iBiology Videos

A mile or more below the surface of the ocean, microbes dominate the deep sea life. In this seminar, Dr. Julie Huber describes her research to better understand the microbial ecosystem in the rocky crust below the ocean floor. She begins the series by describing how reactions between seawater and the elements in ocean rocks enable chemosynthetic ecosystems to exist in the deep sea. She then introduces us to the tools scientists use to study microbial deep sea life below the ocean floor.

Hastings hypothesizes that luciferases, and thus bioluminescence, evolved as a mechanism to protect bacteria from oxidative damage as the Earth’s atmosphere became oxygenated 2.5 billion years ago.

In the late 1960s, Hastings was studying bioluminescence in the marine bacteria Vibrio fischeri. He and his post-doc, Kenneth Nealson, discovered that bacteria could communicate by secreting a small peptide. This allowed V. fischeri to sense the concentration of their fellow bacteria and, when the density reached a critical level, turn on bioluminescence. Hastings named this process autoinduction, also known as quorum sensing. Quorum sensing has since been shown to play a critical role in bacterial behaviors such as toxin production and biofilm formation.

In his second part, Hasson explores how the ability of the storyteller to be coupled to and shape the neural responses of listeners is used as a tool to share memories across brains. Furthermore, the studies reveal the tight connections between remembering and imagining and expose the ways by which the storyteller’s perspective shape the audience point of view.

How does your brain change with each story that you hear? How can storytelling shape your memories? In this talk, Dr. Uri Hasson explores how brain activity is shared between listeners of the same story, and how those shared neural responses are coupled to and shaped by the neural activity in the storyteller’s brain. In his studies, Hasson observed higher coupling between listener’s and storyteller’s neural activity as a function of the ability of the listener to understand the story. As Hasson explains, efficient communication occurs when the storyteller’s and listeners’ brain responses are coupled.

Dr. Leland Hartwell started his scientific career studying a fundamental question in biology: how do cells know that they have everything they need in order to divide. By studying the morphology of temperature sensitive mutants in yeast, Hartwell identified many of the key regulators of the cell cycle. In this conversation, Hartwell talks to Dr. Sue Biggins about his Nobel Prize winning discoveries and the experiments that led to his seminal findings.

In his second talk, Haber explains in greater detail the molecular steps that take place during the repair of a DNA double strand break.  It turns out that the process of mating type switching in S. cerevisiae requires site-specific cutting and repair of a yeast chromosome and this is an excellent model for studying DNA DSB repair.  Working in this system and using techniques such as Southern blots, PCR and chromatin immunoprecipitation, Haber’s group was able to identify the proteins and enzymatic steps in DNA repair.

Dr. Haber begins his talk by explaining that broken chromosomes frequently arise during the process of DNA replication. In healthy cells, these double strand breaks (DSBs) are repaired by homologous recombination, an orderly process that preserves the genome.  If the homologous recombination machinery is impaired, DNA truncations, translocations, and deletions often occur, resulting in genome instability and cancer. All mechanisms of homologous recombination have one common principal; the broken ends of the DNA are repaired by base pairing with a sequence that is identical or nearly identical and acts as a template for repair enzymes.  Haber explains the general principles of homologous recombination and its critical role in maintaining genome stability.

In his second presentation, Haas shares an example of how cryocrystallography has aided structure-based drug design.

In his postdoctoral studies, David Haas set out to reduce radiation damage to protein crystals during X-ray crystallography. In 1970, he published a paper on his invention of macromolecular cryocrystallography – freezing crystals to extend their lifetime in the X-ray beam. The widespread use of the synchrotron beginning in the 1970s made cryo-cooling essential, and today nearly all protein crystal structures deposited in the international Protein Data Bank use this method.