Silver nanoparticle inhibition of polycyclic aromatic hydrocarbons degradation by Mycobacterium species RJGII-135
S R Mueller-Spitz1, K D Crawford
1Department of Biology and Microbiology, University of Wisconsin Oshkosh, Oshkosh, WI, USA.
Unlabelled:
Polycyclic aromatic hydrocarbons (PAH) are a common environmental contaminant originating from both anthropogenic and natural sources. Mycobacterium species are highly adapted to utilizing a variety of PAH. Silver nanoparticles (AgNP) are an emerging contaminant that possess bactericidal properties, interferes with the bacterial membrane and alters function. Mycobacterium sp. strain RJGII-135 provided a model bacterium to assess changes in carbon metabolism by focusing on PAH degradation, which is dependent upon passive uptake of hydrophobic molecules into the cell membrane. A mixture of 18 PAH served as a complex mixture of carbon sources for assessing carbon metabolism. At environmentally relevant PAH concentrations, RJGII-135 degraded two-, three-, and four-ring PAH within 72 h, but preferentially attacked phenanthrene and fluorene. Total cell growth and PAH degradation were successively reduced when exposed to 0·05-0·5 mg 1(-1) AgNP. However, 0·05 mg l(-1) AgNP inhibited degradation of naphthalene, acenaphthylene and acenaphthalene. RJGII-135 retained the ability to degrade the methylated naphthalenes regardless of AgNP concentration suggesting that proteins involved in dihydrodiol formation were inhibited. The reduced PAH metabolism of RJGII-135 when exposed to sublethal concentrations of AgNP provides evidence that nanoparticle pollution could alter carbon cycling in soils, sediment and aquatic environments.
Significance And Impact Of The Study:
Silver nanoparticle (AgNP) pollution threatens bacterial-mediated processes due to their antibacterial properties. With the widespread commercial use of AgNP, continued environmental release is inevitable and we are just beginning to understand the potential environmental ramifications of nanoparticle pollution. This study examined AgNP inhibition of carbon metabolism through the polycyclic aromatic hydrocarbon degradation by Mycobacterium species RJGII-135. Sublethal doses altered PAH metabolism, which is dependent upon cell membrane properties and intracellular proteins. The changed carbon metabolism when exposed to sublethal doses of AgNP suggests broad impacts of this pollution on bacterial carbon cycling in diverse environments.
Insights
Silver nanoparticles (AgNP) disrupt polycyclic aromatic hydrocarbon (PAH) degradation by Mycobacterium bacteria. This nanoparticle pollution impacts bacterial carbon cycling in various environments.
Area of Science:
- Environmental Science
- Microbiology
- Nanotechnology
Background:
- Polycyclic aromatic hydrocarbons (PAH) are widespread environmental contaminants.
- Mycobacterium species are known for their ability to degrade PAH.
- Silver nanoparticles (AgNP) are emerging contaminants with bactericidal properties.
Purpose of the Study:
- To assess the impact of silver nanoparticles (AgNP) on the carbon metabolism of Mycobacterium sp. strain RJGII-135, specifically focusing on PAH degradation.
- To understand how sublethal concentrations of AgNP affect bacterial growth and PAH utilization.
Main Methods:
- Utilized Mycobacterium sp. strain RJGII-135 as a model organism.
- Exposed the bacteria to a mixture of 18 PAH as carbon sources.
- Introduced varying concentrations of AgNP (0.05-0.5 mg L⁻¹) to assess inhibition of PAH degradation and cell growth.
Main Results:
- Mycobacterium sp. strain RJGII-135 degraded various PAH within 72 hours, with a preference for phenanthrene and fluorene.
- Sublethal AgNP concentrations (0.05-0.5 mg L⁻¹) reduced overall PAH degradation and cell growth.
- Specific PAH like naphthalene were inhibited at 0.05 mg L⁻¹ AgNP, while methylated naphthalenes were still degraded, indicating targeted protein inhibition.
Conclusions:
- Silver nanoparticle pollution significantly inhibits bacterial PAH metabolism, affecting essential carbon cycling processes in soil, sediment, and aquatic ecosystems.
- The antibacterial properties of AgNP interfere with bacterial cell membranes and intracellular proteins crucial for hydrocarbon degradation.
- Understanding these impacts is critical given the inevitable environmental release of AgNP and their potential ramifications.
