ISSN: 1314-6246 Ceylan et al. J. BioSci. Biotech. 2014, SE/ONLINE: 35-42 RESEARCH ARTICLE SPECIAL EDITION / ONLINE Section “Cell & Molecular Biology” Third Balkan Scientific Conference on Biology, Plovdiv, May 30 – June 1, 2014 35 Ozgur Ceylan 1 Aysel Ugur 2 Nurdan Sarac 3 In vitro antimicrobial, antioxidant, antibiofilm and quorum sensing inhibitory activities of Bellis perennis L. Authors’ addresses: 1 Laboratory of Microbiology, Apiculture Program, Vocational School of Ula Ali Kocman, Mugla Sıtkı Kocman University, Ula, Mugla 48000, Turkey. 2 Laboratory of Microbiology, Section of Medical Microbiology, Department of Basic Sciences, Faculty of Dentistry, Gazi University, Ankara 06100, Turkey. 3 Laboratory of Microbiology, Department of Biology, Faculty of Science, Mugla Sıtkı Kocman University, Mugla 48000, Turkey. Correspondence: Ozgur Ceylan Laboratory of Microbiology, Apiculture Program, Vocational School of Ula Ali Kocman, Mugla Sıtkı Kocman University, Ula, Mugla 48000, Turkey. Tel: +90 252 211 3284 e-mail: ozgceylan@hotmail.com ABSTRACT The aqueous and ethanolic extracts of the aerial parts of Bellis perennis, widely used for edible vegetable in southwest Anatolia, were isolated and its antimicrobial, antioxidant, anti-biofilm, and quorum sensing inhibitory activities were investigated. Its antimicrobial activity was evaluated against 15 bacterial strains and Candida albicans using the disc diffusion assay and broth microdilution assay. Among the microorganisms tested, the most susceptible strains were Staphylococcus epidermidis MU 30 and Staphylococcus aureus MU 38. The antioxidant capacity was determined by the ferric thiocyanate (FTC) and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free-radical scavenging assays. Extracts showed weak radical scavenging activity with the DPPH method. IC 50 values were found as 37.85 mg/ml for ethanolic extract and 96.98 mg/ml for aqueous extract, respectively. Results obtained from FTC assay showed 16.98% inhibition for ethanolic extract and 58.14% inhibition for aqueous extract compared with BHT (63.36% inhibition) and ascorbic acid (77.67% inhibition). The antibiofilm effect of the extracts was measured by microplate biofilm method. Ethanolic extract of B. perennis did not inhibit biofilm formations of the tested microorganisms, however the aqueous extract inhibited limited anti- biofilm activity against P. aeruginosa ATCC 27853, P. fluorescens MU 181 and S.epidermidis MU 30 at 10 mg/ml concentration. Anti-Quorum Sensing (QS) activity of extracts was determined using biosensor bioassay with Chromobacterium violaceum CV026. At the concentration of 100 mg/ml of aqueous extract of B. perennis showed promising anti-QS activity on Chromobacterium violaceum CV026 with zone of pigment inhibition 10 mm. Inhibition of QS-regulated violacein production in Chromobacterium violaceum ATCC 12472 and swarming motility in Pseudomonas aeruginosa PA01 were carried out using standard methods. Aqueous and ethanol extracts of B. perennis inhibited swarming by 9.5% and 38.1%, respectively. The results suggest that B. perennis could be an alternative source to explore for useful contents in the fight against bacterial infections. Key words: Bellis perennis, antimicrobial, antibiofilm, antioxidant, Quorum sensing Introduction Biofilm is a community of cells attached to either a biotic or abiotic surface enclosed in a complex exopolymeric substance (EPS)(Flemming et al., 2000). The biofilm forming bacteria are resistant to antimicrobial agents due to the lack of penetration of antimicrobial agents (Frank & Koffi, 1990). The biofilm have been found to cause a wide variety of microbial infections in the body, such as urinary tract infections, catheter infections, middle-ear infections,