Characterization of Microbacterium sp. F10a and its role in polycyclic aromatic hydrocarbon removal in low-temperature soil

2009 ◽  
Vol 55 (5) ◽  
pp. 529-535 ◽  
Author(s):  
X. F. Sheng ◽  
L. Y. He ◽  
L. Zhou ◽  
Y. Y. Shen
Keyword(s):  
Low Temperature ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Cell Surface ◽  
Aromatic Hydrocarbon ◽  
Cell Surface Hydrophobicity ◽  
Surface Hydrophobicity ◽  
Bacterial Inoculation ◽  
Polycyclic Aromatic ◽  
Plant Growth Promoting ◽  
Growth Promoting

A polycyclic aromatic hydrocarbon degrading bacterium isolated from oil-polluted soil was identified as Microbacterium sp. F10a based on 16S rDNA gene sequence analysis. Plant growth promoting characteristics of the strain, degradation rate of phenanthrene and pyrene, and cell surface hydrophobicity characteristics of the strain were further characterized. The strain was also evaluated for promoting the growth of wheat and phenanthrene and pyrene removal from soil artificially contaminated with a mixture of phenanthrene (200 mg·kg–1) and pyrene (150 mg·kg–1) in pot experiments. The strain had the plant growth promoting characteristics of producing indole acetic acid, siderophore, and 1-aminocyclopropane-1-carboxylate deaminase activity and solubilizing inorganic phosphate. The strain also has a cell surface hydrophobicity that could increase the aqueous polycyclic aromatic hydrocarbon solubility. High-performance liquid chromatographic analysis showed that the degradation rates of phenanthrene (50 mg·L–1) and pyrene (20 mg·L–1) were 98% and 65%, respectively, under 28 °C after 7 days. Inoculation with the strain was found to significantly increase (p < 0.05) the growth of wheat and phenanthrene and pyrene removal in the unplanted or planted soils in a low-temperature environment. There were no significant differences in culturable bacterial numbers between live bacterial inoculation and dead bacterial inoculation controls in the unplanted and planted soils. However, the numbers of polycyclic aromatic hydrocarbon degrading bacteria were significantly greater in the inoculated planted or unplanted soils compared with the dead bacterial inoculation controls.

scholarly journals The LuxI/LuxR-Type Quorum Sensing System Regulates Degradation of Polycyclic Aromatic Hydrocarbons via Two Mechanisms

2020 ◽  
Vol 21 (15) ◽  
pp. 5548
Author(s):  
Zhiliang Yu ◽  
Zeyu Hu ◽  
Qimiao Xu ◽  
Mengting Zhang ◽  
Nate Yuan ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Quorum Sensing ◽  
Cell Surface ◽  
Aromatic Hydrocarbons ◽  
Bacterial Cell ◽  
Regulatory Gene ◽  
Cell Surface Hydrophobicity ◽  
Surface Hydrophobicity ◽  
Bacterial Cell Surface ◽  
Polycyclic Aromatic

Members of the Sphingomonadales are renowned for their ability to degrade polycyclic aromatic hydrocarbons (PAHs). However, little is known about the regulatory mechanisms of the degradative pathway. Using cross-feeding bioassay, a functional LuxI/LuxR-type acyl-homoserine lactone (AHL)-mediated quorum sensing (QS) system was identified from Croceicoccus naphthovorans PQ-2, a member of the order Sphingomonadales. Inactivation of the QS system resulted in a significant decrease in PAHs degradation. The QS system positively controlled the expression of three PAH-degrading genes (ahdA1e, xylE and xylG) and a regulatory gene ardR, which are located on the large plasmid. Interestingly, the transcription levels of these three PAH-degrading genes were significantly down-regulated in the ardR mutant. In addition, bacterial cell surface hydrophobicity and cell morphology were altered in the QS-deficient mutant. Therefore, the QS system in strain PQ-2 positively regulates PAH degradation via two mechanisms: (i) by induction of PAH-degrading genes directly and/or indirectly; and (ii) by an increase of bacterial cell surface hydrophobicity. The findings of this study improve our understanding of how the QS system influences the degradation of PAHs, therefore facilitating the development of new strategies for the bioremediation of PAHs.

Modeling Soot Formation Using Reduced Polycyclic Aromatic Hydrocarbon Chemistry in n-Heptane Lifted Flames With Application to Low Temperature Combustion

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Gokul Vishwanathan ◽  
Rolf D. Reitz
Keyword(s):  
Low Temperature ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Internal Combustion Engines ◽  
Soot Formation ◽  
Numerical Study ◽  
Low Temperature Combustion ◽  
Temperature Combustion ◽  
Lifted Flames ◽  
Polycyclic Aromatic

A numerical study of in-cylinder soot formation and oxidation processes in n-heptane lifted flames using various soot inception species has been conducted. In a recent study by the authors, it was found that the soot formation and growth regions in lifted flames were not adequately represented by using acetylene alone as the soot inception species. Comparisons with a conceptual model and available experimental data suggested that the location of soot formation regions could be better represented if polycyclic aromatic hydrocarbon (PAH) species were considered as alternatives to acetylene for soot formation processes. Since the local temperatures are much lower under low temperature combustion conditions, it is believed that significant soot mass contribution can be attributed to PAH rather than to acetylene. To quantify and validate the above observations, a reduced n-heptane chemistry mechanism has been extended to include PAH species up to four fused aromatic rings (pyrene). The resulting chemistry mechanism was integrated into the multidimensional computational fluid dynamics code KIVA-CHEMKIN for modeling soot formation in lifted flames in a constant volume chamber. The investigation revealed that a simpler model that only considers up to phenanthrene (three fused rings) as the soot inception species has good possibilities for better soot location predictions. The present work highlights and illustrates the various research challenges toward accurate qualitative and quantitative predictions of the soot for new low emission combustion strategies for internal combustion engines.

1,1’-Biaceanthrylene and 2,2'-Biaceanthrylene: Models for Linking Larger Polycyclic Aromatic Hydrocarbons via Five-Membered Rings

2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Electronic Properties ◽  
Aromatic Hydrocarbons ◽  
Model Systems ◽  
Redox Potentials ◽  
Dimer Model ◽  
Optical And Electronic Properties ◽  
Polycyclic Aromatic

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>

1,1’-Biaceanthrylene and 2,2'-Biaceanthrylene: Models for Linking Larger Polycyclic Aromatic Hydrocarbons via Five-Membered Rings

2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Electronic Properties ◽  
Aromatic Hydrocarbons ◽  
Model Systems ◽  
Redox Potentials ◽  
Dimer Model ◽  
Optical And Electronic Properties ◽  
Polycyclic Aromatic

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>

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