ld condenser  (Carl Zeiss)

Journal: bioRxiv

Article Title: Directional Matching of Swimming Polarity Provides a Competitive Advantage During Bacterial Magneto-Aerotaxis

doi: 10.64898/2026.01.09.698624

Figure Lengend Snippet: To study aerotactic band formation, cultures were adjusted to the same optical density and loaded into glass microcapillaries. Capillaries were sealed at one end to establish a unidirectional oxygen gradient and examined by dark-field microscopy under both NF (A) and SF (B) settings. NF and SF cultures were precultured in uniform magnetic fields oriented parallel and antiparallel to the oxygen gradient, respectively. GMF cultures were incubated in the ambient geomagnetic field, ZF cultures in zero field. Aerotactic band intensity profiles and dark-field micrographs shown correspond to the 180-min time point, when aerotactic bands had stabilized; imaging settings were kept constant across experiments. Arrows indicate magnetic field ( ) direction; gradient-filled triangles indicate oxygen gradient direction. Peak intensity (from intensity profiles) was used as a proxy for the number of cells within the aerotactic band. Intensity profiles represent the mean ± standard error of the mean (SEM) from n = 3 independent experiments. Scale bars: 50 µm (apply to all images; shown only in the leftmost images).

Article Snippet: The microscope was equipped with a Nikon S Plan Fluor ELWD 20× DIC N1 objective (NA 0.45), a Nikon dark-field condenser (NA dry 0.80 - 0.95), and a pco.edge 4.2 sCMOS camera (PCO).

Techniques: Microscopy, Incubation, Imaging

Journal: bioRxiv

Article Title: Directional Matching of Swimming Polarity Provides a Competitive Advantage During Bacterial Magneto-Aerotaxis

doi: 10.64898/2026.01.09.698624

Figure Lengend Snippet: Δ mamAB cells were pre-cultured and analyzed in microcapillaries using procedures identical to those applied to the wild-type strain. Band intensity profiles (mean ± SEM, n = 3) were determined from dark-field micrographs after 180 min. Unlike the wild type, Δ mamAB cultures showed consistent aerotactic band intensity profiles across all precultivation conditions. Arrows denote the direction of the magnetic field ( ), while gradient-filled triangles indicate oxygen gradient directions. Scale bars: 50 µm (apply to all images; shown only in the leftmost images).

Article Snippet: The microscope was equipped with a Nikon S Plan Fluor ELWD 20× DIC N1 objective (NA 0.45), a Nikon dark-field condenser (NA dry 0.80 - 0.95), and a pco.edge 4.2 sCMOS camera (PCO).

Techniques: Cell Culture

Journal: bioRxiv

Article Title: Directional Matching of Swimming Polarity Provides a Competitive Advantage During Bacterial Magneto-Aerotaxis

doi: 10.64898/2026.01.09.698624

Figure Lengend Snippet: Individual frames from a representative time-lapse recording of wild-type cells using dark-field illumination are shown. The excitation light source for fluorescence imaging (GFP filter set) was activated at 5 s and switched off at 35 s. Blue light (BL) induced a unidirectional movement of cells toward the meniscus, suggesting that phototactic behavior is mechanistically coordinated with aerotaxis. Colored bars indicate the position of the aerotactic band, with each color assigned to a specific location. When the band shifts between time points, the bar color changes accordingly. The movement of the band between two images is visualized by the spatial separation of bars of different colors in the respective frames. Time stamps are indicated in each image. The white arrow shows the direction of the magnetic field ( ), while the colored triangle indicates oxygen gradient direction. Scale bar, 50 µm, in the leftmost image applies to all images.

Article Snippet: The microscope was equipped with a Nikon S Plan Fluor ELWD 20× DIC N1 objective (NA 0.45), a Nikon dark-field condenser (NA dry 0.80 - 0.95), and a pco.edge 4.2 sCMOS camera (PCO).

Techniques: Fluorescence, Imaging