Triphynel methane dyes are recalcitrant owing to their xenobiotic nature and exhibit high resistance to degradation processes. In the present study, two different bacteria Gram positive “Bacillus cereus” and Gram negative” Pseudomonas earoginosa” isolated from soil samples contaminated with industrial effluent, collected from Jeddah industrial city, Saudi Arabia, were analyzed for Triphynel methane dyes, Malachite Green (MG), and Crystal Violet (CV) biodegradation. The physicochemical parameters such as aeration, incubation periods, adding carbon and nitrogen sources, pH, and temperature affecting the biodegradation of (MG) and (CV) were tested. The maximum (MG) and (CV) degradation was found to be the maximum at 95.2%, 96.3% by B. cereus and P. aeruginosa at shaking conditions after 3 days of incubation. The optimum temperature was 37°C for decolorizing by both bacterial strains. The optimum pH to decolorize (MG) and (CV) was 7 by B. cereus and it was 8 to decolorize (MG) and (CV) by P. earoginosa. Studying the effect of dye concentration showed that B. cereus recorded the highest percentage at (100 mg/L) with 91.2% and 88.3% for MG and CV respectively, and P. aeruginosa were able to decolorize malachite green and crystal violet at a the same concentration up to 90%. Glucose was the best carbon source for malachite green and crystal violet which increased the rate of decolorization up to 90% after 72 hours of incubation by B. cereus, followed by fructose. P. aeruginosa recoded a high percentage for MG and CV at 95.3% and 91% respectively. Peptone was the best nitrogen source for the decolorzation of malachite green while yeast extract was the best source of nitrogen which showed high percentage in decolorization of crystal violet. UV-Visible spectrum analysis demonstrated disappearing of major peaks of (MG) and (CV) at 590 nm and 619 nm, at visible area and formation a new peaks at UV area
