*4.11. Growth and Attachment on Shrimp Shells*

Six millimeter diameter circular disks were prepared from the exoskeleton of Vannamei shrimps (description in Supplementary Material). Bacterial cultures (WT and mutants) were grown in 5 mL MB in 50 mL flasks at 25 ◦C, 200 rpm overnight. The cultures were diluted to 104 CFU/mL in artificial seawater (3% sea salt, Sigma, S9883) and incubated with or without shrimp shells in 1.5 mL Eppendorf tubes. Samples of the suspension were taken after 0, 2, 5, 7, 10 days incubation and plated after serial dilution. The tubes were sonicated five minutes at 50/60 Hz in an ultrasonic bath (Emmi D20 Q, EMAG, Mörfelden-Walldorf, Germany) and vortexed 10 s to remove bacteria attached to the shrimp shells [54]. A suspension of cells with known cell counts was subjected to the same sonication and

cell counts done after sonication, demonstrating that this procedure did not reduce cell counts. Then serial dilutions and colony counts were done to determine cell densities. The experiment was done in biological duplicate.
