4.2 plus camera

M. primoryensis were streaked onto a marine broth plate without antibiotic. A single colony of bacteria was used to inoculate marine broth (10 ml) and cultured at 4°C without shaking for 4 to 5 days until reaching an optical density (OD_600nm) of 0.2 to 0.5 in a ThermoFisher Scientific Multiskan Go spectrometer (21 (link)). Both F. cylindrus and C. neogracile were grown as previously described (48 (link), 49 (link)). Thus, diatoms were grown in F/2 medium at 4°C with light and shaking. Bacteria cultured to an OD_600nm of 0.2 to 0.4 were incubated with diatoms overnight at 4°C with light and shaking before being visualized with an Andor Zyla 4.2 Plus camera paired with an Olympus IX83 inverted fluorescence microscope modified with a custom-built cooling stage (50 (link)).

Electron microscopy images were collected using a Hitachi S-3000N scanning electron microscope (SEM) (Queen’s University, Canada). Bacteria and diatom mixtures were prepared for SEM as previously described (47 ). Briefly, 1 ml of bacterial diatom sample was pelleted by centrifugation. The pellet was dehydrated by gradually increasing the ethanol concentration to 15, 50, and 100%. The pellet was resuspended in 100% ethanol and diluted 10-fold with 100% ethanol. Next, an aliquot (200 μl) of the diluted sample was dried onto an aluminum foil for 10 min at 90°C. The dried samples were cut into approximately 2-cm squares and visualized by SEM. Light and fluorescence microscopy images were taken with an Andor Zyla 4.2 Plus camera paired with an Olympus IX83 inverted fluorescence microscope.