**Abstract**

Silver nanoparticles (AgNPs) received tremendous attention due to their fascinated applications. Extensive research reports are available on the physical, chemical, and biological synthesis of colloidal Ag NPs. Research on biological systems mediated silver nanoparticle synthesis is essential to explore more applications. Microbial synthesis has been recognized as an eco-friendly and influential source among biological sources. Therefore, the bacteria are often considered an exciting reducer for silver and gold nanoparticles fabrication. Further, the synthesized nanoparticles incorporated different biological agents from what we need as bio reducing agents. The cell membrane of microorganisms plays a crucial role in the endogenous synthesis of nanoparticles. The cell membrane interacts electronically with the charged metal ions because it is charged. Enzymes inside the cell membrane biodegrade metal ions into nanoparticles, which eventually propagate through the cell membrane in small volumes. The fabricated silver nanoparticles were characterized by different spectroscopy techniques, to reveal the structural and functional properties. The synthesized nanoparticle reacts against many pathogens and insects and is used in medical fields. One of the pesticide industry's significant applications is mosquito larvicidal application. This chapter dealt with the microbial-mediated synthesis of silver nanoparticles, characterization, and mosquito larvicidal applications.

**Keywords:** bacteria, silver nanoparticle synthesis, mosquito larvicidal activity, intracellular and extracellular synthesis
