Optimization of an inducible, chromosomally encoded benzo [a] pyrene (BaP) degradation pathway in Bacillus subtilis BMT4i (MTCC 9447)

Abstract

Benzo [a] pyrene (BaP), a pentacyclic polyaromatic hydrocarbon, is 1 of the 12 target compounds defined in the new US Environmental Protection Agency strategy for controlling persistent, bioaccumulative, and toxic pollutants. We previously isolated a novel strain Bacillus subtilis BMT4i capable of utilizing BaP as sole source of carbon and energy. The present study investigated (1) whether the BaP degradation pathway is inducible, and (2) whether it is plasmid-encoded. Furthermore, physical (temperature, pH, and UV-induced photolysis of BaP) and chemical (BaP concentration, surfactant, and ionic strength) parameters for BaP degradation were determined. Our findings revealed a ten-fold enhanced degradation rate in induced vs noninduced culture in the presence of chloramphenicol, suggesting that the BaP degradation pathway is inducible. Physical methods demonstrated the lack of plasmid in BMT4i-a result further complimented by plasmid curing, which had no effect on BaP degradability thus a chromosomal localization can be inferred. Maximum BaP degradation in BMT4i was observed under the following physical and chemical conditions: 30°C, pH 8.0, UV-induced photolysis of BaPbasal salt mineral medium (BSM), 150 μg/ml BaP, 0.01% Tween-20, and 400-1,800 μM MgSO 4 . These conditions could be beneficial in the development and standardization of effective bioremediation protocols using B. subtilis BMT4i.

Prevalence of polycyclic aromatic hydrocarbons (PAHs) degrading bacteria in contaminated tropical soil in Lagos, Nigeria: involvement of plasmid in degradation

“…Furthermore, the bacterial isolates which possessed plasmid and after total curing of their plasmid showed no change in PAHs degradability suggested that their PAHs degradability could be chromosomally mediated as earlier reported (Lily et al, 2010). In addition, the observed altered growth on PAHs by acridine orange treated isolates indicated that the presence of chemicals may possibly induce the translocation or recombination of some gene(s) in the bacteria.…”

Production, Partial Purification and Characterization of α-Amylase from High Molecular Weight Polycyclic Aromatic Hydrocarbons (HMW-PAHs) Degrading Bacillus subtilis BMT4i (MTCC 9447)

“…Bacillus subtilis strain: The Bacillus subtilis BMT4i (MTCC 9447), isolated from automobile contaminated soil is an efficient degrader of HMW-PAHs including BaP, a potent carcinogen [16][17][18] was used in this study. The culture was maintained on nutrient agar slants at 4 o C.…”

“…In view of the above, the present study reports the production, partial purification, and characterization of α-amylase from a novel benzo-a-pyrene (BaP) degrading Bacillus subtilis BMT4i (MTCC 9447) previously isolated from automobile contaminated soil that is capable of degrading high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) including BaP [16][17][18]. Production conditions were also optimized (time, pH, carbon source, nitrogen source and CaCl 2 concentration) to achieve high enzyme production and better enzyme activity.…”

Benzo(a)pyrene degradation pathway in Bacillus subtilis BMT4i (MTCC 9447)

“…However, limited information is available on BaP degradation pathway in genus Bacillus despite of its species being shown as potent BaP degraders [19,22,23]. A bacterial consortium of Bacillus cereus and Bacillus vireti isolated from petrochemical soil has been reported to degrade BaP into cis-4-(8-hydroxy-pyren-7-yl)-2-oxobut-3-enoic acid, a ring cleavage product of 9,10-dihydrodiol [23].…”

“…A bacterial consortium of Bacillus cereus and Bacillus vireti isolated from petrochemical soil has been reported to degrade BaP into cis-4-(8-hydroxy-pyren-7-yl)-2-oxobut-3-enoic acid, a ring cleavage product of 9,10-dihydrodiol [23]. We have shown previously that B. subtilis BMT4i (MTCC 9447) degrades BaP very efficiently up to 84.66% in 28 days via chromosomally encoded pathway [19,22].…”