V. fischeri JB10 was grown in marine broth to exponential phase and then transferred (1%) to a defined minimal medium (Studer et al., 2008). Cultures were grown at 28°C and 200 rpm in 250 mL shake flasks with a working volume of 50 mL for 8 h. Treatments were added at 8 h and exposure/growth continued for 4 h. At 12 h of total growth, 2 mL of cells were harvested by centrifugation at 2000 × g (5 min). Cells were treated with 2 mg/mL lysozyme in TE buffer for 10 minutes and then homogenized with a needle and syringe. RNA was extracted with PureLink RNA Mini Kit (Ambion) and on-column DNA digestion was performed with PureLink PCR Micro Kit (Invitrogen). qPCR was performed on a BioRad CFX96 Real Time System with a C1000 Thermal Cycler. Data was analyzed by the Livak method (ΔΔCt) and fold changes were determined by using 2−ΔΔCt.
Primers were designed for luxR and luxA with NCBI's Primer-BLAST. Primer sequences for luxA were ATCCCCATCTTCGTGAACGG and ACAGAACATGGCCACGACAT. Primer sequences for luxR were CGTGGGCGAGTGAAGGAAAA and TGGCGCCAGTTAAAATTGCT. Primer sequences for the 16S rRNA gene were GTTTGATCATGGCTCAGATTG and CTACCTTGTTACGACTTCACC (Hoffmann et al., 2010). The 16S rRNA gene was used as the reference gene. All primers were ordered from Integrated DNA Technologies (Coralville, Iowa). Genomic DNA from V. fischeri JB10 was amplified with the primers and sequenced by Selah Genomics (Columbia, SC) to check the accuracy of the primers.