Microbial diversity of Azadirachta indica (Neem) gum: An unexplored niche

Abstract

Azadirachta indica (Neem) gum resists extreme environmental conditions due to its chemical nature. The composition of neem gum with respect to microbial load is yet to be investigated. Moreover, the population structure and their diversity of bacteria in neem gum are also poorly known. The current investigation is about isolation and recognizing the bacterial diversity of neem gum and characterizing their plant growth-promoting (PGP) attributes. Using 12 different growth media, a total of 130 bacterial isolates were obtained, of which 50 isolates displayed significant differences in morphology, biochemical, and molecular features. Amplified ribosomal DNA restriction analysis (ARDRA) followed by 16S rRNA gene homology-based identification suggested the presence of twenty putative bacterial forms in neem gum. The species of Enterobacter, Bacillus, Pseudomonas, Paenibacillus, and Brevibacterium were predominantly present. Out of these 50 isolates, 44 isolates showed IAA production up to 2–730 µg/mL. Similarly, siderophore and HCN production were exhibited by 21 and 12 different bacterial isolates, respectively. Isolates also exhibited phosphate (6), potassium (6), and zinc (18) solubilizing ability. In addition, the isolates were able to produce hydrolytic enzymes such as amylase (13), cellulose (12), lipase (14), and pectinase (31). The results of the study indicate that isolates may aid agricultural practices and optimize plant uptake of nutrients under adverse conditions.