Isolation, Phenotypic Diversity, and Biochemical Characterization of Cultivable Endophytic Microorganisms Associated with Avicennia marina from the Mangrove Ecosystem of Navsari, Gujarat

Abstract

Endophytic microorganisms residing within mangrove plants endure extreme abiotic stresses, making them valuable candidates for bioprospecting. This study evaluated the phenotypic diversity, biochemical characteristics, and metabolic capabilities of cultivable endophytic microorganisms associated with Avicennia marina from the mangrove ecosystem of Navsari, Gujarat, India. A total of 43 morphologically distinct isolates were obtained across three sampling events. From these, 15 representative isolates (14 bacterial and 1 fungal) were selected for detailed characterization. Stem tissues yielded the highest recovery of bacterial endophytes (57.1%), followed by root and leaf-tip tissues (21.4% each). Phenotypic profiling demonstrated a predominance of Gram-positive, rod-shaped bacteria (64.3%). Biochemical assays revealed universal catalase, oxidase, and nitrate reductase activities across all bacterial isolates, indicating robust aerobic respiratory metabolism. Differential substrate utilization highlighted distinct functional capabilities, including gelatinase activity and acetoin production in isolate ISOLATE 7, urease activity in ISOLATE 11, citrate utilization in ISOLATE 15, and broad carbohydrate fermentation with gas production in ISOLATE 6. These findings demonstrate substantial metabolic versatility among A. marina endophytes, highlighting their potential application as sources of novel extracellular enzymes and bioactive secondary metabolites.