Metagenomics of a Photo-Fermentative Bacterial Solution and Its Effect on the Growth and Yield of Mini Green Cos Lettuce

Photosynthetic bacteria (PSB) are widely utilised in agriculture to enhance plantngrowth and crop quality by improving nutrient uptake and phytohormone production. This study aimed to analyse the metagenomic composition of a photo-fermentative bacterial solution derived from fermentation and assess its effects on the growth and yield of Mini Green Cos lettuce. Metagenomic analysis revealed that Bacteroidota (38%) was the most abundant phylum, followed by Proteobacteria (23%), Thermotogota (17%) and Firmicutes (15%). Within Proteobacteria, Alphaproteobacteria was dominant followed by Gammaproteobacteria. At the genus level, Petrimonas (22%), uncultured clones belonging to family Petrotogaceae (17%), Rhodopseudomonas (11%), Rubrivivax (6%), and an unidentified genus from Lentimicrobiaceae (4%) were the most prevalent. These findings highlight the microbial diversity of PSB solution, suggesting its potential role in plant growth promotion. A plant growth experiment was conducted using a Completely Randomised Design (CRD) with four treatments: control (T1), chemical fertiliser (T2), undiluted PSB solution (T3) and PSB solution diluted at a 1:1 ratio (T4), with 10 replicates per treatment. Among all treatments, lettuce irrigated with undiluted PSB solution (T3) exhibited the highest growth rate, yield and total chlorophyll content. However, its performance was not significantly different from that of the chemical fertiliser treatment (T2). These results suggest that PSB can effectively promote plant growth and yield, yielding results comparable to chemical fertilisers. Therefore, photo-fermentative bacterial solutions offer a sustainable and eco-friendly alternative to chemical fertilisers, supporting environmentally conscious agricultural practices.