Vol. 9, Issue 7, Part T (2025)

Bacillus thuringiensis is a widely used entomopathogenic bacterium known for its bio pesticidal potential. Beyond insecticidal activity, its ability to form biofilms enhances persistence, stress tolerance, and sporulation. In present study, twenty indigenous Bt isolates along with standard Btk HD-1 strain were evaluated for biofilm formation under static (non-agitated), farmer-friendly conditions across different time intervals (24 to 96 h). The study involved qualitative and quantitative assessments of biofilm formation, in different biofilm components (ring and pellicle). At 24 h, only SA-18 formed a ring. At 48 h, SY-4, SJa-2, SA-22, SDa-1, and HD-1 developed both ring and pellicle; SGd-1, SA-18, and SUd-2 formed ring only; and 12 other isolates formed pellicle only, while SBn-2 showed no visible biofilm. At 72 and 96 h, most isolates (including HD-1, SA-6, SA-20, SGd-1, SY-4, and others) produced both ring and pellicle, whereas SBn-2, SGn-4, and SAk-12 showed only pellicle formation. Based on intensity and coverage, 8 isolates were classified as strong ring biofilm producers and 10 isolates were classified as weak ring biofilm producers whereas 15 isolates were classified as strong pellicle biofilm producers and 6 isolates were classified as weak pellicle biofilm producers. The Isolate SA-18 showed the highest OD and biomass (60.5 mg) in ring component, while SAk-12 recorded the highest OD and biomass (113.5 mg) in pellicle component. These results reveal high variability in biofilm formation among Bt isolates, supporting their potential use as persistent and efficient biocontrol agents under simple and low-cost cultivation methods.