There is not a great deal known about the microbiology of leachate, but it is considered to be toxic owing to the accumulation of heavy metals and other components. Thus, we decided to investigate the microbial composition of leachate from the working landfill site.
I have taken microbiology to some diverse places – school classrooms, a shopping centre, science festivals and even a beer festival. However, the oddest place (so far at least) has to be a landfill site! This happened after I was contacted by Glasgow-based Tern TV, who were making a documentary for BBC4. The programme, The Secret Life of Landfill, aimed to make the audience think about modern society’s ‘out of sight, out of mind’ relationship with domestic waste, and hoped to change perceptions of what ‘waste’ actually is. The team wanted to set up a pop-up lab on location at a working landfill site where they would run a variety of experiments ranging from material degradation tests to real-time microbiological analysis. At that point, they were not sure what the ‘real-time microbiological analysis’ would entail but after some initial discussion we came up with an interesting experiment.
For those not familiar with what happens at a landfill site, waste from a local area is, essentially, compacted and buried in the ground and covered to allow it to degrade naturally. Gas extraction wells capture gases, which form during breakdown, and these are used to generate electricity for the National Grid. As water falls onto the site, it passes through the waste, collecting liquids and solids and forming leachate, which is collected and treated before disposal.
There is not a great deal known about the microbiology of leachate, but it is considered to be toxic owing to the accumulation of heavy metals and other components. Thus, we decided to investigate the microbial composition of leachate from the working landfill site. Given that we had no idea what would be in it, and the likelihood that many of the microbes would be unculturable, the obvious way forward was to attempt to do a real-time sequence analysis using Nanopore MinION technology. So that is exactly what I did! Obviously, I had to do a bit of road-testing in the lab first, with a potential obstacle being the quality of the leachate sample and whether we could obtain enough microbial material for sequence analysis. Thankfully, the lab test was successful, and I took a bunch of kit to the landfill site to set up the pop-up lab (including microscope, electrophoresis kit, microfuge and MinION kit) that would allow me to extract and analyse in a day. Of course, there were a few challenges – we had to hire a generator and being on the coast, it was somewhat windy. We also needed some shelter. However, the Tern TV team made the magic happen and we had a functioning ‘lab’ on site!
You are probably wondering about the outcome… As it happens, landfill leachate is teeming with microbial life. In a short 50 min sequencing run, we identified just over 3,800 reads comprising 5.1 Mb, with an average read length of over 1.3 kb. Of these, seven hundred were matched to sequences in the database. More than 3,100 reads were unclassified, suggesting that there could be a plethora of as yet unknown microorganisms lurking in the landfill site. Could we potentially identify microbes to help us break down our waste more efficiently? Who knows, but there is a wealth of data waiting for someone!
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