K2hpo4

The Campylobacter jejuni strains shown in S1 and S2 Tables were isolated and characterized by Luangtongkum et al. [22 (link)], and were stored at -80°C in 80% Mueller Hinton broth (MHB: Oxoid, UK) with 20% glycerol. They were then grown on Mueller-Hinton agar (MHA; Oxoid, UK) at 42°C under microaerobic conditions (5% O₂, 10% CO₂, 85% N₂) for 24 h. The second passage from each culture was used in the experiments. When necessary, MHA was supplemented with selective medium (SR01176; Oxoid, UK) and growth medium (SR0232E; Oxoid, UK) (MHA-SS), 30 mg/L kanamycin (Merck, Germany), or 4 mg/L ciprofloxacin (Merck, Germany). The Vibrio harveyi BB170 reporter strain [19 (link),23 (link)] was grown on autoinducer bioassay (AB) medium at 30°C, which contained 17 g/L NaCl (Merck, Germany), 12.3 g/L MgSO₄ (Merck, Germany), 2 g/L casamino acids (BD Bacto; Fisher Scientific), 1 mM K₂HPO₄ (Kemika, Croatia), 0.1 mM L-arginine (Sigma Aldrich, Germany), and 1% (v/v) glycerol (Kemika, Croatia).

Campylobacter jejuni NCTC 11168 and C. jejuni 11168ΔluxS [19 (link),27 (link)] provided by Klančnik A. and Bezek K. (University of Ljubljana) were stored at −80 °C in 20% glycerol and 80% Mueller–Hinton broth (MHB; Oxoid, UK). They were grown on Mueller–Hinton agar (MHA; Oxoid, UK) at 42 °C under microaerobic conditions (5% O₂, 10% CO₂, 85% N₂) for 24 h. The second passage from each culture was used in the experiments. When necessary, MHA was supplemented with selective medium (SR01176; Oxoid, UK) and growth medium (SR0232E; Oxoid, UK) (MHA-SS) or 30 mg/L kanamycin (Merck, Darmstadt, Germany). The Vibrio harveyi BB170 reporter strain [27 (link),28 (link)] was grown on autoinducer bioassay (AB) medium at 30 °C, which contained 17 g/L NaCl (Merck, Darmstadt, Germany), 12.3 g/L MgSO₄ (Merck, Darmstadt, Germany), 2 g/L casamino acids (BD Bacto, Fisher Scientific, Hampton, NH, USA), 1 mM K₂HPO₄ (Kemika, Zagreb, Croatia), 0.1 mM L-arginine (Sigma Aldrich, Steinheim am Albuch, Germany), and 1% (v/v) glycerol (Kemika, Zagreb, Croatia).