What we see now might be as optimal as it gets, constrained by the electron transport systems that cannot deal with too much energy coming in. It could mean free radicals destroying the cell from inside. ETA and even if this particular problem is dealt with, accelerated sugar synthesis requires more efficient water transport (= changes in whole body development -> tradeoffs with reproduction and ability to withstand cold seasons) and CO2 intake (= thinner cuticle, larger stomata etc. -> increased susceptibility to disease).
And when you optimize for those things, a life form threatening existing ecosystems is entirely possible.
One of the big constraints on photosynthetic land plants today is the sheer difficulty of fixing CO2 into organic molecules in the presence of oxygen, plus the resultant water stress.
Each of the double bonds of CO2 has an electron configuration remarkably similar to the electron configuration of the O2 double bond. Even though the RuBisCo enzyme that cracks CO2 and sticks it on an organic molecule to enlarge it is optimized to grab CO2, the ambient oxygen level is >400 times the ambient CO2 level. At that concentration difference, even a very selecti...
Does anyone know something about this alteration of Klebsiella planticola? Paywalled paper here. (If someone has got access please PM me, I would like to read the paper to write a more fleshed out article.)
While I am not convinced that it would really have spread to every terrestrial ecosystem, or even every wheat field and I am not even sure if it could compete successfully with the wild type, I certainly would not bet the world on that. Even if it might only have become a nasty crop bug instead of an ecosystem killer, I think this may be the closest encounter with a true existential risk we have had so far. This suggests, that even our current low end biotech may be the greatest existential risk we face at the moment. Or is this just hyped bullshit for some reason I do not see right now (without reading the paper)?
Edit: Upon reading the original paper I am quite sure Cracked.com greatly exagerated the potential threat. 10^8 cfu (colony formin units) K. planticolata per gram soil (dry weight) was added on day 0, but after 8 weeks only 10^2 cfu survived (this is true for both wild type and modified K. planticolata). This suggests, that K. planticolata in the wild has typical densities more like 10^2 cfu per g than 10^8 cfu per g. 10^2 cfu per g is nowhere near enough to produce lethal ethanol concentrations in the soil, even if the modified strain could compete in the wild. Furthermore the concentration of the modified K. planticolata decreased faster than the concentration of the wild type suggesting reduced fitness of the GMO. On the other hand after 8 weeks both K. planticolata strains arrived at the same density of 100 cfu per g indicating comparable medium term survivability in unsterilized soil (I am not sure if indigenous K. planticolata which could compete with the GMO was present in the soil sample used). Yes, they did avoid the obvious failure mode of not differentiating between wild type and modified K. planticolata during recovery of K. planticola strains from the samples.