One of the microbial products produced from dibenzothiophene by Pseudomonas abikonensis or P. jianii was identified as a new substance, trans-4 [2-(3-hydroxy)-thianaphthenyl]-2-oxo-3-butenoic acid, and the other as its hemiacetal form. From the structures of the products, an oxidation pathway of dibenzothiophene was suggested. Moreover, the culture broth and the isolated products were examined for plant growth activities on rice plants.