How do Planctomycetes divide?

One of the particular features of Planctomycetes, and some other PVCs, is that they have lost the otherwise ubiquitous FtsZ gene. FtsZ is the main building block of the constriction ring that all other bacterial cells use to divide by fission. It is so important that it is one of the few proteins that are found in all bacteria, with very few exceptions. One of them, of course, are some of the PVCs, and in particular almost all Planctomycetes. And we know they have lost it, because the dcw cluster is still present but showing different degrees of erosion in actual PVCs, demonstrating that it was present in the Last PVC Ancestor, and most likely functional (see fig. 2 in the Pilhofer 2008 publication). So the very important question of "how do Planctomycetes divide, and in particular achieve the last steps of cytokinesis?".

This is the question that Jogler et a., 2102 Jbact address in their latest publication. Initial Phylogenetic analysis (Fig. 1)

provided a phylogenetic criterion to leave anammox bacteria out of our analysis

This is already important since it clearly splits the Planctomycetes in two group, the anammox on one side and all other non-anammox planctomycetes on the other. Anammox have been claimed to be early branching Planctomycetes and have particular biochemical reactions, endomembrane organization and dividing mode (most likely). Thus, it make sense to separate them from the other planctomycetes. This first analysis clearly puts them apart from the others.
The authors then go on to define the (non-anammox) planctomycetal core genome, by identifying those genes that have homologues in all selected genomes and discarding the ones that are also found in 'classical' bacteria such as E. coli and B. subtilis. They identified 114 clusters of exclusively planctomycetal proteins. No doubt that some of them should be related to the particular mode of division of those organisms. By example, one such cluster contain 39 membrane-coat like proteins that are structurally related to eukaryotic ones and likely to be involved in the membrane organisation in Planctomycetes (see Santarella-Mellwig et al., 2010 PLoS Biology,). Interestingly, a new FtsZ-like protein was recently described and found in a few Planctomycetes. However, Jogler et al. failed to detect homoloues in all other sequenced planctomycetes despite the use of a very similar strategy. Thus this FtsZ-like family might not be involved in division, at least not in all Planctomycetes.

They then provide an interesting analysis of the proteins found in this core planctomycetal genome and their domain composition.
One of the most interesting result is the finding that Planctomycetes are very poor in DNA-binding one-component systems (classical receptor-operator single proteins in bacteria, direct link between signal and output), but very rich in Ser/Thr protein kinases, which are common among eukaryotes and usually rare in bacteria. Again another striking relationship between those bacteria and eukaryotes.
They also found more two-components systems that are orphan genes, pointing toward a more complex regulation in planctomycetes.
But even more interesting, is their finding related to ECFs. ECFs are extracytoplasmic function sigma factors. In contrast to other bacteria, all planctomycetes are particularly rich in ECFs. Most planctomycetes ECFs can NOT be classified in the previously defined classes, which is probably just a reflexion of the bias towards model bacteria. G. obscuriglobus in particular is the second most ECF-rich bacteria, with the deltaproteobacterium Plesiocystis pacifica. They also identified a new class of ECFs that is specific to G. obscuriglobus. This class also contain more than half of the ECFs in the G. obscuriglobus genomes pointing to a recent evolution of those genes. Importantly, these are also the first membrane-anchored ECFs in bacteria. Given the conspicuous endomembrane organisation in this organism, it make sense that those proteins will play an important role in its regulation.

In conclusion, very interesting paper, even if not resolving the mystery of PVC division. On the other side, I would have found it interesting to do the same analysis on all PVC members. No doubt though that PVCs remains fascinating organisms, as this article beautifully illustrates.

HGT, no HGT?

By now you should know that PVC bacteria are very interesting for their particular features. Some of those are usually NOT observed in bacteria and usually more associated with eukaryotes or archaea. This is the base of the controversy around the PVCs, of which the McInerney paper is a good example. This point will also be addressed at the EMBO PVC workshop 2013 (please come, listen and contribute!).

Addressing the origin of those features is a difficult issue. Mostly because for the majority of those, we don't even know the proteins that are behind them. In addition, evaluating the origin of genes or proteins requires the elaboration of a multiple sequence alignment with satisfying quality assessment. This is only possible for a couple of such PVC features.

In a recent article, just published in the Frontiers PVC research topic, Budd and Devos review the few cases in which such phylogenetic reconstruction have been achieved for the PVC features. They found out that contrarily to what has been published (eg the reply to the Devos and Reynaud 2010 Science paper), no agreement has been reached on the origins of those features (which once again are only a small portion of the peculiar PVC features). In fact, about half of those analysis actually conclude against lateral gene transfer. They conclude that the HGT origin of those PVC features is still not established. In addition, they highlight the importance of taking into account alternative models and scenarios, including alternatives to the 'classical' 16S rRNA based (ie Woese-type) tree of life and HGT/no-HGT models.

Whatever it is, there is certainly more interesting surprises to expect from this intriguing bacterial superphylum.

Two PhD positions in Bioinformatics

Two PhD positions in bioinformatics are available in the lab of Dr. DP devos. Those PhD positions are purely bioinformatics. The main references for both proposals would be Devos et al. PNAS 2006 and Santarella et al. PLoS Biology 2010.
A strong background on protein structures and sequences analysis is required. Some knowledge of programming would be an advantage.
Starting date are 1st January 2013 and June 2013.

Please contact him directly and not through this web site.

DGZ publication 2012

Nice summary of one of the main hypothesis and our work has just been published in the Newsletter of the German Society for Cell Biology. Basically a sum up of previous paper and a few to come. Enjoy.

Frontiers research topic

Just want to point out a recent research topic in the Frontiers serie in Evolutionary and Genomic Microbiology dedicated to the PVC superphylum. This serie contains interesting contributions on the condensed state of the Planctomycetes genome, on the molecular signatures for the PVC clade, ... .

Of particular interest, is the article by Speth et al. whose genomic analysis indicates the presence of an asymmetric bilayer outer membrane in Planctomycetes and Verrucomicrobia. Very interesting article that provides more evidences against the exceptional aspect of the Planctomycetes membranes organisation. The presence of key genes in the Planctomycetes genomes indicates that the outer membrane is at least related to the outer membrane of other 'classical' (if there is any such thing) Gram-negative bacteria, see also the commentary by Yıldırım and Linke about the definition of a Gram-negative.

EMBO PVC workshop

It is my pleasure to announce the very first meeting exclusively dedicated to the bacterial PVC superphylum. The EMBO PVC workshop will take place from Feb. 28th to March 2nd 2013, in Heidelberg, Germany. It promises to be a very interesting conference with fascinating talks about those peculiar bacteria. In order to promote interaction between biologists, we recommend all participants to at least present a poster and if possible a short talk. This EMBO workshop will be the first one to focus on the characterization and fundamental understanding of the PVC members. The Workshop will bring together researchers working on such bacteria and provide a broad coverage of those exceptional bacterial features and evolutionary scenarios. The scope of the symposium is to facilitate discussion among researchers who recently advanced the field by investigating particular features in PVC-bacteria and scientists who hypothesize on the impact PVC-bacteria had on eukaryotic or archaeal cell evolution. Addressing the current controversy is encouraged. I am looking forward to meet you there.

Support basic research!

Why study those weird bacteria with bizarre endomembranes? Why would we care? Well, in addition to their intrinsic interest and beauty, as well as their potential evolutionary link with our own kind of cells, there is an important part of research which is implied by its name. It is "research", we don't know what we are going to find, we don't know what will be interesting, relevant or useful, but that is the reality of basic research. It is always worth reminding us that there will not be any applied research without basic research. Everything else is coming from basic research. A nice call in favor of basic research from the NIH director Francis Collins has just been published in Science. Let's hope it will be heard, and not only in the states!

Darwin vs Lamarck

So, reading this book about the process of insight, an important issue, for scientist, I found plenty of trick to favor the development of it. But this led me to wonder, how do you recognize the right insight?

Consider Darwin and Lamarck. Sure Lamarck also had his 'Eureka' moment. But it was a wrong Eureka. However, because it made so much sense, he just followed and pushed his idea for most of his life, and is now recognized as an important contributor to evolutionary theory albeit a wrong one. So, how do you recognize good intuition from wrong intuition? In the case of Darwin vs Lamarck, it must be very difficult, even impossible for Lamarck at the time to recognize, even less admit, that he was wrong, partly because the idea was so good, it made so much sense. It is easy for us now a posteriori to say that Lamarck was wrong but at the time, with the knowledge and tools they had, it sure sounded like a good idea, and he had many followers.

I guess a few clues could have come from evaluating and pushing his theory to the limit. By example, Lamarck did not explain the origin of new species. An all important point in evolution. Or may be I should say didn't explain it as convincingly as Darwin's. I guess that a more critical evaluation of his own theory might have helped Lamarck to realize his mistake, eg there is no 'improvement' of the race in animal breeding, so well explained by Darwin, it is selection, not adaptation.

Can 'Eureka' be learned?

Was just reading a Science book review entitled 'Facilitating "A-ha!" moments'. The book is about how to expand creativity, apparently loaded with anecdotes and 'tricks' to facilitate it. Interesting example includes the fact that building planners locate bathrooms in places that force people that are not used to meet to come together to the same place. Apparently, this has been shown to increase a company's creativity. I have been told that this kind of planning to force people to meet is increasingly taken into account into scientific buildings eg at the Janelia Farm campus, VA. More importantly, there is apparently a call to change our education system in order to promote creativity in children. The book is apparently great fun. It is still not clear if reading it would improve your creativity, but it can certainly not hurt. I was not convince if I should buy it or not, but the call to change education to promote creativity got me. I will buy it and tell you more about it soon.


Got it, very nice book. Had trouble to put it down. Lots of interesting stuff, some you know, some you guessed and some you never thought about. By example there is an important distinction between insights and sustained focused attention during long period of intensive work. Coffee and other drugs might help with the later, but not with the former.

Ciliary pore complex

The protocoatomer hypothesis suggest a common evolutionary origin for key eukaryotic complexes like nuclear pores complexes (NPC) and coated vesicles based on a typical domain architecture, the membrane coat (MC) architecture, found only in some of the proteins forming those complexes. Adding to a growing list of data, Kee et al. (2012) Nat. Cell Biol. 14, 431–7, see also the preview by Obado and Rout (2012) Developmental Cell 22, 693-4, suggest that this connection should be increased to include cilia, another key eukaryotic feature. The presence of karyopherins and of a Ran gradient in both systems (Dishinger et al., 2010) already provided some links between the NPC and the cilia. At least one karyopherin recognize a CLS (ciliary localization sequence) that is suspiciously similar to a NLS (nuclear localization sequence). In addition, MC proteins are also found inside the cilia in the transport complexes (Taschner et al., 2012) and components of the BBSome (a multi-protein complex involved in cilia transport) share related structural organization with the coat complexes (Jin et al., 2010). Because this protein architecture is also found in clathrin, COPI and COPII complexes, this suggests a common evolutionary origin to NPCs, coated vesicles and some ciliary components in, to cite the original protocoatomer hypothesis,

an early membrane-curving module that led to the formation of the internal membrane systems in modern eukaryotes,

which can now possibly be expanded to include the cilia or its ancestor.

The origin of the eukaryotic cell is becoming a more complex but also more fascinating issue.

Topics sections in PLoS Computational Biology

New topic sections has appeared in PLoS Comp. Bio., 8(3): e1002446 in an attempt to promote contribution and recognition of it in Wikipedia. There is no way to deny the ever increasing role of Wikipedia in basic research. This is an attempt to induce biologist (computational ones) to contribute to it. I am even more excited because the first highlighted example, on circular permutations in proteins is by a friend of mine. Excellent article.
Interesting initiative, let see how it develops and may be contribute. As the paper suggests in ending:

Who knows what you might be contributing to?

Time for a new genetics curriculum

Biology is changing fast. In an excellent article in Plos Biology, 10(7): e1001356, Redfield RJ, consider that the way we use to teach genetics is updated and propose alternative to teach useful and interesting material. Although we might not agree on everything she propose, it is to be admitted that the historical perspective in genetic teaching is outdated and in need of a shaking.

However, I personally believe that the historical aspect is part of the beauty and attraction of biology. I remember very well that learning about the elegance and beauty of the classical experiments by eg Jacob and Monod, amongst many others was part of the fascination to become a biologist. By example, I recently very much enjoyed an historical perspective on the first tree of life by Woese written by Pace et al., PNAS 2012. I believe that the combination of historical context and realization of the implications that it had and still has, is fascinating.

It is true that with the pace of change in current biology, it should probably be forming a separate less central aspect of a modern curriculum. I would however favor to keep the historical perspective because of the intrinsic beauty of the experiments and the lessons it teaches about scientific thinking.

The before last sentence is highly stimulating:

As long as we remain comfortable with teaching largely irrelevant material, we don't have to worry about changing it.

It has now to be seen how this develop in a new course and how this modifies the potential interest of the student.

COS symposium

Latest poster for the COS symposium can be found below.

NCBS meeting wrap-up publications

An excellent summary of the NCBS meeting has just been published by the organizers in Nature Cell Biology 14, 651 (2012). And another one by the American Society for Biochemistry and Molecular Biology.
We are preparing something on those lines for the NSF EvolCellBio meeting. Coming soon. In addition, the slides of some of the talks are available here. I recommend particularly recommend to look at the one of W. Martin.

Post NSF workshop

So, it was nice, very nice.

Lots of discussions in every directions, from fundamental questions about the role of robustness in evolution to the more concrete needs in terms of fundings and education. Most documents are available on the web site of ECB, and we are working on a report that will be available at the NSF website. But the big ideas included the need for more 'Experimentally Tractable Organisms' (ETOs), mapping the existing ones on the Tree of Life, and developing new ones in non-covered areas, that this new field doesn't need a new journal or new conferences, but more applications of evolutionary thinking into the existing framework. We are working on a document that will be published as a call to increase the consideration of the complementarity that exist between evolutionary biology and cell (and molecular) biology.

It is only in achieving those goals discussed at the NSF worshop that the light of evolution will eventually illuminates the available data to make sense of molecular and cellular biology, and the other way around..

NSF Evolutionary Cell Biology workshop

Going to this NSF-sponsored workshop on the new field of Evolutionary Cell Biology at the end of the month. The stated goal is to identify and address the major gaps in knowledge about the evolution of cell biological systems. This also includes a focus on education and new infrastructures, fundings, ... needed for the new field. Sounds fascinating. The participant list is as fascinating, from well-established 'old dogs' to younger ones, including some well known faces, most of them we have already seen at the EvolCell2012 NCBS meeting, last year in India.

A few of the questions that will be debated includes the roles of physical constraints in convergent evolution, the issue of the mutational cost of increased complexity in the evolution of cellular features, the rise of cell biological structures novelty, amongst other. We will attempt to identify the needs to move the field forward, eg what would it take to create a hypothesis-driven evolutionary cell biology? But also what new toolds, technologies and infrastructures are needed to advance this new field. Education will also be addressed as we will attempt to identify what the changes that are needed at all levels of education to push evolutionary cell biology forward.

An impressive program has been sent to all participants. Interesting discussions to be expected but looking forward to be there. Will keep you posted!

First PVC meeting

Hip hip hourra!!

That is it, we obtained a grant from the EMBO workshop and course program to organize the first meeting entirely dedicated to the PVCs. This event will be entitled: "EMBO workshop on Planctomycetes, Verrucomicrobia, Chlamydiae superphylum: exceptions to the bacterial definition?"  It will be organized by DP Devos (COS, Heidelberg Uni., Germany) with the help of co-organizers C Jogler (Harvard, Massachusetts, USA) and JA Fuerst (Brisbane Uni., Australia) and will be held in Heidelberg, Germany from the 28th of Feb. to the 2nd of March 2013. It will be the first time that scientists working on so different organisms will assemble together in the same room. Fascinating keynote talks have been secured and both tenants of the controversy about PVC phylogenetic link to eukaryotes will be invited. This promise to be a very exciting meeting. More details will come soon, but I want to share this excellent news with you. So mark you calendar for the 28th of Feb. 2013.

Please send me an email if you are interested, intend to come or just are thinking about it at microplatypus@gmail.com. Thanks.

NCBS 2012 III: Divers

Two recurrent themes throughout the conference were 1) the limits of detection by sequence-only based methods, and 2) the apparent extreme complexity of the LECA, the Last Eukaryotic Common Ancestor. This was best illustrated by MC Field in his contribution entitled "Finding things that are not there - lessons at the nuclear envelope". He demonstrated that a combination of molecular biology experiments combined with bioinformatics, essentially structural predictions, were able to detect proteins that could not be detected by Blast searches. This was illustrated in the case of the nuclear pore complex of the trypanosome. Of course, in this case, extreme care has to be taken to discriminate the real signal from the noise. He extended his analysis from the nuclear pore complex to the transporter that ensure the transfer of the cargo through the nuclear envelope, the karyopherins. He showed that karyopherins are conserved and ancient, with at least 14 being most likely present in the LECA, again adding to the complexity of this elusive ancestor. Eventually concluding on the detection of things that are not there, he showed conclusive data about the presence of Lamin analogue in Trypanosome which was so far thought not to possess such an intranuclear protein (a work in press in PLoS Biology).

On a related theme, but different organism, Margaret 'Rossie' Robinson presented her last work on the detection of a new, the fifth, adaptor complex, AP5. The list of adaptor complex was thought to be complete, prompting some article title like 'Adaptins: the final recount' (MBoC 2001). It is genuine to wonder about how many such discovery are still awaiting out there.

MP Rout then presented his work on the structure of the nuclear pore complex by integrative modeling. I won't go back to the details of the work published in 2007, but they have pushed the limits of the method to achieve a model of a major building block of the complex, the so-called Nup84 complex, to a precision of ~1.5 nm. This amazing work has just been published in JCB (Fernandez-Martinez et al., 2012). The suggestions derived from the structure about a possible ancestral two fold symmetry at the core of the Nup84 complex was very inspiring and very much in line of the evolution of the nuclear pore complex and thus the protocoatomer hypothesis.
It is so beautiful that I can't resist to show you the inspiring figure taken from the publication

You can see the possible axis of duplication and the losses of the Nup85/Seh1 equivalent, as well as the reductive loss of Nup84 Nt-domain and Sec13 equivalent. Very inspiring.

NCBS 2012 IV and end: WF Martin

The meeting closed by a spectacular show by William Martin. Clearly deeply involved in what he was presenting, Bill started by a thorough recapitulation of all evolutionary scenarios that have been proposed for the origin of the eukaryotes, starting back in 1910, a century ago. The presentation was very comprehensive and Bill's own style ensured the audience of a great show.
Bill went on to present his latest work, including the Evolutionary network of gene in eukaryotes where they present a new method to solve the evolution of eukaryotic genes based on a network of lateral gene transfer. This is based on the fact the the origin of much eukaryotic genes shared with prokaryotes are found all over the tree of life. The conclusions stress the importance of archaea and of mitochondria in the origin of eukaryotic genes, and thus of the eukaryotes.
Bill ended up by discussing the Energetics of genome complexity according to which eukaryogenesis was only possible thanks to the release of the energetic constraints on the genome due to the internalization of the mitochondria. We were even treated by evolutionary movies during the questions. In conclusion, a very complete, entertaining and stimulating presentation by Bill Martin.

There were many other very interesting talks at the conference, including M Munson on the exocyst, Mara Duncan on the linear motifs interaction in the clathrin adaptors, M Bettencourt-Dias on the centrosome, and Frances Brodsky on clathrin, amongst many others. However, time and space constraints and the subject of this blog don't allow me to describe them here. Contributions from other attendees are welcome to present those talks not covered here or even to correct, comment or contribute to the discussion of those covered. The conference itself was actually preceded and followed by tutorials on Cell biology and immunology as well as on Evolutionary and informatic approaches.

All together, a very interesting conference. As I said, one of the most interesting and most interactive I have been to. Thanks a lot to Frances Brodsky, Satyajit Mayor and Mukund Thattai for the organization and ensuring its success. Words are circulating that there might be a follow up to this one, may be in Europe in two years. I will certainly be looking forward to it.

NCBS 2012 II: DP Devos

Damien Devos (EMBL, Heidelberg Germany, moving to the Center of Organismal Studies (COS) at the Heidelberg University) then presented his talk entitled "Microbiology's platypus". He first recapitulated the origin of the protocoatomer hypothesis, starting from a structural analysis of the nuclear pore complex; again highlighting the limits of sequences-only based methods. The first part of his talk ended with the importance of the membrane coat innovation as they form the core of the multi-protein complexes sustaining most divisions of the eukaryotic endomembrane system. As such, they must have been present in the LECA (him again) and probably in the ancestor of.
He then developed a method to use structure (since sequence search is limited, remember?) to search for this particular protein architecture and found it only in some of the PVC proteomes. Immunological characterization located such bacterial membrane coat-like proteins in the paryphoplasm of Gemmata cells. However, the differences of interpretation between him and the previous speaker, John Fuerst, became clear at that moment. Damien doesn't interpret the planctomycetes cell plan as different from the classical bacterial one, but just as an extension of it, when John interprets it as fundamentally different. An interesting discussion ensued and was followed over tee. Damien then presented his last work, where they reconstructed in three-dimensions various complete Gemmata cells. He showed a movie that first went through the tomogram of a cell, followed by the process of modeling the membranes and other features and ending with the final model. Unlike the previous speaker, no isolated compartments or even nucleoid envelope could be observed in this study. It would be interesting to pursue this analysis and resolve this issue. Damien then ended with his interpretation of the possible evolutionary connections between the PVC and the eukaryotic or archaeal features. He made the parallel between the special features found in PVC and the eukaryotes or archaea and the avian or reptilian ones found in the mammal platypus, hence the title of his talk.

NCBS 2012 I: JA Fuerst

What a conference! You should have been there.

It was very very nice. Sincerely, one of the best conference I have been to. The conference was entitled Evolutionary Origins of Compartmentalized Cells. It was thus not strictly concerned with PVCs, but we had some interesting talks and discussion, including some pretty hot ones, about them. The protocoatomer hypothesis was present throughout the conference. Similarly, the LECA (Last Eukaryotic Common Ancestor) was refereed to in many many talks. An agreement, as supported in many publications, is that the LECA must have been very very complex. After two talks on conservation and innovation in membrane traffic in a divergent eukaryote and on assembly of division ring, John Fuerst (Queensland Uni., Brisbane, Au) took the stage. He first gave a nice and quite complete review of the PVCs and their particular traits. He insisted quite rightly about the limits that classical searches based on sequence only seem to have reached. This was also a recurrent theme that we repeated throughout the conference. John then insisted on the difference between the planctomycete paryphoplasm and the classical bacterial periplasm. The data invoked to justify this difference were not so convincing and left most of the audience suspicious. He then presented a model of the gemmata nucleoid envelope that is supposed to completely surround the bacterial genetic material. Unfortunately, he didn't present the data from which this model was derived. He ended by presenting images and the reconstruction of a nuclear pore complex-like structure that is claimed to be found in the nucleoid envelope of the bacteria. The resolution was not great, but if confirmed this would represent an impressive achievement. However, some doubts about the identity and localization of this complex remains. The round of questions were dominated by a heated exchange with William Martin that strongly criticized the data presented and the claims about their relationships with the eukaryotes. Both sides stood on their claims and the discussion continued during the tea break.

EvolCell2012, NCBS, India.

Next (and first in this blog) conference in February 2012 on the Evolutionary Origins of Compartmentalized Cells at the National Centre for Biological Sciences, Bangalore, India. Interesting speakers includes: John Fuerst, Mike Rout, Monica Bettencourt-Dias and William Martin amongst others. This promises to be a very exciting conference.

Here is the very beautiful Aborginal style poster: .

I will keep you updated by regular posts.

New RuBisCO in Verrucomicrobia

Methanotrophy and methanogenesis are central to the Earth's methane balance. The origins of both C1 transfer chemistry reactions are still unknown. Genomic analysis suggests that a compelte set of genes encoding the enzymes of the CBB cycle are present in the Verrucomicrobiae Methylacidiphilum fumariolicum, as reported in Khadem et al., J Bact 2011. This suggest that these methanotrophs may be able to fix CO2, probably using CH4 mainly as an energy source. The authors demonstrate that M. Fumariolicum strain SolV is able to grow using only CH4. Additionally, phylogenetic analysis of RuBiscCO showed that the verrucomicrobial enzyme formed a distinct group in the phylogenetic tree. Additionally, the authors suggest that the verruco RuBiscCO is most likely solubles in those bacteria, and not included in carboxysomes as in cyanobacteria and other nitrifying bacteria. Additional information like gene arrangement suggest that the Methylacidiphilum RuBisCO has 

"medium to low affinity for CO2, indicating an adaptation to environments with medium to high CO2 but with O2 present."

The conclusions speak for themselves:

"M. fumariolicum strin SolV is an autotrophic methanotroph. It fixes CO2 via the CVV cycle, with CH4 as the energy source. It uses a non-carboxysoe-associated RuBisCO, in agreement with a high requirement for CO2. RuBisCOs in verrucomicrobial methanotrophs form a new group most closely related to type IC."

The authors postulate that RuBisCO of the verrucomicrobial methanotrophs represents a new type of form I RuBisCO.