CHARACTERIZATION OF SOIL BACTERIA THAT DESULPHURIZE ORGANIC SULFUR-COMPOUNDS .1. CLASSIFICATION AND GROWTH-STUDIES

Six soil isolates originally selected for growth on dibenzothiophene ( DBT), dibenzothiophene sulphone (DBTS), or benzene sulphonic acid (BSA ) were identified as species of the genera Pseudomonas, Arthrobacter, Corynebacterium and Moraxella. All the isolates grew optimally at 28 d egrees C, but the optimum pH for growth varied from 6.7 to 7.7. For th e DBTS isolates, a significantly higher percentage desulphurization (6 6 to 84%) was determined at the shaking rates of 170 and 255 rpm, whil e the BSA isolate showed no difference in the percentage desulphurizat ion (greater than or equal to 82%) at 0, 85, 170, and 255 rpm. The DBT isolate had a percentage desulphurization of <3.5% regardless of the shaking rate. The generation time of each soil isolate was determined under varying nutrient conditions utilizing nutrient broth (NB), a sul phur-free benzoate mineral salts broth (EMS), and a sulphur-free miner al salts broth amended with the appropriate organosulphur compound (OS MS). For all soil isolates, the required time for the population to do uble was of the order: NE < BMS < OSMS. The shorter generation time in the EMS medium versus the OSMS compound suggested that very little su lphur was required to support the growth of these organisms. Tests eva luating substrate specificity indicated a restricted range of utilizab le heterocyclic organosulphur compounds.