Another interesting bacteria

I do not know them. National University of Singapore is a hot number at least regionally.

I am not familiar enough with bioenergy literature to know if this is a startling advance. It does sound that way. Science Advances is where you go if you don't quite make the cut in Science. Silver medal, one might say.

Quick look at the article indicates a tiny bit of sleight-of-hand that a (very) few care about. In general terms they refer to lignocellulose which is fancy name for wood. However all of their work is done with cellulose; lignin having been removed in one way or another. It is not trivial for microbial enzymes to get past lignin to yummy cellulose underneath (but still within) cell walls. Whether 'doing' bioenergy in a flask, or in a forest decaying wood.

 

Li et al. fed bacteria with cellulose or xylan. Latter is similar to cellulose but with a couple of decorations that are not sugar. Cellulose by the way is a pure sugar polymer that humans among others lack enzymes to break down.

Heard of dietary fiber? That stuff you're supposed to eat several grams of per day? Cellulose and xylan. After conferring health benefits on you (those I cannot actually explain), it's out the back door.

It would not be a good thing to have Li et al.'s bacteria making butanol in your guts. Nor would it be likely. Butanol is somewhat toxic.

 

You know how enzymes work. In general they fit exactly on a target molecule, bend it a little bit, and lower the energy of activation for some reaction. Like catalysis.

This works of the target molecule has a consistent structure. Cellulose does, along with many other polymers. Lignin does not. It is a jumble.

Enzymes able to break lignin do so indirectly. They produce a free radical or other highly oxidizing chemical that just float away. If it happens to hit lignin it reacts. The deed is done with no 'lock and key' matchup.

Clumsy? sure but no alternative exists in biology. Dangerous? Free radicals etc. are tiny bombs. All are produced (in lignolysis) external to (fungal) cells. Inside would be suicidal.

I've not thought of this as a puzzle. Puzzle pieces fit together.

 

Most plant cell walls are one layer, cellulose; flimsy and permeable. To haul water through long tubes this is not good enough. You need a triple layer cell wall with lignin in each. Thus you can make a tree.

Many plant cell walls are easy work for microbial enzymes. Although there are many cellulytic enzymes, each hitting just one type of connection. Triple layer lignin walls need heavy machinery.

 

Lignin is unusual both in construction and deconstruction.

Some termites (by way of gut microbes) undo a bit of lignin. More often, termite poops 'away from home' are almost pure lignin in that everything else has already gone down to CO2.

"Into the intercellular spaces". Emphatically, exo extra outside. It is perhaps odd that plants externally make liggy cell-wall ornaments with a class of 'what the heck?' enzymes. That very similar enzymes later found their way into fungi, and then lignin-wood became decomposable and the age of massive coal deposition was much diminished.

Much effort has been expended to make all that seem not so odd. But I think it is odd, and plants once took a shot at opposing gravity. Only one ping, Vasili

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Now we have earth's 'third forest' (as I am fond of saying) moving 10 petagrams atmos. C into wood. By coincidence this ~equals old-C burning for energy.

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Innovations such as presented here may present new ways to use 'last year's wood' for human energy transduction. I am not much of a fan. Dead wood entering its 1 to 100 year endgame does biodiversity very well, especially in terms of microbial 'I hate everyone not like me and make chemicals to prove it'.

Such things, of course, would not matter, were there not an entirely different set of microbes that 'eat' humans and have found ways past our current chemicals to kill them. This is the very typical and perhaps tiresome plea on behalf of small-critter biodiversity. Don't let that stuff slip away because 300 plus millions years of microbial cross-hate is not something we might re-create in a few decades of lab work, even with fabulous funding.