[permaculture] Suspicions of bacteria’s role in rotting wood finally proven | Research | Chemistry World

Lawrence London lfljvenaura at gmail.com
Sat Dec 1 11:41:47 EST 2018

Suspicions of bacteria’s role in rotting wood finally proven | Research |
Chemistry World

Suspicions of bacteria’s role in rotting wood finally proven

By Bradley van Paridon30 November 2018

A long held hypothesis that bacteria, and not just fungi, are involved in
the decomposition of lignin, a tough structural component of wood, has
finally been confirmed. The work could help unlock the economic potential
of lignin allowing these complex organic polymers to be turned into useful

The team from the University of British Colombia, Canada, used a novel
blend of stable isotope probing and metagenomics. By labelling several
synthetically produced woody biomass substrates, including lignin, with a
carbon isotope the researchers discovered which soil microbes incorporated
the label into their DNA by sequencing them. They were able to confirm
their role in decomposition while simultaneously identifying bacteria and
enzymes involved. This technique circumvents the need to culture bacteria,
a long standing barrier to bacterial identification.

‘There’s been a controversy in the literature for quite some time as to how
important bacteria might be,’ says study authour William Mohn
<http://www.microbiology.ubc.ca/research/labs/mohn/pi>. Bacteria’s role in
lignin decomposition has been suspected since the 1970s but due to its
complex structure normal experimental methods have proved difficult.
However, this new approach by Mohn and colleagues showed that bacteria from
the families *Comamonadaceae *and *Caulobacteraceae *are involved in lignin
degradation and that most species are highly specialised, often
incorporating only a single label from one lignin polymer.

For Mohn, the motivation for this research is, first off, curiosity about
soil ecology but also biotechnology applications. ‘Bacterial enzymes have
many advantages in biotechnological applications and it may be much more
practical to employ bacterial enzymes, rather than fungal ones for the
breakdown of lignin.’

Lignin is difficult to breakdown and right now its potential is largely
wasted. This could all change, Mohn explains, ‘if we can engineer bacteria
to convert lignin into commodity chemicals the whole concept of a
biorefinery becomes more economically viable and environmentally
sustainable’. Lignin, once broken down, can be used to make many products
currently produced by petroleum. Unlocking these molecules then replaces
petroleum and reduces dependence on fossil fuels.

Mohn is now working to isolate and test the industrial application of the
new found enzymes but the results are also exciting for soil ecologists
interested in carbon cycling. ‘If we want to target our carbon dioxide
emissions we really need to understand the natural carbon cycle, of which
terrestrial decomposition is a big player,’ says Kathe Todd Brown
<https://biology.pnnl.gov/people/kathe-todd-brown>, a computational
biogeochemist designing computer models focused on carbon cycling in soil
at the Pacific Northwest National Laboratory in the US. She adds that these
results can feed into decomposition models to improve them. By knowing what
is breaking down what in the soil, ‘hopefully it will help us to better
project how carbon dioxide flux will evolve from the soil under different
conditions’, says Brown.

R C Wilhelm *et al*,* ISME J.*, 2018, DOI: 10.1038/s41396-018-0279-6

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