Assimilatory reduction of sulfate and sulfite by methanogenic bacteria

Abstract

A variety of sulfur-containing compounds were investigated for use as medium reductants and sulfur sources for growth of four methanogenic bacteria. Sulfide (1 to 2 mM) served all methanogens investigated well. Methanococcus thermolithotrophicus and Methanobacterium thermoautotrophicum Marburg and ΔH grew well with S0, SO32-, or thiosulfate as the sole sulfur source. Only Methanococcus thermolithotrophicus was able to grow with SO42- as the sole sulfur source. 2-Mercaptoethanol at 20 mM was greatly inhibitory to growth of Methanococcus thermolithotrophicus on SO42- or SO32- and Methanobacterium thermoautotrophicum Marburg on SO32- but not to growth of strain ΔH on SO32-. Sulfite was metabolized during growth by Methanococcus thermolithotrophicus. Sulfide was produced in cultures of Methanococcus thermolithotrophicus growing on SO42-, SO32-, thiosulfate, and S0. Methanobacterium thermoautotrophicum Marburg was successfully grown in a 10-liter fermentor with S0, SO32-, or thiosulfate as the sole sulfur source.