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16 posts tagged with Evolution and microbiology. (View popular tags)
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For Safer Food, Just Add Viruses

In March 2012, inspectors from the U.S. Department of Agriculture uncovered a problem in Elgin, Texas. Beef sausage from a small family-run meat processor appeared to have been contaminated with a nasty bacterium called Listeria monocytogenes. The bug can make people sick and, in rare cases, be deadly. The processor had to recall more than a ton of sausage. It’s the kind of story that strikes terror in the hearts of other sausage peddlers, including Mike Satzow, so he uses phages to keep his small company's sausages safe to eat.
posted by Blasdelb on Oct 1, 2013 - 58 comments

The rise of the tick

With incisor-like claws that can tunnel beneath your skin in seconds, ticks are rapidly establishing themselves as the Swiss Army knife of disease vectors. Carl Zimmer walks into the woods to find out why these tiny beasts appear to be skyrocketing in number – and outsmarting environmental scientists trying to control them with every bite.
posted by Blasdelb on May 2, 2013 - 79 comments

Woese once said of himself and his work that when a wise man points out the moon, only a fool looks at the finger. Let us all be fools if just for a moment .

Microbiology's Scarred Revolutionary(PDF), Carl Woese (pron.: /ˈwoʊz/), a biophysicist and evolutionary microbiologist whose discovery 35 years ago of a “third domain” of life in the vast realm of micro-organisms altered scientific understanding of evolution, died on Sunday at his home in Urbana, Ill. He was 84. [more inside]
posted by Blasdelb on Jan 2, 2013 - 26 comments

Deciphering the Tools of Nature’s Zombies

Deciphering the Tools of Nature’s Zombies: The ability of parasites to alter the behaviour of their hosts fascinates both scientists and non-scientists alike. One reason that this topic resonates with so many is that it touches on core philosophical issues such as the existence of free will. If the mind is merely a machine, then it can be controlled by any entity that understands the code and has access to the machinery. This special issue of The Journal of Experimental Biology highlights some of the best-understood examples of parasite-induced changes in host brain and behaviour, encompassing both invertebrate and vertebrate hosts and micro- and macro-parasites. Full issue annotated inside: [more inside]
posted by Blasdelb on Dec 9, 2012 - 13 comments

Evolution of Multicellularity In Lab Yeast

In just a few weeks single-celled yeast have evolved into a multicellular organism, complete with division of labour between cells. This suggests that the evolutionary leap to multicellularity may be a surprisingly small hurdle. More from Scientific American blogs. [Full Text PDF of the Publication of Note] [more inside]
posted by Blasdelb on Nov 9, 2012 - 18 comments

The players in a mutualistic symbiosis: insects, bacteria, viruses, and virulence genes.

One of the many problems farmers of various kinds of legumes need to deal with is the pea aphid. They reproduce incredibly fast and live by sucking the sap out of the plants, an electron micrograph of one in action. However, while they are terrifying parasites of legumes, they have their own yet more horrific parasites, a parasitoid wasp. Here is a really nice close up picture of one doing its thing, a video of the act, and here is a brain meltingly horrific video of a dissection of the mummified aftermath 8 days later. Essentially, these wasps deposit their eggs in a pea aphid and the growing larva feeds on it, developing there for about a week, and then consuming the host from the inside out like a Xenomorph. When it’s done, the wasp larva dries the aphid’s cuticle into a papery brittle shell and an adult wasp emerges from the aphid mummy. Legume farmers love them, and you can even order their mummies online these days. However, farmers noticed that the wasps didn't work as effectively on all of the aphids, and so researchers went to work figuring out why. It turns out that all aphids have a primary bacterial endosymbiont living inside their cells, in addition to and just like a mitochondria, and that many have some combination of five other secondary endosymbionts. Interestingly, two of those other five, Hamiltonella defensa and Serratia symbiotica have been shown to confer varying levels of resistance to the parasitoid wasp, allowing the aphid to survive infection. However, it turns out that there is yet one more layer to this story, [more inside]
posted by Blasdelb on Oct 22, 2012 - 50 comments

Virulence-transmission trade-offs and population divergence in virulence

"Why do parasites harm their hosts? Conventional wisdom holds that because parasites depend on their hosts for survival and transmission, they should evolve to become benign, yet many parasites cause harm. Theory predicts that parasites could evolve virulence (i.e., parasite-induced reductions in host fitness) by balancing the transmission benefits of parasite replication with the costs of host death. This idea has led researchers to predict how human interventions—such as vaccines—may alter virulence evolution, yet empirical support is critically lacking." Two papers demonstrate empirical evidence for related models predicting the origin of virulence: [more inside]
posted by Blasdelb on Oct 21, 2012 - 23 comments

The Puzzle of Plastid Evolution

The Puzzle of Plastid Evolution: A comprehensive understanding of the origin and spread of plastids remains an important yet elusive goal in the field of eukaryotic evolution. Combined with the discovery of new photosynthetic and non-photosynthetic protist lineages, the results of recent taxonomically broad phylogenomic studies suggest that a re-shuffling of higher-level eukaryote systematics is in order. Consequently, new models of plastid evolution involving ancient secondary and tertiary endosymbioses are needed to explain the full spectrum of photosynthetic eukaryotes. [Full Text HTML] [Full Text PDF] [more inside]
posted by Blasdelb on Oct 20, 2012 - 8 comments

Mitigating Mutational Meltdown in Mammalian Mitochondria

Mitigating Mutational Meltdown in Mammalian Mitochondria PLoS Biol 6(2): e35. [The PDF, where you can read the paper in its much prettier intended format.]
Mitochondria are remarkable microorganisms. About two billion years ago, their distant free-living ancestors hooked up with a truly foreign lineage of archaebacteria and started a genomic merger that led to the most successful coevolved mutualism on the planet: the eukaryotic cell. Along the way, evolving mitochondria lost a lot of genomic baggage, entrusted their emerging hosts with their own replication, sorted out genomic conflicts by following maternal inheritance, and have mostly abstained from sex and recombination. What mitochondria did retain was a subset of genes that encode critical components of the electron transport chain and ATP synthesis enzymes that carry out oxidative phosphorylation. Because mitochondria house the biochemical machinery that requires us to breathe oxygen, it was first assumed that mitochondrial genes would show very slow rates of molecular evolution. So it was big news almost 30 years ago when mitochondrial DNA (mtDNA) evolution was observed to be quite rapid [1]. How could the genes for a highly conserved and critical function sustain the consequences of high mutation pressure and permit rapid rates of nucleotide substitution between species? Without the benefits of recombination, where offspring can carry fewer mutations than either parent, mutations should accumulate in mitochondrial genomes through the random loss of less-mutated genomes, a process referred to as Muller's ratchet [2,3]. How have mitochondria avoided a mutational meltdown, or at least significant declines in fitness?
Here is a jaw droppingly beautiful 3D animation of what Mitochindria look like in action. [more inside]
posted by Blasdelb on Oct 19, 2012 - 37 comments

Constitutive formation of caveolae in a bacterium.

Constitutive formation of caveolae in a bacterium. [Full Text]
Caveolin plays an essential role in the formation of characteristic surface pits, caveolae, which cover the surface of many animal cells. The fundamental principles of caveola formation are only slowly emerging. Here we show that caveolin expression in a prokaryotic host lacking any intracellular membrane system drives the formation of cytoplasmic vesicles containing polymeric caveolin. Vesicle formation is induced by expression of wild-type caveolins, but not caveolin mutants defective in caveola formation in mammalian systems. In addition, cryoelectron tomography shows that the induced membrane domains are equivalent in size and caveolin density to native caveolae and reveals a possible polyhedral arrangement of caveolin oligomers. The caveolin-induced vesicles or heterologous caveolae (h-caveolae) form by budding in from the cytoplasmic membrane, generating a membrane domain with distinct lipid composition. Periplasmic solutes are encapsulated in the budding h-caveola, and purified h-caveolae can be tailored to be targeted to specific cells of interest.
Elio Schaechter writes in plain English about how fantastically amazing and unexpected the researchers actually pulling this off is, and he also talks about it in more detail in his podcast.
posted by Blasdelb on Oct 18, 2012 - 22 comments

Provirophages and transpovirons as the diverse mobilome of giant viruses

Provirophages and transpovirons as the diverse mobilome of giant viruses
Abstract: A distinct class of infectious agents, the virophages1 that infect giant viruses of the Mimiviridae family, has been recently described. Here we report the simultaneous discovery of a giant virus of Acanthamoeba polyphaga (Lentille virus) that contains an integrated genome2 of a virophage (Sputnik 2), and a member of a previously unknown class of mobile genetic elements3, the transpovirons4. The transpovirons are linear DNA elements of ∼7 kb [kilobases]5 that encompass six to eight protein-coding genes, two of which are homologous6 to virophage genes. Fluorescence7 in situ hybridization8 showed that the free form of the transpoviron replicates within the giant virus factory and accumulates in high copy numbers inside giant virus particles, Sputnik 2 particles, and amoeba cytoplasm. Analysis of deep-sequencing data showed that the virophage and the transpoviron can integrate9 in nearly any place in the chromosome of the giant virus host and that, although less frequently, the transpoviron can also be linked to the virophage chromosome. In addition, integrated fragments of transpoviron DNA were detected in several giant virus and Sputnik genomes. Analysis of 19 Mimivirus strains revealed three distinct transpovirons associated with three subgroups of Mimiviruses. The virophage, the transpoviron, and the previously identified self-splicing introns10 and inteins11 constitute the complex, interconnected mobilome12 of the giant viruses and are likely to substantially contribute to interviral gene transfer.
[Full Text PDF] and two explanations in English [more inside]
posted by Blasdelb on Oct 16, 2012 - 28 comments

Pertussis Epidemic — Washington, 2012

Since mid-2011, a substantial rise in pertussis [Whooping Cough] cases has been reported in the state of Washington. In response to this increase, the Washington State Secretary of Health declared a pertussis epidemic on April 3, 2012. By June 16, the reported number of cases in Washington in 2012 had reached 2,520 (37.5 cases per 100,000 residents), a 1,300% increase compared with the same period in 2011 and the highest number of cases reported in any year since 1942 [Make sure you don't miss Figure 1]. Commentators are already drawing corellations with the fact that Washington State leads the nation in vaccine non-compliance, Washington State's recent cutbacks in public health funding, and increases in the number of uninsured (PDF). [more inside]
posted by Blasdelb on Sep 27, 2012 - 111 comments

0.0001 micromoles of oxygen per liter per year

If we look at how fast they metabolize, it would take them a thousand years just to reproduce themselves. They may be much older than this. There’s no way of knowing.

Microbes found deep under the North Pacific Gyre in 86-million-year-old red clay, potentially millions of years old, force us to rethink the timescales, ranges, and conditions that life can attain. (The main text of the paper is unfortunately paywalled.)
posted by jjray on May 19, 2012 - 34 comments

U.S. Measles Cases Hit 15-Year High

So far this year there have been 118 cases of measles reported in the United States. [more inside]
posted by Blasdelb on May 25, 2011 - 173 comments

The beauty of Molecular, Cell, and Microbiology

There has been a new discipline developing in molecular biology for some time now, Bioanimation! Projects have ranged in size from WEHI's colossal compilation to Harvard Biovision's magnum opus "Inner Life of the Cell" to commercially produced masterpieces to smaller projects by university PIs and enthusiasts. much [more inside]
posted by Blasdelb on Sep 25, 2010 - 29 comments

How did that get there?

The origins of the vagina Only mammals have 'em. Why? (via markmaynard).
posted by klangklangston on Jan 23, 2007 - 36 comments

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