## 3 Results and Discussion
### Taxonomic Distribution of Wooden Table Bacteria  
In recent years, the Illumina technology has been widely applied to reveal the entire bacterial composition of raw materials used in food production in order to also determine the dormant and/or viable but not cultivable bacterial community before processing [38; 39; 40]. In this study the DNA extracted from the biofilms collected in replicate collections from the four wooden table samples was successfully amplified in the bacterial V3-V4 16S rRNA gene region. A total of 320,396 paired-end sequences were obtained. The taxonomy classification allowed the identification of eight phyla, 16 classes, 25 orders, 47 families and 50 genera. The relative abundance (%) of the operational taxonomy units (OTUs) identified from the biofilms is reported in Figure 3.  
Figure 2: Scanning electron microscopy (SEM) observations of wooden splinters from wooden tables used during PDO Provola dei Nebrodi cheese production. Pictures of the wooden splinters from dairy factories A–D (**a–d**). The OTUs with an individual relative abundance \(<0.1\%\) were not considered since this is the threshold indicated for abundant communities [41]. All wooden tables were characterized for the presence of _Corynebacterium_, _Bifidobacterium_ and LAB. In particular, the LAB genera detected on all four wooden tables were _Lactobacillus_, _Streptococcus_ and _Lactococcus_. The abundance of these groups were greatly variable with _Corynebacterium_ ranging from 0.29 to 5.80%, _Bifidobacterium_ from 0.29 to 17.69, _Streptococcus_ from 0.22 to 1.84%, _Lactococcus_ from 0.10 to 2.65% and, especially, _Lactobacillus_ from barely 0.29 in WTD to 78.61% in WTC. The LAB group also included other genera found only in one sample like _Weissella_ in WTB, or two samples like _Enterococcus_ in WTA and WTD and _Pediatricococcus_ in WTB and WTC or three samples as per _Leuconostoc_ (with the species _Lactoconostoc mesenteroides_) in WTB-WTD. In dairy environments, Corynebate represent part of the surface community of smear cheeses [42] and are also found on the wooden shelves used for cheese ripening [13; 16]. Since they are not involved in curd acidification they colonize the wooden surfaces of the tables analysed as a result of an environmental contamination or they are transferred from the raw milk [43]. The presence of bifidobacteria on dairy equipment is not negative, since this bacteria are common human probiotics [44], but they do not have to interfere with the activities of LAB during cheese production [45]. It is not surprising that LAB constituted the dominant populations of wooden table biofilms. In fact, LAB form stable biofilms on the surfaces of the wooden vats used for cheese curdling [5; 8; 9; 10; 46; 47; 48] and a similar LAB development was even more expected on the surfaces of the tables used for the overnight curd acidification. Figure 3: Relative abundances (%) of bacteria identified by MiSeq Illumina in wooden table biofilms. Abbreviations: WT, wooden table; A–D, dairy factory A–dairy factory D.  
Dermabacteraceae, _Kocuria_, _Chryseobacterium_, _Sphingobacterium_ and _Staphylococcus_ were not found in sample WTC. Among these, only _Kocuria_ in WTD and _Chryseobacterium_ in WTB were detected at very consistent levels (20.84 and 22.58%, respectively). Dermabacteriaceae and Staphylococcus have been recently detected in raw milk used to process Italian hard cheeses [49]. In particular, _Staphylococcus_ is part of the raw cow's milk bacterial community [50]. _Kocuria_ is also found in raw cow's milk [51] and is even selected as adjunct culture to enhance flavour and sensory attributes of traditional cheeses [52]. Several _Chryseobacterium_ species (_C. joostei_, _C. oranimense_ and _C. hafense_) have been recently identified from raw milk [53; 54; 55]. These bacteria are generally psychrotolerant, lipolytic and proteolytic and, for these reasons, undesirable because they might cause alteration of cheeses.