, respectively. The MIC of AYS against hyphae of C. albicans at $37^{\circ}C\;was\;600{\mu}g/ml$. Scanning electron microscopic analysis revealed that yeast cells treated with AYS had an irregular form with a wrinkled and rough surface.

• 한국미생물·생명공학회지
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• 제37권4호
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• pp.361-364
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• 2009

AYS(Anti-yeast substance)는 열에 의해 항효모 활성이 쉽게 약화되는 물질로서 trehalose의 사용이 AYS의 열에 대한 불안정성을 어느 정도 극복할 수 있을 것인지를 조사하기 위해 trehalose가 첨가된 AYS와 trehalose가 첨가되지 않은 AYS에 대한 항효모 활성을 비교 측정하였다. 그 결과 trehalose가 첨가된 AYS는 고온($50-70^{\circ}C$)에서 단시간(2 hr) 동안 열처리한 경우에 trehalose가 함유되지 않은 AYS에 비해 그 활성이 비교적 잘 유지되었다. 따라서 trehalose를 AYS에 첨가하면 열처리 후에도 AYS의 항효모 활성을 다소 보호할 수 있다.

• Journal of Microbiology and Biotechnology
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• 제11권4호
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• pp.693-699
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• 2001

An intracellular levansucrase gene, lscR from Rahnella aquatilis ATCC 15552, was cloned and its nucleotide sequence was determined. Nucleotide sequence analysis of this gene revealed a 1,238 bp open reading frame coding for a protein of 415 amino acids. The levansucrase was expressed by using a T7 promoter in Escherichia coli BL21 (DE3) and the enzyme activity was detected in the cytoplasmic fraction. The optimum pH and temperature of this enzyme for levan formation was pH 6 and $30^{\circ}C$, respectively. The deduced amino acid sequence of the lscR gene showed a high sequence similarity (59-89%) with Gram-negative levansucrses, while the level of similarity with Gram-positive enzymes was less than 42%. Multiple alignments of levansucrase sequences reported from Gram-negative and Gram-positive bacteria revealed seven conserved regions. A comparison of the catalytic properties and deduced amino acid sequence of lscR with those of other bacterial levansucrases strongly suggest that Gram-negative and Gram-positive levansucrases have an overall different structure, but they have a similar structure at the active site.

• Journal of Microbiology and Biotechnology
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• 제13권2호
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• pp.230-235
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• 2003

A 1.25 kb DNA fragment including the lscR gene, which encodes a levansucrase of Rahnella aquatilis ATCC 15552, was subcloned into a high-expression vector, pET-29b, and the recombinant enzyme was overexpressed in Escherichia coli. Most of the levansucrase activity was detected in the cytoplasmic fraction after induction with isopropyl ${\beta}-D-thiogalactoside$. The recombinant enzyme with a tag of six histidine residues at the C-terminus was purified 146-fold by affinity and gel-filtration chromatographies. The molecular mass of the purified LscR was approx. 49 kDa as determined by SDS-PAGE. The optimum pH and temperature of this enzyme for levan formation was pH 6.0 and $30^{\circ}C$, respectively. The optimum substrate concentration for levan formation was 300 mM sucrose. Levan formation was increased by the increase of the enzyme concentrations. Maxium yield of levan formation at optimum substrate concentration, pH, and temperature after 24 h of reaction was approximately 80%.

• The Plant Pathology Journal
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• 제26권1호
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• pp.63-69
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• 2010

The effect of Acibenzolar-S-methyl (ASM) and Rahnella aquatilis Ra39 against apple fire blight disease caused by Erwinia amylovora were tested as a possible alternative to streptomycin. In vitro studies, no inhibition effect against the pathogen was found when ASM was tested. Under greenhouse conditions, application of R. aquatilis Ra39 with the highly susceptible M26 rootstock resulted in a marked disease suppression. Application of ASM and strain Ra39 caused a high decrease of the disease, 82% and 58% respectively; this was correlated with a reduction of the growth of the pathogen within host plants up to 64% and 49.5% respectively. Further studies in the field under artificial infection condition during full bloom revealed that application of ASM and R. aquatilis Ra39 with Gala variety resulted in a control effect up to 21 and 29% respectively. In physiological studies, enhanced activities of PR-proteins (chitinase and $\beta$-1, 3-glucanase) were detected, which are well known as biochemical markers for systemic acquired resistance. Application of ASM to apple shoots caused the highest chitinase activity followed by strain Ra39. The enzyme activity was increased after 2, 4 and 6 days from application. In addition, ASM-treatment caused the higher $\beta$-1, 3-glucanase activity than strain Ra39. Maximum enzyme activity was recorded after 6 days from application and then decreased after 8 and 10 days from application.

• Journal of Microbiology and Biotechnology
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• 제14권6호
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• pp.1232-1238
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• 2004

To investigate the production and characteristics of thermostable levan sucrase from Rahnella aquatilis ATCC 33071, the levan sucrase gene from R. aquatilis was cloned and expressed in Escherichia coli without induction system. Expression of levansucrase gene in E. coli had no notable or detrimental effect on the growth of host strain, and the recombinant levan sucrase exhibited levan synthesis activity. Levansucrase was secreted to the periplasm in E. coli, and addition of $0.5\%$ glycine yielded further secretion of levansucrase to the growth medium and resulted in an increase of total levansucrase activity. Furthermore, the cellular levansucrase was evaluated for the production of levan by using toluene­permeabilized whole-cells. The levansucrase was thermostable at $37^{\circ}C$. The molecular size oflevan was $1{\times}\;10^{6}$ Da, as determined by HPLC, and the degree of polymerization of levan varied with incubation temperatures: Low incubation temperature was preferable for the production of high-molecular size levan. The present study demonstrated that the mass production of levan and levan oligosaccharides can be achieved by glycine supplementation to the growth medium or by toluene­permeabilized whole-cells.

• Journal of Microbiology
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• 제44권4호
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• pp.396-402
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• 2006

[ ${\beta}-Galactosidase$ ] is extensively employed in the manufacture of dairy products, including lactose-reduced milk. Here, we have isolated two gram-negative and rod-shaped coldadapted bacteria, BS 1 and HS 39. These strains were able to break down lactose at low temperatures. Although two isolates were found to grow well at $10^{\circ}C$, the BS 1 strain was unable to grow at $37^{\circ}C$. Another strain, HS-39, evidenced retarded growth at $37^{\circ}C$. The biochemical characteristics and the results of 16S rDNA sequencing identified the BS 1 isolate as Rahnella aquatilis, and showed that the HS 39 strain belonged to genus Buttiauxella. Whereas the R. aquatilis BS 1 strain generated maximal quantities of ${\beta}-galactosidase$ when incubated for 60h at $10^{\circ}C$, Buttiauxella sp. HS-39 generated ${\beta}-galactosidase$ earlier, and at slightly lower levels, than R. aquatilis BS 1. The optimum temperature for ${\beta}-galactosidase$ was $30^{\circ}C$ for R. aquatilis BS-1, and was $45^{\circ}C$ for Buttiauxella sp. HS-39, thereby indicating that R. aquatilis BS-1 was able to generate a cold-adaptive enzyme. These two cold-adapted strains, and most notably the ${\beta}-galactosidase$ from each isolate, might prove useful in some biotechnological applications.

• 한국미생물·생명공학회지
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• 제24권4호
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• pp.493-499
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• 1996

Lactan gum produced by Rahnella aquatilis is a high viscous, anionic polysaccharide and has shear thinning behaviour. Lactan gum yield and cencentration was greater on disaccharide such as lactose and sucrose than on monosaccharides such as glucose and galactose. When initial carbon source concentration was 45g/l of sucrose of lactose, the microorgnisms produced 28 g/l and 27 g/l of lactan, respectively with a yield more than 60%. $\beta$-Galactosidase, hydrolyzing lactose into galactose and glucose, was induced by lactose or galactose. When initial corbon source was 45 g/l of mixed carbon I (glucose:galactose=1:1), lactan gum concentaration was higher than that from 45 g/l of monosaccharide (glucose pf galactose) but was similar to the result from 45 g/l of lactose. Therefore, lactose hydrolysis reaction by $\beta$-galactosidase does not seem to be a rate determining step in lactan gum biosynthesis. When initial carbon source was 45 g/l of mixed carbon II (glucose:fructose=1:1). total carbon source consumption rate was slower than that from sucrose, but glucose consumption rate was faster than that from fructose.