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In the following context, what does "they" refer to?

You probably learned in biology class that mitochondria, let’s all say it together, are the powerhouses of the cell. They charge up energy-rich molecules, when oxygen's around. But they do other stuff too: like manufacture certain essential proteins. This newly discovered microbe, and others that live in low-oxygen environments, use different, oxygen-free pathways to make energy. But they usually still have mitochondria for that protein assembly job. The new bug apparently pulls off the protein-synthesis by using a system that it picked up from bacteria, in what’s known as a lateral gene transfer. The findings are in the journal Current Biology.


The following is the whole transcript where the above excerpt is from.

[Added:] Here is my second question: Do the newly found microbes have mitochondria?

If you were searching for a life form unlike anything known to science, where would you look? Scientists at Charles University, in Prague, looked in the poop of a pet chinchilla. "They were isolating a lot of various strains from various environments—including their own pets." Anna Karnkowska, an evolutionary biologist who collaborated on the work, who is now at the University of British Columbia. "Scientists like to isolate things from everywhere possible."

They found a relative of the parasite Giardia, called Monocercomonoides. It’s eukaryotic, meaning it has organelles and a nucleus enveloping its DNA. Just like our cells, or the ones in plants, or fungi. But unlike bacteria, which don’t have those things.

And upon closer examination, the new critter was different from every other eukaryote known to science. Because it’s missing a key organelle—it seems to have no mitochondria.

You probably learned in biology class that mitochondria, let’s all say it together, are the powerhouses of the cell. They charge up energy-rich molecules, when oxygen's around. But they do other stuff too: like manufacture certain essential proteins. This newly discovered microbe, and others that live in low-oxygen environments, use different, oxygen-free pathways to make energy. But they usually still have mitochondria for that protein assembly job. The new bug apparently pulls off the protein-synthesis by using a system that it picked up from bacteria, in what’s known as a lateral gene transfer. The findings are in the journal Current Biology.

Karnkowska says the microbe's ancestors probably had mitochondria at some point—then lost them once they’d acquired the bacterial system. And she says other microbes might share a similar story. "We know now that probably there are more of these weird things." And as this study suggests, they could be found in some weird places.

  • they="others that live in low-oxygen environments". – Tᴚoɯɐuo Jul 12 '16 at 9:13
  • The prose is informal and sloppy. – Tᴚoɯɐuo Jul 12 '16 at 9:18
  • @TRomano: The first answer does not agree with your previous comment. – Jack Jul 12 '16 at 23:56
  • What do you want me to do about that? The article clearly states that the newly discovered "bug" does not have mitochondria. – Tᴚoɯɐuo Jul 13 '16 at 0:04
2

They refers to "this newly discovered microbe, and others that live in low-oxygen environments."

The only reason it's not "oxygen-free pathways" is because it doesn't make sense for "oxygen-free pathways" to "still have mitochondria for that protein assembly job."

  • Thanks for your answer. Would you take a look at TRamano's comment? I don't understand why "this newly discovered microbe" should be also included. It is said right after the sentence that "The new bug apparently pulls off the protein-synthesis by using a system that it picked up from bacteria". – Jack Jul 13 '16 at 0:08
  • @Jack I think this answer is right. It refers back to "this newly discovered microbe, and others that live in low-oxygen environments", making a statement about a larger set to which this newly discovered microbe belongs: they usually have mitochondria (=most members of this set have mitochondria, but this one is different). Because of the word usually, it's possible for this newly discovered microbe to be included in the set the author refers to without saying that it too has mitochondria. That's how I read it, so I upvoted this answer. – snailcar Oct 11 '16 at 7:58

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