Termites eat decaying wood, but it’s hard to digest so they rely on a gut full of bacteria to break down the cellulose. Researchers at the California Institute of Technology (Caltech) have used the polymerase chain reaction (PCR) and a number of other research techniques to find out more about the process, and have discovered an entirely new bacterium.
Termites have several hundred different microorganisms in their guts, but until now their roles haven’t been clear. One of the steps of breaking down the wood into something the termites can metabolise is known as acetogenesis. In this step the carbon dioxide generated by the protozoa in the cut is converted into acetate.
To find out which bacteria are responsible, the researchers took RNA from the termite gut microbiome and looked for activity in formate dehydrogenase (FDH) genes, which code for a protein necessary for acetogenesis. They then used a form of the polymerase chain reaction known as digital PCR to screen the individual microorganisms and identify which carried these actively transcribed genes.
Some of the FDH genes were found in types of bacteria known as spirochetes, but these didn’t account for all the acetogenesis in the termite gut. Further searching found that the gene activity was greatest portion of the gut extract that contained wood chunks and larger microbes, such as the protozoans. The most active FDH gene turned out to be expressed in a previously unstudied species from a group of microbes known as the deltaproteobacteria. This was the first evidence that a substantial amount of acetate in the gut may be produced by a non-spirochete.
Using a color-coded visualization method called hybridization chain reaction-fluorescent in situ hybridization, or HCR-FISH, the researchers found that the bacterium lives on the surface of a larger particular hydrogen-producing protozoan in the termite gut. The larger organism produces the hydrogen by degrading the wood in the termite gut, and the smaller bacterium hitches a ride, keeping as close as possible to the hydrogen source it relies on. The research was published in PNAS.
As well as providing new information on the biology of termites, this research could be applied in biotechnology, improving the production of chemicals and fuels from biomass.
Suzanne Elvidge is a freelance science, biopharma, business and health writer with more than 20 years of experience. She has written for a range of online and print publications including FierceBiomarkers, FierceDrugDelivery, European Life Science, the Journal of Life Sciences (now the Burrill Report), In Vivo, Life Science Leader, Nature Biotechnology, New Scientist, PR Week and Start-Up. She specialises in writing on pharmaceuticals, biotechnology, healthcare, science, lifestyle and green living, but can write on any topic given enough tea and chocolate biscuits. She lives just beyond the neck end of nowhere in the Peak District with her second-hand bookseller husband and two second-hand cats.