Vertical structure of bacterial communities in peats of the Yakhroma river floodplain
The abundance and taxonomic structure of soil bacterial communities have been studied in different geomorphological parts of the Yakhroma floodplain. It has been found that the numbers of bacteria reach a peak in calcareous peat soil under forest near the floodplain terrace, decreasing to a minimum in soddy alluvial soil near the riverbed. All soils are characterized by the presence of different ecological-trophic bacterial groups capable of peat destruction. Seasonal dynamics of the structure of bacterial communities and, in some soil types, its spatial dynamics accounted for by changes in the botanical structure of peat across its profile have been revealed. All peat soils in the floodplain have high contents of organic matter and neutral pH and, therefore, are favorable biotopes for the development of saprotrophic bacteria. This, in turn, largely accounts for high productivity and stability of this agroecosystem as a whole.
Quantity and taxonomic composition of ultramicrobacteria in soils
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.
Rapid multipoint method for quantification of various physiological groups of bacteria in soil
Abstract A modified multipoint method for enumeration of bacteria capable of various biochemical degradation reactions in soil is described. The method is a combination of multipoint inoculation of a dilution series and the most probable number (MPN) technique. Five serial soil dilutions are prepared and inoculated directly on plates containing different substrates. Five replicates of a constant amount of each dilution are transferred with a multipoint inoculator to plates suitable for visualization of the physiological groups involved. At least five replicate plates of each substrate are recommended. Degradation zones at the inoculation sites are scored, and a MPN method is used for enumeration of the bacterial groups in question. A MPN table is provided for the dilution series used. The inoculation method is rapid, allowing the same soil sample to be plated on many different substrates in a short time. The use of plates instead of tubes simplifies the method and allows long incubation periods, and only one plate is required for 25 inoculation sites. For comparison, a general isolation technique for evaluation of various physiological groups of bacteria in soil was conducted.