Tag Archives: Archaea

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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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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New Species: July 11 to July 20

by Piter Kehoma Boll

Here is a list of species described from July 11 to July 20. It certainly does not include all described species. Most information comes from the journals Mycokeys, Phytokeys, Zookeys, Phytotaxa, Zootaxa, International Journal of Systematic and Evolutionary Microbiology, and Systematic and Applied Microbiology, as well as journals restricted to certain taxa.

Pseudoechthistatus sinicus(top) and P. pufujiae are two of the more than 40 new species of beetles described in the last 10 days.

Pseudoechthistatus sinicus (top) and P. pufujiae (bottom) are two of the 40 new species of beetles described in the last 10 days.
















Cartilaginous fishes

Ray-finned fishes


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A Brief History of the Kingdoms of Life

by Piter Kehoma Boll

Since ancient times, living beings were classified as either plants or animals and Linnaeus retained this system in his great work Systema Naturae in the 18thcentury, where he divided nature in three kingdoms: Regnum Animale (animal kingdom), Regnum Vegetabile (plant kingdom) and Regnum Lapideum (mineral kingdom). This system was not intended to reflect natural relationships among living organisms, since Linnaeus was a Christian and believed that all life forms were created separately by God himself just as they are today, but was created to make the study of living beings easier.

Linnaeus and the two kingdoms of life. Painting by Alexander Roslin, 1775.

When the first unicellular organisms were discovered by Antoine van Leeuwenhoek in 1674, they were placed in one of the two kingdoms of living beings, according to their characteristics. It remained so until until 1866, when Ernst Haeckel proposed a third kingdom of life, which he called Protista, and included all unicellular organisms in it.

Haeckel and the three kingdoms. Photo by the Linnean Society, 1908.

Later, the development of optic and electronic microscopy showed important differences in cells, mainly according to the presence or absence of distinct nucleus, leading Édouard Chatton to distinguish organisms in prokaryotes (without a distinct nucleus) and eukaryotes (with a distinct nucleus) in a paper from 1925. Based on it, Copeland proposed a four-kingdom system, moving prokaryotic organisms, bacteria and “blue-green algae”, into the kingdom Monera. The idea of a ranking above kingdom came from this time and so life was separated in two empires or superkingdoms, Prokaryota (Monera) and Eukaryota (Protista, Plantae, Animalia).

Two empires and four kingdoms

Since Haeckel, the position of fungi was not well established, oscillating between kingdoms Protista and Plantae. So, in 1969, Robert Whittaker proposed a fifth kingdom to include them, the called Kingdom Fungi. This five-kingdom system remained constant for some time; Monera were prokaryotes; Plantae were multicellular autotrophs (producers); Animalia multicellular consumers; and Fungi multicellular saprotrophs (decomposers). Protista was like the  trash bag, where anything that doesn’t fit in the other 4 kingdoms was placed in.

Whittaker and the five kingdoms. Photography source: National Academy of Sciences: Robert H. Whittaker (1920—1980) – A Biographical Memoir by Walter E. Westman, Robrt K. Peet and Gene E. Likens.

With the dawn of molecular studies around 1970, significant differences were found inside the Prokaryotes, regarded, for example, to the cell membrane structure. Based on those studies, Carl Woese divided Prokaryota in Eubacteria and Archaeobacteria, emphasizing that the differences between those two were as high as the ones between them and the eukaryotes. This later gave rise to a new higher classification of life in three domains, Bacteria, Archaea and Eukarya.

Woese and the three domains. Photo from Photo from News Bureau – University of Illinois, given by IGB (Institute for Genomic Biology).

By the end of the 20th century, Thomas Cavalier-Smith, after intense study of protists, created a new model with 6 kingdoms. Bacteria and Archea were put together in the same kingdom, called Bacteria. Protists were divided in two kingdoms: (1) Chromista, including Alveolates (Apicomplexa, parasitic protozoa like Plasmodium; Ciliates and Dinoflagellates), Heterokonts or Stramenopiles (brown algae, golden algae, diatoms, water moulds, etc) and Rhizarians (like Radiolaria and Foraminifera), among others; and (2) Protozoa, including Amoebozoa (amoebas and slime moulds), Choanozoa (choanoflagellates) and a set of flagellated protozoa called Excavata. Glaucophytes, red and green algae were classified inside the kingdom Plantae.

Cavalier-Smith and his two new kingdoms. Photo from Department of Zoology – University of Oxford.

From the 21th century on, a phylogenetic approach to classify living beings has gained strength. After a lot of molecular analyses using different genes, the real evolutionary relationship among Eukaryotes is still not clear. However, the following groups are supported by most phylogenetic trees:

(1) Archaeoplastida (or Plantae): glaucophytes (Glaucophyta), red algae (Rodophyta) and green plants and algae (Viridiplantae)

(2) Chromalveolata: Stramenopiles or Heterokonta, haptophytes (Haptophyta), cryptomonads (Cryptophyta) and Alveolata.

(3) Rhizaria: Foraminifera, Radiolaria and some amoeboid protozoa

(4) Amoebozoa: amoebas and slime moulds

(5) Opisthokonta: animals, fungi, choanoflagelates

(6) Excavata: many flagellate protozoa. This group, however, isn’t as well supported as the other ones.

The current (maybe not so) well-established groups of organisms

So, as we can see, the Eukaryotes’ case is yet to be solved, but we hope that further molecular studies will help us understand better how the tree of life branches.

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Baldauf, S. L. et al. 2000: A Kingdom-Level Phylogeny of Eukaryotes Based on Combined Protein Data. Science 290, 972-977.

Cavalier-Smith, T. 2004: Only six kingdoms of life. Proceedings of the Royal Society B 271, 1275-1262.

Rogozin, I. B. et al. 2009: Analysis of Rare Genomic Changes Does Not Support the Unikont–Bikont Phylogeny and Suggests Cyanobacterial Symbiosis as the Point of Primary Radiation of Eukaryotes. Genome, Biology and Evolution 1, 99-113.

Wikipedia. Kingdom (Biology). Available on-line in: <en.wikipedia.org/wiki/Kingdom_(biology)>. Acess on December 5th, 2011.


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