## 4 Discussion  
In the present study, for the isolation of psychrotolerant bacteria, rhizosphere and phyllosphere of 11 wild plants were collected from three areas of the Andes Mountains and one area of Patagonia during winter of the year 2015. In this study, 130 psychrotolerant bacterial isolates were characterized, 79% from the rhizosphere and 21% from the phyllosphere (Table 2). A higher number of strains were isolated from the rhizosphere than from the phyllosphere in 9 of the 11 wild plants studied. More strains from phyllosphere than from rhizosphere were isolated only from the _Berberis_ sp. plant. Several reports point to a higher richness and microbial diversity in the rhizosphere than the phyllosphere of plants [41; 64; 65; 66]. This bacterial diversity is correlated with the total community size. The rhizosphere and the phyllosphere present different sizes of the total bacterial population. In the phyllosphere, the bacterial abundance is estimated to be approximately \(10^{6}\) cells g\({}^{-1}\), while the number of bacteria in the rhizosphere can reach up to \(10^{8}\) cells g\({}^{-1}\) dry weight [65]. Notably, this is the first study of bacteria associated with _Calycera_, _Orites_, and _Chusqua_ plant genera. Previous reports highlight the isolation of bacteria with plant growth-promoting properties from _Thalspi_, _Baccharis_, _Nothofagus_, _Haplopappus_, _Guapholium_, and _Gaultheria_[67; 68; 69; 70; 71; 72; 73]. In contrast, only pathogenic bacteria have been associated with _Berberis_[74]. In our study, 6 of the 11 wild plants presented zero or very low number of isolates from the phyllosphere (Figure 2). Under the conditions carried out in this study, the detection limit was \(10^{3}\) CFU mL\({}^{-1}\) (1 CFU on the plate), obtaining a number \(<\)\(10^{3}\) CFU mL\({}^{-1}\) (no isolates on the plate) for _Baccharis_ sp., _Nothofagus_ sp., _Orites_ sp., and _Chusqua_ sp., while \(2\times 10^{3}\) CFU mL\({}^{-1}\) (2 isolates) were obtained for _Nothofagus_ sp. in association with the lichen _Usnea_ sp., _Haplopappus_ sp., and _Gaultheria_ sp. The low bacterial number can be partly explained due to the antimicrobial activities of some of these wild plants and the lichen [75; 76; 77; 78; 79; 80; 81; 82], and the low recovery rates of culturable bacteria from the rhizosphere and phyllosphere of plants [83; 84] under the conditions used in this study. Seventy of the 130 bacterial isolates that presented a value \(\geq\)33% BCS were further characterized. Interestingly, the Valparaiso Region presented the highest number of psychrotolerant strains (55.7%). These bacteria were isolated from Paso Internacional Los Libertadores (Portillo, Valparaiso Region, Chile), which was the highest altitude wild flora sampling site (3149 m.a.s.l.) and presents a winter (from April to October) with tem  
Figure 9: Growth in ACC and ACC deaminase activity of bacterial strains. (**a**) Growth in DF medium with ACC addition as sole carbon and nitrogen source. (**b**) ACC deaminase activity in \(\mu\)mol \(\alpha\)-KB mg protein\({}^{-1}\) h\({}^{-1}\) of strains with positive growth. Each value is a mean \(\pm\) SD of three independent replicates. Abbreviations: NC, negative control; PC, positive control (_Achromobacter_ sp. 188); BC, bacterial consortium; ACC, 1-aminocyclopropane-1-carboxylic acid; \(\alpha\)-KB, \(\alpha\)-ketobutyrate. peratures below 0 \({}^{\circ}\)C, reaching \(-20\)\({}^{\circ}\)C ([[http://www.gobernacionlosandes.gov.cl/inicio/](http://www.gobernacionlosandes.gov.cl/inicio/)]([http://www.gobernacionlosandes.gov.cl/inicio/](http://www.gobernacionlosandes.gov.cl/inicio/)) (accessed on 5 February 2021)). The identification by the 16S rRNA gene sequence analysis indicated that these 70 strains belong to 18 different bacterial genera of four bacterial phyla (Figure 2). In our study, Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes are among the most abundant bacterial phyla in the rhizosphere and the phyllosphere, in accordance with previous reports [65; 66].