German and Spanish scientists have conducted a study of the organism Mycoplasma pneumoniae, a microbe considered extremely “simple” compared to most life-forms. With only a fifth as many genes as E. coli, M. pneumoniae is a good starting point for biologists to learn more about how cells work. The surprise, however, is that its genetic workings are “much more subtle and intricate than were previously considered possible in bacteria,” write two University of Arizona biologists in a Science commentary on the research.
M. pneumoniae is a good starting point for biologists to learn more about how cells work.
The team studying M. pneumoniae spent time documenting the proteins used by the microbes, recording gene activity, mapping the microbe’s physical structure, and taking note of the chemical reactions inside the organism. “What emerged was a picture of surprising complexity,” Keim writes. The findings challenge scientists’ ideas about how genes work, showing that, as Keim explains,
Groups of genes thought to work in unison did so only intermittently. At other times they worked in isolation, or in unexpected configurations.
Just as importantly, the study showed that the 3-D arrangement of the genome is crucial to cellular function. More information is stored in genes than in its base pairs. “Linear mapping of genes to function rarely considers how a cell actually accomplishes the processes,” write the University of Arizona scientists, who add, “There is no such thing as a ‘simple’ bacterium.”
Anne-Claude Gavin of the European Molecular Biology Laboratory, who co-led the project, explained, “What we’ve learned is that if you want to understand any cell and the protein complexes it makes, you can’t infer what happens from the order the genes are in.”
Her colleague Peer Bork added, “There were a lot of surprises. Although it’s a very tiny genome, it’s much more complicated than we thought.”
That complexity shouldn’t be a surprise, though: as our knowledge of the cell and life’s genetic basis increase, we continue to encounter workings that transcend our understanding. But virtually none of this complexity was visible to Darwin. Would he hold on to faith in the idea of evolution if he was aware of the challenges posed to it by even the simplest of cells?
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