ABSTRACT
p
-Nitrophenol (4-NP) is recognized as an environmental contaminant; it is used primarily for manufacturing medicines and pesticides. To date, several 4-NP-degrading bacteria have been isolated; however, the genetic information remains very limited. In this study, a novel 4-NP degradation gene cluster from a gram-positive bacterium,
Rhodococcus opacus
SAO101, was identified and characterized. The deduced amino acid sequences of
npcB
,
npcA
, and
npcC
showed identity with phenol 2-hydroxylase component B (reductase, PheA2) of
Geobacillus thermoglucosidasius
A7 (32%), with 2,4,6-trichlorophenol monooxygenase (TcpA) of
Ralstonia eutropha
JMP134 (44%), and with hydroxyquinol 1,2-dioxygenase (ORF2) of
Arthrobacter
sp. strain BA-5-17 (76%), respectively. The
npcB
,
npcA
, and
npcC
genes were cloned into pET-17b to construct the respective expression vectors pETnpcB, pETnpcA, and pETnpcC. Conversion of 4-NP was observed when a mixture of crude cell extracts of
Escherichia coli
containing pETnpcB and pETnpcA was used in the experiment. The mixture converted 4-NP to hydroxyquinol and also converted 4-nitrocatechol (4-NCA) to hydroxyquinol. Furthermore, the crude cell extract of
E. coli
containing pETnpcC converted hydroxyquinol to maleylacetate. These results suggested that
npcB
and
npcA
encode the two-component 4-NP/4-NCA monooxygenase and that
npcC
encodes hydroxyquinol 1,2-dioxygenase. The
npcA
and
npcC
mutant strains, SDA1 and SDC1, completely lost the ability to grow on 4-NP as the sole carbon source. These results clearly indicated that the cloned
npc
genes play an essential role in 4-NP mineralization in
R. opacus
SAO101.
摘要
p
-硝基苯酚(4-NP)被认为是一种环境污染物,主要用于制造药物和杀虫剂。迄今为止,已分离出几种降解 4-NP 的细菌,但遗传信息仍然非常有限。本研究从一种革兰氏阳性细菌中发现了一个新的 4-NP 降解基因簇、
乳清红球菌
SAO101 中的一个新型 4-NP 降解基因簇。推导出了
npcB
,
npcA
和
npcC
与热葡糖苷酸革囊菌的苯酚 2-羟化酶 B 组份(还原酶,PheA2)显示出相同性
与 2,4,6-三羟基苯酚还原酶 B 组份(还原酶,PheA2)的同一性。
的 2,4,6-三氯苯酚单加氧酶(TcpA)的同一性。
的 2,4,6-三氯苯酚单加氧酶(TcpA
JMP134(44%),以及羟基喹啉 1,2-二氧 化酶(ORF2)
节杆菌
菌株 BA-5-17 的羟基对苯二酚 1,2-二氧化酶(ORF2)(76%)。在
npcB
,
npcA
和
npcC
基因克隆到 pET-17b 中,分别构建表达载体 pETnpcB、pETnpcA 和 pETnpcC。当大肠杆菌的粗细胞提取物与 4-NP 的混合物混合时,可观察到 4-NP 的转化。
大肠杆菌
在实验中使用含有 pETnpcB 和 pETnpcA 的大肠杆菌粗细胞提取物混合物时,观察到了 4-NP 的转化。该混合物将 4-NP 转化为羟基苯酚,还将 4-硝基邻苯二酚(4-NCA)转化为羟基苯酚。此外,大肠杆菌的粗细胞提取物
大肠杆菌
含有 pETnpcC 的大肠杆菌细胞提取物将羟基苯酚转化为马来乙酸酯。这些结果表明
npcB
和
npcA
编码双组分 4-NP/4-NCA 单加氧酶,而
npcC
编码羟基喹啉 1,2-二氧合酶。npcA
npcA
和
npcC
突变株 SDA1 和 SDC1 完全丧失了以 4-NP 为唯一碳源的生长能力。这些结果清楚地表明,克隆的
npc
基因在 4-NP 矿化过程中发挥了重要作用。
R. opacus
SAO101。