Microorganisms are by far the most important group of organisms introducing metal nutrients into the life cycle by extracting them from minerals. After the microorganisms assimilate the metals or dissolve them, other organisms can also have access to them. The Bio-Strategies project addresses two important aspects of these processes:
1) How do microorganisms adapt to the mineral environment where they live in order to retrieve the mineral nutrients they need? As minerals have different chemical composition and resilience to chemical attack, do microorganisms use different strategies in different environments to attack the minerals and obtain the desired metals? Particularly, how do the strategies change as the minerals become progressively depleted of metal nutrients?
2) How does the release of metal nutrients by microorganisms help to introduce these metals into the life cycle? Plants are obvious beneficiaries from the activity of microorganisms. How much of the metals released by microorganisms become immediately available to plants?
These questions are central to understanding how metal nutrients are incorporated and circulate in the food chain, which is necessary in order to maintain healthy natural habitats and productive agricultural soils. For this end, it is required to progress in the understanding of the influence of minerals on microbial activity and colonization patterns, to monitor and model soil genesis and to understand the symbiosis of plants and microorganisms. With this knowledge, it will be possible to use low-cost and efficient environmental, agricultural and industrial processes based on mineral-microbe interaction and plant-fungus symbiosis.
The objectives of the project are:
1) To reveal he microbial habitability of a series of silicate minerals of different metal nutrient content, which represent soils in different stages of degradation.
2) To investigate the microbial strategies for chemical attack and extraction of metal nutrients by a bacterium (Bacillus subtillis) and microbial fungus (Aspergillus niger), both of which are abundant in soils.
3) To determine the availability of the metal nutrients released by the microorganisms to plants, particularly liverworts, with and without symbiotic fungi.
The conclusions of the action cannot be yet described completely as some aspects are still under evaluation. The mineral substrate had a large effect in the activity of the microorganisms, greater for the fungus than the bacterium. This effect is observed in the intensity of the attack on the minerals, and the type of attack is now under evaluation. Metals released by the microorganisms were available to the plants, but in different degrees depending on mineral and microorganism, which affected plant growth.
