Bacteria of various types are remarkably adaptable to harsh environments--a sort of "if you can't beat it, defeat it." Think of the ones living on thermo vents on hydrogen sulfide, which is toxic as all get out to most life forms. There are acidophiles that live in conditions that would melt metal. Then there's D. radiodurans, which pays no attention to massive doses of radiation and is one of the most bizarre extremophiles out there. This doesn't "defeat Darwin" in any way. Rather, it is a prime example of evolutionary selection in action.
Bugs (slang for bacteria) do what they do to survive. They are adapatable, evolvable, and very good at it. Nothing here is challenging scientific principles, evolution, or our understanding of life.
In fact, it remains to be seen how complete the exchange is. They grew their bug under positive selection for arsenate incorporation, but it's almost impossible to eliminate trace phosphorous from all their reagents. There's a way to go before they prove arsenate has completely replaced phosphate in all aspects of metabolism.
Science works by adapting its hypotheses to available data. Hypotheses are tested by attempts to disprove them: that's what we do. Scientists love cool stuff that challenges the existing hypothesis and demands we refine it. Which is how we went from the central dogma in Molecular Biology (DNA makes RNA makes protein) to discover exceptions to the rule, like reverse transcriptase, RNA editing, and self-splicing proteins.
It's funny, but non-scientists seem to think we scientists are unreasonably rigid, that anything unexpected pulls the rug out. Not so: we just demand evidence. We keep it simple. Our mantra is Occam's razor:
entia non sunt multiplicanda praeter necessitatem (entities must not be multiplied beyond necessity)So There's a lot of cool stuff out there, especially in microbes. Just ask any microbiologist why they do what they do!
In the meantime, this is a really cool example of a potentially adaptive response to an extreme environment. I will look forward to reading more of their work as they figure out how far it goes.
I must admit I don't see any theological component to this at all. I don't need to invoke a god to make it fit. I just need to adjust the model. The fact that there are still wonderful new things to discover in How Things Work continues to cheer me up.
Bug picture from Science Magazine. Mono Lake picture from IT's photo album