Project description:Several soil organisms are known to be capable of growth on caprolactam as soil carbon and nitrogen source, but the enzymes of the catabolic pathway have not been described. We isolated a caprolactam-degrading strain of Pseudomonas jessenni, and identified genes putatively involved in the caprolactam metabolism using quantitative mass spectrometry-based proteomics. This led to the discovery of a caprolactamase and an aminotransferase that are involved in the initial steps of caprolactam conversion. Additionally, various proteins were identified likely to be involved in later steps of the pathway. The identified caprolactamase consisted of 2 subunits and demonstrated high sequence identity to the 5-oxoprolinases. E. coli expressing this caprolactamase did not convert 5-oxoproline but was able to hydrolyze caprolactam to form 6-aminohexanoic acid in an ATP dependent manner. Characterization of the aminotransferase revealed that the enzyme deaminated 6-aminohexanoic acid to produce 6-oxohexanoate with pyruvate as amino acceptor. The amino acid sequence of the aminotransferase demonstrated high similarity to subgroup II ω-aminotransferases of the PLP fold type I proteins. Finally, analyses of the genome sequence demonstrated the presence of a caprolactam catabolism gene cluster consisting of all genes involved in the conversion of caprolactam to adipate.
Project description:The goals of this study are to use Next-generation sequencing (NGS)to detect bacterial mRNA profiles of Pseudomonas aeruginosa PAO1 in response to 0, 1, 20 and 25 mg/L AgNPs or 0, 1,30 and 300 mg/L AgNRs for 2 h, using Illumina HiSeq 2500.The NGS QC toolkit (version 2.3.3) was used to treat the raw sequence reads to trim the 3’-end residual adaptors and primers, and the ambiguous characters in the reads were removed. Then, the sequence reads consisting of at least 85% bases were progressively trimmed at the 3’-ends until a quality value ≥ 20 were kept. Downstream analyses were performed using the generated clean reads of no shorter than 75 bp. The clean reads of each sample were aligned to the E. coli reference genome (NC_000913) using SeqAlto (version 0.5). Cufflinks (version 2.2.1) was used to calculate the strand-specific coverage for each gene, and to analyze the differential expression in triplicate bacterial cell cultures. The statistical analyses and visualization were conducted using CummeRbund package in R (http://compbio.mit.edu/cummeRbund/). Gene expression was calculated as fragments per kilobase of a gene per million mapped reads (FPKM, a normalized value generated from the frequency of detection and the length of a given gene.
