MANAGE - Application-based investigation of Microbial biofilms on Arsenic-mitigation, Nitrogen-fixation Augmentation, and Genetic Evaluation

Arsenic (As) contamination continues to be the world's largest silent killer, affecting millions of human lives and countless livestock. Reports suggest that the global distribution of As is massively spreading over the USA, Asian countries, the UK, and European countries due to a combination of both geogenic and anthropogenic factors. According to FAO, an overwhelming number of countries have reported the presence of As in their agricultural soil, contaminating associated crops.

This As-uptake is primarily dependent on the redox speciation of As in soil, which in turn depends on the soil physico-chemical parameters. In the paddy field soil, the oxic/anoxic cycle continues, and this also influences the microbial community in that soil. Most microbes produce different extracellular polymeric substances (EPS) that form biofilm and are responsible for beneficial processes associated with, for example, key geochemical cycles.

Given that reactive nitrogen is the second most limiting elemental nutrient for organisms, including in biofilms, the nitrogen-fixing and nitrogen-self-sufficient biofilms we propose to explore will reveal fundamental new features of these complex bacterial communities. Nitrogen fixation in biofilms-here occurring in the air-is also likely to be important in sustaining these communities, specifically in environments that are limited in reactive nitrogen, such as most soils.

Diazotrophs can fix atmospheric nitrogen into plant-available forms under specialised culturing conditions. Ambient oxygen has hitherto been considered a main barrier to developing nitrogen bio-fertilisers. Biofilm formation on roots has been reported, but their capacity to fix nitrogen has not.

We propose to study the unexplored biology of nitrogen-fixing biofilms on plants to provide the molecular knowledge base to ultimately develop nitrogen bio-fertilisation for agriculture. To do so, we will explore the genetic and molecular underpinnings of nitrogen fixation in biofilms in the air, how the nitrogen-fixing biofilms form on plant roots, and quantify and improve the nitrogen benefits they render to plants.

Each of the objectives is expected to be productive on its own terms and have an individual impact on the socio-environmental benefits. The distribution of As in soil depends on its physico-chemical properties and associated microbial communities. From our previous research, it is expected that the soil As mobility and bioavailability will be less in aerobic soil with frequent water application for crop cultivation.

The results will be supported by the metatranscriptomics data of biofilm/EPS-responsive genes and proteins under differential soil-plant setups. This will confirm the optimum soil profile for supporting bacterial biofilm formation and stability. Soil microbial diazotrophs will be screened for EPS-responsive genes to understand the degree of biofilm formation in natural conditions and after EPS-gene over-expression.

The As adsorption on the biofilm surface with simultaneous N-fixation will be traced. While implementing the diazotrophs at plant roots, there will be a higher uptake of available nitrogen. Higher N-uptake and minimized As translocation will certainly promote plant growth.

Biofilm N-fixation and subsequent release to the plant rhizosphere will make it readily available for plant root uptake. The present era is fighting with mainly three aspects of environmental issues: (i) soil health quality and its biotic management which is indicative of SDG 15 (Life on land), (ii) food crises and crop productivity minimizing global hunger status, the indicator of SDG 2 (Zero hunger) and (iii) human health issues and their management which is connected to SDG 3 (good health and well-being).

The ideology of this project revolves around three pillars- soil arsenic mitigation, nitrogen fixation for plant uptake and crop quality enhancements with less As loading. These three aspects are directly linked to the mentioned SDGs.