BIOFILM FORMATION AND GROWTH PROMOTING ABILITY OF BACTERIA ISOLATED FROM COIR OF COCOS NUCIFERA

Abstract

Background: Salinity is a critical threat to agricultural productivity, reducing crop yield and soil fertility in arid and semi-arid regions. Conventional remediation methods such as leaching and chemical desalination are expensive, unsustainable, and environmentally harmful. Therefore, the development of biological approaches using halotolerant bacteria provides a sustainable alternative for reducing salinity and enhancing crop growth under salt stress.

Objective: This study aimed to isolate and characterize halotolerant bacterial strains from coco-coir and evaluate their potential to form biofilms for desalination and plant growth promotion under saline conditions.

Methods: Coco-coir samples were aseptically collected from Lahore Garrison University and cultured on nutrient agar supplemented with 1M, 2M, and 3M NaCl to isolate halotolerant bacteria. Morphological and biochemical characterization, including Gram staining, catalase, oxidase, citrate, indole, and Voges–Proskauer tests, were conducted for identification. Six isolates (AK-1 to AK-6) were screened for biofilm formation using the crystal violet assay. Isolate AK-6, showing the highest tolerance (growth up to 2M NaCl) and strongest biofilm development, was selected for a pilot-scale desalination experiment using 1M artificial seawater with coco-coir and sand as substrata. Zea mays seeds inoculated with five isolates (AK-1, AK-3, AK-4, AK-5, and AK-6) were evaluated for germination and growth parameters under both saline and non-saline conditions.

Results: All isolates formed distinct colonies and biofilms. AK-6 demonstrated strong growth at 2M NaCl and weak growth at 3M NaCl. The pilot setup showed a 46% reduction in Na⁺ concentration over 10 days. Inoculated Zea mays plants exhibited 85% germination under 1M saline conditions compared to 0% in non-inoculated controls. Mean shoot and root lengths increased by 73% and 81%, respectively, in inoculated plants, while chlorophyll a and b levels improved significantly (p < 0.05) compared to controls.

Conclusion: Halotolerant bacterial isolates, particularly AK-6, demonstrated effective biofilm-mediated desalination and promoted Zea mays growth under salinity stress. The integration of such bacterial biofilms offers a cost-effective and eco-friendly solution for managing saline soils and water in agriculture.