Tag Archives: extremophiles

Friday Fellow: Walsby’s Square Haloarchaeon

by Piter Kehoma Boll

After more than a hundred Friday Fellows, there is still one group with no representatives here: the archaeans. But this is going to change today with the indroduction of our first Friday Fellow archaean, and it is a very interesting one for sure.

Scientifically known as Haloquadratum walsbyi, it is sometimes called Walsby’s Square Haloarchaeon and, as its name suggest, it has an unusual square shape.


A drawing showing a set of four cells of Walby’s square haloarchaeon.

This interesting archaean was discovered in 1980 by Anthony Edward Walsby in brine ponds of the Sinai Peninsula. It was later discovered in several other lakes with high concentrations of salt around the world and was first cultivated in the laboratory in 2004, but only in 2007 it was formally described and received a binomial name.

The square cells of the Walsby’s square haloarchaeon are very thin, about 0.2 µm thick, and measure about 2 µm on each side. They grow very slowly, forming a thin sheet over a surface, the largest recorded sheet measuring 40 × 40 µm. If the growing conditions are not ideal, the cells deteriorate to a ragged square or other shapeless flat form.


Photographs of cells of Haloquadrum walsbyi showing the crystal-shaped air vacuoles. Image extracted from Burns et al. (2007).

Inside the cells, the Walsby’s square haloarchaeon has small gas vesicles that look like small crystals. They help the cell remain at the surface of the very salty water they inhabit. In order to survive, this archaean needs water with a concentration of salt of at least 14%, but the conditions become ideal only above 23%.

Although we know some interesting things about this species, there is still much more to learn. Who knows what mysteries this small square-shaped creature is hiding from us?

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Bolhuis, H.; Poele, E. M. t.; Rodriguez-Valera, F. (2004) Isolation and cultivation of Walsby’s square archaeonEnvironmental Microbiology 6(12): 1287–1291.

Burns, D. G.; Janssen, P. H.; Itoh, T.; Kamekura, M.; Li, Z.; Jensen, G.; Rodríguez-Valera, F.; Bolhuis, H.; Dyall-Smith, M. L. (2007) Haloquadratum walsbyi gen. nov., sp. nov., the square haloarchaeon of Walsby, isolated from saltern crystallizers in Australia and SpainInternational Journal of Systematic and Evolutionary Microbiology 57: 387–392.



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Friday Fellow: Conan the Bacterium

ResearchBlogging.orgby Piter Kehoma Boll

Most people would agree that 2016 was a hard year. So let’s try to make 2017 better by starting this year with a tough Friday Fellow, actually the toughest of them all: Conan the bacterium, or Deinococcus radiodurans.

A relative of Taq, Conan the bacterium is a rather large bacterium, measuring 1.5 to 3.5 µm in diameter and usually forming groups of four organisms sticking together, a formation known as tetrad. It is an extremophilic bacterium, able to resist to very harsh environments. Actually, Conan the bacterium is one of the most radiation-resistant organisms known to date and can also resist extremes of cold, dehydration, vacuum, and acid. Its popular name was based on the character Conan the Barbarian.


A tetrad of Deinococcus radiodurans.

Conan the bacterium was discovered in 1956 during an experiment that tried to sterilize canned food using high doses of radiation. One bacterium survived the high doses of gamma radiation and was identified as a new species.

Later, a group of scientists suggested that the high degree of radioresistence was an adaptation to the Martian environment, so this could be an alien bacterium! But that’s actually bullshit. Conan the bacterium has nothing significantly different from other lifeforms on Earth, but how did such a resistance to radiation evolve? Background radiation on Earth is very weak, so it could not appear by natural selection.

The results of some experiments published in 1996 revealed that strains of D. radiodurans that are susceptible to desiccation are also susceptible to radiation. Thus, the most likely explanation is that the high resistance to radiation is simply a side-effect to the resistance to desiccation, a condition much more common in the bacterium’s environment.

The mechanism that allows Conan the bacterium to withstand radiation is very complex, but includes an ability to rebuild DNA strains from fragments, which is helped by the fact that each cells contains four copies of the bacterial chromosome, so that a partially-damaged strain can serve as a model to repair another partially-damaged strain.

Our tiny fellows are always full of amazing surprises!

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Mattimore, V., & Battista, J. (1996). Radioresistance of Deinococcus radiodurans: functions necessary to survive ionizing radiation are also necessary to survive prolonged desiccation. Journal of Bacteriology, 178 (3), 633-637 DOI: 10.1128/jb.178.3.633-637.1996

Wikipedia. Deinococcus radiodurans. Available at <https://en.wikipedia.org/wiki/Deinococcus_radiodurans&gt;. Access on January 2, 2017.

Zahradka, K., Slade, D., Bailone, A., Sommer, S., Averbeck, D., Petranovic, M., Lindner, A., & Radman, M. (2006). Reassembly of shattered chromosomes in Deinococcus radiodurans Nature DOI: 10.1038/nature05160

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Badass bacteria are thriving in your washing machine

ResearchBlogging.orgby Piter Kehoma Boll

You probably have heard of bacteria (and archaeans) that live in extreme environments on Earth, such as hot springs or lakes with high salinity, where most lifeforms would die horribly in a few seconds. We usually think of those places as existing in some remote locations, in the deep sea or in protected areas far away from civilization.

But thanks to human technology, this kind of environment is now available right in our homes, in our dishwashers, washing machines and water heaters.


Buchnera, a genus of bacteria found in the gut of aphids (seen as the several spotted circles inside a gut cell here) was found in extremely hot home environments. Photo by J. White and N. Moran.*

On a recent study published on PeerJ, a group of scientist examined the community of microorganisms living in several home environments and found out that many species thrive in environments with high temperature, extremes pH or extreme concentrations of certain chemical compounds.

Some of the findings were rather unusual… For example, a bacterium found in places with extreme temperature was Buchnera, a genus usually associated with the gut of aphids.

You can read the full article here.

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Savage, A., Hills, J., Driscoll, K., Fergus, D., Grunden, A., & Dunn, R. (2016). Microbial diversity of extreme habitats in human homes PeerJ, 4 DOI: 10.7717/peerj.2376

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*Creative Commons License
This work is licensed under a Creative Commons Attribution 2.5 Generic License.

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