R. F. Rosenzweig – Virtual Seminar – May 22
ExplOrigins & Astrobiology Primer Community Review
Speaker: Frank Rosenzweig
Affiliation: Georgia Institute of Technology, Department of Biological Sciences
Date: Friday, May 22, 2020 – 10:00am
Location: BlueJeans
Host: ExplOrigins Group
Title: Microbial adaptation to chronic nutrient limitation
M. Herron – Virtual Seminar – May 15
ExplOrigins & Astrobiology Primer Community Review
Speaker: Matt Herron
Affiliation: Georgia Institute of Technology, Department of Biological Sciences
Date: Friday, May 15, 2020 – 10:00am
Location: BlueJeans
Host: ExplOrigins Group
Informal talk: Multicellularity in green algae
M. Khademian – Virtual Seminar – May 8
ExplOrigins & Astrobiology Primer Community Review
Speaker: Maryam Khademian
Affiliation: University of Illinois, Department of Microbiology
Date: Friday, May 8, 2020 – 10:00am
Location: BlueJeans
Host: ExplOrigins Group
Title: Oxidative Stress in Anoxic Habitats
Abstract: Bacteroides thetaiotaomicron was examined to determine whether its obligate anaerobiosis is imposed by endogenous reactive oxygen species or by molecular oxygen itself. Previous analyses established that aerated B. thetaiotaomicron loses some enzyme activities due to a high rate of endogenous superoxide formation. However, the present study establishes that another key step in central metabolism is poisoned by molecular oxygen itself. Pyruvate dissimilation was shown to depend upon two enzymes, pyruvate:formate lyase (PFL) and pyruvate:ferredoxin oxidoreductase (PFOR), that lose activity upon aeration. PFL is a glycyl-radical enzyme whose vulnerability to oxygen is already understood. The rate of PFOR damage was unaffected by the level of superoxide or peroxide, showing that molecular oxygen itself is the culprit. The cell cannot repair PFOR, which amplifies the impact of damage. The rates of PFOR and fumarase inactivation are similar, suggesting that superoxide dismutase is calibrated so the oxygen- and superoxide-sensitive enzymes are equally sensitive to aeration. The physiological purpose of PFL and PFOR is to degrade pyruvate without disrupting the redox balance, and they do so using catalytic mechanisms that are intrinsically vulnerable to oxygen. In this way the anaerobic excellence and oxygen sensitivity of B. thetaiotaomicron are two sides of the same coin.
M. Schaible – Seminar
04/17/2020: ” Semester Review and Suggestions for the Future” Micah Schaible (GT) [BlueJeans]
J. Lawrence – Seminar
4/10/2020: “Microbial Diversity and Biosignatures: An Icy Moons Perspective” Justin Lawrence (GT) [BlueJeans]
A. Simpson – Seminar
04/03/2020: “Convergent Evolution and Astrobiology” Anna Simpson (GT) [BlueJeans]
M. Osburn – Seminar
3/13/2020: “Journey to the Center of the Earth: Habitability and Geobiology of Distinct Subsurface Realms” Maggie Osburn (Northwestern)
T. Roche – Seminar
3/6/2020: “Prebiotic Plausibility: Pursuing Parsimony vs Precluding Possibilities” Tyler Roche (GT)
L. Williams – Seminar
2/28/2020: “RNA and Protein: A Match Made in the Hadean” Loren Williams (GT)