Having published a book on origin of life, somehow I missed wet-lab microbiologist Jeffery Errington’s cutting edge investigations of wall-less organisms called “L-forms.” Not surprisingly, Errington -- who resembles Edward Fox a bit (Day of the Jackal) -- was awarded the Royal Society’s Leeuwenhoek Medal in recent years for his “seminal discoveries” in cell morphogenesis and research on L-forms. But aside from being a distinguished scientist, Errington is also an occasional footballer during time off from the lab he directs at Newcastle University in the UK, and knowing how critical teamwork is to victory, accepted the Leeuwenhoek saying the Royal Society honor really belonged to his team.
It is one of many awards Errington’s received through the years, others include: Lwoff Award and Medal (Federation of European Microbiological Societies); Novartis Medal and Prize (UK Biochemical Society); 20th Anniversary Medal and Prize (Biotechnology Organization and Biological Science Research Council).
Jeffery Errington is a Fellow of the Royal Society and a Fellow of the Academy of Medical Science, and has been elected to the European Academy of Microbiology, American Academy of Microbiology, and EMBO (European Molecular Biology Organization).
Errington serves on the editorial boards of EMBO Journal; Molecular Biology; and Current Opinion in Microbiology. He’s co-chaired two Gordon Conferences and organized numerous others.
He is an entrepreneur as well, founder of two spin-out companies working in drug discovery and is currently Director of Demuris Ltd., based in Newcastle, north of London on the river Tyne.
Jeffery Errington’s PhD is in bacterial genetics from the University of Greenwich and his BSc from Newcastle University in genetics and zoology. Errington’s postdoctoral research was done at Oxford University where he later became Professor of Microbiology in the Sir William Dunn School of Pathology. He is presently Director of the Centre for Bacterial Cell Biology, Medical School, Newcastle University, where he works with a staff of 300. Errington is also Professor of Microbiology at Newcastle.
I recently spoke with Jeff Errington by phone at his lab, mostly about his curiosity about L-forms as models of primordial cells, their role in infectious disease, and their potential use in medicine.
Our interview follows.
Suzan Mazur: Congratulations on being honored by the Royal Society with the Leeuwenhoek Medal for your discoveries in cell morphogenesis, and, in particular, for your work with the wall-less L-form bacteria and its potentials for medicine, in developing antibiotics and other drugs.
L-forms were first defined more than 80 years ago by Emmy Klieneberger-Nobel who thought they represented a phase that bacteria go through, some under normal cultural conditions, and others only when exposed to abnormal conditions. In her 1949 paper, Klieneberger-Nobel characterizes the following medium as “ordinary conditions”: “boiled blood agar made from ox-heart infusion peptone broth enriched with horse serum."
Through the years specimens have been scraped from some of the most intriguing corners of life for experiments to transform bacteria into an L-form-like, wall-less state. You’ve said that there’s been a resurgence of interest in L-forms in recent years because of genome sequencing and advances in microscopes. Does science at the moment have any idea how extensive L-forms are in nature or may have been in evolutionary time?
Jeffery Errington: There are several answers to that question. 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.
A lot of people were excited by the notion that L-forms might be involved in infectious disease or chronic or recurrent infections. But if you look at the publications from the 50s and 60s -- and there were many of them -- a lot of those were single patient case studies that were not very carefully controlled.
There was also the problem of investigators looking at specimens under the microscope and seeing L-forms indiscriminately in blob-like objects. It was the pre-molecular era and there just weren’t incisive methods to demonstrate that objects under the microscope were of bacterial origin. And even if researchers had an L-form line that could be bred in the lab, investigators had no way to work out what kind of walled bacterium it came from. So there were all sorts of technical issues about even defining precisely what an L-form was, never mind working out the relevance to disease. All of the above held back the field, and, as mentioned, it petered out in the 70s. It’s only in the last 10 years that more rigorous scientific papers on L-forms have begun to be published.
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: Klieneberger-Nobel also pioneered the study of Mycoplasma, is that right?
Jeffery Errington: She was one of the people who was working on these organisms, although the history is a little difficult to reconstruct right now. Scientific papers from that time indicate that researchers couldn’t tell whether this was Mycoplasma, a highly evolved bacterium, or the temporary variant of a walled bacterium, i.e. an L-form. They just didn’t have the molecular tools to easily make the distinction. The general term PPLO (pleuro-pneumonia-like organism) became used for the whole group of organisms, perhaps reflecting uncertainty about their origins and identities.
Suzan Mazur: What are some of the L-forms occurring naturally that have been identified?
Jeffery Errington: This is really where the cutting edge is presently. Now that we understand the molecular basis for the L-form transition better we’re in a much stronger position to work out the extent to which bacteria live in the L-form versus the walled state. The jury is still out. We just haven’t done enough work on this.
But my lab is now working hard on whether we can find L-forms in various clinical situations, especially involving chronic or recurrent infections. None of this is published but we’re quite excited about the results we’re getting, especially with recurrent urinary tract infections.
Suzan Mazur: So you tend to think L-forms were extensive in earlier evolutionary time.
Jeffery Errington: Yes. For example, what we’re finding is that very similar triggers to those that will turn a Gram-positive bacterium [i.e., bacteria with a single thick peptidoglycan wall] like Bacillus subtilis into an L-form will also convert E. coli into the L-form state. And these two species of bacteria are separated by about a billion years of evolution.
Suzan Mazur: That’s fascinating.
Jeffery Errington: This suggests to us that this is a general physiological state that’s very ancient.
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.
Suzan Mazur: Do viruses play a role in regulating L-form bacteria?
Jeffery Errington: That’s a good question. Of course, much of the research on bacteriophages has shown that they tend to bind to components of the cell wall, so certainly you’d anticipate that L-forms would be resistant to many forms of virus. But I don’t know if much work has been done on this.
Suzan Mazur: You’ve said “a vast number” of bacteria can be induced to an L-form state. How many species have you been able to convert to an L-form-like state?
Jeffery Errington: According to the scientific literature, a very wide range of pathogenic bacteria can switch to L-form state. There are historical reviews by Gerald Domingue. In our lab we’ve chosen to work with about a half dozen bacteria – organisms from very diverse backgrounds. They mostly seem to behave in more or less the same way, if we give them an osmoprotective agar medium and trick them with a particular antibiotic, most will switch to the L-form state.
Suzan Mazur: You say it’s basically simple geometry to transform a walled bacterium into an L-form, that it’s a matter of making excess membrane which results in deformation of the cell, that is, you drive changes by increasing surface area. L-forms then reproduce by non-binary fission via membrane tubulation and also blebbing, i.e., they generate blob-shaped descendants. Is that right?
Jeffery Errington: Yes.
Suzan Mazur: Getting back to the Mycoplasma, have you been able to induce wall-less bacteria like Mycoplasma or Phytoplasma to form a cell wall and would it be useful to try and do so?
Jeffery Errington: That’s a really interesting question. My feeling is that because they’ve been evolving for hundreds of millions of years without a wall, and they’ve lost most of the genes needed to make the wall – that it would be pretty difficult to do that.
However, the L-forms we make in the lab from walled bacteria can generally switch back into the walled state relatively easily.
Suzan Mazur: Some scientists characterize reports about horizontal gene transfer (HGT) being rampant in evolution as a reflection of “HGT industry” hype and say that HGT has been a “negligible factor” in evolution. But you’ve said, assuming that the vesicles of ancient organisms had similar structure to today’s organisms, and that they used L-form proliferation, that horizontal gene transfer would have been massive because vesicles would have contained multiple genomes. Can you say a bit more about this?
Jeffery Errington: I think it’s likely that HGT was fairly rampant in the primordial L-form-like cells. However, my feeling is that invention of the cell wall (perhaps separately in archaea and bacteria – which have completely distinct cell wall structures) could have brought an abrupt halt to the primordial HGT. Once the wall was in place, new mechanisms of HGT may need to have emerged to enable DNA transfer across the wall barrier.
Suzan Mazur: You’ve also said “It seems likely that further detailed studies of the cell envelopes of deeply rooted bacterial groups will provide insights into the early evolutionary history of the bacteria,” and that “sequenced-based analytical methods are still inadequate for defining early steps in bacterial radiation.” If you were laying out a Tree of Life, how would you organize the domains in light of these difference in cell wall structure since you say that the ingredients for cell walls are produced within the cell itself and then flipped to the outside?
You go into some interesting detail in your Royal Society paper about bacteria having either (1) one thick PG (peptidoglycan) wall or (2) one thinner PG wall plus an outer membrane; and archaea exhibiting a variety of protective layers -- most often a paracrystalline proteinaceous shell (otherwise known as an “S-layer”) -- with some families of archaea displaying a PG-like layer (called a pseudomurein) but made via a different pathway than a true PG wall is made. eukaryotes, on the other hand, don’t have either a PG wall or a paracrystalline proteinaceous shell.
So the question is how would you organize the domains on the TOL?
Jeff Errington: 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.
Suzan Mazur: And the archaea are antibiotic resistant, aren’t they?
Jeffery Errington: Yes, in general, because they’re much more like eukaryotes, and so lack the molecular targets of antibacterial compounds. For example, all of the antibiotics we use that act on the PG wall of bacteria don’t work at all on archaea. As I mentioned before, one of the ideas I particularly like is that a key step in the evolution of cellular life was the invention of a cell envelope structure that would allow cells to survive outside of the “muddy puddles” that Darwin suggested may have been the birth place of life. There were two distinct evolutionary solutions to the problem of how to tolerate osmotically unstable conditions. One was the PG wall, which is common to all modern bacteria, and the other was the pseudomurein or proteinaceous “S-layer”-type walls, which were invented by the ancestors of the archaea. I like this explanation, but of course, it’s difficult to go back in evolutionary time to do experiments!
Suzan Mazur: There’s an interesting challenge coming from the North, from Charles Kurland and Ajith Harish in Sweden, who think we only assume bacteria are the earliest organisms, that this reflects Aristotelian thinking. Their perspective is that the modern TOL is a rerooted tree from a now extinct biosphere and that the most recent common ancestor was actually a complex organism. They base this on their computations that 75% of the Superfamily proteome of the three domains -- archaea, bacteria and eukayotes – are shared ancestral Superfamilies. Some of their work has been supported in part by the Nobel Committee for Chemistry of the Royal Swedish Science Academy. Any comment?
Jeffery Errington: I have a colleague here at Newcastle University named Martin Embley who’s been very prominent in this TOL discussion. Martin and his team have done incisive work that I think supports the idea that there are only two domains and that the eukaryotes are derived from a group within the archaea rather than being an out group and separate from the archaea. The latest textbooks are starting to show the two- domain tree instead of the Woese three-domain tree.
Suzan Mazur. You started two spin-out companies that are working on discovering and developing antibiotics. Are any of these products close to phase III trials?
Jeffery Errington: No, they’re really still in early development.
Suzan Mazur: Can you talk about it?
Jeffery Errington: Yes. I’ve been involved with this for about 20 years now. The first company was started while I was at Oxford. I was at Oxford for about 25 years, latterly in the department where Florey, Chain and co-workers first purified penicillin in the 1940s. [Note: Jeff Errington was Professor of Microbiology at Oxford University’s Sir William Dunn School of Pathology.] So I was acutely aware of the importance of antibiotic discovery.
My interest really began at the end of the 1990s when the pharmaceutical companies switched the way they did drug discovery to a new “target led” approach. The idea was that to find new antibiotics, you should go after essential genes within the bacteria that hadn’t been targeted by existing antibiotics, and then look for chemical compounds that work specifically on the new targets. The thinking was that you’d find new chemistries and new antibiotics. Companies at the time were limited in their development because of the poor understanding then about basic bacterial science.
We were working on a number of genes and proteins that are involved in fundamental aspects of bacterial life, such as the cell division machinery, and we tried to find chemical inhibitors of some of those compounds. We set up the first company, called Prolysis, in Oxford. We went through about £15 M in funding. To make a long story short, a couple of new compounds were very promising but the company wasn’t able to raise enough funds to take these compounds into clinical trials. The two compound series are still in play, though, with a couple of biotech companies on the East Coast of the US. Years later, here in Newcastle, I founded Demuris.
Following from the Prolysis experience we realized was that if you try to find chemicals that work on a single enzyme target, you’re almost always going to come up with a problem of resistance. It turns out to be very easy for bacteria to make very small, simple, genetic changes to the enzyme that will prevent the compound from binding without compromising the activity of the enzyme.
The resistance frequency turns out to be the most difficult problem to get around. Our present strategy is to return to looking at natural product molecules made by bacteria. These organisms have been carrying out a kind of biological warfare for perhaps a billion years. To have been retained by evolution these molecules are much more sophisticated. They often either have a double mode of action, so simple mutations don’t generate resistance, or they work on a non-protein target, such as binding to the cell wall. It’s very difficult for the bacterium to alter the chemistry of its cell wall without changing many genes.
So Demuris is going back to old-fashioned natural product discovery but using modern methods to try and find compounds that work in different ways from the compounds that have been discovered in the past. We have several very promising molecules that look as if have novel modes of action, but they’re still pretty early-stage.
Suzan Mazur: Fascinating. Good luck with your ongoing investigations.
Jeffery Errington: Thank you.
Suzan Mazur: Oxford University physiologist Denis Noble once said, “No one needs to be just a scientist.” Noble, for instance, likes to perform medieval Catalonian songs of love and chivalry as much as possible with his group, the Oxford Trobadors. Do you make time for recreation outside of the lab, do you still have an interest in football, for instance?
Jeffery Errington: Soccer for you in the US. Football is more like English rugby, you need to be either very big or very fast when you play that sort of game. I play soccer. I actually played last night. It’s great when I’m running around chasing a ball, all my worries and concerns, scientific models and contrary data are forgotten about for at least an hour. . .
I like music as well, and travel. I get to travel a lot as a scientist. Yes, I’m enjoying life and science immensely. It’s a fantastic career, as a scientist. I feel hugely privileged to be able to do this.