10.22376/ijpbs.2019.10.1.p1-12 Volume 11 Issue 2 2020 (April-June) Green chemistry approaches to find extensive application in the biosynthesis of metallic nanoparticles, due to its readily abundant nature, Sustainable materials were used as a base material for the synthesis of nanoparticles. Herein, we have established a simple, eco-friendly, low-cost, and photo-light induced biosynthesis (PLNB) of silver particles blue green algae extract from lessThan i greaterThan Lyngbya majuscula lessThan /i greaterThan . The physicochemical characteristic of PLNB-AgNPs was characterized by various spectroscopic and microscopic techniques such as UV-spectroscopy, Fourier transform infrared spectroscopy (FT-IR), Zeta ζ-potential analyzer, High-resolution transmission electron microscopy (HR-TEM), and Atomic force microscopy (AFM). The size of the synthesized AgNPs was found to be 16 nm. The antibacterial efficacy of the AgNPs obtained and biosynthesized from lessThan i greaterThan L. majuscula lessThan /i greaterThan was evaluated and compared with known antibiotics streptomycin and erythromycin which was used as control against gram negative and gram positive bacteria, respectively. The membrane permeability results of AgNPs showed that the antibacterial activity with inhibition of 99% on lessThan i greaterThan E. coli lessThan /i greaterThan (18 μg/mL) and lessThan i greaterThan B. cereus lessThan /i greaterThan (23 μg/mL). The morphological changes and cell membrane damage AgNPs induced by a microbial cell were evaluated by AFM microscopic analysis. The membranes were disrupted in the cells of lessThan i greaterThan E. coli lessThan /i greaterThan and lessThan i greaterThan B. cereus lessThan /i greaterThan treated with biosynthesized AgNPs and showed that shrunken membrane and with oozed out cytoplasmic content were found attached on the cell surface. The results of this study showed that AgNPs could effectively inhibited the bacterial strain lessThan i greaterThan E. coli lessThan /i greaterThan and lessThan i greaterThan B. cereus lessThan /i greaterThan . Hence the AgNPs could be used in food packaging material and bio-sensing microbial presence in food samples. Nallusamy Duraisamy, Sakthivel Muthu, and Kathiravan Krishnan Lyngbya Majuscula, Blue Green Algae, AgNPs, Antibacterial Activity, AFM Analysis. 83-91