Xiangwen Luo

Genome Sequence of Pyrethroid-Degrading Bacterium Rhodopseudomonas palustris Strain JSC-3b

ABSTRACT Rhodopseudomonas palustris strain JSC-3b is a facultative, thermophilic bacterium, which was isolated from water in a canal adjacent to a vegetable field. Strain JSC-3b biodegrades several varieties of pyrethroid residues effectively through cometabolic pathways. Here, we present the genome sequence of this biodegrader.

Biodegradation of fenpropathrin by a novel Rhodopseudomonas sp. strain PSB07-8

The aim of our study was to isolate a fenpropathrin-degrading bacterial strain and to determine its effectiveness in bioremediating fenpropathrin-contaminated soil in the laboratory. We isolated a bacterial strain from soils and named it as PSB07-8, and showed that this organism was able to degrade pyrethroid pesticide fenpropathrin. The organism was identified as a strain of Rhodopseudomonassp.The strain PSB07-8 degraded fenpropathrin in a co-metabolic way, and the optimal condition of degradation was at temperature of 30°C and pH value of 7. Moreover, the strain PSB07-8 could effectively degrade cypermethrin and bipthenthrin, but only slightly for deltemethrin, cyfluthrin and esfenralerate. We found that the degradation rate was negatively correlated with the fenpropathrin concentration in a certain range. In addition, our soil degradation test showed that in sterilised soils with 20 mg/l or 40 mg/l fenpropathrin, the strain PSB07-8 could complete 100% or achieve 44.7% of fenpropathrin degradation in 15 days. To our best knowledge, this is the first report of a strain of genus Rhodopseudomonas with an ability of degrading fenpropathrin in soil.

Cloning and characterization of a pyrethroid pesticide decomposing esterase gene, Est3385 , from Rhodopseudomonas palustris PSB-S

Full length open reading frame of pyrethroid detoxification gene, Est3385, contains 963 nucleotides. This gene was identified and cloned based on the genome sequence of Rhodopseudomonas palustris PSB-S available at the GneBank. The predicted amino acid sequence of Est3385 shared moderate identities (30–46%) with the known homologous esterases. Phylogenetic analysis revealed that Est3385 was a member in the esterase family I. Recombinant Est3385 was heterologous expressed in E. coli, purified and characterized for its substrate specificity, kinetics and stability under various conditions. The optimal temperature and pH for Est3385 were 35 °C and 6.0, respectively. This enzyme could detoxify various pyrethroid pesticides and degrade the optimal substrate fenpropathrin with a Km and Vmax value of 0.734 ± 0.013 mmol·l−1 and 0.918 ± 0.025 U·µg−1, respectively. No cofactor was found to affect Est3385 activity but substantial reduction of enzymatic activity was observed when metal ions were applied. Taken together, a new pyrethroid degradation esterase was identified and characterized. Modification of Est3385 with protein engineering toolsets should enhance its potential for field application to reduce the pesticide residue from agroecosystems.

A single-step reverse transcription loop-mediated isothermal amplification assay for rapid and accurate detection of Pepper vein yellows virus

Abstract Pepper vein yellows virus (PeVYV) is a member of Polerovirus and infects solanaceous crops worldwide. In this study, a highly efficient and easy-to-use single-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed for PeVYV detection. This assay used two outer (F3 and B3), two inner (FIP and BIP) and two loop (LF and LB) primers in a single reaction. The optimized reaction was determined to be at 62°C for 45 min and the whole reaction took less than 1 h. This assay was about 10 times more sensitive than the conventional one-step RT-PCR. This RT-LAMP assay should allow specific detection of PeVYV in plant tissues. We recommend this PeVYV-specific RT-LAMP assay for large scale field studies of PeVYV infection.

Development of a reverse transcription loop-mediated isothermal amplification assay for the rapid detection of Pepper mottle virus

Abstract Pepper mottle virus (PepMoV) is a widespread threat to vegetable crop production in the USA and south-east Asia. We describe the development of a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay to detect PepMoV. The RT-LAMP assay was based on a set of four primers that match a specific region of the coat protein gene in the PepMoV genome. The detection limit of conventional RT-PCR detection was 1.47 × 10−4 µg µL−1 of cDNA, whereas RT-LAMP was 10 times more sensitive. Using RT-LAMP, PepMoV detection was also highly specific, showing no cross-activity with four other potyviruses. Sixty-nine field samples collected from symptomatic pepper plants growing in five South China provinces were tested for the presence of PepMoV infection by performing an RT-LAMP assay as well as a conventional RT-PCR. Both methods detected PepMoV in 18 samples, demonstrating that the PepMoV-specific RT-LAMP assay could be a useful alternative tool for the diagnosis and epidemiological surveillance of PepMoV infections. The RT-LAMP assay also has the advantages that it can be performed in a low-tech environment and is quicker and cheaper to perform than conventional RT-PCR.