Microbial Diversity of Psychrotolerant Bacteria Isolated from Wild Flora of Andes Mountains and Patagonia of Chile towards the Selection of Plant Growth-Promoting Bacterial Consortia to Alleviate Cold Stress in Plants  
[PERSON]  
1 Molecular Microbiology and Environmental Biotechnology Laboratory, Department of Chemistry, Universidad Tecnica Federico Santa Maria, Avenida Espana 1680, Valparaiso 2390123, Chile; [EMAIL_ADDRESS] (G.B. ); [EMAIL_ADDRESS] (A.V. ); [EMAIL_ADDRESS] (M.V. ); ingrid@[EMAIL_ADDRESS] (I.-N.V.); [EMAIL_ADDRESS] (I.A.) [PERSON]  
2 Center of Biotechnology Dr. [PERSON]\({}^{\ast}\), Universidad Tecnica Federico Santa Maria, General Bari 699, Valparaiso 2390136, Chile; [EMAIL_ADDRESS] (M.S. ); ingrid.ramirez@gmail. more frequent in the last years due to climate change. In the United States of America, there are higher economic losses from frost damage than from any other weather-related phenomenon [2]. In Chile during the year 2013, frosts caused a reduction of 22% in exportable fruit, which represented a loss of more than US $800 million [3]. Climate change affects the natural systems, human health, and agricultural production [4], and with the increase in temperature, the cold acclimatization of plants occurs later in autumn or early winter [5]. This disorganized cold acclimatization causes a higher susceptibility of plants to erratic temperature events [5]. Due to climate change, extreme weather events, such as frost (<0 \({}^{\circ}\)C), are increasing. Therefore, cold stress is an important challenge for agriculture [3; 6; 7]. In this context, the plant growth-promoting microorganisms play an essential role for plants during their growth and adaptation to the changing environment through some mechanisms, such as nitrogen fixation, phosphate solubilization, modifying plant hormone levels, and improving plant defense responses to biotic and abiotic stresses [8; 9; 10; 11]. The agricultural importance of cold-tolerant microorganisms arises because crops are subject to temporary cold periods, which are detrimental to mesophilic microbial processes associated with plant growth-promoting activities [12]. Plant growth-promoting bacteria (PGPB) can employ one or more different strategies to allow higher tolerance and additionally promote plant growth under abiotic stress [8]. The identification of PGPB that retain their potential to promote plant growth at low temperatures, is a worldwide trend in the field of agricultural inoculation technology [13; 14]. On the other hand, the formulation of bacterial consortia (\(\geq\)2 compatible bacteria) can increase the efficiency of agricultural crop production particularly under challenging environmental conditions, due to exploitation of their complementary and synergistic characteristics, compared to a single bacterium [15; 16]. Various studies report plant growth-promoting effects with the application of a single bacterium, such as _Pseudomonas_, _Bacillus_, _Serratia_, _Pantoa_, and _Panaburbholderia_ strains on canola, wheat, grapevine, and tomato under cold stress [17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27]. The formulation of bacterial consortia to alleviate cold stress in plants has been scarcely reported. A bacterial consortium formulated with _Bacillus_ and _Brevibacillus_ strains protects and promotes the growth of rice seedlings under cold stress [28]. Another consortium composed of _Bacillus_ and _Serratia_ strains promotes the survival of tomato plants subjected to cold stress [29]. The application of PGPB consortia is an eco-friendly alternative to agriculture that has the potential to increase crop yield under normal and stressful conditions. In addition, the use of PGPB reduces the application of chemical products, decreasing the environmental impact in agriculture (e.g., soil erosion), and increasing the microbial diversity and functionality of agricultural soils with the concomitant production of healthy and safe foods [16].