Single-Cell Real-Time Visualization and Quantification of Perylene Bioaccumulation in Microorganisms

Tween-80 enhanced biodegradation of naphthalene by Klebsiella quasipneumoniae

Accidental spillage of petroleum products and industrial activities result in various hydrocarbons in the environment. While the n-hydrocarbons are readily degraded, the polycyclic aromatic hydrocarbons (PAHs) are recalcitrant to natural degradation, toxic to aquatic life and are responsible for diverse health challenges in terrestrial animals; suggesting the need for faster and more eco-friendly ways of removing PAHs from the environment. In this study, the surfactant tween-80 was used to enhance a bacterium's intrinsic naphthalene biodegradation activity. Eight bacteria isolated from oil-contaminated soils were characterised using morphological and biochemical methods. The most effective strain was identified as Klebsiella quasipneumoniae using 16S rRNA gene analysis. High-Performance Liquid Chromatography (HPLC) analyses showed that the detectable concentration of naphthalene was decreased from 500 to 157.18 μg/mL (67.4%) after 7 d in the absence of tween-80, while 99.4% removal was achieved in 3 d in the presence of tween-80 at 60 μg/mL concentration. The peaks observed in the Fourier Transform Infra-Red Spectroscopy (FTIR) spectrum of control (naphthalene), which were absent in that of the metabolites, further established naphthalene degradation. Furthermore, Gas Chromatography-Mass Spectrometer (GCMS) revealed metabolites of single aromatic ring, such as 3,4-dihydroxybenzoic acid 4-hydroxylmethylphenol, which confirmed that the removal of naphthalene is by biodegradation. Tyrosinase induction and laccase activities suggested the involvement of these enzymes in naphthalene biodegradation by the bacterium. Conclusively, a strain of K. quasipneumoniae that can effectively remove naphthalene from contaminated environments has been isolated, and its biodegradation rate was doubled in the presence of non-ionic surfactant, tween-80.

Organ and tissue-specific distribution of selected polycyclic aromatic hydrocarbons (PAHs) in ApoE-KO mouse

Polycyclic aromatic hydrocarbons (PAHs) are one of the most prevalent classes of environmental pollutants resulting from the incomplete combustion of hydrocarbons. Exposure to PAHs is implicated in the pathogenesis of the cardiovascular disease, pulmonary disease, and even cancer. However, little is known about organ- and tissue-specific distribution patterns of PAHs in animals at macro-tissue and microscopic levels. Here, by combining GC-MS and single-molecule fluorescence microscopy (SMFM), we revealed the distribution characteristics of four different PAHs (phenanthrene (Phe), pyrene (Pyr), perylene (Per), and benzo[a]pyrene (BaP)) in atherosclerosis model mice (ApoE-KO mice) at macro-tissue and micro-region level after long-term oral exposure. Average PAH concentrations detected by GC-MS in seven tissues ranged from 6.44 to 441 ng/g. The gastrointestinal tract, epididymal fat pat, and lung accumulated higher levels of PAHs, whereas relatively lower PAH residuals were found in the liver, brain, and kidney. Correlation analysis showed that PAHs with higher molecular weight (r: -0.972 to -0.746), Log K_ow (r: -0.984 to -0.746) and lower water solubility (r: 0.720 to 0.994) were less prone to bioaccumulate. For the first time, SMFM demonstrated a distinct heterogeneous distribution of Per in the tissue slices. More interestingly, we observed many micro-cluster regions, namely hotspots, showed much higher Per fluorescent intensity than the other common regions. In the area of atherosclerotic plaque, the Per hotspots were colocalized with the micro-regions with the most severe inflammatory response. The hotspots with very high enrichment in PAHs were likely to stimulate the local inflammation and cause excessive damage of the aorta, which resulted in a significant increase of the relative area of atherosclerosis lesion and aggravated atherosclerosis, as observed in PAH exposed mice.