## 4 Discussion  
In this study, we demonstrated that broth cultures of the surface microbiota of wooden boards obtained from three cheese-ripening processes are inhibitory towards _L. monocytogenes_ 2203. In addition, we characterized the resident inhibitory microbiota communities and showed that specific members of these communities may participate in the observed inhibitory effects. These results confirm the \"Jameson effect\" proposed by [PERSON] et al. [27], which posits that a well-established indigenous microbial community can inhibit the growth of _L. monocytogenes_, and further verify other findings [28], which reported the inhibitory effect of the surface microbiota of smear cheese wooden shelves on _L. monocytogenes_. We attempted to recreate a condition similar to that used in cheese ripening by performing our experiments in a low-temperature environment. This likely compounds the challenges that _L. monocytogenes_ must overcome when colonizing and establishing on wooden cheese boards. As such, we expected that any persistence of _L. monocytogenes_ in the presence of these inhibitory microbiota would likely be at low numbers, relative to other members of the microbial community. This is supported by our 16S rRNA analysis of the cheese board communities, where samples that were not inoculated with _L. monocytogenes_ 2203 did not contain any OTUs classified as _Listeria_. Our analyses of five cheese board microbiotas inoculated with _L. monocytogenes_ 2203 revealed communities dominated by a handful of genera. Two distinct microbiotas were observed, which were dominated by either _Carnotbacterium_ or _Leuconstoc_. Additionally, our diversity analyses indicated that control and experimental sets of all cultured communities were not significantly different from one another (Figures 3-5). Several studies have reported that bacteriocins produced by various species of _Carnotbacterium_ and _Leuconstoc_ are capable of inhibiting _L. monocytogenes_. A previous report [29] demonstrated that _Carnotbacterium_ can persist at refrigeration temperatures and produce Carnobacterial class IIa bacteriocins that inhibit the growth of various _Listeria_ spp. These authors suggested that  
Figure 6: Inhibition of _L. monocytogenes_ 2203 (LM) by _L. mesenteroides_ and _S. equorum_ isolated from an inhibitory microbial community (board E). LM corresponds to LM 2203 alone (negative control); LM+E corresponds to growth of LM 2203 in presence of microbial community of board E (positive control). LM+_S. equorum_ and LM+_L. mesenteroides_ illustrate growth of LM 2203 in the presence of these species that were isolated from the microbiota of board E. Symbols represent the mean \(\pm\) SEM CFU/mL from a single experiment. _Carnobacterium_ could be used as a protective culture against _L. monocytogenes_. Surprisingly, we did not isolate colonies of _Carnobacterium_ spp. from our TSB cultures, despite our 16S rRNA analysis indicating that it was a dominant member of the community. This suggests that either it is not a dominant member of our cultures (16S rRNA analyses cannot differentiate live from dead bacterial cells) or our culture conditions were incapable of isolating _Carnobacterium_. _Leuconostoc_ is also known to produce bacteriocins with inhibitory effects on _L. monocytogenes_. For example, ref. [30] showed the antimicrobial effects of a _Leuconostoc mesenteroides_ isolate from goat's milk and demonstrated that bacteriocins produced by this isolate had a narrow inhibitory spectrum limited to _Listeria_ spp. Our finding that a _Leuconostoc mesenteroides_ isolate from board E was capable of strongly inhibiting _L. monocytogenes_ 2203 (Figure 6) may explain, in part, the inhibitory activity of the microbiota from board E on _L. monocytogenes_ 2203. Overall, our findings are consistent with studies by other investigators on the use of wood in the production of artisan cheese.