## 5 Bio-Phytoremediation by Microorganisms
### Microbial bioremediation under Abiotic Stress Conditions  
It is important to understand the relationships in plant development that promote rhizobacteria and abiotic and biotic factors in the mechanisms of bioremediation and energy production [103]. Various pressures arise from diverse surrounding conditions, such as heavy metals, drought, UV light, freezing, salinity, hypoxia, too-low and high temperatures, and bright light [104; 105]. There are few or no studies dedicated to the use of microorganisms under various abiotic stresses, particularly in the case of uncontrolled bioremediation techniques, such as in situ methods. Undoubtedly, bioremediation involving the utilization of microorganisms and different abiotic stresses, as well as their effects on the latter, does not act separately in nature.  
Figure 2: Adverse impacts of soil salinity on plants and microorganisms.  
Microorganisms may be able to play a key role in this regard if we can take the use of their unique features of extreme tolerance, ubiquity, genetic variety, and interaction with crop plants, as well as develop ways for their successful deployment in agriculture production [24]. Bacteria and Archaea, as well as members of the fungal kingdom, are known to be able to adapt to a wide range of variations in external osmolarity. Increases in soil salinity have been linked to changes in microbiota composition, and research into the functional interactions between plants and microorganisms that contribute to salt stress resistance is gaining traction [78]. A range of physiological, metabolic, and molecular pathways are also involved in plant adaptation and resistance to salt stress [57].  
The efficiency of bioremediation is determined by a number of factors, including amendments, such as activated carbon and biochar [106], the type of organisms used, the prevailing environmental parameters at the polluted site, and the level of contaminants present. Temperature, low nutrient concentrations, and other conditions that are difficult to manage can obstruct their use and the efficacy of the bioremediation process [107]. In the ecosystem, representatives of the genera _Pseudomonas_, _Flavobacterium_, _Bacillus_, _Azobacter_, _Microbacterium_, _Hydrogenomonas_, _Achromobacter_, and _Xanthomonas_ are the most common co-metabolizers [108]. The incomparable metabolic power of such organisms highlights the strong implementable ability of PGP members of such genera to alleviate crop stress caused by contaminated soils, paving the way for bioremediation [109].  
To deal with toxic solutes and survive under stressful conditions, microbes have evolved a multitude of adaptive networks [110]. It has been shown that halophile-produced enzymes can be important biological substances, such as phytohormones and exopolysaccharide-charides, which are important in plant-microbiome interactions [111]. These are also beneficial for the bioremediation of pollutants in salty environments [112; 113]. In a study, the screening of microbial multi-abiotic stress tolerance led to the selection of the strain _Pseudomonas azotoformans_ BioRPAz-3: pH (6, 7, 8, and 10), temperature (20 \({}^{\circ}\)C, 30 \({}^{\circ}\)C, 40 \({}^{\circ}\)C, and 45 \({}^{\circ}\)C), salinity up to 600 mM, drought up to 2.4 Mpa, Pb (100 \(\mu\)g/mL, 200 \(\mu\)g/mL, and 500 \(\mu\)g/mL), and Cu (200 \(\mu\)g/mL, 500 \(\mu\)g/mL, and 1000 \(\mu\)g/mL). This strain can be used efficiently for Pb and Cu bioremediation [114]. Different species of PGPB have been identified, facilitating heavy metal remediation and crop performance under drought and salinity stress [115].