{"676605":{"#nid":"676605","#data":{"type":"news","title":"The Geometry of Life: Physicists Determine What Controls Biofilm Growth","body":[{"value":"\u003Cp dir=\u0022ltr\u0022\u003EFrom plaque sticking to teeth to scum on a pond, biofilms can be found nearly everywhere. These colonies of bacteria grow on implanted medical devices, our skin, contact lenses, and in our guts and lungs. They can be found in sewers and drainage systems, on the surface of plants, and even in the ocean.\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003E\u201cSome research says that 80% of infections in human bodies can be attributed to the bacteria growing in biofilms,\u201d\u0026nbsp;\u003Ca href=\u0022https:\/\/physics.gatech.edu\/user\/aawaz-pokhrel\u0022\u003E\u003Cstrong\u003EAawaz Pokhrel\u003C\/strong\u003E\u003C\/a\u003E\u003Cstrong\u003E\u0026nbsp;\u003C\/strong\u003Esays, lead author of a groundbreaking new study that uses physics to investigate how these biofilms grow.\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003EThe paper, \u201c\u003Ca href=\u0022https:\/\/www.nature.com\/articles\/s41567-024-02572-3\u0022\u003E\u003Cstrong\u003EThe Biophysical Basis of Bacterial Colony Growth\u003C\/strong\u003E\u003C\/a\u003E,\u201d was published in\u0026nbsp;\u003Cem\u003ENature Physics\u003C\/em\u003E this week, and it shows that the fitness of a biofilm \u2014 its ability to grow, expand, and absorb nutrients from the medium or the substrate \u2014 is largely impacted by the contact angle that the\u0026nbsp;biofilm\u2019s edge makes with the substrate. The study also found that this geometry has a bigger influence on fitness than anything else, including the rate at which the cells can reproduce.\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003E\u201cThat was the big surprise for us,\u201d says corresponding author\u0026nbsp;\u003Ca href=\u0022https:\/\/yunkerlab.gatech.edu\/\u0022\u003E\u003Cstrong\u003EPeter Yunker\u003C\/strong\u003E\u003C\/a\u003E, an associate professor in Georgia Tech\u2019s\u0026nbsp;\u003Ca href=\u0022https:\/\/physics.gatech.edu\/user\/peter-yunker\u0022\u003E\u003Cstrong\u003ESchool of Physics\u003C\/strong\u003E\u003C\/a\u003E. \u201cWe expected that the geometry would play an important role, and we thought that figuring out exactly what the geometry is would be important for understanding why the range expansion rate, for example, [the rate at which the biofilm spreads across the surface over time] is constant. But we didn\u0027t start the project thinking that geometry would be the single most important factor.\u201d\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003EUnderstanding how biofilms grow \u2014 and what factors contribute to their growth rate \u2014 could lead to critical insights on controlling them, with applications for human health, like slowing the spread of infection or creating cleaner surfaces. \u201cWhat got me excited was this opportunity to use physics to learn about complex biological systems,\u201d Pokhrel,\u0026nbsp;\u003Ca href=\u0022https:\/\/yunkerlab.gatech.edu\/members\/\u0022\u003E\u003Cstrong\u003Ewho is also a Ph.D. student in Yunker\u2019s lab\u003C\/strong\u003E\u003C\/a\u003E, adds. \u201cEspecially on a project that has so many applications. The combination of the importance for human health and exciting research was really intriguing for me.\u201d\u003C\/p\u003E\u003Ch3\u003E\u003Cstrong\u003EA new method\u003C\/strong\u003E\u003C\/h3\u003E\u003Cp dir=\u0022ltr\u0022\u003EWhile biofilms are ubiquitous in nature, studying them has proven difficult. Because these \u201ccities of microorganisms\u201d are comprised of tiny individuals, scientists have struggled to image them successfully.\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003EThat changed in 2015, when Yunker began wondering if\u0026nbsp;\u003Cem\u003Einterferometry\u003C\/em\u003E, a commonly used imaging technique in physics and materials science, could be applied to biofilms. \u201cGiven my background in physics, I was familiar with its use in materials applications,\u201d Yunker recalls. \u201cI thought applying this technique more broadly might be interesting, because we know from decades of physics that surface interfaces contain a lot of information about the processes that create them.\u201d\u0026nbsp;\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003EThe technique proved to be simple, effective, and time-efficient, providing nanometer-scale resolution of bacterial colonies. \u201cIt allows us to essentially get a picture of the topography \u2014 the shape of the surface of the bacterial population \u2014 with super-resolution,\u201d Yunker adds.\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003ELeveraging interferometry, the team began conducting new biofilm experiments, investigating how colonies\u2019 shapes changed over time. Co-first author\u0026nbsp;\u003Ca href=\u0022https:\/\/weitzgroup.umd.edu\/people\/\u0022\u003E\u003Cstrong\u003EGabi Steinbach\u003C\/strong\u003E\u003C\/a\u003E, formerly a postdoctoral scholar in Yunker\u2019s lab and now a scientific research coordinator at the University of Maryland, noticed that every colony had a specific shape when it was small: a spherical cap, like a slice from the top of a sphere, or a droplet of water. It\u2019s a shape that shows up often in physics, and that sparked the team\u2019s interest.\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003E\u201cA spherical cap in physics is very interesting, because it is a surface-minimizing shape,\u201d Pokhrel adds. \u201cI was curious why a biological material was growing in this shape, and we started wondering if there was some physics to it \u2013 perhaps geometry was involved. And that made us think that maybe we could develop a model. And that got me really excited.\u201d\u003C\/p\u003E\u003Ch3\u003E\u003Cstrong\u003EA mathematical mystery\u003C\/strong\u003E\u003C\/h3\u003E\u003Cp dir=\u0022ltr\u0022\u003EHowever, the researchers soon hit a roadblock. \u201cWhile we could see that the colonies were spherical caps at first, they would deviate from that shape as they grew,\u201d Pokhrel says. \u201cAnd the shape that they grew into was difficult to describe with existing spherical cap geometry.\u201d\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003E\u201cThe middle didn\u2019t grow as quickly as it should to keep the spherical cap shape, and we wanted to connect all of this to the range expansion [the rate at which the colony spread across a surface],\u201d Yunker adds. \u201cBut we knew that somehow, geometry was playing a very important role.\u201d\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003EFinally,\u0026nbsp;\u003Cstrong\u003EThomas Day\u003C\/strong\u003E, a former graduate student in Yunker\u2019s lab, now a postdoctoral fellow at the University of Southern California, and one of the authors of the paper, suggested a quirky problem of geometry called the\u0026nbsp;\u003Cem\u003Enapkin ring problem.\u003C\/em\u003E\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003E\u201cAs soon as we started to think about the napkin ring problem, we were able to start developing a mathematical toolkit,\u201d Yunker says, though the solution wasn\u2019t effortless. \u201cWe couldn\u0027t find anyone who\u0026nbsp; had ever looked at a spherical cap napkin ring before, because the application is very rare.\u201d\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003EPokhrel, alongside two co-authors, was responsible for working out the geometry. He discovered that the cells grew exponentially at the edge of the shape, expanding further onto the medium, while the cells in the middle grew upward, creating a shape not unlike an egg in a frying pan \u2014 if the egg white was expanding outwards, while the yolk was only growing taller.\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003EThis was the breakthrough discovery: Because the cells at the middle were only contributing to the biofilm\u2019s height, the team only needed to account for how many cells were at the edge of the biofilm, and the shape they needed to be in to grow and spread.\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003EAfter incorporating their findings into a mathematical model, the team found that the contact angle was the most important factor: the angle that the very edge of the biofilm made when it touched the surface it was growing on. That single geometric quality is even more important to a biofilm\u2019s growth than the rate at which it can reproduce cells.\u003C\/p\u003E\u003Ch3\u003E\u003Cstrong\u003EThe physics-biology connection\u003C\/strong\u003E\u003C\/h3\u003E\u003Cp dir=\u0022ltr\u0022\u003EOverall, the project took more than three years, from conception to publication.\u0026nbsp;\u003Cstrong\u003E\u201c\u003C\/strong\u003EAawaz really made an incredible effort seeing this work through,\u201d Yunker says. \u201cIt was many years and many, many experiments. But the finished product is 100% worth it.\u201d\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003EThe team hopes the research will pave the way for future studies, which could lead to applications like controlling biofilm growth to help prevent infections.\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003E\u201cGoing forward, there are still a lot of research avenues,\u201d Pokhrel says. \u201cFor example, looking at competition experiments between biofilms \u2014 do taller colonies change their contact angle so that they can spread faster? What role does this geometry play in competition?\u201d\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003E\u201cBiology is complex,\u201d Yunker adds. In nature, the surface a biofilm grows on may not be as consistent as a laboratory surface, and colonies may have different mutations or may consist of more than one species. And while the model is based on how biofilms behave in a controlled lab environment, it\u2019s a critical first step in understanding how they may behave in nature.\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003E\u003Cstrong\u003ECitation\u003C\/strong\u003E: Pokhrel, A.R., Steinbach, G., Krueger, A. et al. The biophysical basis of bacterial colony growth. Nat. Phys. (2024). https:\/\/doi.org\/10.1038\/s41567-024-02572-3\u003C\/p\u003E\u003Cp dir=\u0022ltr\u0022\u003E\u003Cstrong\u003EFunding information:\u003C\/strong\u003E This research was funded by the NIH National Institute of General Medical Sciences and NSF Biomaterials\u003C\/p\u003E","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EFrom plaque sticking to teeth to scum on a pond, biofilms can be found nearly everywhere.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"From plaque sticking to teeth to scum on a pond, biofilms can be found nearly everywhere."}],"uid":"36454","created_gmt":"2024-09-06 18:48:57","changed_gmt":"2024-09-06 18:49:39","author":"swilliamson40","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2024-07-09T00:00:00-04:00","iso_date":"2024-07-09T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"674870":{"id":"674870","type":"image","title":"biofilm.jpg","body":null,"created":"1725648543","gmt_created":"2024-09-06 18:49:03","changed":"1725648543","gmt_changed":"2024-09-06 18:49:03","alt":"biofilm","file":{"fid":"258434","name":"biofilm.jpg","image_path":"\/sites\/default\/files\/2024\/09\/06\/biofilm.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/2024\/09\/06\/biofilm.jpg","mime":"image\/jpeg","size":826490,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/2024\/09\/06\/biofilm.jpg?itok=SDxd0Hpo"}}},"media_ids":["674870"],"groups":[{"id":"1292","name":"Parker H. Petit Institute for Bioengineering and Bioscience (IBB)"}],"categories":[{"id":"138","name":"Biotechnology, Health, Bioengineering, Genetics"}],"keywords":[{"id":"187423","name":"go-bio"}],"core_research_areas":[{"id":"39441","name":"Bioengineering and Bioscience"}],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EWritten by \u003Ca href=\u0022mailto:%20sperrin6@gatech.edu\u0022\u003E\u003Cstrong\u003ESelena Langner\u003C\/strong\u003E\u003C\/a\u003E\u003C\/p\u003E","format":"limited_html"}],"email":["sperrin6@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}