Collaborative Research: Evolution of Early Metabolism: Carbon Fixation, Anaerobic Respiration and ROS Detoxification in the Anaerobic Vent Bacterium, Thermovibrio ammonificans

Rutgers University New Brunswick, New Brunswick NJ

Investigators

Abstract

Bacteria that can live without oxygen (anaerobes) and survive in hot environments (thermophiles) inhabit extreme environments such as deep-sea hydrothermal vents that resemble the early Earth. These modern-day bacteria co-evolved with our planet, and as a result, these organisms carry both ancestral and more recently acquired genes and can be used as models to reconstruct the evolution of microbial processes, including how these bacteria obtained energy and the carbon needed to grow. To gain insight into these processes Thermovibrio ammonificans, an organism that inhabits deep-sea hydrothermal vents, will be studied. Integrated into these studies will be outreach activities for middle and high school students. Lesson plans will be developed and used in after-school programs, in professional training programs for K-12 educators, and informal activities such as the 4-H Summer Science Program. Anaerobic chemolithoautotrophic bacteria inhabiting deep-sea hydrothermal vents are critically important from an ecological standpoint; by fixing carbon dioxide of geothermal/magmatic origin in the absence of oxygen, they are the primary producers in these environments. This project will provide insight into the evolution of early and acquired bacterial metabolism by leveraging different types of culture approaches (batch and continuous cultures) with comparative genomic analyses of the model organism, Thermovibrio ammonificans. Experiments will address whether an early Earth ancestor of T. ammonificans was originally a hydrogen-oxidizing, sulfur-reducing bacterium that could form needed organic substances from simple inorganic substances (such as carbon dioxide). With the gradual rise of oxygen in the atmosphere, more efficient terminal electron acceptors became available and this bacterium acquired genes that increased its metabolic flexibility - e.g., the capacity to use nitrate as well as carbon dioxide - while retaining ancestral metabolic traits (such as the ability to live without oxygen and survive high temperatures). The mechanisms of carbon fixation, anaerobic respiration and detoxification of reactive oxygen species in T. ammonificans will be investigated using a combination of transcriptomic, proteomic and biomass carbon stable isotope analyses. This study will provide invaluable information on gene expression in T. ammonificans grown under chemical and nutrient conditions that reflect, as closely as possible, those encountered in its natural environment and will provide insight on gene regulation and expression in response to changing environmental conditions. This study is anticipated to help reconstruct the ancestral and acquired metabolic traits of this deep-branching organism and shed light into the emergence and evolution of autotrophic carbon fixation pathways.