Culturable halophilic bacteria inhabiting Algerian saline ecosystems: A source of promising features and...

This paper aims to characterize halophilic bacteria inhabiting Algerian Saline Ecosystems (Sebkha and Chott) located in arid and semi-arid ecoclimate zones (Northeastern Algeria). In addition, screening of enzymatic activities, heavy metal tolerance and antagonistic potential against phytopathogenic fungi were tested. A total of 74 bacterial isolates were screened and phylogenetically characterized using 16S rRNA gene sequencing. The results showed a heterogeneous group of microorganisms falling within two major phyla, 52 strains belonging to Firmicutes (70.2%) and 22 strains (30.8%) of γ-Proteobacteria. In terms of main genera present, the isolates were belonging to Bacillus, Halobacillus, Lentibacillus, Oceanobacillus, Paraliobacillus, Planomicrobium, Salicola, Terribacillus, Thalassobacillus, Salibacterium, Salinicoccus, Virgibacillus, Halomonas, Halovibrio, and Idiomarina. Most of the enzymes producers were related to Bacillus, Halobacillus, and Virgibacillus genera and mainly active at 10% of growing salt concentrations. Furthermore, amylase, esterase, gelatinase, and nuclease activities ranked in the first place within the common hydrolytic enzymes. Overall, the isolates showed high minimal inhibitory concentration values (MIC) for Ni²⁺ and Cu²⁺ (0.625 to 5 mM) compared to Cd²⁺ (0.1 to 2 mM) and Zn²⁺ (0.156 to 2 mM). Moreover, ten isolated strains belonging to Bacillus, Virgibacillus and Halomonas genera, displayed high activity against the pathogenic fungi (Botrytis cinerea, Fusarium oxyporum, F. verticillioides and Phytophthora capsici). This study on halophilic bacteria of unexplored saline niches provides potential sources of biocatalysts and novel bioactive metabolites as well as promising candidates of biocontrol agents and eco-friendly tools for heavy metal bioremediation.