Adaptation of Congo Red Agar Method and Microtiter Plate Assay to Study Biofilm Formation in Streptomyces

Streptomyces has many advantages for exploration in biotechnological applications because of their ability to elaborate a multitude of bioactive molecules and secondary metabolites. Despite the importance of this genus in biotechnology, biofilm formation in Streptomyces is under-investigated. The objective of this research is to adapt two assays for the assessment of biofilm formation in Streptomyces. In the present investigation, we assess and follow biofilm formation in eight Streptomyces strains using quantitative and qualitative methods. The quantitative study based on a staining of the retained biomass in the microtiter plate with crystal violet “5%” and destaining using ethanol/acetone mixture, the concentration of crystal violet in the alcoholic solution reflect the intensity of the attached biofilm. On the other hand, the qualitative one consists of using modified freeman’s method a modified congo red agar method based on the color of colonies. Quantification of biomass by crystal violet staining method confirmed that Streptomyces bellus A43 and Streptomyces bellus A61 are biofilm-forming and this ability increase with the period of incubation. Our results showed that sixStreptomyces strains arenon-slime producing/non-biofilm forming. Two Streptomyces strains are slime producing/biofilm forming; this character vanishes at five days. Further research on genes responsible for biofilm formation in Streptomyces is highly recommended for better understanding of the phenomenon.