Small Things Considered

Talmudic Question #147

by Bernie Strauss
CRISPR-cas9 supposedly has its antecedents in an immune type mechanism to protect bacteria from virus infections. How does this discovery fit with the Luria-Delbrück demonstration that resis­tance develops as a result of spontaneous mutation rather than being induced by infection? Of course, it is possible that both mecha­nisms operate but I haven't seen the question discussed... Read more →

Old Enzymes Tell Stories

by Elio
Offhand, what can you say about the enzymes of the earliest cells? Surely, a few things pop up, for example, they were fewer in number and probably simpler than the ones we have now. They must have had fewer frills than the modern ones, which tend to have clear-cut tastes for substrates and... Read more →

Curioser and Curioser

by Elio
Curious indeed is an organism called Kakabekia barg­hoorn­ia­na. It is known to exist both as an ancient fossil and as a present-day cultivable creature. Just as curious is that it has been shuttled across the great biological divide, now to apparently having landed firmly in the eukaryotic camp. However, there still seems to be... Read more →

tRNA Chop Shop: Retrotransposons Beware

by Jamie Henzy
Vertebrate genomes are teeming with sequences from retroviruses that have infected the cells of the germ line over the course of evolution. Known as endogenous retroviruses (ERVs), the vast majority of these once fierce foes have been defanged by mutations that make them incapable of expressing viral proteins, let alone infectious particles. Read more →

Thinking About Science

by Roberto
One of the features I most treasure of the nearly fifty years I have been involved in science has been the capacity to take time and simply think. Call it a privilege, call it a luxury; I call it a necessity. Read more →

TWiM #158: The bottom line

Prokaryotic viral DNA in mammalian brain, and how diarrhea is beneficial, by clearing enteric pathogens. Read more →

A Fascination with Caves

by Elio
Caves captivate everybody. They are totally unlike our usual landscape, bewildering and challenging in design. No wonder that they attract casual visitors and explorers alike. Among the latter, we count speleomicrobiologists who search such secluded environments for unusual microbiota. The subject is well developed and even the topic of specialized meetings. But do not think that a cave is just a cave... Read more →

Accidental Complexity

by Christoph
You may wonder why you read the same motto twice in a week in STC but there's a reason. I will follow up Merry's recent post, her lucid description of in silico  and in vivo  experiments demonstrating that evolution can achieve complexity by small incremental steps if they confer... Read more →

Evolutionary Ways

by Merry Youle
Evolution skeptics point to complex biological features as evidence that the amazing intricacy of the biological world could not be the product of blind mutation. The de novo  creation of such com­­plexity, they argue, would require far too many coordinated mutational changes before the new form provided any fitness benefit. Thus, evolution simply cannot explain such apparent leaps. Evo­lutionists, beginning with Darwin, and... Read more →

Of Terms in Biology: Zoospore

by Elio
Forget about everyday spores, by which most microbiologists mean the endospores of Bacillus, Clostridium, and a few other bacteria. Zoospores are motile asexual spores made by some protists, fungi, and bacteria that actively travel and propagate their species. They are distinctly not resting structures. In the eukaryotic microbes, zoospores come in several varieties,... Read more →