Harnessing biocrust-isolated bacteria from semiarid soils to promote plant growth in ecological restoration

Restoration of drylands is crucial to reverse global land degradation because these areas cover around 40% of the Earth surface and host one third of the world population. Restoration efforts are often unsuccessful in drylands and alternative approaches need to be developed, i.e., biocrust-based restoration, to promote plant growth and increase soil fertility and stability. In this research, we cultured several biocrust-forming organisms to inoculate them on degraded soils. We designed a more effective inoculum based on biocrust-forming heterotrophic bacteria with plant growth promotion properties (PGP) and key enzymatic activities. We hypothesised that inoculation of native seeds with a consortium of selected heterotrophic bacteria would enhance seed germination and establishment. We sampled incipient and developed biocrusts from three study sites located in semi-arid areas from SE Spain, and isolated 48 bacterial strains. We performed a screening within the bacterial collection to find those strains with key PGP properties and enzymatic activities. Specifically, we analysed their capacity to fix N₂, solubilize P and K, produce biofilms, auxins and siderophores, and the extracellular activity of DNAse, amylase, protease, catalase, and lipase. Then, we assessed the best performing bacterial strains for co-culturing to avoid possible antagonistic effects and identified them by sequencing the 16S rRNA gene. The next step of this project will focus on assessing the effects of seed pelleting with the best-performing consortium on germination and establishment of native plants.