Nov pristop za gnojenje rastlin, ki temelji na mikrobnih biokatalitičnih agregatih

Soil quality is decreasing worldwide, due to erosion and intensive use of farmland. Crop plants are not adapted to reduced nutrient content, which is why we need to develop novel soil fertilization approaches delivering nutrients to the vicinity of the roots. In alpine oligotrophic soils mineral-weathering microbes accumulate in “hotspots” in the rhizosphere, in order to increase their efficiency and speed up the mineral dissolution process. Simulating this system, we will implement artificial encapsulation and immobilization of a microbial consortium incorporating mineral-weathering rhizobacteria, N2-fixators, degraders of polysaccharides, and strains for plant biocontrol, The bacteria will be immobilized onto surfaces of carriers to study their effect on nutrient release into the soil and promotion of plant growth. Inoculation of bacteria into an agricultural systems is not simple and straightforward, but mostly inefficeint, due to washing off, preadtion and competition. To solve these problems, we are proposing an approach, where the bacterial cells are locally concentrated by immobilization onto a protective carriers, mineral and organic, to form artificial nutrient-weathering ""hotspots"". Immobilization of cells helps mimic the conditions in natural systems, where the bacteria are not free-living, but mostly directly attached to surfaces of soil particles or entrapped within a biofilm’s extracellular matrix. Several cell immobilization techniques will be applied to bring the selected bacterial cells and the surface of the nutrient substrate into close proximity. Our prototype hotspots, i.e. microspheres and macrocarriers, will be constructed for the purposes of studying bacterial activity and effcieincy of delivery of nutrients to the plant root. Techniques like layer-by-layer (LBL) electrostatic deposition of charged polyelectrolytes and conventional entrapment into a polymer matrix will be implemented to modify the cell surface and to encapsulate and immobilize the cells. Cell immobilization will ensure survival of bacteria and increase the activity of cells. Past studies have not yet studied such an approach, nor have they systemically examined how a bacterium can interact with other bacteria in the consortium and the surface of the nutrient source. In the proposed project we will collect a large collection of bacterial strains and will characterize gentically and chemically the selected candidates. Further on, the surface of cells of the selected candidates will be electrostatically modied to construct cellular aggregates and artificial biofilms, forming the basis of the prototype hotspots. Using the most potent isolates combined in a consortium, we will examine bacterial interaction with the surface of the substrate on carriers, directly by measuring the production of weathering compounds, availability of N, P, C, micronutrients and metals. The up-scaling of our prototype hotspots will finally help conduct a case study using plant experiments. Plants like maize, monocot and agriculturally important crop, and arabidopsis, a dicot model plant suitable for biochemical assays, will help assess the improvement of plant production at greenhouse conditions, where different types of delivery of the bacterial immobilized systems will be used. The proposed study will advance the general scientific knowledge on weathering bacteria, bacterial cell physiology and plant-microbe interactions, particularly by gaining more insight on the characteristics of the cell surface, cell division, growth and activity, bacterial cell-surface interactions and bacterial promotion of plant growth. The value of the proposed work is ground setting, will form the basis for future applicative solutions and will be transferable to other fields, like industrial biotechnology and medicine.