We have a new paper on the vertical growth of biofilms.
The primary mode for microbial life on Earth is the biofilm, in which microbes attach to a surface and then reproduce, forming crowded, growing communities. As these colonies develop, they expand horizontally and vertically. While horizontal growth across the surface is well studied, much less is known about the vertical growth of biofilms. This knowledge gap persists despite the importance of vertical growth for determining access to nutrients and oxygen—as well as the fact that vertical growth dynamics represent a fundamental aspect of biofilm physiology.
The lack of clarity about vertical growth dynamics is due in part to the experimental difficulty in measuring the height of a biofilm with sufficient precision over many different time scales in a non-destructive manner. Common techniques for characterizing the height and topographies of colonies lack the requisite resolution (e.g., confocal microscopy), are too slow and potentially destructive (e.g., atomic force microscopy), or do not allow time lapse measurements (e.g., scanning electron microscopy). Thus, we lack an empirical picture of how vertical growth dynamics proceed over short and long time scales. We overcome these barriers using white-light interferometry, which enables us to continuously measure the topography of developing biofilms with nanometer resolution out-of-plane. With this technique, we measured the topographies of a diverse cohort of microbes, including: prokaryotes and eukaryotes, gram positive and gram negative bacteria, anaerobic and aerobic species, different cell sizes and shapes, and differences in extracellular matrix production. Thanks to their unprecedented high spatial and temporal resolution, these measurements enabled us to determine how, exactly, vertical growth proceeds.