Rene biodegradation, will help in the 
development of potential bioremediation applications. Aerobic bacterial biodegradation of aromatic compounds employ the use of many enzymes which include HIF-2��-IN-1 web various dioxygenases and dehydrogenases [19]. Central to PAH degradation processes is the opening of the thermodynamically stable benzene rings by aromatic ring cleaving dioxygenases (ARCDs) [20,21,22]. The focus of this research was based on the expression activities of ARCD genes 117793 namely: phdF (coding for an extradiol dioxygenase), phdI (coding for 1-hydroxy-2-naphthoate dioxygenase/gentisate-1,2-dioxygenase), pcaG and H (coding for the alpha and beta subunits of protocatechuate-3,4-dioxygenase respectively). These genes were positively expressed in the bacteria Mycobacterium gilvum 23977191 PYR-GCK, in response to pyrene induction in a previous proteomics study [20]. Extradiol dioxygenase has been proposed to catalyze the conversion of the four-ringed dihydrodiol: 4,5-dihydroxypyrene, and the three-ringed dihydrodiol: 3,4-dihydroxyphenanthrene into their lesser ringed carboxylate counterparts in the pyrene degradation pathway [23,24] while 1-hydroxy-2-naphthoate dioxygenase cleaves a singly hydroxylated aromatic ring present in 1-hydroxy-2-naphthoate to produce trans-2-carboxy benzal pyruvate [25,26]. Protocatechuate 3,4-dioxygenase enzyme subunits catalyze protocatechuic acid cleavage and not catechol in Streptomyces sp. strain 2065 [27], breaking the final aromatic substrate ring into b-carboxy- cis, cis-muconate and subsequently releasing the pyrene degraded intermediates into the central metabolic pathway [23,25,27]. Mycobacterium gilvum PYR-GCK (ATCC 700033), isolated from the sediment of the Grand Calumet River in Northwestern Indiana based on its ability to utilize pyrene as a growth substrate [28], was used for this research due to the availability of necessaryFigure 1. Pyrene degradation profiles showing the residual pyrene ( ) in the various cultures. Graph of culture induced with pH states of 5.5, 6.5 and 7.5 (A) and NaCl concentrations of 0 M, 0.17 M, 0.5, 0.6 and 1 M (B). pH states correspond to acidic nature of the oceans and polluted terrestrial environments while the NaCl concentrations correspond to the saline nature of the ocean and some industrial waste effluents. Data and standard error are means from two replicates. doi:10.1371/journal.pone.0058066.gRing-Cleavage Dioxygenase Genes in Mycobacteriapurchased from Sigma-Aldrich Company (St. Louis, USA) and Tokyo Chemical Industry (Tokyo, Japan).Growth media and strain cultivationM.gilvum PYR-GCK cells were grown in 500 ml flasks of 300 ml basal medium containing, per litre: NaNO3, 0.5 g; (NH4)2SO4, 1.0 g; Na2HPO4; 2.5 g; KH2PO4, 1.0 g; MgSO4N7H2O, 0.1 g; Fe(NH4)2(SO4)2, 5 mg; 1 ml filter-sterilized Vitamin solution (containing, per litre: p-aminobenzoic acid, 200 mg; biotin, 200 mg; folic acid, 200 mg; nicotinic acid, 200 mg; Ca-panthothenate, 100 mg; pyridoxine-HCl, 100 mg; riboflavin, 100 mg; thiamine, 100 mg and vitamin B12, 1 mg) and 1 ml Trace Elements solution (containing, per litre: MnCl2N2H2O, 23 mg; H3BO3, 31 mg; CoCl2 6H2O, 36 mg; CuCl2N2H2O, 10 mg; NiCl2 6H2O, 20 mg; ZnCl2, 50 mg and Na2MoO4N2H2O, 30 mg) sterilized separately. The pH of the various culture flasks were adjusted to 5.5, 6.5 and 7.5, at zero salinity. 
Pyrene was dissolved in dimethyl sulfoxide and added to the induced culture-flasks at a final concentration of 25 mM while the control-culture flask had no substrate.Rene biodegradation, will help in the development of potential bioremediation applications. Aerobic bacterial biodegradation of aromatic compounds employ the use of many enzymes which include various dioxygenases and dehydrogenases [19]. Central to PAH degradation processes is the opening of the thermodynamically stable benzene rings by aromatic ring cleaving dioxygenases (ARCDs) [20,21,22]. The focus of this research was based on the expression activities of ARCD genes namely: phdF (coding for an extradiol dioxygenase), phdI (coding for 1-hydroxy-2-naphthoate dioxygenase/gentisate-1,2-dioxygenase), pcaG and H (coding for the alpha and beta subunits of protocatechuate-3,4-dioxygenase respectively). These genes were positively expressed in the bacteria Mycobacterium gilvum 23977191 PYR-GCK, in response to pyrene induction in a previous proteomics study [20]. Extradiol dioxygenase has been proposed to catalyze the conversion of the four-ringed dihydrodiol: 4,5-dihydroxypyrene, and the three-ringed dihydrodiol: 3,4-dihydroxyphenanthrene into their lesser ringed carboxylate counterparts in the pyrene degradation pathway [23,24] while 1-hydroxy-2-naphthoate dioxygenase cleaves a singly hydroxylated aromatic ring present in 1-hydroxy-2-naphthoate to produce trans-2-carboxy benzal pyruvate [25,26]. Protocatechuate 3,4-dioxygenase enzyme subunits catalyze protocatechuic acid cleavage and not catechol in Streptomyces sp. strain 2065 [27], breaking the final aromatic substrate ring into b-carboxy- cis, cis-muconate and subsequently releasing the pyrene degraded intermediates into the central metabolic pathway [23,25,27]. Mycobacterium gilvum PYR-GCK (ATCC 700033), isolated from the sediment of the Grand Calumet River in Northwestern Indiana based on its ability to utilize pyrene as a growth substrate [28], was used for this research due to the availability of necessaryFigure 1. Pyrene degradation profiles showing the residual pyrene ( ) in the various cultures. Graph of culture induced with pH states of 5.5, 6.5 and 7.5 (A) and NaCl concentrations of 0 M, 0.17 M, 0.5, 0.6 and 1 M (B). pH states correspond to acidic nature of the oceans and polluted terrestrial environments while the NaCl concentrations correspond to the saline nature of the ocean and some industrial waste effluents. Data and standard error are means from two replicates. doi:10.1371/journal.pone.0058066.gRing-Cleavage Dioxygenase Genes in Mycobacteriapurchased from Sigma-Aldrich Company (St. Louis, USA) and Tokyo Chemical Industry (Tokyo, Japan).Growth media and strain cultivationM.gilvum PYR-GCK cells were grown in 500 ml flasks of 300 ml basal medium containing, per litre: NaNO3, 0.5 g; (NH4)2SO4, 1.0 g; Na2HPO4; 2.5 g; KH2PO4, 1.0 g; MgSO4N7H2O, 0.1 g; Fe(NH4)2(SO4)2, 5 mg; 1 ml filter-sterilized Vitamin solution (containing, per litre: p-aminobenzoic acid, 200 mg; biotin, 200 mg; folic acid, 200 mg; nicotinic acid, 200 mg; Ca-panthothenate, 100 mg; pyridoxine-HCl, 100 mg; riboflavin, 100 mg; thiamine, 100 mg and vitamin B12, 1 mg) and 1 ml Trace Elements solution (containing, per litre: MnCl2N2H2O, 23 mg; H3BO3, 31 mg; CoCl2 6H2O, 36 mg; CuCl2N2H2O, 10 mg; NiCl2 6H2O, 20 mg; ZnCl2, 50 mg and Na2MoO4N2H2O, 30 mg) sterilized separately. The pH of the various culture flasks were adjusted to 5.5, 6.5 and 7.5, at zero salinity. Pyrene was dissolved in dimethyl sulfoxide and added to the induced culture-flasks at a final concentration of 25 mM while the control-culture flask had no substrate.
