Tuning and Assessing Bacterial Predation Efficiency in Complex Environments

Predatory bacteria prey on a range of other bacterial species and are poised to serve as important biocontrol agents. For example, the bacterial predator to be investigated with this award, Bdellovibrio bacteriovorus (Bb), is known to degrade microbial biofilms, including antibiotic resistant ones, plays a role in wastewater treatment, and shows potential to curb infections in animals and plants, earning it the title of “living antibiotic”.

Understanding both Bb’s hunting strategy and life cycle are prerequisites toward exploiting Bb as a biocontrol agent. What is more, the ability to leverage bacteria as antibiotics has clear advantages as compared to small molecule antibiotics as bacterial predators provide us with many more tunable knobs to help potentially activate, modulate, or turn off their hunting at will.

In recent work, the investigators explored how Bb use fluid motion around themselves as they propel through their fluid environments to passively push themselves towards surfaces where their prey, such as the bacterial species E. coli, are in abundance. This motion in search for its prey requires the predator to expend energy and begs the following four questions:

1) How do Bb use cues from their surroundings to determine whether it is worth expending their limited resources to swim in order to locate prey?

2) Under starvation conditions and other extreme environments, how do Bb, depending on chance encounters with their prey to replicate, adapt their speed to efficiently locate their prey? In other words, do they swim at constant speed or alternate between rapid and slow motion to explore their environment while preserving their energy resources as much as possible?

3) How does confining Bb in tight environments (as would be the case if Bb were hunting in a crevasse or a crack characteristic of the environments they live in) amplify the fluctuations in the levels of predator? In other words, can we maintain a steady population of Bb in an environment if we eventually use Bb as a biocontrol agent downstream or will their populations always undergo major variations?

4) How can we determine the rate at which these bacterial predators hunt in environments (such as within living animals) where we cannot see them? In other words, how can we monitor their predation efficiency when we cannot use microscopes to observe Bb hunting for prey as Bb may be hunting too deep within a sample in regions inaccessible to microscopes?

Put together, answers to these questions form the basis of this award's goals. The longer term national interest of this work is therefore the ability to tune bacterial predators poised to become resilient, and adaptable, tools in wastewater treatment, the fight against harmful bacteria, both natural and introduced by terrorist threat, as well as to degrade microbial biofilms.

This award will also contribute to STEM education. In Arizona, minority students overwhelmingly begin their academic path by attending community and other public colleges which are ∼70% minority. While minority students are slightly more interested in STEM fields than their white peers, this interest doesn’t translate into college graduation in STEM.

To help ASU’s large incoming community college demographic acclimate to STEM, we propose a two-week Summer Data Analysis Program (SDAP). SDAP will cover a broad range of topics on the treatment of data and uncertainty and is directly inspired by the data-driven efforts of this project. Student attendees of SDAP will be recruited from programs already aimed at integrating community college recruits and other minority students into the university community (such as ASU’s SUNDIAL Program and IDEAs program).

Students will be offered a full stipend over the 2 week bootcamp to help reduce economic disincentives associated with cutting back on summer work to attend SDAP. Each day in SDAP will consist of two parts: mornings will include a 2-3 hr tutorial followed by assigned computational projects (on laptops provided by the PI). ASU’s College Research and Evaluation Services Team (CREST) will help evaluate both short and long term impact of the project.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.