Isolation, Characterization, and Identification of Nitrogen Fixing Bacteria from Rhizosphere ofSonneratia apetalaCollected from Sundarbans

Abstract Nitrogen is a crucial element for plant growth, driving vibrant greenery, photosynthesis, and overall vitality. This research focused on isolating, characterizing, and identifying nitrogen-fixing bacteria from the rhizosphere of Sonneratia apetala in the Sundarbans, Khulna, Bangladesh, with the goal of assessing their potential as biofertilizers. Despite the Sundarbans’ rich microbial diversity, less than 5–10% of species have been identified due to challenges in culturing, which has limited exploration of their applications. In this study, nitrogen-fixing bacteria were isolated using nitrogen-free media, including yeast extract mannitol agar(YEMA) and Burks media, followed by an ammonification test to select ammonia-producing bacteria. This process yielded ten nitrogen-fixing bacterial isolates capable of producing indole-3-acetic acid (IAA). Various biochemical tests, including oxidase, catalase, methyl red, indole, urease, citrate, triple sugar iron, and starch hydrolysis, were conducted. The isolates, designated AK1 to AK10, were identified as Rossellomorea sp., Clostridium sp., Achromobacter sp., Pseudomonas sp., Gluconacetobacter sp., Scytonema sp., Pseudomonas sp., Nesterenkonia sp., Gluconacetobacter sp., and Bacillus sp., respectively. Additionally, isolates AK1, AK3, AK4, and AK10 were confirmed through 16S rRNA sequencing. A pot test further revealed that isolate AK-1 significantly stimulated the growth and development of maize seedlings. Future studies are needed to examine the impact of these bacterial isolates on crop yield and seed quality, to better determine their suitability as biofertilizers.