Microbial and chemical characteristics of elemental sulfur beads in agricultural soils
Lawrence, J.R.; Germida, J.J.
Soil Biology and Biochemistry 23(7): 617-622
Beads of elemental sulfur (S.degree.) and glass beads were placed in S.degree.-treated and control soils and recovered periodically. Adherent and associated microbial communities were monitored using most probable number procedures and appropriate selective media. Organic coatings (1-7 .mu.g glucose equivalents cm-2) on both kinds beads were detected using fluorescence microscropy and chemical methods. The principle colonizers detected on both kinds of beads were heterotrophic microorganisms, including heterotrophs that produced either thiosulfate and tetrathionate or sulfate as end products during S.degree. oxidation in vitro. Heterotrophs which reduced S.degree. and thiosulfate to H2S were also detected (range 0.16 .times. 101 to 2.1 .times. 102 and 0.13 .times. 101 to 2.0 .times. 101 cells cm-2 respectively). Autotrophic S.degree. oxidizers were not detected on glass or S.degree. bead surfaces; however, autotrophic thiosulfate oxidizers (up to 3.9 .times. 102 cells cm-2) were detected on the S.degree. beads. During 10 days exposure in soil S.degree. beads were colonized by communities oxidizing and reducing S.degree. Heterotrophic colonization appeared non-specific and related to organic coatings, whereas the autotrophic colonization was selective and limited to S.degree. beads. Chemical analysis of S.degree. bead surfaces indicated the presence of thiosulfate, tetrathionate and sulfate. The proportions of these oxidation products on S.degree. beads were consistent with the differences in the detectable communities of S oxidizers. The presence on S.degree. beads of microbial communities which oxidized and reduced S compounds indicated the potential for concerted microbial activity during the oxidation of S.degree. in soil.