Interrelations between Soil bacteria and Rye Secale cereale L. in the presence of nitroaromatic compounds

Abstract

Historically 2,4,6-Trinitrotoluene (TNT) was the most widely used military explosive. TNT is toxic and mutagenic compound, having a serious impact on the environment. The aim of this study was to evaluate an efficiency of bioaugmentation in combination with nutrient amendments and rye S. cereale. Design of 30-days soil column experiment provided the control of nitroaromatics (NA) distribution from topsoil (4cm) to deeper layers of soil horizon (20cm). For bioaugmentation, consortium with 5 isolates belonging to Pseudomonas fluorescens and Stenotrophomonas maltophilia, was used. For biostimulation, molasses and plant extract was added to soil. At the beginning of the experiment, only topsoil was contaminated with TNT and its degradation products (75mg NA/kg). After 30 day experiment, the NA concentration in soil amended with nutrients and bacteria consortium was decreased in topsoil from 75 mg/kg to ~4 mg/kg. In the sets with planting rye and nutrient amendments, NA migration to deeper layers of soil horizon was detected. To compare microbial activity in different experimental sets, enzymatic activity (i.e. fluoresceine diacetate hydrolysis, FDA) was measured. After 30-days experiment, FDA activity in soil with bacteria consortium was two-fold higher, as compared to non-augmented soil. An increase of microbial enzymatic activity was detected only in topsoil. Growth of rye was more active in the presence of bacteria consortium. In turn, TNT and its degradation products inhibited plant development. Thus, the results of this experiment indicated to the active role of bioaugmentation and biostimulation in the process of NA degradation. In turn, the growth of rye in the presence of nutrient amendments was not efficient in terms of NA biodegradation.