Category Archives: microbe

Melaninized fungi use ionizing radiation for energy

Blogging about Peer-Reviewed ResearchA recent paper in PLoS One entitled Ionizing Radiation Changes the Electronic Properties of Melanin and Enhances the Growth of Melanized Fungi describes some pretty amazing results that have gotten some press lately. The lead author, Dr Dadachova, spoke on NPR’s Science Friday last week about how melanized fungi are able to use ionizing radiation for energy as seen in the enhanced growth in their experiments.

While this is the first report of such as result, the fact that innovation occurs wherever there is free energy is not surprising. As mentioned by Arturo Casadevall this story in the spring when he was gave a seminar at Berkeley, marine organisms that live near undersea hydrothermal vents have been able to photosynthesize the infrared light emitted from the vent. He discussed the radiation utilization of melanized fungal work at the end of his talk, and said that it has been an epic process to get it published — that this work had been in review for four years at several high profile journals, but I guess that it was controversial enough to not be accepted there. I guess Nature and Science get it now since they wrote news briefs…

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Social Slime Mold

Slime molds are interesting organisms that receive surprisingly little attention. Take the case of Dictyostelium discoideum, a single-celled amoeba that, when starved, will aggregate with other D. discoideum amoeba cells in the neighborhood to create a motile, multicellular structure known as a slug. Eventually the slug differentiates into a reproductive structure, with some individuals making a long stalk and others producing spores. In other words, some individuals help other reproduce but do not reproduce themselves.

D. discodium lifecycleBut why form a slug? Why would a single celled organism decide to cooperate with other, genetically different individuals, particularly when it may provide no direct passage of its genes? The evolutionary benefits of kin relationships aside, previous work has shown that slugs do provide multiple benefits to the population as a whole. Continue reading Social Slime Mold

Gut check

Ever wonder what goes on in a cow’s multi-chambered stomach? Probably not. I did think about it a little more after a trip to a teaching farm during grad school where we saw a cow with a fistula. This hole provides access to the cows stomach so that samples can be drawn of the community living in the gut and understand how the bovine stomach can digest the recalcitrant cellulose of grasses.

Of course all kinds of lovely things live in the dark, anaerobic environment. In fact there is a delicately balanced community of species. When cows are fed corn instead of grass this affects the rumen acid content and allows pathogenic E. coli like O:157 to survive. So far I don’t seen any JGI proposal for sequencing of the gut communities of rumens, but maybe that should be proposed.

Rumen fungi are probably not on your keyword list, but these fungi are extremomophiles living in highly anaerobic environment. A paper in Microbiology details an analysis of the genome of the anaerobic fungus Orpinomyces.

Experimental cooperative evolution

Blogging about Peer-Reviewed ResearchA paper in Nature this week describes how a few mutations can alter the interactions between species in a biofilm from competitive to cooperative system. This is a great study that goes from start to finish on studying community interactions, looking at an evolved phenotype, and understanding the genetic and physiological basis for the adaptation.

Acinetobacter sp. and Pseudomonas putida were raised in a carbon-limited environment with only benzyl alcohol as the carbon source. Acinetobacter can processes the benzyl alcohol, while P. putida is unable to. Acinetobacter takes up the bezyl alcohol and secretes benzoate that P. putida can then use as a carbon source. The research group propagated these in chemostats and looked at different starting concentrations of the organisms. They found that evolved P. putida had a different morphology and did several experiments to determine the relative fitness of the derived and ancestral genotype.

They went on to also map the mutations in P. putida and found two independent mutations in wapH (I think this is the right gene)—a gene involved in lipopolysaccharide (LPS) biosynthesis. They then engineered the ancestral strain to have a mutation in P. putida and found the rough colony phenotype morphology indistinguishable from the strain derived from experimental evolution.

There are various evolutionary and niche adaptation implications arising from this study. One application to mycology is to how lichens evolved in that an algael cell and a fungal cell must communicate and cooperate.

Tripartate symbioses with fungi

Ants, fungi, and bacteria

I have to admit that I am fascinated by co-evolution of symbiotic and mutalistic systems. A review by Richard Robinson gives an overview. A great example is the mutalism between ants and fungi where the ants cultivate the fungi for food. There are more layers to the relationship as a fungal parasite (Escovopsis) attacks the cultivated fungi, and a bacteria. Several researchers have studied the coevolution of these studies including Ulrich Mueller and Cameron Currie. Currie and Mueller have published several great studies describing the patterns of coevolution and the nature of the cooperation.
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