Name: Dr. Anna-Louise Reysenbach
Institution: Portland State University
Location: Portland, Oregon, USA
(Photo from https://www.pdx.edu/profile/anna-louise-reysenbach)
Tell me a bit about how you came to be interested in Archaea and what your work entails.
I was doing an undergrad when Carl Woese and George Fox proposed the three domain of life. It was in the same year that deep-sea hydrothermal vents were discovered, and then a few years later when some very unusual Archaea were described by Holger Jannasch and also Karl Stetter. What a time to be a student interested in the marine environment, in ecology and microbiology! At the time, other than the methanogens, Archaea seemed to represent unusual life in extreme environments. And that just fascinated me. Life in high temperature high pressure ecosystems was even more extreme to me than the obligate anaerobe that I worked on for my PhD! At deep-sea vents one could explore the temperature limits of life. I was fortunate enough to land a postdoc in a lab (Jody Deming) and that’s where I isolated my first Archaea from deep-sea vents and became fascinated about how little we knew about the diversity in these high temperature ecosystems. I subsequently joined Norman Pace’s lab and started working in Yellowstone hot springs. Norm, being close friends with Carl, realized that the 16S rRNA gene could be used to explore the diversity of the hidden uncultivated microbial majority. And it was during my time in Norm's lab that the Korarchaeaota were discovered in Obsidian Pool, Yellowstone, and when we started to detect novel Archaea, related to Crenarchaeota (previously only represented by extremophiles) in almost every environment we looked - these later would turn out to be the Thaumarchaeota. These exciting times, when the molecular sequencing revolution was evolving and we were gaining exponential insights into the extent of the diversity of the Archaea, formed the basis for my continued fascination with this domain.
My lab still explores the diversity and ecology of microbial life in high temperature ecosystems. We use a combination of molecular (and metagenomic) ecological-based approaches to explore patterns of microbial diversity and then use these insights to provide an informed and directed approach to grow and study some of the unusual and ecological interesting novel lineages in these ecosystems.
The devil blob with 2 horns. Images of DHVE2 (deep-sea hydrothermal vent euryarchaeotic 2), a thermoacidophilic archaeon found in deep-sea hydrothermal vents. Image is reproduced from the following article: A ubiquitous thermoacidophilic archaeon from deep-sea hydrothermal vents. Anna-Louise Reysenbach, Yitai Liu, Amy B. Banta, Terry J. Beveridge, Julie D. Kirshtein, Stefan Schouten, Margaret K. Tivey, Karen L. Von Damm and Mary A. Voytek. Nature 442, 444-447(27 July 2006)
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?
There are so many!! In my specific area of expertise, I think the discovery of new clades, first the Korarchaeaota, the Nanoarchaeota and then Thaumarchaeota, which now all have representatives in culture or enrichment cultures. Then recently the insights from metagenomes that suggest there are even more lineages in the Archaea that are providing new avenues for studying (and controversy) the evolution of Archaea and life in general.
Some of the novel archaeal viruses are shedding light on how little we understand about viral ecology. Then there are Archaea that are capable of reverse methanogenesis because they are in association with some bacteria. And well, while I am at it, take a look at the termite gut, look at transcription...
Where is it headed? Maybe in new ways to understand the roles that the Archaea play in ecosystems. This will involve new approaches to grow and study some of the proposed new lineages of Archaea, so that we understand their role in global biogeochemical cycles, their mechanisms of gene regulation and their place during eukaryal evolution.
What would you like the public (and general microbiological audience) to appreciate about Archaea?
The Archaea are our kin… they are closer to us evolutionarily or in some fundamental processes than are Bacteria. But they are also important players in global climate change, including the methanogens, and have roles in fundamental biogeochemical pathways, including the ammonia oxidizing Thanumarchaeota. On top of that, the Archaea have challenged our concepts of what is thermodynamically possible because they share their world with Bacteria, including the ANMEs (studied by Orphan, Joye and others). They also have some unique features, as illustrated by the Nanoarchaeota, which are symbiotic but do not follow all the same gene reduction trends shown in other known symbioses.
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)?
Barns, SM et al., Perspectives on archaeal diversity, thermophily and monophyly from environmental rRNA sequences. Proc Natl Acad Sci U S A. 20;93(17):9188-93 (1996).
One of first reports to show Archaea are pivotal in out understanding of the evolution of life and the eukarya.
Huber, H. et al. A new phylum of Archaea represented by a nanosized hyperthermophilic symbiont. Nature 417(6884):63-7 (2002).
The discovery of Nanoarachaeota. A really interesting new symbiosis, and the only one between two Archaea. Pointing to the prevalence that these sorts of associations may be more common that we expect in the microbial world.
Preston CM, et al. A psychrophilic crenarchaeon inhabits a marine sponge: Cenarchaeum symbiosum gen. nov., sp. nov. Proc Natl Acad Sci U S A. 25;93(13):6241-6 (1996).
The first discovery of Crenarchaeota in sponges. Archaea in sponges?! These then turned out to be our canaries in the gold mine to discover the ammonia oxidation by the now Thaumarchaeota.
Könneke M., et al. Isolation of an autotrophic ammonia-oxidizing marine archaeon. Nature. 437(7058):543-6 (2005).
First example of a Thaumarchaeota in culture, demonstrating that they are ammonia oxidizers.
Orphan VJ, et al., Multiple archaeal groups mediate methane oxidation in anoxic cold seep sediments. Proc Natl Acad Sci U S A. 28;99(11):7663-8 (2002) and McGlynn SE, et al., Single cell activity reveals direct electron transfer in methanotrophic consortia. Nature. 22;526(7574):531-5 (2015)
Two very interesting papers demonstrating reverse methanogenesis.