Thesis

Isolation and Characterization of Rhizobium as Nitrogen-Fixing Bacteria

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This study focuses on the isolation and characterization of Rhizobium strains as
nitrogen-fixing bacteria. The primary objective was to assess their nitrogen fixation activity, evaluate
their indole-3-acetic acid (IAA) production capability, investigate phosphate solubilization potential,
examine enzymes solubilization, and determine their resistance to salinity and pH variations. The
isolation process involved obtaining root nodules from the sample of Pueraria javanica and
subsequently culturing the bacteria. Nitrogen fixation activity was determined using the
nitrogen-free bromthymol (NFB); the test showed that most of the isolates could convert
atmospheric nitrogen into a biologically available form. IAA production was assessed through the
colorimetric Salkowski's method. The Rhizobium isolates exhibited significant IAA production,
indicating their potential to enhance plant growth and development through hormone synthesis.
Phosphate solubilization was evaluated using Pikovskaya's agar medium. The Rhizobium strains
demonstrated the ability to solubilize insoluble forms of phosphate, which could improve the
availability of this vital nutrient for plants. Enzyme solubilization potential was assessed by examining
the ability of the Rhizobium isolates to produce extracellular enzymes, including amylase, cellulase,
and protease. Results indicated the strains exhibited diverse enzymatic activities, suggesting their
potential involvement in nutrient cycling and organic matter degradation. The Rhizobium isolates
were subjected to salinity and pH stress tests to investigate their adaptability to challenging
environmental conditions. The strains displayed varying degrees of resistance, highlighting their
potential to thrive in adverse soil conditions. Overall, this study successfully isolated and
characterized nitrogen-fixing Rhizobium strains. The findings demonstrate their ability to fix nitrogen,
produce IAA, solubilize phosphate, exhibit enzymatic activity, and tolerate salinity and pH
fluctuations. These characteristics underscore the potential of Rhizobium as beneficial plant
symbionts and contributors to sustainable agriculture practices. However, this study failed to find an
isolate that can excel in all the conducted tests.

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Availability

Detail Information

Series Title

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Call Number

BT 23-022

Publisher

i3L, Jakarta : i3L, Jakarta., 2023

Collation

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Language

English

ISBN/ISSN

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Classification

NONE

Content Type

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Media Type

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Carrier Type

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Edition

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Subject(s)

Rhizobium
nitrogen fixation
indole-3-acetic acid
phosphate solubilization
enzyme solubilization
salinity resistance
pH resistance

Specific Detail Info

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Statement of Responsibility

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