# The Role of Fluctuating Environmental Conditions in the Evolution of Bacterial Growth Control

> **NIH NIH F32** · UNIVERSITY OF TEXAS AT AUSTIN · 2020 · $61,850

## Abstract

Research Summary
The rates of population growth for individual bacterial species are partially determined by the permissiveness
of external environmental conditions. Even under the most ideal conditions, however, different species are
capable of dramatically different rates of growth that range from minutes to days. Which genomic features
contribute to this capacity for growth, and how environmental variability constrains and facilitates the evolution
of these features remain largely unknown. Currently, most molecular studies focus on how mutations to
proteins and regulatory sequences affect cellular growth and fitness measured over hours and days.
Evolutionary methods, by contrast, are most powerful when studying long time-scales associated with the
fixation of mutations. The adaptation and evolution of bacterial populations over intermediate time-scales on
the order of weeks, months, and years is thus difficult to study within existing frameworks, and these time-
scales may profoundly influence the evolution of growth rates and associated genomic features.
Here, I will investigate how environmental variability can constrain and facilitate the evolution of gene
regulatory mechanisms. Mathematical models of cellular growth are capable of making informative predictions
about physiological growth under various conditions ranging from nutrient-poor to nutrient-rich environments. I
will extend existing models to consider how the translational and nutritional constraints that they identify may
ultimately arise from—and partially shape—genome sequence evolution. I will use a combination of
mathematical modeling and empirical bioinformatics to investigate how selection for optimal translational
control strategies between different classes of genes may arise according to whether genes are dominantly
expressed during periods of slow- or rapid-growth. To connect these results to evolutionary differences in
growth capabilities between species, I will compile separate databases of maximal growth rates measured in
vitro and in situ to determine how the phenotype of growth capacity has evolved across the bacterial
phylogenetic tree. Finally, I will apply and develop phylogenetic comparative methods to determine the relevant
time-scales for changes in growth strategies between species, and the genomic features that predict (and are
predicted by) these changes.
This project will form the foundation for the continued development of evolutionary methods that explicitly
incorporate cellular growth and growth rate variability across time. Ultimately, understanding the interplay
between cellular growth, environmental variability, and translational regulation will lead to improved strategies
for administering and cycling therapeutics to fine-tune selective pressures on individual proteins, pathways,
and bacterial populations.

## Key facts

- **NIH application ID:** 9991626
- **Project number:** 5F32GM130113-02
- **Recipient organization:** UNIVERSITY OF TEXAS AT AUSTIN
- **Principal Investigator:** Adam John Hockenberry
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $61,850
- **Award type:** 5
- **Project period:** 2019-06-01 → 2021-05-09

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9991626

## Citation

> US National Institutes of Health, RePORTER application 9991626, The Role of Fluctuating Environmental Conditions in the Evolution of Bacterial Growth Control (5F32GM130113-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9991626. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*