## 4 Discussions
Bacterial extracellular enzymes reflect the spectrum of available polymeric substrates and play relevant roles in the processes of colonization of root tissues and biocontrol of plant pathogens [68]. Cellulase was the most common enzyme, expressed by 62% of the isolates, followed by amylase, proteases, lipases and chitinase, expressed by 48%, 32%, 27% and 13% of the isolates, respectively. These frequencies are similar to those reported for PGP bacteria isolated from the endosphere of _Halimione portucaloides_, with the exception of lipolytic activity, which was comparatively less represented in the rhizosphere and root endosphere isolates of _S. ramossissima_ (27% compared to 46% in _H. portulacoides_) [69]. The release of cellulase accelerates the process of colonization of plant tissues, and this appears to be crucial for the close interaction between bacteria and plants under stressful environmental conditions [64; 65]. Cellulolytic PGP used in agriculture not only improves plant growth but also contributes to the degradation of plant material in soils, improving fertility and also providing a biocontrol effect against plant pathogens [70]. Bacterial cellulase, lipase, protease and chitinase degrade major components of the fungal cell wall [71; 72; 73] and therefore contribute to the biocontrol effect of PGP bacteria. Only three isolates, identified as _Bacillus austrilaris_, _B. vietnamensis_, and _B. infants_ (Appendix A, Table A1), expressed all enzymes, confirming the potential of Bacilli as biocontrol agents [74]. Approximately one third of the isolates expressed two extracellular enzymes. The most frequent combination was cellulase and amylase, indicating a positive selection of the enzymatic capacity to directly interact with plant tissues. Positive correlation between extracellular enzymatic activity, especially cellulolytic, and sediment properties like organic matter content and conductivity have been reported [75; 76]. This correlation was also evident in the present study. The frequency of cellulolytic and lipolytic isolates was the highest in the Av1 and AV3 subsets, respectively (Appendix A, Table A2), which corresponds to sediments with high organic matter content and electrical conductivity (Table 1). The bacterial production of extracellular polymeric substances (EPS) can aid plants in resisting drought and salinity [77; 78]. EPS-producing bacteria accounted for 72% of the cultivable isolated bacteria in our study (Appendix A, Tables A1 and A2). The highest frequency of EPS-producing isolates was observed in the most saline sediments and pore waters, AV1 and AV2, accounting for 90% and 81% of the isolates, respectively, and 90% of the isolates in the Al site were characterized by highly saline pore waters. Salinity can act as a positive environment for EPS, as their production is enhanced in response to osmotic stress [79]. EPS are also involved in the sequestration of minerals [80]. Therefore, EPS production can also be regarded as a PGP trait contributing to plant access to nutrients, in parallel with the expression of siderophores, nitrogen fixation and phosphate solubilization capacities. Approximately 60% of the isolates were able to solubilize phosphate or produce siderophores, and 44 isolates (\(\sim\)37%), identified as _Bacillus argabhattai_, _B. austrilarnaris_, _B. cereus_, _B. horneckiae_, _B. lwangjinpoensi_, _B. tianshenii_, _Halomonas titanicae_, _Kocuria palustris_, _Kushneria phyllosphaerae_, _Microoccus aloeverae_, _Oceanobacillus picturae_, _Providencia rettgeri_, _Pseudomonas juntendi_, _P. orgzilubitans_, _Psychrobacter faecalis_, _Salinicola endophysticus_, _Sporosarcina luteola_, _Staphylococcus epidermidis_, _S. xylosus_ and _Steenotrophomonas rhizophila_, could do both (Appendix A, Table A1). Phosphorus (P) is the least accessible macronutrient for plants due to the propensity to form insoluble complexes with cations, and in saline soils, P is even less available [75; 81; 82].