Seed bacterization with plant growth-promoting endophytes: Impact on Okra productivity, nutraceuticals and antimicrobial properties
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Date
2025
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University of Namibia
Abstract
The growing challenges of population expansion, climate change, rising food costs,
and unpredictable rainfall patterns have intensified the need for sustainable agricultural
practices that boost crop productivity while minimising environmental impacts. One
promising strategy involves the combined use of plant growth-promoting endophytic
bacteria (PGPEB) with the environmentally friendly hydroponic technique to enhance
plant growth and functional quality. This study investigated the influence of seed
bacterization with three PGPEB strains, Kosakonia cowanii (KC), Bacillus
licheniformis (BL), and Cupriavidus metallidurans (CM), previously isolated from
Myrothamnus flabellifolius, on the productivity, nutraceutical accumulation, and
antimicrobial activity of okra (Abelmoschus esculentus L. Moench) under hydroponic
(Kratky method) conditions. Okra seeds were soaked in single and combined bacterial
inocula, germinated under dark conditions, and cultivated in a randomised complete
block design with three plants per pot, four replications, and eight treatments. Results
revealed significant improvements (P < 0.001) in seed germination percentage and
seedling vigour index among inoculated treatments compared to controls, with KC and
CM demonstrating strong individual and synergistic effects. BL was notably more
effective when used in combination with other bacteria. Furthermore, methanolic
extracts of okra pods from bacterized plants exhibited enhanced nutraceutical
properties, including elevated total phenolic content (TPC), antioxidant activity (up to
91% DPPH inhibition), and increased inhibition of α-amylase (92%) and αglucosidase (88%), key enzymes linked to diabetes management. Thin-layer
chromatography confirmed the presence of carotenes, while polysaccharides were
detected across all treatments. Antimicrobial assays revealed substantial activity
against pathogens such as Mycobacterium avium, Salmonella typhi, Candida albicans,
and Staphylococcus aureus, with the strongest effects observed in methanolic extracts
of BL-CM consortia. These findings underscore the potential of PGPEB consortia as
eco-friendly bio-stimulants to enhance okra seedling establishment, yield functional
bioactive compounds, and contribute to sustainable agriculture and novel nutraceutical
and antimicrobial development. Further exploration of PGPEB-based biofertilizers
may offer solutions for addressing chronic diseases and rising antibiotic resistance
Description
A thesis submitted in fulfilment of the requirements for the Degree of Master of Science in Microbiology
Keywords
Plant Growth-Promoting Endophytic Bacteria (PGPEB), Hydroponics, Okra (Abelmoschus esculentus), Seed germination, Seedling vigour index, Nutraceuticals, Antioxidant, Antidiabetic, Antimicrobial activity, Namibia, University of Namibia