Romine M F, Fredrickson J K, Li S-M W
Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
J Ind Microbiol Biotechnol. 1999 Oct;23(4-5):303-313. doi: 10.1038/sj.jim.2900750.
Enzyme induction studies with Sphingomonas aromaticivorans F199 demonstrated that both toluene and naphthalene induced expression of both naphthalene and toluene catabolic enzymes. However, neither aromatic compound induced expression of all the enzymes required for complete mineralization of either naphthalene or toluene. Activity measurements in combination with gene sequence analyses indicate that growth on either aromatic substrate in the absence of the other is, therefore, sub-optimal and is predicted to lead to the build-up of metabolites due to imbalance in toluene or naphthalene catabolic enzyme activities. Growth on toluene may be further inhibited by the co-expression of two toluene catabolic pathways, as predicted from gene sequence analyses. One of these pathways may potentially result in the formation of a dead-end intermediate, possibly benzaldehyde. In contrast, either p-cresol or benzoate can support high levels of growth. Analyses of promoter region sequences on the F199 aromatic catabolic plasmid, pNL1, suggest that additional regulatory events are modulated through the interaction of BphR with Sigma54 type promoters and through the binding of a regulator upstream of p-cresol catabolic genes and xylM. We hypothesize that the unusual gene clustering in strain F199 is optimized for simultaneous degradation of multiple aromatic compound classes, possibly in response to the heterogeneous composition of aromatic structures in the fossil organic matter present in the deep Atlantic Coastal Plain sediments from which this bacterium was isolated.
对食芳烃鞘氨醇单胞菌F199进行的酶诱导研究表明，甲苯和萘均可诱导萘和甲苯分解代谢酶的表达。然而，这两种芳香化合物均未诱导萘或甲苯完全矿化所需的所有酶的表达。结合基因序列分析进行的活性测量表明，因此，在不存在另一种芳香底物的情况下，在任一种芳香底物上生长都不是最优的，并且预计由于甲苯或萘分解代谢酶活性的不平衡会导致代谢物的积累。基因序列分析预测，两条甲苯分解代谢途径的共表达可能会进一步抑制在甲苯上的生长。这些途径之一可能会导致形成一个末端中间产物，可能是苯甲醛。相比之下，对甲酚或苯甲酸盐都可以支持高水平的生长。对F199芳香分解代谢质粒pNL1上启动子区域序列的分析表明，通过BphR与Sigma54型启动子的相互作用以及对甲酚分解代谢基因和xylM上游调节剂的结合，可调节其他调控事件。我们推测，菌株F199中异常的基因簇是为同时降解多种芳香化合物类别而优化的，这可能是对该细菌所分离的大西洋沿岸平原深部沉积物中化石有机质中芳香结构的异质组成的一种响应。
