Pseudomonas spp. cultures were spotted (5 µL) onto Petri dishes containing Congo red agar (10 g/L tryptone, 40 µg/mL Congo red (Sigma), 15 µg/mL Coomassie brilliant and 1.5% agar) and incubated at 15 °C for 72 h. The interaction of Congo red with EPS produced the appearance of red colonies (biofilm producers). EPS production was also detected in the swimming assay performed in LB supplemented with 40 µg/mL Congo red and 15 µg/mL Coomassie brilliant, as described above.
Congo red
Manufactured by Merck Group
Sourced in United States, Germany, India, France, Italy, Sao Tome and Principe, China, Poland, United Kingdom
Congo red is a synthetic dye used as a laboratory reagent. It is a dark red crystalline powder that is soluble in water and certain organic solvents. Congo red is commonly used as an indicator in various analytical and diagnostic applications, particularly in the identification of amyloid proteins.
Automatically generated - may contain errors
Lab products found in correlation
Calcofluor white, by Merck Group (31 mentions)
Thioflavin t, by Merck Group (21 mentions)
Sodium chloride (nacl), by Merck Group (16 mentions)
Hydrochloric acid (hcl), by Merck Group (15 mentions)
Sodium hydroxide (naoh), by Merck Group (13 mentions)
Coomassie brilliant blue, by Merck Group (10 mentions)
Dimethyl sulfoxide (dmso), by Merck Group (10 mentions)
Sodium dodecyl sulfate (sds), by Merck Group (10 mentions)
Sucrose, by Merck Group (9 mentions)
Ethanol, by Merck Group (9 mentions)
Calcofluor white cfw, by Merck Group (7 mentions)
Coomassie brilliant blue g 250, by Merck Group (7 mentions)
Methylene blue, by Merck Group (7 mentions)
Crystal violet, by Merck Group (6 mentions)
Rhodamine b, by Merck Group (6 mentions)
Calcofluor, by Merck Group (6 mentions)
Ferric chloride, by Merck Group (6 mentions)
Methyl orange, by Merck Group (6 mentions)
Dulbecco modified eagle medium (dmem), by Thermo Fisher Scientific (6 mentions)
Tunicamycin, by Merck Group (6 mentions)
403 protocols using congo red
1
Assessing Pseudomonas Biofilm Formation
2
Quantifying Pseudomonas EPS Production
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Pseudomonas spp. cultures, selected for motility assays, were spotted (5 μL) onto Petri dishes containing Congo red agar (10 g/L tryptone, 40 μg/mL Congo red (Sigma), 15 μg/mL Coomassie brilliant and 1.5% agar) and incubated at 15°C for 72 h. The interaction of Congo red with EPS produced the appearance of red colonies (biofilm producers). EPS production was also detected in swimming assay performed in M63 supplemented with 40 μg/mL Congo red and 15 μg/mL Coomassie brilliant, as described above. In order to quantify EPS, selected cells (1 × 103 CFU/mL) were cultivated in M63 broth for 72 h. At the end of incubation each culture was centrifuged at 10397 × rpm for 5 min at room temperature, and the supernatant was discarded. The pellets were resuspended in 1 mL of 40 μg/mL Congo red and incubated with vigorous shaking at 15 min intervals of time for at least 90 min at room temperature. The samples were again centrifuged (9600 × rpm, 5 min) and the OD of the supernatants was measured at 490 nm. A standard curve was constructed by measuring the OD490 nm of Congo red at 40, 20, 10, 5, and 2.5 μg/mL; un-inoculated medium was used as a blank and as diluent for the standard curve.
3
Evaluating Curli Production in E. coli Strains
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Curli production was determined in the strains by Congo Red assay as previously described (Zhou et al., 2013 (link)). Congo Red agar plates was made by preparing yeast extract and Casamino acid agar (YESCA; 1 g L-1 yeast extract, 10 g L-1 casamino acids, 20 g L-1 agar) and after autoclaving, filter sterilized Congo Red (50 μg ml-1 final concentration; Sigma) and filter sterilized Brilliant Blue G (10 μg ml-1 final concentration; Sigma) were added. E. coli strains were grown in LB broth and incubated at 37°C overnight. Five microliters of the overnight culture of each strain was spotted on the center of a thick Congo Red agar plate. The plates were incubated at 28°C for 48 h. Images were captured with Canon CanoScan 9000F MKII Flatbed Scanner at 600 dpi.
4
Immunohistochemical Detection of Amyloid-Beta
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Five sections spanning the entire brain were stained with a 6E10 antibody (1:1000, Biolegend) or Congo red (Sigma) to detect Aβ plaques in the brain (the 6E10 antibody was used to stain compact and diffuse Aβ; Congo red was used to stain for compact Aβ). CAA was manually assessed in Congo red‐stained hippocampal sections under a microscope (Wilcock et al., 2006 (link)).
5
Cellulose Production Detection in Bacteria
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Cellulose production was detected by growing bacteria on LB agar supplemented with 200 μg/mL calcofluor (Sigma-Aldrich, Milan, Italy). Plates were incubated at 37 °C for 2–4 days. Colonies were visualized under a 366-nm light source [40 (link)]. Congo red binding was detected by growing bacteria on LB agar supplemented with Congo red (40 μg/mL; Sigma-Aldrich, Milan, Italy).
6
Streptococcus suis Biofilm and Host Cell Interactions
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The wild-type SS2 strain ZY05719 is an isolate from Jiangsu Province and was grown in Todd-Hewitt broth (THB) medium (Difco, BD, Franklin, NJ, USA) at 37°C on a gently rocking shaker. The bacteria were cultured to the mid-exponential phase and were collected in media for the experiment using planktonic cells. SS2 biofilms were identified with Congo Red Agar composed of 3% THB, 0.08% Congo Red (Sigma Aldrich, St. Louis, Mo, USA), 0.5% glucose (Biosharp, Anhui, China) and 1.5% agar powder. Neutrophils from the bones of mice were cultured in RPMI 1640 (Gibco-BRL, Thermo Fisher Scientific, Waltham, MA, USA) supplemented with 2% heat-inactivated fetal bovine serum (FBS) at 37°C in 5% CO2. RAW264.7 cells (ATCC® TIB-71™) were purchased from the American Type Culture Collection (ATCC) and were cultured in Dulbecco's modified Eagle's medium (DMEM; Wisent, Canada) supplemented with 10% FBS at 37°C in 5% CO2.
7
Visualizing Macrophage TLR9 and Curli
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To visualize TLR9 and curli, TLR9-GFP expressing macrophages were seeded at 1x106 per well in a 48-well dish upon circular coverslips (Fisher, 1254581 coated with poly-L-lysine (Sigma, P8920). After attachment, macrophages were incubated with 75 nM LysoTracker Blue DND-22 (ThermoFisher, L7525) and 10 μg/mL Congo red-labeled curli-DNA complexes for 10 minutes at 37°C and 5% CO2. To label curli with Congo red, 1 mg/mL purified curli-DNA fibers were incubated with 50 μg/mL Congo red (Sigma, C6767) for 15 minutes protected from light. The curli fibers were pelleted by centrifugation at 12,000 rpm for 5 minutes. The pellet was washed with 500 μL sterile PBS five times, and then resuspended in 1 mL of sterile PBS. After 10 minutes of stimulation, cells were washed with sterile PBS three times and visualized using a Leica SP5 Microscope with a TCS confocal system using sequential scanning to prevent auto-fluorescence from multiple lasers. LysoTracker Blue DND-22 was visualized at an excitation wavelength of 373 nm and emission of 422 nm, and Congo red-labeled curli was visualized at an excitation wavelength of 514 nm and emission of 650–750 nm.
8
Yeast Plasmid Shuffling Assay for Gea1 and Gea2 Mutants
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Yeast plasmid shuffling assays were used to assess in vivo sufficiency of Gea1 and Gea2 mutants (Gea2ΔC is residues 1-766). Double-deletion strains (gea1Δgea2Δ and gea1Δgea2Δarf1Δ) were maintained by a copy of GEA2 on a URA3 plasmid. LEU2 plasmids carrying the mutant constructs were introduced, and cells were cultured overnight in –Leu media. Cells were plated at threefold dilutions onto synthetic complete media or media with 5-fluoroorotic acid (5-FOA) and incubated at 30°C for two days before imaging.
To test for sensitivity to the drug Congo Red, shuffled cells were plated at threefold dilutions onto synthetic complete media containing either 50 or 100 ng/µl Congo Red (Sigma) and incubated at 30°C for 2 d before imaging.
To test for sensitivity to the drug Congo Red, shuffled cells were plated at threefold dilutions onto synthetic complete media containing either 50 or 100 ng/µl Congo Red (Sigma) and incubated at 30°C for 2 d before imaging.
9
Phenotypic Characterization of Mycobacterium smegmatis Mutants
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Msm and its mutant strains were used for growth curve analysis, sliding motility assay, Congo Red assay, and biofilm assay. Bacteria culture were adjusted to an optical density at 600 nm (OD600) of 0.2, and growth curves were obtained from OD600 detected at intervals of 3 h. 2 μL culture of each bacterial strain was dispensed on the medium (LB medium supplemented with 100 μg/mL Congo Red (Sigma) and 20 μg/ml kanamycin, Sauton liquid medium, and 7H9 medium supplemented with 0.3% agar) and then was used for corresponding Congo Red assay, biofilm assay, and sliding motility assay (Zanfardino et al., 2016 (link); Lai et al., 2018 (link)). Cells were incubated at 37°C for 3 days.
10
Screening Cellulose and Curli Fimbriae Production
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Three microliters of overnight culture (from a single colony grown in 5 mL BHI broth) from all strains were dropped on span agar plates (H. Carroux, Germany) with or without sodium chloride (5%) and congo red solution [0.5% congo red (Sigma-Aldrich, Taufkirchen, Germany) and 0.25% coomassie-brilliant-blue (Carl Roth, Karlsruhe, Germany) diluted in ethanol]. Plates were incubated for 5 days at 28°C (Romling, 2005 (link); Richter, 2011 ). Following an initial comprehensive screening to detect differences between WT and PCV strains regarding their cellulose and/or curli fimbriae production, follow-up runs were performed on plates containing and lacking sodium chloride for all strains (Table 2 ). These follow-up runs were repeated six times. Reference strains (AAEC189, Blomfield et al., 1991 (link), IMT26949, and W3110 Hayashi et al., 2006 (link)) were included in all runs for all plates and at all temperatures.
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