Biodegradation of 4-nitrophenol by a Rhodococcus species and a preliminary insight into its toxicoproteome based on mass spectrometry analysis

ABSTRACT

Aim: The objective of this study was to understand the possible fate of 4-NP through the molecular mechanism and to identify potential enzymes involved in 4-NP biodegradation by Rhodococcus sp. strain BUPNP1 Methodology: Biodegradation of 4-NP was detected spectrophotometrically at 400 nm and also confirmed by TLC and HPLC. Comparative study of proteomes was performed by 2-D gel electrophoresis followed by peptide mass fingerprinting and bioinformatic analysis to identify and/ or predict the possible functions of over-expressed proteins in 4-NP treated cells of BUNP1. Results: Utilization of 4-nitrophenol and its hydrolysis intermediate 4-nitrocatechol (4-NC) and 1,2,4-Benzenetriol as sole carbon source indicated the presence of genomic information encoding the enzyme necessary for the operation of 4-nitrophenol degradation pathway in the strain BUPNP1. It could transform 4-NP into 4-NC by monooxygenase whose major activity was detected during initial stage of degradation. The 4-NC further depleted in the medium to release nitrite ions. In order to investigate the molecular changes occurring during degradation, a comparative study of proteome profiles was carried out where; 4-nitrophenol treated cells were compared against cells grown on glucose as control. The comparative study indicated expression of several protein spots under 4-nitrophenol treated condition. Interpretation: This study showed the potential of BUPNP1 strain belonging to genus Rhodococcus towards induced expression of some unique proteins which might have possible role in 4-NP biodegradation process