Formaldehyde homeostasis and damage repair in a bacterial formaldehyde specialist

PROJECT SUMMARY
Formaldehyde is a naturally occurring metabolite found in all cell types. Although it has been implicated in human
disease including dementia and diabetes, it has also shown to have critical roles in beneficial processes such as
memory formation and purine biosynthesis. In methylotrophic bacteria, one-carbon metabolites such as
methanol can serve as growth substrates in pathways where formaldehyde is an obligate central intermediate.
Due to its high chemical reactivity, formaldehyde balance in these organisms is critical; however, their
formaldehyde stress response systems have remained elusive. EfgA and TtmR are central players of two distinct
systems that modulate formaldehyde resistance and disrupt formaldehyde homeostasis in the methylotroph
Methylorubrum (formerly Methylobacterium) extorquens. EfgA is a newly identified conserved formaldehyde
sensor that halts growth and translation in response to elevated formaldehyde levels. TtmR is a MarR-family
transcription factor that regulates many genes involved in regulation, signaling, and stress response, including
efgA. Our work will characterize the EfgA and TtmR homeostasis systems to understand how cells sense and
respond to formaldehyde levels to prevent otherwise inevitable cellular damage. Specifically, we will employ
unbiased sequencing-based approaches and experimental evolution to home in on the mechanisms of these
systems and define their regulation. Formaldehyde-mediated cellular damage is a readout of the status of
formaldehyde homeostasis; however, the in vivo reactivity of formaldehyde is poorly understood. Our data
suggests that protein damage is the predominant cause of cytotoxicity in M. extorquens. We will use proteomics
approaches to define the impact of formaldehyde on the proteome and identify cellular strategies for
counteracting formaldehyde-induced protein damage. Through this work, we will leverage a model bacterium
that is well adapted to maintain formaldehyde homeostasis to explore the burgeoning field of formaldehyde
regulatory biology. The results from this work will define essential cellular processes and has implications for
analogous homeostasis systems for toxic metabolites. We envision this work will have substantial impacts on
the understanding of how cells sense and regulate formaldehyde levels, how cells navigate and avoid
accumulation of toxic metabolites generally, and how metabolite-specific and global systems of stress response
intersect to provide balanced cellular metabolism and growth.

Grant Number: 5R35GM146904-04
NIH Institute/Center: NIH
Principal Investigator: Jannell Bazurto