Maintained by Robin Tecon, microbiologist and postdoctoral researcher at the Swiss Federal Institute of Technology Zürich. This blog is about bacteria (and other microbes) and the scientists who study them.

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Sunday, January 29, 2012

Since last November, the scientific community has been shaken by what the journal Science has called "a media storm" on H5N1 research. I don't really have an a priori opinion about the potential risks of this research – I am not a virologist, after all – but this is a fascinating controversy which is of importance for microbiologists in general. Science provides us with a special page archiving the news and commentaries related to these events.

It all started with experiments on H5N1 avian influenza virus that were meant to study what mutations can increase its transmissibility in ferrets (commonly used as a model animal for influenza research). Two virologists in different countries – Ron Fouchier in the Netherlands and Yoshihiro Kawaoka in the USA/Japan – have managed to create H5N1 strains that are transmissible between ferrets (and thus, potentially, between human beings) and want to publish their independent results in Science (Fouchier) and Nature (Kawaoka). The question that these researchers are willing to answer is: can H5N1 cause a human pandemia, and if yes, what mutations would allow it to do so? Fouchier argues, for instance, that knowing the mutations will allow the researchers to look for them in the field, thus being proactive against the virus spread.

Saturday, January 21, 2012

In this blog, I use the term ‘bacteria’ (with a lower case),
as a generic term equivalent to prokaryotes (that is, Bacteria and Archaea). In
this I follow the example of the Brock Biology of Microorganisms, a reference
textbook in microbiology (and a wonderful read, by the way).

If you are not familiar with these denominations, here is a
brief recap:

Whitman and his colleagues noted that the actual total
number of bacterial cells had never been assessed, ‘because an estimation of the number of prokaryotes would seem to
require endless cataloging of numerous habitats’. It certainly seemed to me
that way, but they ended up with a convincing estimation after looking for
representative habitats in both aqueous and terrestrial environments. What is
striking is that many habitats that show very high densities of bacteria, such
as, say, animals’ gut (up to 1011 per g of human colon), account for a
negligible fraction of the total. The main crowd is apparently to be found in
subsurface sediments and terrestrial subsurface (probably >95%). Hence, what
is directly accessible to us (plants, animals, soil, oceans, lakes, etc.)
represents a mere 5% of the total bacterial environment. Talking about the tip
of the iceberg…