Characterization of Plant Growth Promoting Rhizobacteria from Dominant Weeds Inhabited in Kaligarang River Delta, Indonesia

Delta is a bulk mass of river sedimentation encompassing a variety of vegetation and soil microorganisms with beneficial relationships. Kaligarang river delta in Semarang, Indonesia has typical type weed vegetations of Ageratum conyzoides, Galinsoga parviflora, Eleusine indica, and Kylinnga brevifolia with impressive growth that possibly were encouraged by rhizobacteria. Therefore, this study aimed to characterize rhizobacteria from the mentioned deltaic weed vegetation, commencing from the colonies' morphology, cell morphology, and biochemical and phytohormone exploration with genotypic analysis of the notable performance one. The result displayed distinctive colonies from A. conyzoides and G. parviflora rhizosphere samples as 3 of each. Meanwhile, K. brevifolia and E. indica rhizosphere unveiled 4 and 2 isolates, respectively. Most of the colonies were Gram-positive bacil bacteria with circular or punctiform form, entire edge, and convex elevation and having the potential of catalase, starch hydrolysis, nitrogen fixation, phosphate solubilization, potassium solubilization and auxin production. One of A. conyzoides isolates achieved all biochemical competence and uppermost auxin enhancement during 48 h incubation with no endospore. The sequence homology and phylogenetic tree of 16S rRNA analysis suggested that the colony was B. cereus. The isolate characterization was in line with other research on B. cereus colony features with tryptophan-dependent indole acetic acid biosynthesis pathway.