## 5 Conclusions  
Based on previous discussion using a helium-based plasma set-up for the inactivation of single-species _Listeria monocytogenes_ and _Salmonella_ Typhimurium model biofilms, it can be concluded that more membrane damage can be obtained when (i) no oxygen is added to the gas flow, (ii) a direct treatment is applied, and (iii) the discharge power increases. On the other hand, more DNA damage can be obtained when (i) no oxygen is added to the gas flow, (ii) an indirect treatment is applied, and (ii) the discharge power decreases. As the overall log-reduction values (see [PERSON] et al. [17]) were higher when no oxygen was added to the gas flow while using the highest discharge power and the DBD electrode, it can be concluded that membrane damage has a higher contribution to the bactericidal effect of CAP for biofilm-associated cells than damage to the (intracellular) DNA. Nevertheless, more research is still required to specifically examine which species are responsible for this observed phenomenon. In addition, the effect of CAP on the intracellular macromolecules (e.g., enzymes) should also be examined in future research.  
Individual contributions of each of the authors to the research are the following: conceptualization, M.G., C.S. and J.F.M.V.I; methodology, M.G. and C.S.; software, M.G.; validation, M.G. and C.S.; formal analysis, M.G. and C.S.; investigation, M.G.; resources, J.L.W. and J.F.M.V.I; data curation, M.G.; writing-original draft preparation, M.G.; writing-review and editing, M.G., C.S., J.L.W. and J.F.M.V.I; visualization, M.G.; supervision, M.G., C.S. and J.F.M.V.I; project administration, M.G.; funding acquisition, J.F.M.V.I. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the KU Leuven Research Council, project number C24/18/046 and the Fund for Scientific Research-Flanders, project number G.0863.18.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{_Listeria monocytogenes_} \\ \hline  & **DBD-0\%-** & **DBD-1\%-** & **DBD-0\%-** & **DBD-1\%-** & **SDD-0\%-** & **SDD-1\%-** & **SBD-0\%-** & **SBD-1\%-** \\  & **21.88 V** & **21.88 V** & **13.88 V** & **13.88 V** & **21.88 V** & **21.88 V** & **13.88 V** & **13.88 V** \\ \hline Intracellular & No & Yes & Yes & Yes & No & Yes & No & No \\ ROS & & Yes & Yes & No & No & No & Yes & Yes \\ \hline Log-reductions & & & & & & & & & \\ due to UV light (\textgreater{}1 log\textgreater{}10 & Yes & Yes & No & No & No & No & Yes & Yes \\ (CFU/cm\({}^{2}\))) & & & & & & & & & \\ \hline Membrane damage & Yes & Yes & Yes & Yes & Yes & Yes & Yes & No \\ \hline DNA damage & No & Yes & Yes & No & Yes & Yes & Yes & No \\ \hline Clear indication & & & & & & & & & \\ of an increased porosity & & & & & & & & \\ \hline \multicolumn{6}{c}{_Salmonella Typhimurium_} \\ \hline  & **DBD-0\%-** & **DBD-1\%-** & **DBD-0\%-** & **DBD-1\%-** & **SSD-0\%-** & **SSD-1\%-** & **SSD-0\%-** & **SSD-0\%-** & **SSD-1\%-** \\  & **21.88 V** & **21.88 V** & **13.88 V** & **13.88 V** & **21.88 V** & **21.88 V** & **13.88 V** & **13.88 V** \\ \hline Intracellular & Yes & Yes & Yes & Yes & No & Yes & Yes & Yes \\ ROS & & Yes & Yes & No & Yes & No & No & No \\ Log-reductions & & & & & & & & \\ due to UV light (\textgreater{}1 log\textgreater{}10 & Yes & Yes & No & No & No & No & No \\ (CFU/cm\({}^{2}\))) & & & & & & & & & \\ \hline Membrane damage & Yes & Yes & Yes & Yes & Yes & Yes & Yes \\ \hline DNA damage & No & No & Yes & Yes & Yes & Yes & Yes & Yes \\ \hline Clear indication & & & & & & & & & \\ of an increased porosity & No & No & No & No & No & No & No \\ \hline \hline \end{tabular}
\end{table}
Table 3: Summary table indicating whether the CAP inactivation mechanism for both biofilm forming species was (partially) due to (i) the generation of intracellular ROS, (ii) the presence of UV light, (iii) leakage of the membrane, and/or (iv) DNA damage. In addition, it was also indicated whether CAP treatment resulted in an increased porosity of the biofilms.