Evolutionary relationship of biphenyl-catabolic genes in soil bacteria

联苯（BP）利用菌广泛分布于环境中。根据BP分解代谢bph基因的同源性和BP环裂解双加氧酶的免疫学特性，将32株不同的BP菌株分为4类。假产碱假单胞菌（Pseudomonaspseudoalcaligenes）KF 707的bph操纵子结构为bphA 1A 2A 3A 4 BCXD，联苯双加氧酶是由bphA 1编码的末端脱氧酶大亚基和bphA 2编码的末端脱氧酶小亚基、bphA 3编码的铁氧还蛋白和bphA 4编码的铁氧还蛋白还原酶组成的多组分酶。bphB编码BP-二氢二醇脱氢酶，bphC编码BP-环间位裂解双加氧酶，bphD编码水解酶。bph操纵子与恶臭假单胞菌（Pseudomonasputida）F1的甲苯分解代谢tod操纵子在基因结构和核苷酸序列上非常相似。研究了bph和tod操纵子之间负责底物特异性的基因组分。末端双加氧酶和环间位裂解复合物水解酶的大小亚基对它们的离散代谢特异性至关重要。从本研究中获得的结果可以推测，利用BP的细菌，沿着与其他利用芳烃的细菌，可能参与植物木质素的最终降解。

Biphenyl(BP) utilizing bacteria are widely distributed in the environment. Thirty two different BP-strains isolated far clasified into four groups according to the homologies of BP-catabolic bph genes and immunological properties of BP-ring-cleavage dioxygenases. The bph operon of Pseudomonas pseudoalcaligenes KF707 is organized as bphA1A2A3A4BCXD.Biphenyl dioxygenase is a multi-component enzyme which composed of large subunit(encoded by bphA1) and small subunit(encoded by bphA2)of terminal deioxygenase, ferredoxin(encoded by bphA3)and ferredoxin reductase(encoded by bphA4). bphB encodes BP-dihydrodiol dehydrogenase, bphC encodes BP-ring meta-cleavage dioxygenase, and bphD encodes hydrolase. The bph operon is very similar to toluene catabolic tod operon of Pseudomonas putida F1 in the gene organization and nucleotide sequences. The gene components responsible for substrate specificity between the bph and tod operons were investigated. The large and small subunits of the terminal dioxygease and the ring meta-cleavage compound hydrolase were critical for their discrete metabolic specificities. From the results obtained in this study it can be postulated that BP-utilizing bacteria, along with other aromatics utilizing bacteira, might be involved in the final degradation of plant lignin.