## 3 Results
### Rhizosphere and Endosphere Bacterial Isolates
The taxonomic identification of the most tolerant isolates was Alphaproteobacteria (genus _Thalassspira_), Gammaproteobacteriabacteria (genera _Halomonas_, _Brevibacterium_, _Providence_, _Kushneria_, _Salinicola_, _Idiomarina_, _Psychroducer_, _Pseudomonas_), Bacilli (genera _Bacillus_, _Staphylococcus_, _Exiguobacterium_, _Oceanobacillus_, _Lysinibacillus_, _Planococcus_, _Virgibacillus_, _Bhargavaea_) and Actinobacteria (genera _Microoccus_ and _Kocuria_) (Appendix A, Table A1). Figure 3: Non-metric multidimensional scaling (NMDS) plot of OTU abundances (violet points) among sampled sites, onto which the sediment parameters Table 1 have been mapped. ECe: electrical conductivity of the sediment saturation extract; ECw: electrical conductivity of pore water; Sediment pHw: pH of sediment determined in water suspensions; SOM: sediment organic matter content. The profile of extracellular hydrolytic activities (amylase, cellulose, chitinase, lipase, protease) represented in the collection of isolates is depicted in Figure 5. The most common hydrolytic activity was cellulase, detected in 75 isolates (62.5%), followed by amylase, protease and lipase, found in 51 (42.5%), 35 (29.2%) and 32 (26.7%) isolates, respectively. chitinase activity was the least represented (16 isolates). Only isolates SB4 (Av3), SF59 (Av2) and SB102 (Av3), all rhizosphere bacteria of the genus _Bacillus_, (Appendix A, Table A1), tested positive for all the enzymes. Forty-three isolates produced at least two different extracellular enzymes, and the association cellulase + amylase was the most frequent (14). The proportion of enzyme-producing bacteria in each site is shown in Appendix A, Table A2. Isolates from the Al site stand out for proteolytic activity, but were not prolific cellulase, chitinase and amylase producers. Higher production of chitinase and amylase were detected mainly in Av2 isolates, which in turn were lower protease producers. Av3 isolates produced predominantly lipase and cellulase. Cellulosic activity was also abundant in isolates from Tg and Av1. Tg isolates were the less frequent lipase producers (Appendix A, Table A2). Figure 4: Percent distribution of isolates by levels of salinity tolerance, defined as the maximum concentration of salt (g L\({}^{-1}\) NaCl) for which growth was observed. Figure 5: Number of isolates expressing different extracellular enzymatic activities (**a**); number of isolates expressing each extracellular enzymatic activity (**b**); number of isolates combining the expression of 1, 2, 3, 4 or 5 different activities (**c**). The results of plant-growth promoting traits (siderophores, IAA, EPS (Exopolysaccharide-charides), ACC-deaminase activity, phosphate solubilization or nitrogen fixation) for the collection of 120 isolates is presented in Appendix A, Table A1, and summarized in Figure 6 and Appendix A, Table A2. EPS production (71%), phosphate solubilization capacity (61%) and siderophore production (58%) were well represented in the collection of isolates. Almost half of the isolates collection (45%) produced interesting levels of IAA. On the contrary, only 5 isolates (4%) affiliated with _Psychroacter_ (R13), _Stenotrophomonas_ (EH7), _Bacillus_ (ES2), _Halomonas_ (ES10) and _Brevibacterium_ (EB3) genus (Appendix A, Table A1) showed evidence of nitrogen fixation capacity. None of the isolates combined all the tested PGP traits. In contrast, approximately 25% of the isolates (33) showed activity for only one of the traits. A total of 12 isolates (EL13, RL18, EH2, ES4, ES14, EB7, EB39, EB40, EB41B, RA9, RA33 and SF91), affiliated with genera _Salinicola_, _Pseudomonas_, _Oceanobacillus_, _Halomonas_, _Providenceia_, _Bacillus_, _Kocuria_ and _Staphylococcus_, shared four PGP activities: phosphate solubilization, production of siderophores, production of IAA and ACC-deaminase activity. In addition, 2 isolates with nitrogen-fixation capacity, identified as _Psychroacter_ (RL3) and _Brevibacterium_ (EB3) (Appendix A, Table A1), also produced siderophores and IAA and expressed ACC-deaminase activity.