Winter 2017 – GoMRI Researcher Interview with Dr. Jacinta Conrad

Dr. Jacinta Conrad. Photo provided by Dr. Conrad.

Dr. Jacinta Conrad. Photo provided by Dr. Conrad.

(From Winter 2017 Newsletter) Dr. Jacinta Conrad from the University of Houston answered a few questions about her RFP-V project on the Role of Microbial Motility for Degradation of Dispersed Oil.

1. Thank you so much for talking with us! Tell us a bit about your research. What are the goals of your RFP-V project?

Our RFP-V project explores the role of bacterial motility on adhesion to oil-water interfaces during the initial stages of biodegradation. This project was inspired by one of the most striking findings from earlier GoMRI work – that oil was disappearing much more rapidly than expected and was thought to be due to bacteria-driven biodegradation. Most work to understand biodegradation had focused on biology, whereas I am a physical scientist – the ocean is a highly heterogeneous environment that features gradients in temperature, pressure, and salt and organic matter concentration. I was interested in trying to understand how the heterogeneity in the ocean environment might affect the ability of bacteria to first find dispersed oil and then consume it. For this project, I recruited three great collaborators: Arezoo Ardekani at Purdue, a computational scientist focused on complex and multiphase fluids (such as a solution of polymers or an emulsion of oil drops suspended in water) who studies the motility of microscale swimmers; Douglas Bartlett at the University of California San Diego Scripps Institution of Oceanography, a microbiologist interested in deep sea microbial diversity and ecology who has studied how microbes adapt to the high pressures and low temperatures of the deep-sea ocean; and Roseanne Ford, a chemical engineer who was one of the first to quantitatively study bacterial chemotaxis (their directed motion toward a chemical attractant) and apply mathematical models. Given the team’s expertise, our goals are to explore four factors that may influence the motion of hydrocarbon-degrading bacteria near or towards dispersed oil and hence affect the rate of biodegradation: chemotaxis; elevated pressure; the presence of dispersants, used in an oil spill scenario to break up oil drops; and viscoelastic fluids and interfaces. We’re hoping that insights derived from these studies can be used to improve predictive models for bacterial biodegradation and inform and enhance future efforts to clean spilled oil.

2. Can you talk more about how information related to the four factors in your proposal might be used in oil spill cleanup efforts?

Our project will measure and characterize fundamental microscale transport properties: how fast bacteria swim or are transported towards oil drops under different conditions (high pressure versus low pressure, as one example), or in the presence or absence of organic matter (which leads to viscoelastic fluid behavior) or at dispersant-coated interfaces (which again leads to viscoelasticity). Our team will systematically test these different factors and incorporate these measurements into models to predict microbial motility and (ultimately) relate motility to the rate at which bacteria degrade oil. We have hypothesized that this information is essential for improving models to predict the rate of natural biodegradation in very different physical settings; for example, to predict the rate of degradation in the Arctic as compared to the Gulf of Mexico. In turn, we expect that better understanding of the rate at which bacteria will degrade oil will suggest strategies used by humans in oil spill cleanup efforts. For example, if in the presence of organic matter bacteria move very slowly toward oil drops, then this may suggest that biodegradation will occur at a reduced rate and more active intervention is needed to clean oil. (This is a speculation only! I would welcome thoughts and suggestions from other GoMRI researchers here).

3. What is your background and how did you get involved with this kind of work?

Eclectic! My undergraduate degree is in mathematics. My Ph.D. is in soft matter physics; as a graduate student, I studied the non-equilibrium phase behavior of suspensions of microscale colloidal particles. Finally, I was a postdoc in a materials science department and studied the flow and transport of colloidal suspensions. I started working with bacteria at the very end of my postdoc, in collaboration with a faculty member (Gerard Wong, now at the University of California Los Angeles) – he had done work on the structure of bacterial membranes and was interested in looking at near- surface bacterial motility, whereas I had experience in imaging and tracking thousands of micron-sized particles over time. Surprisingly, these kinds of high- throughput methods had not been applied to bacteria, and so we published several papers on the motility of bacteria near surfaces using methods from soft matter physics.

When I started my faculty position in chemical engineering, I wanted to understand how the near- surface motility of bacteria was altered by the surface properties – this question has strong relevance for designing antifouling surfaces and for controlling biofilm formation but requires skills and methods from multiple disciplines. My group used materials science methods to make and characterize solid surfaces and applied our bacteria-tracking algorithms to identify how motility and adhesion were affected thereon. Our GoMRI project is a natural extension of this work – now we are looking at bacterial motility near the interface between two liquids (i.e., between oil and water) rather than a solid and a liquid.

4. What are some of the most significant or exciting findings so far from your RFP-V project?

Although we’ve just gotten up to full staffing, I nonetheless want to highlight some early accomplishments. Arezoo published our project’s first paper in Physical Review Letters last year, in which she and her graduate student showed that the effects of fluid elasticity can be very different for a suspension of micron-sized swimmers than for a single swimmer — for a certain swimming mechanism, the elasticity of the fluid can cause the swimmers to aggregate. This result is significant because physicists are currently very interested in understanding why and how organisms move collectively (examples include swarming or flocking), and Arezoo is one of the first to study how fluid properties affect collective behavior. Doug has collected twenty-three different strains of bacteria that can degrade oil and is testing them for motility and chemotaxis at elevated pressures. This will be one of the first studies to look at these processes at pressures characteristic of the deep ocean. Roseanne is developing a mathematical model to predict how bacteria will move in response to multiple different hydrocarbon stimuli; in parallel, she is building a microfluidic device that will allow her to test this model. Finally, my group has made a simplified model of an oil spill using microfluidics – we create oil drops of uniform size and stabilize them with different surfactants. We’ve just started looking at how different strains of bacteria adhere to these drops – but we see differences between adhesion by oil-degrading and non-oil-degrading strains in our preliminary experiments.

5. If funding were not an issue, what would you add to your project?

An ocean voyage to collect microorganisms from oil spills or oil seeps :-) – but mostly because I think it would be an interesting experience! More seriously, most of the experiments that we have proposed are focused on behavior of bacteria at the microscale – it would be both interesting and practically relevant to design an experiment or simulation that would try to probe the consequences of the microscale properties at larger scales. Similarly, I would love to examine multispecies microbial consortia – in terrestrial biofilms, there are well-known examples of competing or cooperating microbes. Do hydrocarbon-degrading bacteria compete or cooperate to move towards and attach to oil- water interfaces? And does this depend on the local microenvironment?

6. Your group is involved in education and outreach activities; visit Dr. Conrad’s website for more information! Have you done any outreach using the science from your RFP-V project? If so, please tell us more about it!

Yes! Our overarching goal is to improve scientific literacy on topics related to our RFP-V proposal and specifically to oil spill remediation and to microbial motility. So far, teams from Purdue, Virginia, and Houston have incorporated their GoMRI science into outreach events. Arezoo and her students at Purdue have worked with the Women in Engineering program at Purdue to teach high school students about challenges in collecting spilled oil and, more broadly, about how microbes move and self-propel through viscous fluids. Roseanne and her students at Virginia, working with their Center for Diversity in Engineering, used the concept of oil spill remediation to introduce high school juniors and seniors to the theory and practice of engineering. Roseanne developed a wonderful demonstration that contrasts the efficacy of physical (skimmers, booms, absorbents) versus chemical (dispersant) strategies to clean spilled oil. Finally, I’ve incorporated my GoMRI work into two University of Houston public outreach efforts. UH Energy, a cross-cutting, university-wide initiative, sponsors a table of scientific demonstrations at the Houston Earth and Energy Day Festivals. These events are hosted by the city of Houston and open to the public, free of admission. My first GoMRI-related outreach activity was a very simple demonstration of how dispersants work at the Earth Day program in the spring; inspired by Roseanne, we added a physical oil- spill cleanup activity at the Energy Day in the fall. We continue to look for new forums in which to talk about our science and to reach different constituencies.

[Back to the Winter 2017 Newsletter]