Penn Dental Medicine Researchers Show that Bacterial Biofilms and Human Cities Share Structured Growth Patterns

PHILADELPHIA, March 26, 2020 /PRNewswire/ -- Microbiologists have long adopted the language of human settlement to describe how bacteria live and grow. A new study in Nature Communications uses super-resolution imaging and a computational algorithm to confirm the aptness of this metaphor: As individual bacteria grow into a biofilm (such as dental plaque), their colonization and expansion patterns mirror those seen in the growth of cities.

This new perspective could inform efforts to promote the growth of beneficial microbes, or kill undesirable biofilms with therapeutics, according to senior author Hyun (Michel) Koo, a professor in the Department of Orthodontics at Penn Dental Medicine. Koo partnered with Geelsu Hwang, assistant professor of in the Department of Preventive and Restorative Sciences, and Amauri Paula, a visiting professor from the Department of Physics at the Universidade Federal do Ceará in Brazil, on the research.

"Usually when people study biofilms, they analyze a single cell in a narrow field of view as it multiplies, becomes a cluster, and starts to build up," says Koo. "We followed multiple individual cells simultaneously to identify patterns at large length-scales."

To do so, Hwang developed powerful time-lapse imaging tools, employing confocal laser scanning microscopy capable of analyzing surface topography and tracking bacteria populating at different locations in three dimensions over time. Paula worked to build an algorithm that could analyze the behavior of the cell growth.

The team used Streptococcus mutans, an oral pathogen that forms dental plaque, bound on a tooth enamel-like material and followed individual microbes over several hours. The growth patterns they found were indeed reminiscent of the formation of urban areas. Some individual "settlers" grew, expanding into clusters of bacteria ("villages") and merging to form "cities" and "megacities."

The researchers were surprised to find that only about 40% of the original bacteria grew into colonies, and that rather than repelling each other when they met, microcolonies often merged together and further developed as a unit.

They confirmed that the gluelike secretion known as extracellular polymeric substances enabled bacteria to pack together tightly and form structurally organized communities.

Koo cautions against taking the urbanization metaphor too far. "We're not saying these bacteria are anthropomorphic," he says. "But this 'bird's eye view' perspective of biofilm growth gives us a multiscale, multidimensional picture of how they grow and expand." Read more >>

Contact: Beth Adams, [email protected]

SOURCE Penn Dental Medicine