MNPs bind to the surface of E. piscicida without affecting its viability. (a) Schematic showing the labeling of E. piscicida with MNPs and their separation from unlabeled bacteria by magnetic capture. (b and c) Size distribution (b) and TEM micrograph (c) of MNPs in the supernatant of a diluted, sonicated, and centrifuged commercial stock solution. n = 312 MNPs. (d) Log10 total colony-forming units (CFU) before (input, blue) and remaining after (output) magnetic capture of E. piscicida incubated with MNPs (MNP+, orange) or phosphate-buffered saline (PBS) (MNP−, gray). (e) Percentage of initial input CFU remaining after magnetic capture of MNP-labeled (MNP+) or mock-labeled (MNP−) E. piscicida from panel d. (f) Cumulative frequency of the number of MNPs labeled to the surface of bacterial cells. Labeled MNPs exceeding 50 are grouped into one bin. n = 102 bacteria. (g) Representative TEM micrograph of an E. piscicida cell with five MNPs labeled to its surface. (h) Log10 viable CFU sampled over 2 h of incubation of E. piscicida with MNPs (orange) or PBS (gray). Data points in panel d are from three independent experiments, each performed with three biological replicates. Shown in panel e are the mean ± s.d. of the means from three independent experiments. Data points in panel h are from three biological replicates at each time point. Scale bars: (c) 500 nm; (g) 1 µm. Data were analyzed using two-tailed unpaired Student’s t-test (d, e, and h). P < 0.05 are displayed and otherwise marked as ns.
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