Interaction of Kreyellidae sp. and plant growth promoting bacteria influences the soil characteristics and root structure of rice plants
Abstract Plant growth and productivity depend on the complex and dynamic interaction between the plant roots and soil microflora. At present, the research on rhizosphere associated microbes’ is largely focused on bacteria and fungi; whereas the interaction of soil protists with plants and other microbes remain unexplored. The present study aimed to investigate the impact of a ciliate (Kreyellidae sp. C5) and two plant growth-promoting bacteria (PGPB) i.e., Pseudomonas sp. (Ps) and Enterobacter sp. (Ec), on the growth of rice plants. It was observed that the protist-PGPB interaction significantly modified the root structure leading to an enhanced outgrowth of lateral roots (272.08% − 380.41%) and seminal roots (190.40% -250.45%), in addition to an increase in the primary root length (Turkey’s HSD, p < 0.05). The Phospholipid Fatty Acid (PLFA) analysis indicated a striking shift in the overall soil microbial communities due to the presence of a predator. The combined treatments (with C5Ps and C5Ec) further increased the Microbial Carbon Biomass (MBC) to 223.59% and 310.57% as compared to control and PGPB treatments respectively. A similar enhancement of dehydrogenase enzyme activity was observed in soil samples of rice plants on combined treatments. In contrast, the alkaline phosphatase and fluorescein diacetate enzyme activities were recorded to be more in soil samples treated with PGPB. The combined treatment of rice plants also enhanced the uptake of N and P moderately, as compared to PGPB treated plants. However, this enhancement was significant compared to control plants. The colony-forming unit (CFU) and most probable number (MPN) was found to be more in C5Ec (131.0 ± 3.70×1011 and 5.12 ± 0.06) and C5Ps (24.10 ± 2.19×1010 and 10.52 ± 0.39), as compared to control and PGPB treated soil samples. In conclusion, this is the first study that demonstrates significant modification of root structure and increased nutrient uptake by rice plants through interaction between Kreyellidae sp. and PGPB. In addition, we also report improved respiration and diverse microbial population in soil samples on combined treatment of rice plants.