Du 640 spectrophotometer

After treatment, RBCs were centrifuged (1800 rpm, 24 °C, 5 min) and Hb concentration in the supernatant was measured by absorbance at 421 nm (Soret’s band) by spectrophotometry (DU-640 Spectrophotometer Beckman, Brea, CA, USA). The absorbance value at 421 nm of the supernatant derived from similar erythrocytes lysed in distilled water was considered as 100% haemolysis.

Chlorophyll was extracted from the DEX-treated seedlings using an overnight incubation in N,N-dimethylformamide at 4 °C. The chlorophyll contents were calculated as described by [49 (link)], using absorbance data obtained from a spectrometry analysis using a DU640 spectrophotometer (Beckman Coulter, Brea, CA, USA).

Cells were lysed in RIPA Buffer (Boston BioProducts #BP-115), supplemented with protease inhibitor cocktail tablets (Roche, complete mini, #11 836 153 001), and 5 mM NaF. Protein was quantified via Bio-RAD Protein Assay Dye Reagent Concentrate (BIO-RAD, #500-0006) on the Beckman Coulter DU640 Spectrophotometer. Proteins were separated by PAGE and electo-transferred to PVDF membranes (Pall Corporation, BioTrace PVDF 0.45 um, P/N 66543). Membranes were blocked in 5% milk tris-buffered saline with tween 20 (0.1%; TBS-T). Primary antibodies were incubated overnight on a rocker in 5% bovine serum albumin in TBS-T at 1:1000 at 4°C. Membranes were washed the following day 3×, 5′, TBS-T, and incubated with either mouse or rabbit horseradish peroxidase secondary (Cell Signaling #7076S and #7074) for 2 hours room temperature. Proteins were detected via film following the Thermo Scientific's SuperSignal West Pico Chemiluminescent Substrate (Thermo Fisher Scientific, #34087) or Thermo Scientific's SuperSignal West Femto Maximum Sensitivity Substrate (#34095) protocol. The following antibodies were purchased from Cell Signaling Technology: B-Actin (#3700), BiP (#3177), CHOP (#2895), ATF-4 (#11815), Rad51 (#8875), Phospho-Histone H2A.X (#2577), H2A.X (#2595), ATM (#2873), Phospho-ATM (#13050), CHK2 (#6334), Phospho-Chk2 (#2661).

The total neutral carbohydrate content of EPSs of both bacterial strains was measured by modified Dubois et al.51 (link) method. Briefly, 200 μl of 2% EPS aqueous solution (w/v) was mixed with 600 μl of concentrated sulphuric acid. The samples were mixed by vortexing for 10 min followed by addition of 120 μl of 5% phenol aqueous solution (pH 5.6). The mixture was heated at 90 °C for 5 min. After cooling at room temperature for 5 min, the absorption was measured at wave length of 490 nm (DU 640 Spectrophotometer, Beckman).
The protein content was measured by Bradford assay52 (link) using bovine serum albumin (BSA, Merck) as a standard, as well as determined by UV spectrophotometry (Nanodrop ND-1000, Thermo Scientific).

Protein in cell samples was quantified using the Lowry method [40 (link)] with modifications. Initially, the Biuret reaction involves the reduction of copper (Cu²⁺ to Cu⁺) by proteins in alkaline solutions, followed by the enhancement stage, the reduction of the Folin–Ciocalteu reagent (phosphomolybdate and phosphotungstate). After incubation with Folin–Ciocalteu′s phenol reagent, samples were centrifuged for 5–10 s and then absorbance was read at 595 nm using a Beckman DU 640 spectrophotometer (Beckman, Brea, CA, USA). The assay was performed in duplicate for each sample.