December update: Small but Mighty
Published on: 1 December 2024
It’s a thrilling prospect – the chance to find and put into practical agricultural use the microbes that could prove a small miracle for millions of farmers across Africa. Currently, high yields of staple crops like maize and sorghum depend on synthetic nitrogen fertiliser. Not only is that expensive, it’s also playing havoc with Africa’s fragile soils.
But by finding and putting into use microbes that have sufficient nitrogen-fixing capacity, we could change the way these crops are grown. That could bring affordable food security – and vastly improved livelihoods – to the farmers who produce 80% of the continent’s food.
Our first move has been to invite Nikki, our former PhD student, to rejoin the team and lead the work needed to get this flagship project off the ground. Nikki is from the University of Nottingham, one of our long-term research partners and recognised as an academic powerhouse for the study of biological nitrogen (and other nutrients) fixation.
Nikki’s focus has been to set up the lab, while also starting to compile a long list of potential microbial strains. It’s a big job, but we’re working with many of our partners and group researchers, as well as trawling through the literature, to try to identify the likely candidates that might have that all-important nitrogen fixation capability.
Can, Do, Share
With that complete, we’ll move on to the next stage: proving their capacity for fixation. This takes three stages. First is an in silico analysis – essentially using simulation software rather than biological studies. Do they have the right genes? Can they fix nitrogen? The DNA sequence for the all-important nitrogenase enzyme – which facilitates the reduction of atmospheric dinitrogen, N2, to ammonia, NH3 – is the crucial discovery. Nitrogenases are the only enzymes known to catalyse this reaction, so it has to be present.
The second stage, when the list’s been whittled down, is to check that those nitrogenase genes are active – do they produce nitrogen? We do this by growing the candidate bacteria on nitrogen-free media, before testing for the presence of nitrogen.
The third, and most important stage, is to see whether they actually excrete this captured and reduced nitrogen – do they share the ammonia they produce? Some species of bacteria are known to only fix nitrogen for themselves; if they don’t have ammonia transporters, then they can’t ‘pump’ it anywhere to be useful.
We’re expecting to have the first set of candidate microbes by Christmas. That will enable us to move into spring with a set of more practical experiments – testing them in a field environment. This will give us an indication of their effectiveness, before we move into proper candidate testing.
Meanwhile, there’s the second part of the project to get underway: building the new production line that will handle the Micropacks needed to distribute the final inoculant in a pack size that’s suitable and affordable for a smallholder with less than a hectare of land. It’s the necessary counterpart to the main research drive – we have to be able to distribute the inoculant without loss of quality or viability, in packaging that’s easily transportable and which delivers exactly the right amount, without wastage.