Uv vis 2802pc spectrophotometer

C. acetobutylicum strain DSM 1731 and its derivatives (Additional file 1: Table S1) were grown in Reinforced Clostridial Medium (RCM) anaerobically at 37 °C [33 (link), 34 (link)]. All E. coli strains were grown aerobically in Luria–Bertani (LB) broth at 37 °C with vigorous shaking at 220 rpm [35 (link)]. E. coli JM109 was employed for gene cloning. Shuttle vector was methylated by transforming E. coli ER2275 bearing plasmid pAN1. Ampicillin (100 μg mL⁻¹) and erythromycin (50 μg mL⁻¹) were used for screening and maintaining of plasmids whenever necessary. Cell growth was monitored by measuring the optical density at 600 nm (OD₆₀₀) with a UV/Vis 2802PC spectrophotometer (Unico, New Jersey, USA).

A list of bacterial strains and plasmids used in this study is presented in Table 2. C. acetobutylicum DSM 1731, as used in our previous studies15 (link)31 (link), was used as the wild-type strain. E. coli JM109 was used for vectors construction. E. coli TOP10 bearing the methylating plasmid pAN2 was used for methylation of plasmids. E. coli strains were grown aerobically at 37 °C with shaking at 220 rpm in liquid LB medium or on LB medium supplemented with 1.5% agar. C. acetobutylicum strains were grown anaerobically at 37 °C in reinforced clostridial medium (RCM)32 . pMTL00817 (link) was used as the backbone to construct different gene insertion plasmids. Ampicillin, erythromycin and chloromycetin were added at concentrations of 100, 50 and 30 μg/mL, respectively, when necessary. All strains were stored in 15% glycerol at −80 °C. Cell growth was monitored by measuring the absorbance at 600 nm (OD₆₀₀) with a UV/Vis 2802PC spectrophotometer (Unico, NJ, USA).

Plasmon resonance absorption (PRA) spectra were measured using a UNICO UV/VIS2802PC spectrophotometer. Transmission electron microscopy (TEM) images were obtained by a Hitachi H600 transmission electron microscope operated at 100 kV. AuNPs samples for TEM measurements were prepared by placing a drop of colloidal solution on carbon-coated copper grid and then dried at room temperature. A WH-3 miniature vortex mixed instrument (Shanghai Hu Xi Analysis Instrument Factory Co., Ltd, Shanghai, China) was used to mix the samples thoroughly.