Electrophoresis equipment

DNA fragments bearing the stsR ORF (372 bp), stsR promoter (338 bp), stsR p1 (154 bp), stsR p2 (184 bp), multiple sugar-binding, ABC transporter promoter, mannitol-specific promoter, lactose-specific promoter, maltose ABC transporter promoter, and mannose-specific promoter were generated by PCR using the primers listed in Supplementary Table S1. The sugar transporter promoters contained the binding regions with StsR predicted using bioinformatical method. The 44 bp fragment stsR p3, containing the palindrome sequence, and the stsR p3mut, in which the palindrome sequence was mutated, were labeled with FITC and annealed with their reverse complement sequence. Amplified DNA fragments were extracted from agarose gels. Then, 20 pmol of DNA fragments were incubated with increasing concentrations of purified StsR in 10 μL of binding buffer (50 mM Tris/HCl, 10 mM NaCl, 0.5 M Mg/acetate, 0.1 mM EDTA, and 5% (v/v) glycerol) for 30 min. The DNA-protein complexes were resolved by electrophoresis on 4 % (w/v) non-denaturing polyacrylamide gels in 0.5× TBS buffer using the BioRad electrophoresis equipment. Gels for genes without FITC were dyed with Ethidium Bromide (EtBr) (Thermo Scientific^TM) for 20 min. These gels were scanned by a phosphorimager and images were analyzed densitometrically using the Scion Image software (Azure Biosystems C400, United States).

Agarose was from Invitrogen (Thermo Fisher Scientific, Waltham, MA, USA), and electrophoresis equipment was from Bio Rad (Hercules, CA, USA). A 0.3% w/v Agarose gel was created by dissolving Agarose in a 1:8 ratio of TAE buffer with a pH of 8.0. Once the gel had solidified, 10 µL samples were applied to each lane, and the gel was electrophoresed at 120 V for 20 min using the same running buffer. Following the electrophoresis run, images of the gel were captured using an Apple iPhone 11 camera to document the positions of the bright red bands derived from AuNPs.