New metabolic pathway for degradation of 2-nitrobenzoate by Arthrobacter sp. SPG.

Pankaj K Arora,Ashutosh Sharma

doi:10.3389/fmicb.2015.00551

Pankaj K Arora, Ashutosh Sharma

Open Access

https://doi.org/10.3389/fmicb.2015.00551

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Abstract

Arthrobacter sp. SPG utilized 2-nitrobenzoate as its sole source of carbon and energy and degraded it with accumulation of stoichiometric amounts of nitrite ions. Salicylate and catechol were detected as metabolites of the 2-nitrobenzoate degradation using high performance liquid chromatography and gas chromatography–mass spectrometry. Enzyme activities for 2-nitrobenzoate-2-monooxygenase, salicylate hydroxylase, and catechol-1,2-dioxygenase were detected in the crude extracts of the 2-nitrobenzoate-induced cells of strain SPG. The 2-nitrobenzoate-monooxygenase activity resulted in formation of salicylate and nitrite from 2-nitrobenzoate, whereas salicylate hydroxylase catalyzed the conversion of salicylate to catechol. The ring-cleaving enzyme, catechol-1,2-dioxygenase cleaved catechol to cis,cis-muconic acid. Cells of strain SPG were able to degrade 2-nitrobenzoate in sterile as well as non-sterile soil microcosms. The results of microcosm studies showed that strain SPG degraded more than 90% of 2-nitrobenzoate within 10–12 days. This study clearly shows that Arthrobacter sp. SPG degraded 2-nitrobenzoate via a new pathway with formation of salicylate and catechol as metabolites. Arthrobacter sp. SPG may be used for bioremediation of 2-nitrobenzoate-contaminated sites due to its ability to degrade 2-nitrobenzoate in soil.

Highlights

Nitrobenzoates (NBs) including 2-nitrobenzoate (2NB), 3-nitrobenzoate (3NB), and 4-nitrobenzoate (4NB) are used in the synthesis of chemicals, pharmaceuticals and dyes (Zylstra et al, 2000)
The oxidative pathway involves an oxygenase-dependent removal of the nitro group as nitrite (Nadeau and Spain, 1995), whereas the initial step in the reductive pathway is a nitroreductasecatalyzed reaction resulting in ammonium release (Chauhan and Jain, 2000; Hasegawa et al, 2000; Pandey et al, 2003)
Bacterial Growth and 2NB Degradation The growth of strain SPG was monitored in minimal medium containing 0.5 mM 2NB as its sole source of carbon and energy

Summary

Introduction

Nitrobenzoates (NBs) including 2-nitrobenzoate (2NB), 3-nitrobenzoate (3NB), and 4-nitrobenzoate (4NB) are used in the synthesis of chemicals, pharmaceuticals and dyes (Zylstra et al, 2000). NBs are white to light yellow colored crystals, which are insoluble in water, but soluble in alcohol. These compounds are toxic to living beings because of their genotoxicity, mutagenicity, and hematologic toxicity (Sundvall et al, 1984; NTP, 1994; Grummt et al, 2006). Bacterial degradation of NBs proceeds either via the oxidative route or through the reductive route (Nadeau and Spain, 1995; Chauhan and Jain, 2000; Hasegawa et al, 2000; Pandey et al, 2003). Bacterial 2NB and 4NB degradations have been found to proceed exclusively via the reductive pathway

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