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.
“AbGradCon (Astrobiology Graduate Conference) provides a unique setting for astrobiologically-inclined graduate students and early career researchers to come together to share their research, collaborate, and network. AbGradCon 2018 marks the 14th year of this conference–each time in a different place and organized by a different group of students, but always with the original charter as a guide.”
“These meetings have been wildly successful both when connected to AbSciCon, and as stand-alone conferences. Since it is organized and attended by only graduate students, post docs, and select undergraduates, AbGradCon is an ideal venue for the next generation of career astrobiologists to form bonds, share ideas, and discuss the issues that will shape the future of the field. Take a look at the AbGradCon 2017 conference website to see what’s happened in the past.”