Korean Journal of Microbiology (미생물학회지)

The Microbiological Society of Korea (한국미생물학회)
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Cold-Sensitive Growth of Bacillus subtilis Mutants Deleted for Putative DEAD-Box RNA Helicase Genes

Bacillus subtilis DEAD-Box RNA Helicase 유전자 결손 균주들의 저온 민감성 생장

  • Oh, Eun-Ha (Department of Life Science and Technology, Pai Chai University) ;
  • Lee, Sang-Soo (Department of Life Science and Technology, Pai Chai University)
  • Received : 2010.07.30
  • Accepted : 2010.09.14
  • Published : 2010.09.30
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Abstract

Four genes (yqfR, yfmL, ydbR, deaD) were identified as putative DEAD-box RNA helicase genes in the genomic sequence of Bacillus subtilis by homology search. To understand the function of these genes, each of the genes was deleted and the constructed strains were tested for their growth charateristics at different temperatures. The growth rate of ydbR deletion mutant ($T_d$=53 min) was a little bit reduced at $37^{\circ}C$ as compared to that of wild type strain (CU1065). But the growth rate of other three (yqfR, yfmL, deaD) deletion mutants ($T_d$=30-40 min) is nearly equal to the growth rate of wild type ($T_d$=32 min). On the other hands, the growth rate of deletion mutants were reduced at $22^{\circ}C$ in order of yqfR ($T_d$=151 min), yfmL ($T_d$=214 min), ydbR ($T_d$=343 min), which showed cold-sensitive phenotype. The deletion mutant of deaD ($T_d$=109 min) grew equally as compared to the growth rate ($T_d$=102 min) of the wild type at $22^{\circ}C$ and did not show cold-sensitive growth. Double, triple and quadruple deletion mutants of these genes were constructed, and growth rate of these mutants were measured at various temperature conditions ($22^{\circ}C$, $37^{\circ}C$, $42^{\circ}C$) using LB broth. Multiple deletion mutations showed more severe cold-sensitive growth than single deletion mutations, and double deletion of ydbR and yfmL ($T_d$=984 min) showed most cold-sensitive growth than any other double mutants. Such a cold-sensitive growth of these mutations is quite similar to the result of csdA or srmB deletion in E. coli and suggested that physiological role of ydbR and yfmL is related with ribosome assembly.

Bacillus subtilis에 존재하는 DEAD-box RNA helicase에 대한 유전자 상동성 검색을 통해 yqfR, yfmL, ydbR, deaD 의 4종류의 유전자를 확인하였고 이들 유전자 각각의 결손 돌연변이체를 제조하였다. 이들 돌연변이체들의 특성을 알아보기 위하여 LB 배양액을 사용하여 여러 온도에서의 생장 속도를 조사하였다. LB 배양액에서 $37^{\circ}C$의 생장 결과 ydbR 결손 균주가 다소 생장이 느려지나($T_d$=53 min) 다른(yqfR, yfmL, deaD) 결손 돌연변이체들은($T_d$=30-40 min) 결손이 없는 야생형 균주 CU1065와($T_d$=32 min) 유사하였다. 반면에 $22^{\circ}C$에서의 생장은 CU1065 ($T_d$=102 min)에 비해 yqfR ($T_d$=151 min), yfmL ($T_d$=214 min), ydbR ($T_d$=343 min) 결손 균주 순으로 생장속도가 느린 저온 민감성을 보인다. deaD의 $22^{\circ}C$에서의 생장 속도는 ($T_d$=109 min) CU1065와 ($T_d$=102 min) 매우 유사하여 저온 민감성을 보이지 않았다. 그리고 이들 유전자들의 이중, 삼중, 사중의 결손 균주들을 제조하였고, 여러 온도에서 ($42^{\circ}C$, $37^{\circ}C$, $22^{\circ}C$) LB 배양액을 사용하여 생장 속도를 측정 하였다. 다중 결손은 단일 결손보다 더 심한 저온 민감성을 보이며, 이중 결손의 경우, ydbR과 yfmL의 결손이 다른 조합의 결손보다 보다 큰 저온 민감성을 나타내었다 ($T_d$=984 min). 이러한 저온 민감성은 E. coli의 csdA 혹은 srmB 결손의 결과와 유사하며 리보솜 조립과 관련이 있는 생리적 기능으로 보인다.

Keywords

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