Response of viable microbial communities to gamma irradiation in agricultural black soils

Abstract

Gamma (γ) irradiation is an effective means of sterilization, however, the response of viable microbial diversity and community structure to γ-irradiation in the distinct contents of soil organic matter (SOM) remains unclear. In this study, viable microbial abundance and community structure in a low organic matter soil (LOM) and a high organic matter soil (HOM) exposed to 0, 10, 20, 30, 50, 70, and 100 kGy doses of γ-irradiation were examined using quantitative PCR (qPCR) and Illumina MiSeq sequencing methods, respectively, after soils treated with DNA-intercalating dye propidium monoazide (PMA). The results showed that the soil microbial abundances were significantly reduced with the increase of γ-irradiation doses, with no detection in both soils at dose of 30 kGy or even more. We detected the sterilizing dose for LOM and HOM soil were 30 kGy and 20 kGy, respectively. The viable bacterial diversity after treated with PMA increased with radiation dose in both soils, but the viable archaeal diversity did not change significantly in the LOM soil. Moreover, γ-irradiation significantly changed the viable microbial community structure and its effect on bacterial community was greater than on archaeal community. The relative abundance of the viable Bacillota and Chloroflexota in both soils were significantly increased at radiation doses of 10 kGy and 20 kGy. However, the relative abundance of the viable archaeal class Nanoarchaeia and Nitrosophaeria did not change at the 10 kGy dose in LOM soil. Moreover, network analysis revealed that γ-irradiation altered the coexistence of viable archaea and bacteria in the soil, stabilized viable microbial networks and activated some radiation resistant viable microbes. This experiment provides important insights into the understanding of the response of viable microorganisms to γ-irradiation in different organic soils and provides a scientific basis for the development of soil disinfection technologies.