Monday Micro – extremophiles & 50 shades of … immunity!

By Siouxsie Wiles 11/03/2013


In last week’s Monday Micro I mentioned horizontal gene transfer (HGT), the process by which bacteria acquire new genes from other microbes in their environment. HGT is one of the primary ways that genes for antibiotic resistance are able to spread between different bacteria. It is also how plenty of bacteria pick up genes for things like toxins which help them cause disease. But it’s not all bad. A few years ago, a team of scientists reported in the journal Nature that the gut microbes of Japanese people had picked up the ability to digest the unique carbohydrates present in seaweed through HGT from a seaweed chomping microbe called Zobellia galactanivorans (1).

This week, in a paper just out in the journal Science, Gerald Schönknecht, Wei-Hua Chen and colleagues report that HGT is the secret to the success of the extremophile Galdieria sulphuraria, an algae that is able to thrive in hot, acidic springs, like those found in Iceland or the Yellowstone National Park. When the researchers sequenced the genome of G. sulphuraria, they found it had acquired at least 5% of it’s protein-coding genes through HGT (2). These genes give G. sulphuraria the ability to detoxify heavy metals, deal with high concentrations of salt, and to consume a variety of unusual food sources.

Galdieria sulphuraria growing on a rock in an  Icelandic hot spring near Reykjavik.  CREDIT: Christine Oesterhelt
Galdieria sulphuraria growing on a rock in an Icelandic hot spring near Reykjavik.
CREDIT: Christine Oesterhelt

And finally, also leading on from last weeks description of the CRISPR system, Michael Criscitiello and Paul de Figueiredo have written a piece in the open access journal PLOS Pathogens challenging the dogma that is the black and white existence of the innate and adaptive immune systems*. Playfully nodding to the Fifty Shades phenomenon, their piece is entitled Fifty Shades of Immune Defense, and lays out the immune system as a continuum (3).

Different immune mechanisms with adaptive properties are being discovered in species originally considered to only possess innate immunity. Taken from (3)
Different immune mechanisms with adaptive properties are being discovered in species originally considered to only possess innate immunity. Taken from (3)

*We are generally taught that the immune system has two parts to it: the innate immune response, in which cells recognise and respond to pathogens in a generic way, but can’t confer long-lasting protection to the host, and the adaptive immune response, in which cells respond in a specific way, and confer long lasting protection to the host.

References:
1. Hehemann, J., Correc, G., Barbeyron, T., Helbert, W., Czjzek, M., & Michel, G. (2010). Transfer of carbohydrate-active enzymes from marine bacteria to Japanese gut microbiota. Nature, 464 (7290), 908-912 DOI: 10.1038/nature08937
2. G. Schonknecht, W.-H. Chen, C. M. Ternes, G. G. Barbier, R. P. Shrestha, M. Stanke, A. Brautigam, B. J. Baker, J. F. Banfield, R. M. Garavito, K. Carr, C. Wilkerson, S. A. Rensing, D. Gagneul, N. E. Dickenson, C. Oesterhelt, M. J. Lercher, A. P. M. Weber. Gene Transfer from Bacteria and Archaea Facilitated Evolution of an Extremophilic Eukaryote. Science, 2013; 339 (6124): 1207 DOI: 10.1126/science.1231707
3. Criscitiello MF, de Figueiredo P (2013) Fifty Shades of Immune Defense. PLoS Pathog 9(2): e1003110. doi:10.1371/journal.ppat.1003110