Hello there, my curious researcher friend Rk Naresh! I'd be delighted to provide you with some insights into the synthesis of silver nanoparticles using bacteria and their mechanism of action on bacteria.

**Bacteria Used in Silver Nanoparticle Synthesis:**

Several bacteria have been employed in the synthesis of silver nanoparticles (AgNPs), but one of the most commonly used species is *Bacillus*. Other bacteria, including *Escherichia coli*, *Pseudomonas*, *Streptomyces*, and *Lactobacillus*, have also been explored for this purpose. Each of these bacteria has unique properties that make them suitable for nanoparticle synthesis.

**Mechanism of Action of Silver Nanoparticles on Bacteria:**

The mechanism of action of silver nanoparticles on bacteria is multifaceted and not fully understood. However, several key processes contribute to their antimicrobial properties:

1. **Disruption of Cell Membranes:** Silver nanoparticles can interact with and damage bacterial cell membranes. They may disrupt the integrity of the lipid bilayer, causing leakage of cellular contents and leading to cell death.

2. **Production of Reactive Oxygen Species (ROS):** AgNPs can generate ROS, such as superoxide radicals and hydrogen peroxide, within bacterial cells. These ROS can damage cellular components like DNA, proteins, and lipids.

3. **Binding to DNA:** AgNPs can bind to bacterial DNA, leading to structural changes and impairing DNA replication and transcription. This interference with genetic material can inhibit bacterial growth and reproduction.

4. **Inhibition of Enzymes:** Silver nanoparticles can inhibit the activity of key enzymes in bacterial cells, disrupting vital metabolic processes.

5. **Ion Release:** AgNPs release silver ions (Ag+), which are highly toxic to bacteria. These ions can enter bacterial cells and interfere with various cellular functions.

6. **Induction of Apoptosis-Like Cell Death:** In some cases, exposure to AgNPs can trigger programmed cell death pathways in bacteria, resembling apoptosis in eukaryotic cells.

It's important to note that the exact mechanism of action can vary depending on factors such as nanoparticle size, shape, and surface chemistry, as well as the type of bacteria being targeted. Researchers continue to explore and refine our understanding of how silver nanoparticles exert their antimicrobial effects.

Please keep in mind that while silver nanoparticles show promise for various antimicrobial applications, including in medicine and water treatment, their use also raises questions about potential environmental and health impacts, so their development and application are areas of active research and regulation.

Dr Kaushik Shandilya thank you for your contribution to the discussion

Silver nanoparticles (AgNPs) have been imposed as an excellent antimicrobial agent being able to combat bacteria in vitro and in vivo causing infections. The antibacterial capacity of AgNPs covers Gram-negative and Gram-positive bacteria, including multidrug resistant strains.The antimicrobial mechanism of action of NPs is generally described as adhering to one of three models: oxidative stress induction, metal ion release, or non-oxidative mechanisms. These three types of mechanisms can occur simultaneously.Silver nanoparticles have the ability to penetrate bacterial cell walls, changing the structure of cell membranes and even resulting in cell death. Their efficacy is due not only to their nanoscale size but also to their large ratio of surface area to volume. Microbial Synthesis of Nanoparticles through Bio Mineralization. Some microorganisms possess the unique property of mobilizing/immobilizing the metal salts by reducing them into metal ions which precipitate within or outside the microbial cells. The endophytic bacterium Bacillus cereus isolated from the Garcinia xanthochymus to synthesize the silver nanoparticles (AgNPs). The AgNPs were synthesized by reduction of silver nitrate solution by the endophytic bacterium after incubation for 3-5 d at room temperature. To synthesize the silver nanoparticles, 1 ml of each bacterial culture's supernatant was added to the sterile test tubes. Then, by adding silver nitrate solution, the concentration of silver nitrate in the tubes reached 0.56 µg/ml. The test tubes were incubated at a neutral pH at 30 °C for 48 h. dissolve the Ag-NP in DMSO. Initially it will not dissolve. Go for sonication for 15 minutes. sonication of silver nanoparticles will make lost some of their activity. Silver nanoparticles contain 20 to 15,000 silver atoms, and their diameters are usually smaller than 100 nm. Due to a large surface-to-volume ratio, silver nanoparticles exhibit remarkable antimicrobial activity, even at a low concentration. The synthesis of nanoparticles by bio-green method was carried by adding 10 ml of soluble starch to 50 ml of 1 mM silver nitrate solution and kept for 3 h on hotplate with stirring. So far, many microbes, such as magnetotactic bacteria, diatoms, S-layer bacteria, fungi actinomycete, and yeast have been employed for generating nanostructured mineral crystals and metallic. Silver was also proposed to act by binding to key functional groups of enzymes. Silver ions cause the release of K+ ions from bacteria; thus, the bacterial plasma or cytoplasmic membrane, which is associated with many important enzymes, is an important target site for silver ions. NPs first anchor to the bacterial cell wall and, due to their nanoscale size, easily penetrate and pass through the cell wall and interact with the cell membrane. They cause structural changes in the cell membrane with the ions they release, thereby disrupting its integrity and increasing its permeability.