MICRObial wettability by particle Contact Angle Measurements

The MicroCAM project explores how bacteria and other microorganisms stick to surfaces, especially where water meets oil, like in polluted water or industrial fluids. This sticking process is often the first step in forming biofilms, which are dense communities of microbes that can either help us (e.g., in cleaning up oil spills) or cause problems (such as infections or equipment fouling). Understanding how and why microbes attach to surfaces is essential for improving technologies and addressing health and environmental challenges. A significant factor in how microbes attach is how their outer surface interacts with water—whether it "likes" water (hydrophilic) or "repels" it (hydrophobic). Surprisingly, despite a century of research, scientists still struggle to measure this property accurately. Existing measurement techniques do not give reliable results. They often rely on indirect observations of large numbers of bacteria, without being able to measure what happens at the level of individual cells at the surface they attach to. These outdated methods cannot tell us whether microbes attach using their cell bodies or at a distance through extended appendages and polymers on their surfaces. MicroCAM aims to fix this by developing a new way to directly look at single microbial cells and measure how they interact with the border between oil and water. This will be done using a highly specialized form of electron microscopy, which allows us to "freeze" the interface and then take detailed images of where and how individual microbes attach. From these images, we can determine how much of each cell is in the oil or water, and from that extract how water-repellent or hydrophobic its surface is. We will extend this method to directly image bacteria that bind to oil surfaces through appendages at a distance. In addition, MicroCAM will explore how microbes change their surface behavior by releasing substances called biosurfactants. These natural chemicals can make the microbes more likely to stick to oily surfaces. We will investigate how much these secretions change how bacteria attach, and how this compares to their natural surface properties. This will help separate what is due to the microbe itself and what is due to its secretions. MicroCAM will give us a more accurate picture of how microbes interact with surfaces, especially poorly researched interfaces between oil and water. This will lead to better ways of controlling harmful biofilms in hospitals and industry, and also improve the use of bacteria in helpful processes like waste treatment and environmental cleanup. The project applies physics to answer questions that have long puzzled biologists and biotechnologists, and it will provide powerful new tools for future research and applications.