Investigation of the effects of atmospheric cold plasmas on different types of planktonic bacteria and biofilms

Biofilms, which account for 80% of microbial life on Earth, are one of the main causes of biological pollution. In order to solve these problems permanently, how to combat biofilms needs to be well researched. In recent years, cold plasmas have emerged as a promising alternative to traditional sterilization methods. Atmospheric pressure cold plasma jets (APCPJ) exhibited the highest antibacterial activity on the planktonic form of Pseudomonas aeruginosa when contacted in filamentous mode, causing erosion of the agar surface, while in diffuse mode without damaging the agar surface. A significant reduction in P. aeruginosa biofilms was observed at 300 seconds. Atmospheric pressure cold plasma (APCP) was applied on Halomonas caseinilytica and complete inactivation was achieved in 180 seconds in direct exposure, while complete inactivation time was determined as 300 seconds in remote exposure. Complete inactivation of H. caseinilytica biofilms in plasma-treated water was achieved in 300 seconds. Field Emission Scanning Electron Microscopy (FE-SEM) was used to investigate structural changes in biofilms. APCPJ was applied on Staphylococcus aureus biofilms and a significant reduction was observed in 300 seconds. Planktonic forms were analyzed by Interference Electron Microscopy. Biofilms were analyzed by Confocal Laser Scanning Microscope, FE-SEM, Atomic Force Microscopy, Fourier Transform Infrared Spectroscopy. The results showed significant changes in morphology and decreased viability. In addition, plasma-treated saline was applied to S. aureus cells and a significant reduction was observed at 600 seconds. In this study, cold plasmas produced at atmospheric pressure were applied on planktonic and biofilm forms of P. aeruginosa, H. caseinilytica, S. aureus bacteria. As a result, it was shown that cold plasmas may be an alternative technology to traditional sterilization methods in the future.