State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, People's Republic of China.
Environ Sci Technol. 2009 Nov 15;43(22):8635-42. doi: 10.1021/es901991d.
A biphenyl (BP)-utilizing bacterium, designated B6-2, was isolated from soil and identified as Pseudomonas putida. BP-grown B6-2 cells were capable of transforming dibenzofuran (DBF) via a lateral dioxygenation and meta-cleavage pathway. The ring cleavage product 2-hydroxy-4-(3'-oxo-3'H-benzofuran-2'-yliden)but-2-enoic acid (HOBB) was detected as a major metabolite. B6-2 growing cells could also cometabolically degrade DBF using BP as a primary substrate. A recombinant Escherichia coli strain DH10B (pUC118bphABC) expressing BP dioxygenase, BP-dihydrodiol dehydrogenase, and dihydroxybiphenyl dioxygenase was shown to be capable of transforming DBF to HOBB. Using purified HOBB that was produced by the recombinant as the substrate for B6-2, we newly identified a series of benzofuran derivatives as metabolites. The structures of these metabolites indicate that an unreported HOBB degradation pathway is employed by strain B6-2. In this pathway, HOBB is proposed to be transformed to 2-oxo-4-(3'-oxobenzofuran-2'-yl)butanoic acid and 2-hydroxy-4-(3'-oxobenzofuran-2'-yl)butanoic acid (D4) through two sequential double-bond hydrogenation steps. D4 is suggested to undergo reactions including decarboxylation and oxidation to produce 3-(3'-oxobenzofuran-2'-yl)propanoic acid (D6). 3-Hydroxy-3-(3'-oxobenzofuran-2'-yl)propanoic acid (D7) and 2-(3'-oxobenzofuran-2'-yl)acetic acid (D8) would represent metabolites involved in the processes of beta- and alpha-oxidation of D6, respectively. D7 and D8 are suggested to be transformed to their respective products 3-hydroxy-2,3-dihydrobenzofuran-2-carboxylic acid (D10) and 2-(3'-hydroxy-2',3'-dihydrobenzofuran-2'-yl)acetic acid. D10 is proposed to be transformed to salicylic acid (D14) via 2,3-dihydro-2,3-dihydroxybenzofuran, 2-oxo-2-(2'-hydroxyphenyl)acetic acid and 2-hydroxy-2-(2'-hydroxyphenyl)acetic acid. Further experimental results revealed that B6-2 was capable of growing with D14 as the sole carbon source. Because benzofuran derivatives may have biological, pharmacological, and toxic properties, the elucidation of this new pathway should be significant from both biotechnological and environmental views.
一株利用联苯的细菌 B6-2 从土壤中分离出来，并被鉴定为恶臭假单胞菌。利用联苯培养的 B6-2 细胞能够通过侧向双加氧酶和间位裂解途径转化二苯并呋喃（DBF）。检测到环裂解产物 2-羟基-4-（3'-氧代-3'H-苯并呋喃-2'-亚基）丁-2-烯酸（HOBB）作为主要代谢产物。B6-2 生长细胞也可以利用联苯作为初级底物共代谢降解 DBF。表达联苯双加氧酶、联苯二氢二醇脱氢酶和二羟基联苯双加氧酶的重组大肠杆菌 DH10B（pUC118bphABC）被证明能够将 DBF 转化为 HOBB。使用由重组菌产生的纯化 HOBB 作为 B6-2 的底物，我们新鉴定了一系列苯并呋喃衍生物作为代谢物。这些代谢物的结构表明，B6-2 菌株采用了一种未报告的 HOBB 降解途径。在该途径中，HOBB 被提议通过两个连续的双键加氢步骤转化为 2-氧代-4-（3'-氧代苯并呋喃-2'-基）丁酸和 2-羟基-4-（3'-氧代苯并呋喃-2'-基）丁酸（D4）。D4 被提议经历包括脱羧和氧化以产生 3-（3'-氧代苯并呋喃-2'-基）丙酸（D6）的反应。3-羟基-3-（3'-氧代苯并呋喃-2'-基）丙酸（D7）和 2-（3'-氧代苯并呋喃-2'-基）乙酸（D8）分别代表 D6 的β-和α-氧化过程中的代谢物。D7 和 D8 被提议转化为各自的产物 3-羟基-2,3-二氢苯并呋喃-2-羧酸（D10）和 2-（3'-羟基-2',3'-二氢苯并呋喃-2'-基）乙酸。D10 被提议通过 2,3-二氢-2,3-二羟基苯并呋喃、2-氧代-2-（2'-羟基苯基）乙酸和 2-羟基-2-（2'-羟基苯基）乙酸转化为水杨酸（D14）。实验结果进一步表明，B6-2 能够以 D14 作为唯一碳源生长。由于苯并呋喃衍生物可能具有生物、药理和毒性特性，因此从生物技术和环境角度来看，阐明这种新途径应该具有重要意义。
