Baggi Grazia, Bernasconi Silvana, Zangrossi Maurizio
Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Università degli Studi, Via Celoria 2, Milan 20133, Italy.
Biodegradation. 2005 Jun;16(3):275-82. doi: 10.1007/s10532-004-1397-6.
A study was made of the metabolic and co-metabolic intermediates of 2- and 3-chlorobenzoate, 2,3- and 3,5-dichlorobenzoate to elucidate the mechanism(s) involved in the negative effects observed on the growth of a chlorobenzoate-degrading microbial consortium in the presence of mixed chlorobenzoates. 2-Chloromuconate accumulated as the end-product in the cultural broths of the microbial consortium during growth on 2-chlorobenzoate; the same 2-chloromuconate was identified in the reaction mixtures of resting cells pregrown on 2-chlorobenzoate and exposed to 3-chloro- and 2,3-dichlorobenzoate, while in similar experiments 1,2-dihydroxy-3,5-dichloro-cyclohexa-3,5-dienoate was detected as dead-end product of 3,5-dichlorobenzoate co-metabolism. These results suggest an initial degradative attack by 2-chlorobenzoate induced dioxygenase(s). The role of 3,5-dichlorobenzoate as an antagonist of 2-chlorobenzoate degradation was also studied: in the presence of mixed 2-chloro- and 3,5-dichlorobenzoate, the 3,5-dichlorobenzoate preferential uptake by the resting cells of the chlorobenzoate-degrading consortium was observed. 2-Chlorobenzoate entered the cells only after the complete removal of the co-substrate. In growing cells experiments, the addition of 1,2-dihydroxy-3,5-dichloro-cyclohexa-3,5-dienoate, the 3,5-dichlorobenzoate co-metabolite, to 2-chlorobenzoate exerted the same antagonistic effect of the parent compound, inhibiting both the microbial growth and the degradative process. These data are discussed, allowing us to attribute the inhibitory effects observed to a substrate/co-substrate competition, though other additional causes may not be totally excluded.
对2-氯苯甲酸酯、3-氯苯甲酸酯、2,3-二氯苯甲酸酯和3,5-二氯苯甲酸酯的代谢及共代谢中间体进行了研究，以阐明在混合氯苯甲酸酯存在的情况下，观察到的对氯苯甲酸酯降解微生物群落生长产生负面影响所涉及的机制。在以2-氯苯甲酸酯为生长底物时，2-氯粘康酸作为终产物在微生物群落的培养液中积累；在预先以2-氯苯甲酸酯培养并暴露于3-氯苯甲酸酯和2,3-二氯苯甲酸酯的静息细胞反应混合物中，鉴定出了相同的2-氯粘康酸，而在类似实验中，1,2-二羟基-3,5-二氯环己-3,5-二烯酸被检测为3,5-二氯苯甲酸酯共代谢的终产物。这些结果表明，2-氯苯甲酸酯诱导的双加氧酶进行了初始降解攻击。还研究了3,5-二氯苯甲酸酯作为2-氯苯甲酸酯降解拮抗剂的作用：在混合2-氯苯甲酸酯和3,5-二氯苯甲酸酯存在的情况下，观察到氯苯甲酸酯降解群落的静息细胞优先摄取3,5-二氯苯甲酸酯。只有在共底物被完全去除后，2-氯苯甲酸酯才进入细胞。在生长细胞实验中，向2-氯苯甲酸酯中添加3,5-二氯苯甲酸酯的共代谢物1,2-二羟基-3,5-二氯环己-3,5-二烯酸，产生了与母体化合物相同的拮抗作用，抑制了微生物生长和降解过程。对这些数据进行了讨论，使我们能够将观察到的抑制作用归因于底物/共底物竞争，尽管其他额外原因可能也不能完全排除。
