Plant Growth-Promoting Bacteria Associated with the Nests of the Seed-Harvester Ant, Trichomyrmex Scabriceps

Colonies of seed harvester ants are commonly found in semiarid and arid areas of the world and have been studied for their seed dispersal behaviour. The present study focused on the bacteria associated with the nests of the harvester ant, Trichomyrmex scabriceps, and reveals that ant colonies link the aboveground resources with the belowground microbial communities as they accumulate organic debris in the close vicinity of their nests via their ecosystem engineering activities. Soil samples were collected from the nest chambers and the external debris piles of T. scabriceps colonies, located in managed ecosystems. The nest soil-associated bacteria were examined for their plant growth-promoting abilities via biochemical assays including phosphate solubilization, Indole acetic acid production, siderophore production and physiological assays including biocontrol potential against the soil pathogen, Sclerotium rolfsii. More than 60% of bacteria isolated from the ant nest-associated soil displayed plant-growth promoting ability. Bacillus sp., Azotobacter sp., Klebsiella sp., Comamonas sp., Tsukamurella sp., and Pseudoxanthomonax sp., demonstrated significantly high levels of gnotobiotic growth of the treated chickpea plants. The activities of phenylalanine ammonia-lyase and peroxidase enzymes were higher in plant growth-promoting bacteria treated and pathogen inoculated plants as compared to the control plants lacking the bacteria. Since T. scabriceps colonies often make their nests in the compact soil of unpaved paths of agroecosystems and gardens, these bacteria can act as highly effective biofertilizers and promote growth of the cultivated plants by increasing soil fertility and disease resistance attributes of the plant.