SALT TOLERANCE, PHENOTYPIC CHARACTERISTICS AND FUNCTIONAL SCREENING OF BACILLUS ISOLATES FROM SALINE SOIL

This study assessed the taxonomic affiliation, sodium chloride tolerance, and preliminary phytohormone-associated colorimetric responses of culturable bacteria isolated from saline soil in Qamashi District, Uzbekistan. Thirteen isolates were characterized by Gram staining and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The identifications obtained were Bacillus halotolerans, B. rugosus, B. safensis, and B. pumilus. Growth was screened on nutrient agar supplemented with 5%, 10%, and 15% (w/v) NaCl. The proportions of isolates showing visible growth were 84.6% (11/13), 76.9% (10/13), and 53.8% (7/13), respectively. Cell-free culture filtrates were evaluated using colorimetric assays associated with indole-3-acetic acid (IAA) and gibberellin-like compounds. The highest gibberellin-associated absorbance was observed for B. rugosus isolate 13 (OD750 = 0.805), whereas B. pumilus isolate 10 showed the highest IAA-associated response (OD450 = 0.776). B. halotolerans isolate 7 combined growth at 15% NaCl with a relatively high gibberellin-associated response (OD750 = 0.734). These findings identify promising locally adapted isolates for further study; however, the colorimetric responses do not establish hormone identity or concentration, and plant growth promotion remains to be experimentally demonstrated.

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