Figure 1 |. Biooxidation of MnCO₃ produces Mn oxide nodules to which two species associate.

a, After incubation, comparison of an uninoculated control flask of basal medium containing bright, unreacted MnCO₃ (left), with the adherent dark oxide products generated in one that had been inoculated with viable material (right). b, c, d, e, Microscopy of Mn oxide nodules generated in agarose solidified MnCO₃ media. b, After incubation of tubes inoculated with viable material, the cloud of bright MnCO₃ particles was clarified towards the air exposed meniscus, concomitant with the generation of larger, discrete dark oxides (enlarged in c). d, Transmitted light micrograph of an acridine orange (nucleic acid) stained Mn oxide nodule from the same agarose tube; e, epifluorescence micrograph of the same, with surface visible biomass localized to the inner clefts; material in clefts appeared orange prior to staining. f, Scanning electron micrograph of an Mn oxide nodule produced by the co-culture. g, Epifluorescence microscopy and fluorescence in situ hybridisation using species-specific rRNA-targeted probes reveal cell distributions in dissolved Mn oxide nodules: Species A (magenta), Species B (green), all DNA stained with DAPI (blue). No third species is present, via independent methods (Extended Data Fig. 3a). Each panel represents observations made from samples of multiple independent cultivation experiments (a, n >100; b,c,d,e, n=7; f, n=4; and g, n=2).