Mutually-beneficial cooperation is a high ideal, but for bacteria and archaea, working together isn’t always a good solution. Now a team at Pennsylvania State University has worked out a system that could work better than inter-domain cooperation: by putting genes from a bacterium into an archaeon, they got the archaeon to do all the work on its own. The study appears in the latest issue of mBio.
To transform organic materials to methane usually calls for the skills of a consortium of bacteria and archaea, but these multi-species food chains are fragile and require painstaking care and feeding. To get around these problems and make a useful product, Lessner et al. placed MekB, a broad- specificity esterase gene from the bacterium Pseudomonas veronii, on a plasmid and put the plasmid in the archaeon Methanosarcina acetivorans. They then fused the gene to a constitutive M. acetivorans promoter. The “Franken-archaeon” put its new gene to good use: it completely converted an industrial solvent and a naturally occurring compound to methane and carbon dioxide. (I wonder if the lab was filled with hysterical cries of “It’s alive!!!” that day?)
“I think this is interesting at two levels,” says Derek Lovley, Distinguished Professor in the Department of Microbiology at the University of Massachusetts and a member of mBio’s Board of Editors. He continues, “One is the practical level, which was you can make methane, a useful fuel. Two is that they show you could expand the range of compounds that a methanogen could make methane from.”
The practical aspects of this work are hard to miss: methane is a valuable biofuel that has some significant advantages over the more well-known ethanol. By expanding the list of substrates for making methane, the engineered pathway created by Lessner et al. could simplify the whole food chain problem and lead to more efficient conversion of complex biomass to methane.
Lovley points out the implications for making other products as well. “They show that maybe you could get more complex substrates to be metabolized in a single organism if you just were to introduce the appropriate genes,” so that industrial process that took many steps might only take one, says Lovley.