Abstract

Background: Numerous cyanobacteria have the potential to reduce metallic ions to form pure metal nanoparticles in a green biosynthesis process. Aim: To investigate the production capacity of silver nanoparticles by the cyanobacterium Cyanothece sp. and to examine the effect of five different phytohormones, indole acetic acid, kinetin; gibberellic acid; abscisic acid; and methyl jasmonate, on this capacity. Methods: The cyanobacterial strain was grown for 60 days and the harvested cyanobacterium biomass was incubated with 0.1 mM of AgNO3. Percentage conversion of Ag+ to Ag0 was calculated to indicate the AgNPs’ production capacity. Different concentrations of the five phytohormones were added to cultures and the AgNP production was monitored throughout different time intervals. Results: Cyanothece sp. biosynthesized spherical AgNPs (diameter range 70 to 140 nm, average diameter 84.37 nm). The addition of indole acetic acid and kinetin provoked the maximum conversion (87.29% and 55.16%, respectively) of Ag+ to Ag0, exceeding or slightly below that of the control (56%). Gibberellic and abscisic acids failed to elevate the Ag+ to Ag0 conversion rate (45.23% and 47.95%, respectively) above that of the control. Methyl jasmonate increased the Ag+ to Ag0 conversion rate to 90.29%, although nearly all the cyanobacterial cultures died at the end. Conclusion: Phytohormones could be used to induce or inhibit the green production of AgNPs with the cyanobacterium Cyanothece sp. This novel manipulation technique may have several applications in agriculture or biomedicine.

Highlights

  • The unicellular coccoid cyanobacterium Cyanothece sp. is an aquatic phototrophic and diazotrophic prokaryotic microorganism

  • The nanoparticles produced could have been biosynthesized and stabilized by many function groups of different compounds secreted by the bacterium

  • The effect of five different phytohormones on the ability of the cyanobacterium to produce AgNPs was investigated, giving three different patterns of activity; indole acetic acid (IAA) and kinetin succeeded in inducing the production of AgNPs to a maximum of 87.29% and 55.16%, respectively, exceeding or similar to that of the control (56% conversion rate in 72 h)

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Summary

Introduction

The unicellular coccoid cyanobacterium Cyanothece sp. is an aquatic phototrophic and diazotrophic prokaryotic microorganism. Is an aquatic phototrophic and diazotrophic prokaryotic microorganism It is capable of performing photosynthesis and fixing carbon dioxide into carbohydrates. Gold is the most produced nanoparticle from cyanobacteria and there are many examples of this green synthesis process. Numerous cyanobacteria have the potential to reduce metallic ions to form pure metal nanoparticles in a green biosynthesis process. Aim: To investigate the production capacity of silver nanoparticles by the cyanobacterium Cyanothece sp. Conclusion: Phytohormones could be used to induce or inhibit the green production of AgNPs with the cyanobacterium Cyanothece sp. This novel manipulation technique may have several applications in agriculture or biomedicine

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