## 4 Discussion  
To investigate the effect of radiation doses on the antimicrobial activity, different time intervals in combination with different distances from the laser source were used. This is a novel approach to enhancing the antimicrobial activity of cyanobacterial extracts by applying non-ionizing visible radiation to avoid the hazards that result from ionizing radiation. Hence, we used the red-visible-light 635 nm diode laser beam to ensure that the cyanobacteria were not subjected to any genetic change. Thus, the risks were minimized, and the effectiveness increased. We also exposed cyanobacterial biomass to compare the antimicrobial action of their extracts to extracts directly exposed to the laser in order to select the best treatment in terms of biosafety, efficacy, and reproducibility. Although  
Figure 3: An agar plate showing the greatest inhibition zone of extract derived from biomass pre-exposed to laser and extract directly exposed to laser and extract directly exposed to laser and extract directly exposed to laser of _Synechococcus elongatus_ against _Pantoea vagans_ at 10 cm. (**a**) Effect of laser treatment for different exposure times with 4 min intervals at a distance of 10 cm. (**b**) Effect of laser treatment for different exposure times with 16 min intervals at a distance of 10 cm. (P) positive control—(N) negative control—(C) an extract derived from cyanobacterial biomass pre-exposed to laser—(E) an extract directly exposed to laser. aqueous extracts' effectiveness may be below that of organic extracts [34] but they are eco-friendlier and more cost-effective. To concentrate bioactive compounds in aqueous extracts as well as to enhance antimicrobial activity, aqueous extracts were incubated at 37 \({}^{\circ}\)C for 72 h after laser treatment. This step increased the inhibition zone diameter considerably. Incubation allowed excess water to evaporate, thus increasing the concentration of the bioactive compounds, as [PERSON] et al. [35] described for concentrating aqueous extracts of _Anabaena spiroides_ at 40 \({}^{\circ}\)C. The split-plot ANOVA provided an insight into the significance or non-significance of the variables tested across groups. Here, we used two main groups: the extract derived from biomass pre-exposed to the laser and the extract directly exposed to the laser, and we tested their interaction with exposure time and distance to show which treatment resulted in the highest significant change from the control. Cyanobacteria contain bioactive antimicrobial agents. Some of these agents are hydrophilic molecules that dissolve in water. In this study, the aqueous extracts of cyanobacteria contained polar molecules and ions in addition to water-soluble pigments. Certain pigments are specifically found in cyanobacteria, and they do have antimicrobial activity. Phycobiliproteins (phycocyanin, allophycocyanin, and phycoerythrin) are a family of water-soluble photosynthetic accessory pigments which all possess antimicrobial activity. Phycobiliproteins are water-soluble proteinaceous pigments [36]. Interestingly, Refs. [37; 38] showed that phycocyanin pigment of _Spirulina platensis_ and _Westiellosis_ sp. has a potent antimicrobial effect against Gram-positive and Gram-negative bacteria. In addition, [PERSON] and [PERSON] [39] reported that phycoerythrin of _Microchaete_ has antibacterial activity against pathogenic bacteria. Both light intensity and quality can impact photosynthetic pigments in cyanobacteria. The control of light conditions by synthetic light can be sufficient to affect cyanobacterial pigment production. This in agreement with [PERSON] et al. [40], who reported that the artificial light LED is a suitable economic energy source that increases the cyanobacterial pigment content. An LED is a red-light, light-emitting diode [41], specific monochromatic light can affect photosynthesis and pigment production [42]. Indeed, the quality of light can influence the photosynthetic pigments' quantity. For example, Ref.