Jeffery Errington: I became interested in the problem because I was aware of L-forms from the scientific literature of the 1950s and 60s. Curiously, however, right around the end of the 1970s or so, publishing on L-forms just sort of petered out. I haven’t really been able to get to the bottom of exactly why that happened.
Suzan Mazur: How pervasive are L-forms in nature now and earlier in evolution?
Jeffery Errington: There are a few bacteria that are naturally cell wall-deficient, like Mycoplasma, which is a pathogen, and Phytoplasma, which inhabits plants. They’re both cell-wall deficient, but if you look at the evolutionary history of these organisms, it’s quite clear they’re derived from much more ancient bacteria – probably resembling modern clostridia, which have conventional cell walls. So the thinking now is that this is retrograde evolution — Mycoplasma lost the ability to make a wall while evolving into specialized pathogens.
Suzan Mazur: Are you saying that this group, Mycoplama, Phytoplasma and related species are the only cell-deficient organisms that now exist naturally – without being generated in the lab?
Jeffery Errington: No. It’s clear that there are L-forms in nature. What I’m saying is that an ancient ancestor of modern Mycoplasma probably started out as an L-form in the distant past and then evolved down a side track becoming a pathogen, meanwhile losing many genes needed for life outside the specialized environment in the host.
Suzan Mazur: Some L-forms can slip back and forth from walled to wall-less states, does that particular talent indicate the organisms are more evolved or less evolved than other life forms?
Jeffery Errington: This ability to change between the two states begins to seem quite a general property of bacteria, which to me suggests that this is a very ancient trait that’s been retained by modern bacteria because it has adaptive significance in situations that are not especially rare.
For example, if the cells experience conditions where lots of osmolytes [like sucrose in plant sap] are present, giving a sufficiently high osmotic pressure around the cell – the organism doesn’t really need its cell wall, and in principle it can slip into the L-form state, dispensing with the wall. We may have missed this in the past due to microbiologists historically using a particular kind of agar [gelatinous substance derived from red algae] to grow bacteria, which is usually incompatible with the growth of L-forms. More.
So then the ability to switch back and forth is a form of stasis from earliest times?
Then perhaps Craig Venter is right; there is not a single origin of life. Note what Errington says about archaea: “I think it’s curious, really curious that the archaea and the bacteria have a fundamental difference in terms of their cell development structure. It reflects also the very fundamental differences in the way they replicate, transcribe and translate DNA.”
Note: Mazur published a book of interviews on the origin of life, Origin of Life Circus (2015).
See also: Lecture: Bacterial cell walls, antibiotics and the origins of life
What we know and don’t know about the origin of life
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