To begin, add 200 microliters of the bacterial inoculum to each well of a sterile polystyrene 96-well plate. Then add 200 microliters of deionized water into the outermost wells to keep the inner wells from drying out. Incubate the 96-well plate at 25 degrees Celsius for 24 hours.
Following incubation, discard the supernatant in each well using a pipette. Carefully add 300 microliters of PBS to each well and remove the PBS again by using the pipette. Add 200 microliters of 1%crystal violet solution to each well before incubating the plate at room temperature for 30 minutes.
Then after dispensing 200 microliters of absolute ethanol in each well, leave the plate for 15 minutes at room temperature. Ensure thorough mixing by pipetting the contents in each well up and down repeatedly. Using a microplate reader, measure the absorbance of the wells at 595 nanometers to determine the biofilm mass.
The number of biofilms varied greatly depending on the strains, ranging from an optical density or OD value of 0.04 to 1.69 All of the Acetobacter isolates, except for A.bouvetii, formed biofilms, while A.radioresistens formed a weak biofilm. A.junii and A.baumannii formed moderate biofilms, and A.pittii and A.ursingii formed strong biofilms.
