I am studying about the inhibition effect of nanosilver particle (AgNP) on growth of microorganism (or nitrification ability) in wastewater treatment plant and have some questions about the mechanism of AgNP inhibition.
1. In my opinion, I think inhibition of AgNP is noncompetitive, but I wonder whether my procedure for leading to this conclusion is okay or not. Why I guessed like above is:
After AgNP is dissolved into dAg, dAg will be adsorbed to intra structure such as protein or DNA (Chemically attached?). It might be an irreversible reaction [1] and have an effect on maximum growth rate [2]. Since I read that noncompetitive inhibition leads to the decreased Vmax (maximum growth rate) and is an irreversible reaction, I thought that inhibition of AgNP is noncompetitive.
2. I also have some question about adsorption of AgNP on cell wall (extra structure).
2-1.This adsorption may be due to the physical attachment? Will desorption occur?
2-2. Does attached AgNP also cause inhibition on growth of microorganism?
(e.g., attachment of AgNP -> decrease of pore size for transferring substrate inside -> increase of Ks (saturation constant for substrate)-> so that there is competitive inhibition?)
Although I read some paper and articles, still I am not sure that I understand properties of nanosilver particle related with its inhibition effect.
If anyone knows the answers for my questions, please tell me!
Reference
[1] Radniecki, T. S., D. P. Stankus, et al. (2011). "Influence of liberated silver from silver nanoparticles on nitrification inhibition of< i> Nitrosomonas europaea." Chemosphere 85(1): 43-49.
[2] Choi, O., K. K. Deng, et al. (2008). "The inhibitory effects of silver nanoparticles, silver ions, and silver chloride colloids on microbial growth." Water research 42(12): 3066-3074.
Hi Pyo,
You are working on a good research topic.
To the best of my knowledge, we use the term competitive/non-competitive/irreversible inhibition when we deal with inhibitors that inhibit enzyme activity. I don’t think that such terms can be used for representing growth or multiplication of cells. It is known that AgNPs possess antimicrobial activity. However, few cells of bacteria might develop some degree of resistance. It is also likely that most or all the AgNPs used might get adsorbed or sequestered by many bacterial cells (which might die). Even if one, two or few bacterial cells escape from AgNPs, they can multiply.
2. It is true that AgNPs often get adsorbed on cell wall or capsule (i.e. extracellular material). Some can penetrate into cells and get sequestered by variety of molecules (especially the ones possessing free –SH, -COOH, -NH2 etc.) including proteins and nucleic acids.
Dear Pardha-Saradhi,
Thank you for your kind reply, and can I ask two more question?
First, since some AgNPs which penetrate into cells can get sequestered by variety of molecules, I thought this leads to lose of function of some proteins resulting in decrease of enzyme activity. this phenomenon cannot be possible??
Second, I found some expressions for describing reversible competitive/noncompetitive inhibition (e.g., 1/(1+[I]/K for noncompetitive inhibition, where [I] is inhibitor concentration and K is michaelis menten constant). However, I couldn't find any expression for irreversible inhibition.. If you know about the expression, please let me know.
Thank you for your reading and I wish my way of writing is polite.
Regards,
SeHee, Pyo
Yes, it is true that AgNPs can bind to proteins and nucleic acids (besides cell wall material). You are also correct in stating that AgNPs do inhibit activities of enzymes. We have been evaluating impact of AgNPs on antioxidant enzymes. It is certain that inhibition is noncompetetive. To the best of my knowledge, it is irreversible. But, the later needs to be confirmed.
Nice question. See this paper. It may give you little idea.
"Potential theranostics application of biosynthesized silver nanoparticles"
Dear Mukherjee,
I read your paper with focus on toxicity mechanism of silver nanoparticle.
Since I am studying about what inhibition type of nanosilver particle is, I need to know specific mechanism of its toxicity on microorganism.
I could know various mechanism related with the toxicity of AgNP and organize my thinking about them.
Thank you for your recommendation and nice help for my study!
Best regards,
SeHee, Pyo
Dear Sehhe,
Carry on. Please let me know any further help is needed if. Nice topics you have choosen. Go ahead.
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