CrazyNeutrino said:
These Ultra-Small Bacteria May Be The Tiniest Life Forms On Earth
Scientists from Lawrence Berkeley National Laboratory and the University of California, Berkeley have captured the first detailed microscopic images of so-called “ultra-small bacteria” that are believed to represent the lowest size limit possible for life on Earth. Scientists have debated the existence of these tiny bacteria for decades since there was never such a detailed observation of the weird microbes—but the debate now seems to be over.
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I wonder how these compare with mycoplasma. Let me check. The first image in link shows a bacteria with length 430 nm and width 250 nm. Mycoplasma are “typically about 100 nm in diameter”. So these new bacterial species are significantly larger than some mycoplasma species. The first subtlety, though, is that the new bacteria are free-living in groundwater whereas mycoplasma are all either parasitic or saprotrophic (living on decaying organic matter).
The second subtlety is that these tiny bacteria are genetically diverse, being closely related to three other well-known lineages of bacteria (WWE3, OP11, OD1). These aren’t archaea.
Worth reading is the section “Ultrastructure and architecture of ultra-small bacteria” in the technical article from Nature communications