# Microbiota and Metabolite Profiling of Spoiled Spanish-Style Green Table Olives
## Results and Discussion
### Correlation between Microbial Communities and Metabolites  
To reveal the relationships between microbial communities and metabolites, a PLS regression analysis was applied using the whole data set. Regarding bacterial communities, _Corynebacterium_, _Enterobacteriaceae_, _Ruminococcus_, _Cardiobacteriaceae_, and _Propionibacterium_ were located in the right party whereas _Natronobacillus_, _Oceanobacillus_, unclassified _Bacillusae_, and _Lactobacillus_ were in the left part of the correlation loading plot on the first two components (Figure 7). The latter group was positively correlated with lactic acid and 3,4-dimethylbenzaldehyde, which were highly correlated among themselves, as mentioned above. Furthermore, [PERSON]'s correlation coefficients between bacterial communities and metabolites (Table S4) showed that _Natronobacillus_ and _Oceanobacillus_ were positively correlated with 3-ethylpyridine; and _Lactobacillus_ was positively correlated with (\(Z\))-3-hexen-1-ol, propyl acetate, and 3-ethylpyridine. On the other hand, _Ruminococcus_, _Cardiobacteriaceae_, and _Propionibacterium_ were negatively correlated with lactic acid. _Ruminococcus_ did not show any significant positive correlation, although correlations for propionic acid (r = 0.462, \(p=0.053\)) and butyric acid (r = 0.452, \(p=0.059\)) were just over the limits of statistical significance.  
_Cardiobacteriaceae_ was positively correlated with butyric acid, valeric acid, caproic acid, 1-octanol, methyl pentanoate, methyl hexanoate, \(p\)-creosol, and \(p\)-creosol. _Propioniibacterium_ was positively correlated with acetic acid, propionic acid, succinic acid, and methyl propanoate. It is known that Propioniobacteria are the microorganisms responsible for the development of the so-called \"fourth stage\" of fermentation in Spanish-style green table olives, with the formation of acetic and propionic acids occurring at the expense of lactic acid [38]. The genus _Corynebacterium_ and family _Enterobacteriaceae_ were negatively correlated with 1-propanol and propyl propanoate (Table S4). The genus _Corynebacterium_ was positively correlated with butyric acid, 2-butanol, benzyl pentanoate, \(p\)-creosol, linalool, and 3-ethyl-4-methylpyridine. The family _Enterobacteriaceae_ was positively correlated with 2-butanol, ethyl hexanoate, \(p\)-ethyl baiaiocl, 4-ethyl phenol, 3-ethylpyridine, 3-ethyl-4-methylpyridine, and 1,4-dimethoxybenzene.  
Figure 7: The PLS regression between microbial communities and metabolites. (**a**) Loading plot. (**b**) Score plot. See Table 5 for the meanings of samples abbreviations.  
Pearson's correlation coefficients between yeast communities and metabolites are shown in Table S5. _Candida apicola_ and _Candida etchellsi_ were positively correlated with lactic acid and 3,4-dimethylbenzaldehyde. _Candida pararugosa_ was positively correlated with methyl hepatomaate. _Dekera bruxellensis_ and _Pichia manshurica_ did not show any significant positive correlation. The family _Dipodascaceae_ was positively correlated with butanoic acid, nonanal, \(p\)-cresol, and dimethyl sulfide. _Pichia membranifaciens_ was positively correlated with \(\alpha\)-terpineol.