Taxonomic Composition of Cultured Fe-and Mn-Oxidizing Bacteria and Microbial Abundance in Fe-Mn Nodules of Different Sizes

Taxonomic diversity and quantitative distribution of cultured forms of Fe-and Mn-oxidizing microorganisms in Fe-Mn nodules of different sizes and fine earth of Gleyic Luvisols formed in the territory not affected by direct anthropogenic impact, were analyzed. The results were obtained using a combination of microbiological, molecular and analytical methods and noninvasive techniques. Most of the microorganisms which were cultured from the nodules were Mn oxidizers. Bacteria of the genera Bacillus, Rhodococcus, Lysinibacillus, Pseudomonas, and Priestia were identified in the nodules. Quantitative distribution of Fe-and Mn-oxidizing microorganisms in the outer and inner zones of the nodules of different sizes demonstrated that Mn-oxidizing microorganisms were involved in all stages of nodules formation and development, while Fe-oxidizing microorganisms participated in the initial phase of their formation. Spherules and porous structures of bacterial nature were observed in the studied nodules. The host fine earth was characterized by differences in the relative abundance of the dominant microbial groups in the profile. Manganese-oxidizing bacteria were represented in the soil fine earth by the genera Prestia and Methylobacterium.