ABSTRACT
Rice tungro is a serious viral disease of rice resulting from infection by two viruses, Rice tungro bacilliformvirus and Rice tungro spherical virus. To gain molecular insights into the global gene expression changes inrice during tungro, a comparative whole genome transcriptome study was performed on healthy and tungroaffected rice plants using Illumina Hiseq 2500. About 10 GB of sequenced data comprising about 50 millionpaired end reads per sample were then aligned on to the rice genome. Gene expression analysis revealedaround 959 transcripts, related to various cellular pathways concerning stress response and hormonal homeostasis to be differentially expressed. The data was validated through qRT-PCR. Gene ontology and pathwayanalyses revealed enrichment of transcripts and processes similar to the differentially expressed genes categories. In short, the present study is a comprehensive coverage of the differential gene expression landscapeand provides molecular insights into the infection dynamics of the rice-tungro virus system
ABSTRACT
Abstract Gram-negative ( G-) bacteria, such as denitrifying bacteria and anaerobic ammonia oxidation bacteria, are highly social organisms capable of sophisticated cooperative behavior mediated via quorum sensing. As signal molecules of the chemical communication, N-acyl-homoserine lactones ( AHLs ) can mediate the quorum sensing of the functional microbial population and regulate the population density. To understand the growth of functional microbial population and the mechanism for biological nitrogen removal in upflow microaerobic sludge reactors ( UMSRs ) treating organic wastewater with low ratio of chemical oxygen demand to total nitrogen, a method was established to simultaneously detect AHLs in the microaerobic processes. Water-sludge mixtures sampled from the UMSRs were pretreated in sequence by liquid-liquid extraction using ethyl acetate, rotary evaporation, constant volume with methanol, separation by C18 column. Gradient elution was carried out using 5 mmol/L ammonium acetate ( containing 0 . 1% formic acid ) and methanol as mobile phases. On the base of multiple reaction monitoring analysis, a triple quadrupole mass spectrometer with an electrospray ionization was introduced to detect the target compounds. Nine kinds of AHLs were used to evaluate the established method and the results showed that the detection limits were 0 . 01-0 . 5 μg/L and all of the AHLs presented excellent linearity with the concentration ranging from 0 . 5 to 100 μg/L. The recovery and relative standard deviation ranged from 62. 5% to 118. 1% and 2. 9% to 12. 1%, respectively. The analysis could be finished within 6. 5 min. The rapid, accurate and precise method for detecting AHLs provided a new insight into the growth and metabolic activity of functional microbial population in the activated sludge processes to understand the mechanism of biological nitrogen removal, suggesting a good application in regulation and operation of wastewater biological treatment processes.
ABSTRACT
PcoI-PcoR is a quorum-sensing (QS) system influencing the biofilm formation and rhizosphere colonization in Pseudomonas fluorescens 2P24. The expression of the pcoI, a N-acyl-homoserne lactone (AHL) biosynthase gene, is under the regulation of a number of chromosomal factors, such as the GacS-GacA two-component system. In this paper, we investigated the upstream regulators that influence the transcription of pcoI gene using a chromosomal pcoI-lacZ fusion reporter strain PM203. Cosmids containing genomic DNA of the wild-type strain 2P24 were introduced into the reporter strain PM203 (gacA—, pcoI-lacZ) to screen positive transcriptional regulators of pcoI gene. One of them named pP32-24, which contained a 5-kb Pst I functional fragment was selected. Further analysis identified that the pcoI was the gene responsible for the increase of the pcoI-lacZ expression. The expression of pcoI-lacZ reporter was alsoimproved in both PM101 (pcoI-lacZ) and its gacAmutant PM203 after addition of exogenous AHL, indicating that the expression of pcoI is positively regulated by AHL (autoinduction) in strain 2P24. In addition, deletion mutagenesis and complementation experiments demonstrated that the transcriptional regulator PcoR positively controlled the expression of pcoI and the formation of biofilm. These results suggest that, in strain 2P24, the expression of PcoI-PcoR QS system is auto-inducted, and the transcriptional factor PcoR is involved in the regulation of pcoI transcription and the biofilm formation.
ABSTRACT
7.5). Overall,the research demonstrates the effect of environmental parameters (temperature and carbon source) on AHL profile production by food-derived Pseudomonas. It lays the foundation for further investigation to elucidate the relationship between quorum sensing and food spoilage,and for the development of new food preservative by blocking the quorum sensing of food spoilage bacteria.
ABSTRACT
Three Gram-negative bacteria from commercial fresh fish were identified as Pseudomonas sp.,an important food spoilage bacteria, on the basis of 16S rDNA sequences.N-aeyl-homoserine lactones (AHLs) were the important quorum sensing molecules and regulated the expression of many characteristics in a cell-density-dependent manner in Gram-negative bacteria.The AHL biosensor detection revealed that three isolates produced AHLs molecules and strains FML05-1 and FML05-2 produced two types of AHLs at least and the main signal mole- cules were N-3-oxo-octanoyl-homoserine lactone(N-3-oxo-C_8-AHL).ALso the amount of AHL in FML05-2 reached to the maximum at 12h throughout growth.This was first study of quorum sensing signal molecule AHLs produced by the pseudomonas from food and layed the foun- dation for new strategies of food preservation based on interfering in quorum sensing of spoilage bacteria.