Project description:Pseudomonas mendocina was identified as a novel endophytic isolate of Murraya koenigii with squalene cyclase activity. The PCR amplification of squalene hopene cyclase (shc) gene from the isolate Pseudomonas mendocina with the primers PA1/PA2 showed a band at 1980 bp specific for the enzyme squalene hopene cyclase. The in silico translation of the squalene hopene cyclase gene showed 96% sequence similarity with squalene hopene cyclase of Pseudomonas agarici (WP-060782422). Docking studies of the template and the modeled protein with the ligand squalene showed that the main interacting residues were Asp376 and Asp377. Squalene hopene cyclase template 1 sqc.1A sequence from Alicyclobacillus acidocaldaruis was used as the template for docking experiments. The gene coding for squalene hopene cyclase from Pseudomonas mendocina has been cloned in pET-28a vector to produce recombinant vector and was expressed in E.coli BL21 (DE3) expression system. Squalene hopene cyclase enzyme was isolated, purified and the molecular weight was confirmed by SDS-PAGE as 75 KDa.
Project description:Pseudomonas mendocina NK-01 can synthesize medium-chain-length polyhydroxyalkanoate (PHA(MCL)) and alginate oligosaccharides (AO) simultaneously from glucose under conditions of limited nitrogen. Here, we report the complete sequence of the 5.4-Mbp genome of Pseudomonas mendocina NK-01, which was isolated from farmland soil in Tianjin, China.
Project description:The tmoABCDEF genes encode the toluene-4-monooxygenase from Pseudomonas mendocina KR1. Upstream from the tmoA gene an open reading frame, tmoX, encoding a protein 83% identical to TodX (todX being the initial gene in the todXFC1C2BADEGIH operon from Pseudomonas putida DOT-T1E) was found. The tmoX gene is also the initial gene in the tmoXABCDEF gene cluster. The transcription initiation point from the tmoX promoter was mapped, and the sequence upstream revealed striking identity with the promoter of the tod operon of P. putida. The tod operon is regulated by a two-component signal transduction system encoded by the todST genes. Two novel genes from P. mendocina KR1, tmoST, were rescued by complementation of a P. putida DOT-T1E todST knockout mutant, whose gene products shared about 85% identity with TodS-TodT. We show that transcription from P(tmoX) and P(todX) can be mediated by TmoS-TmoT or TodS-TodT, in the presence of toluene, revealing cross-regulation between these two catabolic pathways.
Project description:Polyhydroxyalkanoate (PHA) can be produced by microorganisms from renewable resources and is regarded as a promising bioplastic to replace petroleum-based plastics. Pseudomonas mendocina NK-01 is a medium-chain-length PHA (mcl-PHA)-producing strain and its whole-genome sequence is currently available. The yield of mcl-PHA in P. mendocina NK-01 is expected to be improved by applying a promoter engineering strategy. However, a limited number of well-characterized promoters has greatly restricted the application of promoter engineering for increasing the yield of mcl-PHA in P. mendocina NK-01. In this work, 10 endogenous promoters from P. mendocina NK-01 were identified based on RNA-seq and promoter prediction results. Subsequently, 10 putative promoters were characterized for their strength through the expression of a reporter gene gfp. As a result, five strong promoters designated as P4, P6, P9, P16 and P25 were identified based on transcriptional level and GFP fluorescence intensity measurements. To evaluate whether the screened promoters can be used to enhance transcription of PHA synthase gene (phaC), the three promoters P4, P6 and P16 were separately integrated into upstream of the phaC operon in the genome of P. mendocina NK-01, resulting in the recombinant strains NKU-4C1, NKU-6C1 and NKU-16C1. As expected, the transcriptional levels of phaC1 and phaC2 in the recombinant strains were increased as shown by real-time quantitative RT-PCR. The phaZ gene encoding PHA depolymerase was further deleted to construct the recombinant strains NKU-∆phaZ-4C1, NKU-∆phaZ-6C1 and NKU-∆phaZ-16C1. The results from shake-flask fermentation indicated that the mcl-PHA titer of recombinant strain NKU-∆phaZ-16C1 was increased from 17 to 23 wt% compared with strain NKU-∆phaZ. This work provides a feasible method to discover strong promoters in P. mendocina NK-01 and highlights the potential of the screened endogenous strong promoters for metabolic engineering of P. mendocina NK-01 to increase the yield of mcl-PHA.
Project description:To remove nitrate in wastewater treatment plant effluent, an aerobic denitrifier was newly isolated from the surface flow constructed wetland and identified as Pseudomonas mendocina strain GL6. It exhibited efficient aerobic denitrification ability, with the nitrate removal rate of 6.61 mg (N)·L-1·h-1. Sequence amplification indicated that the denitrification genes napA, nirK, norB, and nosZ were present in strain GL6. Nitrogen balance analysis revealed that approximately 74.5% of the initial nitrogen was removed as gas products. In addition, the response surface methodology experiments showed that the maximum removal of total nitrogen occurred at pH 7.76, C/N ratio of 11.2, temperature of 27.8 °C, and with shaking at 133 rpm. Furthermore, under the optimized cultivation condition, strain GL6 was added into wastewater treatment plant effluent and the removal rates of nitrate nitrogen and total nitrogen reached 95.6% and 73.6%, respectively. Thus, P. mendocina strain GL6 has high denitrification potential for deep improvement of effluent quality.
Project description:Endosulfan contamination is one of the major concerns of soil ecosystem, which causes detrimental effects not only to humans but also to animals and plants. Therefore, the aim of this study was to isolate and identify a novel bacterial strain capable of degrading endosulfan in agriculture contaminated soils. A novel bacterial strain was isolated from the sugarcane field contaminated with endosulfan, and was named as ZAM1 strain. The ZAM1 bacterial strain was further identified as Pseudomonas mendocina based on the biochemical and molecular analysis. 16sRNA sequence analysis of ZAM1 strain shows maximum similarity with known endosulfan-degrading bacteria (Pseudomonas putida), respectively. Enrichment was carried out using the endosulfan as sole sulfur source. The ZAM1 strain was able to use ? and ? endosulfan as a sole sulfur source. Our results showed that ZAM1 strain degrades endosulfan >64.5% (50 mg/l) after 12 days of incubation. The residues were analyzed by GC-MS analysis and confirmed the formation of metabolites of dieldrin, 2 heptanone, methyl propionate, and endosulfan lactone compounds. Hence, these results indicate that the ZAM1 strain is a promising bacterial source for detoxification of endosulfan residues in the environment.
Project description:This study aimed to investigate the effects of cytoskeleton protein MreB on bacterial cell morphology and the synthesis of alginate oligosaccharides (AO) and polyhydroxyalkanoate (PHA) by Pseudomonas mendocina NK-01. To overexpress the mreB gene, an expression vector encoding MreB-GFP fusion protein was constructed. The scanning electron microscope (SEM) showed that cells expressing MreB were longer than the wild ones, which agrees with MreB's relationship with the synthesis of peptidoglycan. Cells expressing the MreB-GFP fusion protein emitted green fluorescence under a fluorescence microscope, suggesting that MreB was functionally expressed in strain NK-01. Under a confocal laser scanning microscope, MreB was observed as located around the cell membrane. Furthermore, the recombinant strain could synthesize 0.961 g/L AO, which was 5.86-fold higher than wild-type strain. Through the medium optimization test, we finally selected the addition of 20 g/L glucose as the optimal glycogen addition for AO fermentation based on a high AO yield and high substrate transformation efficiency. The results indicated that overexpression of MreB affected the cell morphology, the activity of AO polymerase, and the efficiency of AO secretion. However, the synthesis of PHA for recombinant strain was slightly reduced. The results suggested that the overexpression of this cytoskeleton protein affected the yield of specific intracellular and extracellular products.