Category Archives: Bacteria

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.

deinococcus_radiodurans

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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References:

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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Friday Fellow: Witch’s Jelly

ResearchBlogging.orgby Piter Kehoma Boll

I wonder how many people can say they have a bacterium that reminds them of their childhood. Well, at least I can say that I have.

When I was a boy and started to know about the amazing world of living beings that fill our planet, I spent most of my time outdoors looking at every small corner of the backyard and nearby woods in search for interesting lifeforms. And one that always caught my attention was a strange brownish green gelatinous mass that appeared on the ground in the rainy season.

nostoc_commune

Have you ever found something like that on the ground? Photo by flickr user gailhampshire.*

At first I thought it was some species of green alga, but was unable to identify the species. Many years later I finally found out what it is, a colony of cyanobacteria called Nostoc commune and commonly known as star jelly, witch’s butter, witch’s jelly and many other names. It is found worldwide, from the tropics to the polar regions.

As in other cyanobacteria, the witch’s jelly is formed by a colony of unicellular organisms connected in chains. Those are embedded in a gelatinous matrix of polysaccharides that gives the colony its jelly appearance.

nostoc_commune

Chains of Nostoc commune in the matrix of polysaccharides seen under the miscroscope. Photo by Kristian Peters.**

During dry periods, the colonies of witch’s jelly dessiccate and become an inconspicuous thin layer on the ground. They may remain in this state for decades, maybe centuries, until the ideal conditions come back.

In some places, especially Southeast Asia, the witch’s jelly is consumed as food, being a traditional food in the Chinese Lunar New Year.

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References:

Lipman, C. (1941). The Successful Revival of Nostoc commune from a Herbarium Specimen Eighty- Seven Years Old Bulletin of the Torrey Botanical Club, 68 (9) DOI: 10.2307/2481755

Tamaru, Y., Takani, Y., Yoshida, T., & Sakamoto, T. (2005). Crucial Role of Extracellular Polysaccharides in Desiccation and Freezing Tolerance in the Terrestrial Cyanobacterium Nostoc commune Applied and Environmental Microbiology, 71 (11), 7327-7333 DOI: 10.1128/AEM.71.11.7327-7333.2005

Wikipedia. Nostoc commune. Available at: < https://en.wikipedia.org/wiki/Nostoc_commune >. Access on September 19, 2016.

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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_aphidicola

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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Reference:

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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Friday Fellow: Taq

by Piter Kehoma Boll

It’s time for us to start to look at the tiny little creatures living with us in this world. We haven’t featured any bacterium yet, so here comes the first one, the magnificent Taq!

Taq stands for Thermus aquaticus, the bacterium’s scientific name. It was initially discovered in hot springs of the Yellowstone National Park, but certainly no one could guess how it would impact science as a whole.

The Great Fountain Geyser in Yellowstone National Park is located near the place where Taq was first found. Photo by Paul Kordwig.*

The Great Fountain Geyser in Yellowstone National Park is located near the place where Taq was first found. Photo by Paul Kordwig.*

Usually with a small rod shape less than 1 µm in diameter and up to 10 µm in length, Taq can also reach more than 200 µm in length when acquiring a filament shape. Living in hot springs all around the world, it thrives at about 70°C. It produces its own food via chemosynthesis by oxydizing inorganic elements in the environment, but it can also associate with some cyanobacteria living in the same habitat to obtain food from their photosynthesis.

Taq under the microscope. The scale corresponds to 1µm. Photo by Diane Montpetit.

Taq under the microscope. The scale corresponds to 1µm. Photo by Diane Montpetit.

But what impact did it have in science? Well, because it lives in such high temperatures, Taq’s proteins need higher temperatures to denature, so they are useful to perform biochemical processes in high temperatures, such as in DNA amplification.

PCR (polymerase chain reaction) is a process used for amplifying short segments of an organism’s DNA. It needs to be performed in high temperatures in order to denaturate the DNA chain so that the primers can align. Primers are very short modified DNA fragments that determinate the beginning and the end of the segments that one wants to amplify. Amplifying a DNA segment means producing a large amount of copies of that segment. The problem in earlier PCRs was that the high temperatures needed to denaturate the DNA also denature the enzyme that produces the copies, called DNA polymerase. As a result, there was a need to add enzyme after every cycle of thermal denaturation. The DNA polymerase of Taq, called Taq polymerase, can resist the high temperatures of denaturation, so that it needs to be added only once.

Thanks to Taq polymerase, DNA amplification has become a much more efficient process, accelerating researches in molecular biology.

Sometimes revolution beginns with the tiniest things.

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References:

Brock, T. D. 1997. The value of basic research: discovery of Thermus aquaticus and other extreme thermophiles. Genetics, 146(4): 1207-1210.

Wikipedia. Thermus aquaticus. Available at: <https://en.wikipedia.org/wiki/Thermus_aquaticus&gt;. Access on January 21, 2016.

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