## 4 Discussion
Different isolates of _Pseudomonas_, _Stenrophonomas_, _Serratia_, _Brevundomonas_, _Arthobacter_, _Pseudarthrobacter_, _Paenarthrobacterium_, _Crutobacterium_, _Brachybacterium_, _Sporosarcina_, _Bacillus_, _Solibacillus_, _Janthinobacterium_, _Flavobacterium_, and _Pedobacter_ described in the rhizosphere and the phyllosphere of plants in the present study, have been reported previously in plants and also in soil, water, ice, and animals [85; 86; 87; 88; 89; 90; 91; 92; 93; 94; 95]. Interestingly, _Frondihabitans_ sp. GpP26d was isolated from the phyllosphere of a _Gaultheria_ plant. Members of the _Frondihabitans_ genus has only been associated with plants and lichens [96; 97; 98; 99; 100]. On the other hand, some members of the _Xanthomonas_ and _Clavibacter_ genera are phytopathogens, which are in the rhizosphere, the phyllosphere, and the endosphere of different plants [44; 63; 101; 102]. In the present study, the bacterial strains that are closely related to phytopathogens, _Xanthomonas_ sp. HsR18 and _Clavibacter_ sp. BmP21 that were isolated from the rhizosphere of _Haplopappus_ sp. and the phyllosphere of _Berberis_ sp., respectively, were discarded for the formulation of bacterial consortia. Except for the _Xanthomonas_ and _Clavibacter_ genera, the psychrotolerance of all the bacterial genera analyzed in this study have been reported [21; 24; 25; 100; 103; 104; 105; 106; 107]. In the present study, _Pseudomonas_ and _Stenrophonomas_ genera showed the highest number of psychrotolerant strains, with 18 and 17 isolates, respectively (Figure 2). Strains of the _Pseudomonas_ genus were isolated in the rhizosphere (16) and the phyllosphere (2). _Stenrophonomas_ strains genus were also isolated from the rhizosphere (12) and the phyllosphere (5). _Pseudomonas_ is the genus of Gram-negative bacteria with the largest number of recognized species, where more than 220 species have been characterized [108]. The ubiquity and metabolic versatility of this genus allow it to colonize a wide range of natural habitats and adopt a variety of lifestyles. _Pseudomonas_ strains have been isolated from each of the ecological niches within plants including roots (rhizosphere), leaves (phyllosphere), and tissues (endosphere) [108; 109]. In previous studies, _Pseudomonas_ strains isolated from Chilean agricultural soils with nematicidal and herbicide-degrading activities have been characterized [110; 111]. On the other hand, the _Stenrophonomas_ genus has been associated with soil and plants [112; 113; 114], showing beneficial effects on plant growth and health [86]. In our study, all the _Stenrophonomas_ strains isolated from the four regions were closely related to _Stenrophonomas rhizophila_ species. _Stenrophonomas rhizophila_ is a rhizosphere-associated species that display antifungal properties [115]. The search for psychrotolerant PGPB that can exert their role of plant growth-promoting at low temperatures is of high importance for agriculture [112; 105; 106]. The benefits of mixed PGPB inoculation are due to the combination of plant growth-promoting (PGP) activities [16]. In this context, for the selection of a group of psychrotolerant bacterial consortia, different PGP activities were evaluated in the 70 selected psychrotolerant strains (Figure 3, Table 3). In addition, antimicrobial activities against well-known phytopathogenic and ice nucleation active bacteria (Table 4), such as _Pseudomonas syringae_ and _Pectobacterium carootororum_ that magnify the stress caused by cold in plants [2; 116], _Agrobacteriumium tunefaciens_ that infects a wide range of plants and causes plant tumors called crown galls [117], and _Clavibacter michiganensis_ subsp. _michiganensis_, which is an important tomato phytopathogen [44; 63; 101], were analyzed. These PGP activities have also been used to select bacterial consortia for plant growth-promotion under stress (cold, drought, salinity) and non-stressful conditions [28; 42; 118; 119; 120; 121; 122].