Sulphate Reduction in Partially Sterilized Soil Exposed to Air

SUMMARY: H2S was evolved from soil treated with CCl4 when moistened with sucrose and (NH4)2SO4 solution and incubated aerobically. H2S formation took place when the soil moisture was less than field capacity, and over a range of pH values from 5 to 8. The organism responsible was isolated and identified as Bacillus megaterium. Several strains of this organism reduced sulphate in well-aerated sterilized soil and liquid media but not in soil or liquid incubated anaerobically.

The action of CCl4 in fresh soil is to check or destroy certain fungi and bacteria which normally inhibit sulphate reduction by B. megaterium. Some of these organisms were isolated and shown to be sensitive to CCl4 and to inhibit sulphate reduction by B. megaterium in sterilized soil. The isolates did not exhibit antibiotic action when grown in certain defined media RESP-3214