Proteomics and Metabolomics Analyses to Elucidate the Desulfurization Pathway of Chelatococcus sp.
Desulfurization of dibenzothiophene (DBT) and alkylated DBT derivatives present in transport fuel through specific cleavage of carbon-sulfur (C-S) bonds by a newly isolated bacterium Chelatococcus sp. is reported for the first time. Gas chromatography-mass spectrometry (GC-MS) analysis of the products of DBT degradation by Chelatococcus sp. showed the transient formation of 2-hydroxybiphenyl (2-HBP) which was subsequently converted to 2-methoxybiphenyl (2-MBP) by methylation at the hydroxyl group of 2-HBP. The relative ratio of 2-HBP and 2-MBP formed after 96 h of bacterial growth was determined at 4:1 suggesting partial conversion of 2-HBP or rapid degradation of 2-MBP. Nevertheless, the enzyme involved in this conversion process remains to be identified. This production of 2-MBP rather than 2-HBP from DBT desulfurization has a significant metabolic advantage for enhancing the growth and sulfur utilization from DBT by Chelatococcus sp. and it also reduces the environmental pollution by 2-HBP. Furthermore, desulfurization of DBT derivatives such as 4-M-DBT and 4, 6-DM-DBT by Chelatococcus sp. resulted in formation of 2-hydroxy-3-methyl-biphenyl and 2-hydroxy -3, 3/- dimethyl-biphenyl, respectively as end product. The GC and X-ray fluorescence studies revealed that Chelatococcus sp. after 24 h of treatment at 37°C reduced the total sulfur content of diesel fuel by 12% by per gram resting cells, without compromising the quality of fuel. The LC-MS/MS analysis of tryptic digested intracellular proteins of Chelatococcus sp. when grown in DBT demonstrated the biosynthesis of 4S pathway desulfurizing enzymes viz. monoxygenases (DszC, DszA), desulfinase (DszB), and an NADH-dependent flavin reductase (DszD). Besides, several other intracellular proteins of Chelatococcus sp. having diverse biological functions were also identified by LC-MS/MS analysis. Many of these enzymes are directly involved with desulfurization process whereas the other enzymes/proteins support growth of bacteria at an expense of DBT. These combined results suggest that Chelatococcus sp. prefers sulfur-specific extended 4S pathway for deep-desulphurization which may have an advantage for its intended future application as a promising biodesulfurizing agent.
ONGC-Center for Petroleum Biotechnology, Department of Molecular Biology and Biotechnology, Tezpur University, Tezpur, 784028, Assam, India.
Naba K
NK
Bordoloi
ONGC-Center for Petroleum Biotechnology, Department of Molecular Biology and Biotechnology, Tezpur University, Tezpur, 784028, Assam, India.
Pabitra
P
Bhagowati
ONGC-Center for Petroleum Biotechnology, Department of Molecular Biology and Biotechnology, Tezpur University, Tezpur, 784028, Assam, India.
Mihir K
MK
Chaudhuri
ONGC-Center for Petroleum Biotechnology, Department of Molecular Biology and Biotechnology, Tezpur University, Tezpur, 784028, Assam, India.
Ashis K
http://orcid.org/0000-0001-9869-858X
AK
Mukherjee
D000393:Air Pollutants / Q000032:analysis* / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000378:metabolism*; D042062:Beijerinckiaceae / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D005742:Gasoline / Q000032:analysis; D055432:Metabolomics; D010802:Phylogeny; D040901:Proteomics; D015398:Signal Transduction; D013455:Sulfur / Q000378:metabolism*
D000393:Air Pollutants; D001426:Bacterial Proteins; D005742:Gasoline; D013455:Sulfur