weird relatives

I've been writing about archaea on and off since the 1990s - there were quite a few of them kicking around at Regensburg biology department when I was there. Until very recently, this field was mainly of interest (especially to me) for its sheer weirdness. Which is why archaea star in some of my weird books, from Life on the Edge onwards.

Now, however, we know for certain that some of our ancestors were archaea. Specifically the Asgard group of archaea, which are extremely difficult to culture, have been shown to include the root out of which all eukaryotes evolved.

I hadn't followed this development all that closely in the last few years, but the recent report of the second Asgard species to be grown in culture has reminded me that I really should, so my latest feature on our ancestors among archaea is out now:

Archaic ancestors

Current Biology Volume 33, Issue 10, 22. May 2023, Pages R377-R379

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See also my Mastodon thread where I highlighted all CB features of 2023.

I'm not on Instagram myself, but I believe if you follow CurrentBiology there, you'll find my features highlighted there as well.

Imaging work with Candidatus Lokiarchaeum ossiferum reveals that actin provides the cell with a complex cytoskeleton reminiscent of eukaryotes. (Image: Margot Riggi, The Animation Lab, University of Utah.)

weird membranes

Today's issue of Current Biology contains a special section on membranes, and my contribution to that is a feature investigating why the membranes of archaea are so weird (sorry, different from all other membranes). Back in the 90s, I did my PhD work next door to Karl Otto Stetter's Archaea Centre at Regensburg, so it was a bit of a nostalgia trip, but I also learned lots of new things about their evolution.


Archaea cloaked in mystery

Current Biology Volume 28, pages R372-R374, April 23, 2018



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Archaea represent a unique life form whose complexities science is only beginning to understand. Researchers in Regensburg and Munich, Germany, are studying the functions of cellular appendages such as the flagella-like archaella of Methanocaldococcus villosus. (Image: Gerhard Wanner, Ludwig-Maximilian University Munich.)

extremophiles feed on formic acid

Researchers have found a new form of energy metabolism in extremely heat-loving (hyperthermophilic) microbes from the genus Thermococcus, which thrive at temperatures above 80 deg C.

Yun Jae Kim, Hyun Sook Lee, and colleagues from several research institutes in Korea, Japan and Russia, demonstrated that several Thermococcus species can produce the cellular energy currency, ATP, using formic acid, the simplest organic acid, as their only fuel. They react formic acid with water, producing bicarbonate and molecular hydrogen.

The researchers discovered the surprising ability in the species T. onnurineus after noticing that its genome contained multiple copies of a gene coding for an enzyme specific for the oxidation of formic acid. When they tested other Thermococcus species for this trait, several, but not all shared the ability to thrive on formic acid. Thermococci form part of the domain of the Archaea, which are as distinct from the Bacteria as from the Eukarya (including all plant and animal species), and which include many species adapted to life under extreme conditions.

Previously, biologists had assumed that this type of reaction would not yield enough energy to fuel the growth of cells. Formate consumption was only known from microbial communities where methane producers can use the hydrogen produced and thereby favour the reaction.

This represents the simplest anaerobic (i.e. oxygen-excluding) metabolism discovered so far, and may well point to ancestral, primitive forms of energy metabolism that were later superseded by more efficient types in most branches of life.

Reference:

Kim et al, Nature 2010, 467, 352.


For background information on extremophiles, see my book:

Life on the Edge

deep sea viruses

We all know about tube worms and black smokers of course, but today I found out from an article in Nature (page 1084 and cover illustration) that viruses play a major role in the biological cycles beyond 1000 m depth. Rather than being eaten by other organisms, the deep sea microbes (which by the way are more likely to be archaea than eubacteria) are most likely to die by viral infection, with the result that they spill their biomolecules into the sea to be eaten by others.

life under the sea floor

In today's issue of Science magazine, a team led by John Parkes of the University of Cardiff reports archaea thriving in rocks more than 1km below the sea floor.

The researchers found these microorganisms in 111 million year old sediment
located 1626 meters below the sea floor, and
living in temperatures of 60 - 100 degrees
Celsius (140 - 212 degrees Fahrenheit). Their
environment is characterized by thermal
energy sources and high concentrations of
methane and hydrocarbons, and these archaea appear to be
metabolically active and dividing in it.

Reference:

Extending the Sub-Sea-Floor Biosphere
Erwan G. Roussel,1 Marie-Anne Cambon Bonavita,1 Joël Querellou,1 Barry A. Cragg,2 Gordon Webster,2 Daniel Prieur,1 R. John Parkes2*

Science 23 May 2008:
Vol. 320. no. 5879, p. 1046
DOI: 10.1126/science.1154545

abstract