ISOLATION AND IDENTIFICATION OF RHIZOBACTERIUM, VAGOCOCCUS FLUVIALIS WITH PLANT GROWTH PROPERTIES USING 16S RRNA GENE SEQUENCING
Abstract
This study aimed to comprehensively characterize the genomic attributes of screened plant
growth-promoting rhizobacteria (PGPR) isolated from maize soil and isolate and
characterize bacteria from maize rhizosphere soil with potential plant growth-promoting
properties. Soil samples were analyzed using serial dilution, pour plating, and streak
plating to obtain pure bacterial cultures. The isolates underwent biochemical tests, PGP
screening, process optimization, molecular identification, and maize seed bioinoculation
trials. Morphological analysis showed flat colony elevation in all isolates except A2. A1
and A2 had rough textures, while A3 was smooth. All isolates were rod-shaped, occurred
in chains, fermented sugars, and tested positive for PGP traits. Isolate A1 showed the
highest nitrogen fixation zone of 2.0 cm. Quantitative analysis revealed that A2 exhibited
nitrogen fixation and zinc solubilization activities of 2.93 and 2.34 μg/mL, respectively.
A1 produced 2.68 μg/mL of indole-3-acetic acid (IAA). Both A1 and A2 exhibited
enzymatic activity, with A1 recording a high amylase activity of 6.50 U/mL. Isolate A2
responded well to 2 g fructose with highest value 2.24, while A3 showed 2.23 in 1 g
potassium nitrate-supplemented medium. All isolates grew in lead-supplemented media,
with no inhibitory effects from other metals. Maximum IAA production of 2.83 μg/mL
was recorded in medium with 8 g sucrose. Molecular identification confirmed the
bacterium as Vagococcus fluvialis. The isolates were resistant to Ampiclox, Zinnacef, and
Amoxicillin. Bioinoculated maize seeds showed improved growth in maize length 2.1 cm
(in vitro), 73.3 cm (field), and 52.0 cm (greenhouse), compared to un-inoculated. These
findings support the potential use of Vagococcus fluvialis as a bioinoculant to enhance
maize growth through multiple PGP mechanisms.
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