“A phylogenetic analysis based upon ribosomal RNA sequence characterization reveals that living systems represent one of three aboriginal lines of descent: (i) the eubacteria, comprising all typical bacteria; (ii) the archaebacteria, containing methanogenic bacteria; and (iii) the urkaryotes, now represented in the cytoplasmic component of eukaryotic cells.”
Carl R. Woese and George E. Fox, in "Phylogenetic structure of the prokaryotic domain: The primary kingdoms", Proceeding of the National Academy of Sciences USA, 74:11, 5088–5090 (1977)
These 44 words, published exactly 40 years to this day, started a new era in Microbiology – one in which life is no longer divided into simply prokaryotes and eukaryotes, but instead recognizes the Archaea as a separate group. In their astonishingly short and simple, yet immensely informative and thought-provoking article, Carl Woese and George Fox used 16S RNA sequences to identify “a third kingdom”. At that time, this phylogenetic group was composed exclusively by some methanogenic “bacteria” that Woese and Fox renamed as “archaeabacteria”, paving the way for the term “Archaea” to emerge and stand on its own, as it does today, requiring no help from their bacterial counterparts. Those were the early days in the study of the Archaea as microorganisms that should no longer be grouped together with bacterial cells, but even back then Woese and Fox already discussed the differences in the biology of archaeal and bacterial cells (including differences in their cell walls, the existence of unique coenzymes, and specific RNA modifications); and debated some of the key questions that are still being tackled today, including the importance of the Archaea for understanding the origins of life and its evolution. For example, these are quotes that could easily appear in articles published in Nature Microbiology in 2017, but are indeed taken from 1977:
“The question that remains to be answered is whether the common ancestor of all three major lines of descent was itself a prokaryote.”, or “One of the three may represent a far earlier bifurcation than the other two, making there in effect only two urkingdoms.”
Since then, the Archaea field has progressed immensely, yet many questions remain unanswered. That is why to mark the 40th anniversary of the emergence of the Archaea as a distinct group we have set up this channel and asked scientists about how they got involved in archaeal research, what they feel were the biggest advances during the past 4 decades, and where they think the field is headed. The list of interviewees is by no means comprehensive or aimed at exhaustively covering the field, but hopefully represents a varied mix of individuals that represent different areas of research, from molecular biology to ecogenomics and evolution. In the following posts, we asked them 4 questions:
Q1. Tell me a bit about how you came to be interested in Archaea and what your work entails.
Q2. Looking back at the last 40 years, what would you describe as the most exciting areas of research linked to the study of the Archaea? And where do you see the field headed in the next decade?
Q3. What would you like the public (and general microbiological audience) to appreciate about Archaea?
Q4. Are there any particular papers that you feel are absolute must reads for those that aren’t necessarily familiar with the field (and briefly, why)?
Their answers are not only delightful to read, but collectively also provide a rough account of the history of the field, highlight where progress has been made, and deliver a forward looking element that may influence future generations. For example, we hear from George Fox about how the initial proposal of Archaea as a separate domain came to be, and from Karl Stetter about how he was inspired by Carl Woese, Otto Kandler and Wolfram Zillig to hunt for new representatives of the Archaea in those early days. Patrick Forterre and Roger Garrett tell us how they moved from studying bacterial cell biology to instead focus on archaeal physiology following the description of the "archaebacteria". The stories flow all the way until recent events, including Thijs Ettema's recount of the discovery of the Asgard archaea and Tanja Woyke's description of ongoing efforts to sequence novel lineages as part of the Microbial Dark Matter II project. We also learn from Anna-Louise Reysenbach about finding new lineages in extreme environments, and discover Dina Grohmann's and Sonja-Verena Albers' fascination with the uniqueness of archaeal cell biology. Filipa Sousa and Simonetta Gribaldo take us on a journey through evolution that would have made Woese proud, from the Last Universal Common Ancestor all the way to our current understanding of the origins of life.
Through these answers, we are also reminded that Archaea aren’t simply “weird bacteria” or just extremophiles, but rather widely distributed across the world's habitats, and that they aren’t just present in such environments but actually have crucial ecological importance in regulating many biogeochemical processes. On top of that, we learn that other areas deserve additional investigation, including the role of Archaea as part of the human microbiome, how they interact with bacteria and viruses in different ecosystems, their biotechnological potential and even their importance when thinking about space exploration.
We hope this teaser is enough to convince you to read each individual "Snapshot" in more detail - we promise you won't be disappointed and they really are a treasure trove waiting to be explored. Collectively, we hope this channel helps to put Archaea research in the spotlight, and illustrates not only how much we have already learned about these microorganisms since their identification, but also how much is still waiting to be discovered.
Note: this post was originally published on November 1st but since updated to acknowledge the contribution of George Fox to the "40 years of Archaea channel".