Diversity of root-associated microbial populations of Tamarix parviflora cultivated under various conditions

Soil microbial communities are shaped by many different biotic and abiotic factors, whose effects, however, are not fully understood. In this study, our objective was to analyze microbial communities in the root zone of Tamarix parviflora grown in pristine, nutrient-rich or legacy contaminated, nutrient-poor soil and how these communities change in response to increased soil salinity (a possible stress factor) and soil inoculation with allochthonous bacteria. Our results reveal significant differences in microbial community structure between horticultural and contaminated soils. When controlling for the effect of soil, microbial community structure was significantly affected by salinization, however inoculation with allochthonous bacteria did not significantly change the total community. The genera Arthrobacter, Bacillus, Burkholderia, Dyella and Ktedonobacter, among others, were significantly enriched in the contaminated root zone, whereas populations in the root zone of horticultural soil were found to be more diverse. In this type of soil, representatives of genera such as Flavobacterium, Ignavibacterium, Sediminibacterium, Terrimonas, Chitinophaga and Hydrotalea were significantly enriched. Regardless of soil type, members of genera Bradyrhizobium, Parachlamydia, Dongia, Vampirovibrio, Flavisolibacter and Rhodomicrobium were enriched in non-salinized soil, while the genus Acidothermus was enriched in salinized soil. Phospholipid-derived fatty acid (PLFA) analysis showed higher bacterial and fungal biomass in horticultural soil as compared to contaminated soil, demonstrating that soil nutrition is one of the most important factors with respect to microbial richness.