Quantity and taxonomic composition of ultramicrobacteria in soils

Abstract

The number, physiological state, and taxonomic composition of ultramicrobacteria and archaea in various soils (alluvial meadow, sod-podzolic, leached chernozem, and peat) were studied. In all of the tested soil samples, a large number of ultramicrobacteria (tens and hundreds of millions of cells per 1 g of soil) was revealed by fluorescence microscopy. The portion of cells with intact membranes was larger among ultra-microbacteria than among the ordinary-size cells (95–98 and 50%, respectively). Ultramicrobacteria were characterized by high taxonomic diversity and included representatives of the main phylogenetic groups widespread in soils, such as Archaea, Actinobacteria, Cytophaga, and Proteobacteria. The results indicate that ultramicrobacteria are widespread in soils in a viable state and are involved in soil processes.