Variations in the abundance and identity of class II aromatic ring-hydroxylating dioxygenase genes in groundwater at an aromatic hydrocarbon-contaminated site

Abstract. Substitution of methyl groups onto the aromatic ring determines the SOA formation from the aromatic hydrocarbon precursor. This study links the number of methyl groups on the aromatic ring to SOA formation from aromatic hydrocarbons photooxidation under low NOx conditions (HC / NO > 10 ppb C : ppb). Aromatic hydrocarbons with increasing numbers of methyl groups are systematically studied. SOA formation from pentamethylbenzene and hexamethylbenzene are reported for the first time. A decreasing SOA yield with increasing number of methyl groups is observed. Linear trends are found in both f44 vs. f43 and O / C vs. H / C for SOA from aromatic hydrocarbons with zero to six methyl groups. An SOA oxidation state predictive method based on benzene is used to examine the effect of added methyl groups on aromatic oxidation under low NOx conditions. Further, the impact of methyl group number on density and volatility of SOA from aromatic hydrocarbons is explored. Finally, a mechanism for methyl group impact on SOA formation is suggested. Overall, this work suggests as more methyl groups are attached on the aromatic ring, SOA products from these aromatic hydrocarbons become less oxidized per mass/carbon.

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Evaluation of Cooking Oil as Processing Addtive for Natural Rubber

ASEAN Journal on Science and Technology for Development ◽

10.29037/ajstd.71 ◽

2017 ◽

Vol 34 (1) ◽

pp. 17 ◽

Cited By ~ 3

Author(s):

Y. M. SYAMIN ◽

S. AZEMI ◽

K. DZARAINI

Keyword(s):

Polycyclic Aromatic Hydrocarbon ◽

Aromatic Hydrocarbon ◽

Natural Rubber ◽

Physical Properties ◽

Aromatic Ring ◽

Rolling Resistance ◽

Cooking Oil ◽

Alternative Option ◽

Rubber Compounds ◽

Polycyclic Aromatic

It was reported recently that high amount of aromatic ring or number of polycyclic aromatic hydrocarbon compounds found in aromatic oil are carcinogenic. This paper discusses the work to evaluate the Malaysian cooking oil as an alternative option to be used as process oil since cooking oil is safe to use and non-toxic. The performance of cooking oil is compared againstaromatic and paraffinioils. The results showed that rubber compounds containing cooking oil produced almostsimilar cure characteristicsas those produced by aromatic and paraffinioils indicating that it did not interfere with the vulcanization reaction. The physical properties of the vulcanizates containing cooking oil were almostsimilar to those of vulcanizates containing aromatic and paraffinioils, except the rebound resilience. The vulcanizates containing cooking oil gave higher resilience than vulcanizates containing aromatic and paraffinioils. High resilience is one of the desired features for a low rolling resistance tyre. Cooking oil provided this extra advantage.

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Hydroxylations of substituted naphthalenes by Escherichia coli expressing aromatic dihydroxylating dioxygenase genes from polycyclic aromatic hydrocarbon-utilizing marine bacteria

Journal of Molecular Catalysis B Enzymatic ◽

10.1016/j.molcatb.2007.06.007 ◽

2007 ◽

Vol 48 (3-4) ◽

pp. 77-83 ◽

Cited By ~ 9

Author(s):

Kazutoshi Shindo ◽

Ayako Osawa ◽

Yuki Kasai ◽

Nobuko Iba ◽

Ayako Saotome ◽

...

Keyword(s):

Escherichia Coli ◽

Polycyclic Aromatic Hydrocarbon ◽

Aromatic Hydrocarbon ◽

Marine Bacteria ◽

Polycyclic Aromatic ◽

Dioxygenase Genes

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Diversity of 16S rRNA and dioxygenase genes detected in coal-tar-contaminated site undergoing active bioremediation

Journal of Applied Microbiology ◽

10.1111/j.1365-2672.2009.04523.x ◽

2010 ◽

Vol 108 (4) ◽

pp. 1252-1262 ◽

Cited By ~ 23

Author(s):

M. Kumar ◽

S. Khanna

Keyword(s):

16S Rrna ◽

Coal Tar ◽

Contaminated Site ◽

Dioxygenase Genes

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Identification of a Novel Dioxygenase Involved in Metabolism of o-Xylene, Toluene, and Ethylbenzene by Rhodococcus sp. Strain DK17

Applied and Environmental Microbiology ◽

10.1128/aem.70.12.7086-7092.2004 ◽

2004 ◽

Vol 70 (12) ◽

pp. 7086-7092 ◽

Cited By ~ 48

Author(s):

Dockyu Kim ◽

Jong-Chan Chae ◽

Gerben J. Zylstra ◽

Young-Soo Kim ◽

Seong-Ki Kim ◽

...

Keyword(s):

Aromatic Ring ◽

Single Point ◽

Open Reading Frames ◽

Gene Encoding ◽

Catabolic Genes ◽

Genes Encoding ◽

Sulfur Protein ◽

Benzene Toluene ◽

Iron Sulfur Protein ◽

Dioxygenase Genes

ABSTRACT Rhodococcus sp. strain DK17 is able to grow on o-xylene, benzene, toluene, and ethylbenzene. DK17 harbors at least two megaplasmids, and the genes encoding the initial steps in alkylbenzene metabolism are present on the 330-kb pDK2. The genes encoding alkylbenzene degradation were cloned in a cosmid clone and sequenced completely to reveal 35 open reading frames (ORFs). Among the ORFs, we identified two nearly exact copies (one base difference) of genes encoding large and small subunits of an iron sulfur protein terminal oxygenase that are 6 kb apart from each other. Immediately downstream of one copy of the dioxygenase genes (akbA1a and akbA2a ) is a gene encoding a dioxygenase ferredoxin component (akbA3), and downstream of the other copy (akbA1b and akbA2b ) are genes putatively encoding a meta-cleavage pathway. RT-PCR experiments show that the two copies of the dioxygenase genes are operonic with the downstream putative catabolic genes and that both operons are induced by o-xylene. When expressed in Escherichia coli, AkbA1a-AkbA2a-AkbA3 transformed o-xylene into 2,3- and 3,4-dimethylphenol. These were apparently derived from an unstable o-xylene cis-3,4-dihydrodiol, which readily dehydrates. This indicates a single point of attack of the dioxygenase on the aromatic ring. In contrast, attack of AkbA1a-AkbA2a-AkbA3 on ethylbenzene resulted in the formation of two different cis-dihydrodiols resulting from an oxidation at the 2,3 and the 3,4 positions on the aromatic ring, respectively.

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Evolution of a Pathway for Chlorobenzene Metabolism Leads to Natural Attenuation in Contaminated Groundwater

Applied and Environmental Microbiology ◽

10.1128/aem.64.11.4185-4193.1998 ◽

1998 ◽

Vol 64 (11) ◽

pp. 4185-4193 ◽

Cited By ~ 99

Author(s):

Jan Roelof van der Meer ◽

Christoph Werlen ◽

Shirley F. Nishino ◽

Jim C. Spain

Keyword(s):

Aromatic Ring ◽

Natural Attenuation ◽

Genetic Recombination ◽

Sequence Data ◽

Gene Clusters ◽

Test System ◽

Contaminated Site ◽

Physiological Characterization ◽

Synthetic Chemicals ◽

Degrading Bacteria

ABSTRACT Complete metabolism of chlorinated benzenes is not a feature that is generally found in aerobic bacteria but is thought to be due to a novel recombination of two separate gene clusters. Such a recombination could be responsible for adaptation of a natural microbial community in response to contamination with synthetic chemicals. This hypothesis was tested in a chlorobenzene (CB)-contaminated aquifer. CB-degrading bacteria from a contaminated site were characterized for a number of years by examining a combination of growth characteristics and DNA-DNA hybridization, PCR, and DNA sequence data. The genetic information obtained for the CB pathway of the predominant microorganism, Ralstonia sp. strain JS705, revealed a unique combination of (partially duplicated) genes for chlorocatechol degradation and genes for a benzene-toluene type of aromatic ring dioxygenase. The organism was detected in CB-polluted groundwater by hybridizing colonies cultivated on low-strength heterotrophic media with probes for the CB pathway. Southern hybridizations performed to determine the organization of the CB pathway genes and the 16S ribosomal DNA indicated that CB-degrading organisms isolated from different wells at the site were identical to JS705. Physiological characterization by the Biolog test system revealed some differences. The genes for the aromatic ring dioxygenase and dihydrodiol dehydrogenase of JS705 were detected in toluene and benzene degraders from the same site. Our results suggest that recent horizontal gene transfer and genetic recombination of existing genes between indigenous microorganisms were the mechanisms for evolution of the catabolic pathway. Evolution of the CB pathway seems to have created the capacity for natural attenuation of CB at the contaminated site.

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