Degradation of BTEX mixture by a new Pseudomonas putida strain: role of the quorum sensing in the modulation of the upper BTEX oxidative pathway

A new Pseudomonas putida strain (AQ8) was isolated from a decommissioned oil refinery's soil in Italy and characterized for its ability to degrade BTEX. The draft genome of the new strain was sequenced and annotated for genes that encode enzymes putatively involved in BTEX degradation and quorum sensing. The strain was transformed with a plasmid expressing lactonase, which cleaves the autoinducer quorum sensing signal molecule, the acyl-homoserine lactone, to obtain a quorum sensing minus strain. P. putida AQ8 depleted the 40% on average of all the components of the initial BTEX concentration in 36 h. The quorum sensing minus strain, in the same time interval, depleted only the 10% of the initial BTEX concentration. The role of quorum sensing in regulating the expression of the annotated benzene/toluene dioxygenase gene (benzA) and biphenyl/toluene/benzene dioxygenase (bphA) genes, which are involved in BTEX degradation, was studied by quantitative RT-real-time quantitative (q)PCR analysis. The qPCR data showed decreased levels of expression of the benzA and bphA genes in the quorum sensing minus strain. Our results showed, for the first time, quorum sensing modulation of the level of transcription of dioxygenase genes in the upper BTEX oxidation pathway.

Combination of highly efficient microflora to degrade paint spray exhaust gas

Spray paint exhaust gas contains recalcitrant volatile organic compounds (VOCs), such as benzene, toluene and xylene (BTX). Treating BTX with a biofilter often achieves unsatisfactory results because the biofilter lacks efficient microbial community. In this work, three strains for BTX degradation were isolated and identified as Pseudomonas putida, Bacillus cereus and Bacillus subtilis by using 16S rRNA sequencing technology. A consortium of highly efficient microbial community was then constructed on a stable biofilm to treat BTX in a biofilter. A relatively suitable ratio of P. putida, B. cereus and B. subtilis was obtained. An efficiency of over 90% was achieved in the biofilter with VOC concentration of 1000 mg/m3 through inoculation with the microbial community after only 10 days of operation. Thus, fast start-up of the biofilter was realised. Analysis of intermediate products by gas chromatography-mass spectrometry indicated that BTX was degraded into short-chain aldehydes or acids via ring opening reactions.

An Investigation of Petrol Metabolizing Bacteria Isolated from Contaminated Soil Samples Collected from Various Fuel Stations

The present study aimed to isolate the high-efficiency petrol metabolizing thermophilic bacteria from petrol contaminated soil samples. Isolation was carried out through enrichment culture, serial dilution and pour plate methods using the petrol supplemented minimal salt media. The isolated bacteria were analyzed to document growth behavior, petrol removal efficiencies, antibiotic resistance profile, and biochemical characteristics. The 16S rRNA based phylogenetic analysis helped to reveal the identity of isolated bacterial species and construct the phylogenetic trees. Total nine bacteria were isolated, out of which three (IUBP2, IUBP3, IUBP5) were identified as Brevibacillus formosus, one (IUBP1) was found similar to Brevibacillus agri, four (IUBP7, IUBP8, IUBP13, and IUBP14) shared homology with Burkholderia lata, and one (IUBP15) with Burkholderia pyrrocinia. All the isolates were fast growing and exhibited considerable petrol degradation potential. The highest petrol removal efficiency (69.5% ± 13.44/6 days) was recorded for the strain IUBP15 at a petrol concentration of 0.1% (v/v). All bacteria studied (100%) were positive for esculinase and phosphatase. Many strains exhibited positive responses for arginine dehydrolase (22%), β-naphthylamidase (11%), β-D-glucosaminide (33%), mannitol (55%), sorbitol (66%) and inulin (88%) fermentation test. While all were sensitive to the antibiotics, some of them were found resistant against chloramphenicol and oxacillin. The remarkable biochemical characteristics and considerable petrol removal potential (40–70%) highlights utilization of the bacteria isolated for petrol bioremediation, mineralization of organophosphates, dairy and food industry, and also as biofertilizers and biocontrol agents.