English: The 100 µm length scale in the microbial ocean
100 µm is a useful yardstick in the microscale world of marine bacteria. While environmental processes affecting microbial ecology often unfold at larger scales, as exemplified by the phytoplankton bloom depicted in blue hues in the background, it is the microscale that most immediately affects the life of marine and aquatic bacteria. Characteristic distances among bacteria, whether motile (flagellated cells) or non-motile (circular, non-flagellated cells), as well as between microbes and viruses occur over scales on the order of 100 µm, here denoted as ‘O(100 µm)’. So, too, do gradients of dissolved organic matter (yellow-green coloration and grey contour lines) emanating for example from phytoplankton (diatom on the top right), to which motile bacteria can respond by directional swimming (thick dashed trajectory). Processes such as turbulence (not depicted) also contribute to spatial heterogeneity at O(100 µm) scales, further increasing the prominence of this scale in microbial ecology