Comparative analysis of the luminescence microscopy and cascade filtration methods for estimating bacterial abundance and biomass in the soil: Role of soil suspension dilution

Abstract

Bacterial abundance and biomass in cultivated soddy-podzolic soil have been studied by luminescence microscopy and cascade filtration. It is found that bacterial biomass determined by cascade filtration is higher than that counted by the direct method of luminescence on slides by one order of magnitude. This result is because the cascade filtration method for the estimation of bacterial biomass is capable to more accurately calculate bacterial abundance with consideration for bacteria from different size groups. This results in a larger bacterial biomass in soils. It should be noted that bacterial abundance calculated for the initial dilution (1: 100 to 1: 10000) decreases in 3, 10, and 20 times rather than in the expected 10, 100, and 1000 times, respectively. The obtained results are of great importance for the correction of concepts about fungal and bacterial biomass ratios in different soil types.