Project description:Horizontal gene transfer (HGT) is the major mechanism responsible for spread of antibiotic resistance. Antibiotic treatment has been suggested to promote HGT, either by directly affecting the conjugation process itself or by selecting for conjugations subsequent to DNA transfer. However, recent research suggests that the effect of antibiotic treatment on plasmid conjugation frequencies, and hence the spread of resistance plasmids, may have been overestimated. We addressed the question by quantifying transfer proteins and conjugation frequencies of a blaCTX-M-1 encoding IncI1 resistance plasmid in Escherichia coli MG1655 in the presence and absence of therapeutically relevant concentrations of cefotaxime (CTX). Analysis of the proteome by iTRAQ labeling and liquid chromatography tandem mass spectrometry revealed that Tra proteins were significantly up regulated in the presence of CTX. The up-regulation of the transfer machinery was confirmed at the transcriptional level for five selected genes. The CTX treatment did not cause induction of the SOS39 response as revealed by absence of significantly regulated SOS associated proteins in the proteome and no significant up-regulation of recA and sfiA genes. The frequency of plasmid conjugation, measured in an antibiotic free environment, increased significantly when the donor was pre-grown in broth containing CTX compared to growth without this drug, regardless of whether blaCTX-M-1 was located on the plasmid or in trans on the chromosome. The results shows that antibiotic treatment can affect expression of a plasmid conjugation machinery and subsequent DNA transfer.
Project description:To explore the interspecies electron transfer and substrate co-metabolism mechanism between denitrifiers and electroactive microorganisms
Project description:Horizontal gene transfer via plasmid conjugation is a major driving force in microbial evolution. Transfer of conjugative plasmids is a complex process that needs to be synchronized with the physiological state of the bacterial host. While several host transcription factors are known to control the plasmid-borne transfer control genes, RNA-based regulatory circuits for host-plasmid communication remain unknown. Here, we describe a post-transcriptional mechanism whereby the Hfq-dependent small RNA, RprA, inhibits transfer of pSLT, the virulence plasmid of Salmonella enterica. RprA employs two different seed pairing domains to recognize and activate the mRNAs of both the sigma-factor S and RicI, a cytoplasmic membrane protein. The latter is a hitherto unknown conjugation inhibitor whose transcription requires S. Together, RprA and S constitute a feed-forward loop with AND-gate logic which tightly controls RicI synthesis for selective suppression of plasmid conjugation under membrane stress. This study reports the first sRNA-controlled feed-forward loop based on double target activation and an unexpected function for a core-genome encoded small RNA in controlling extrachromosomal DNA transfer.
Project description:Plasmid fitness is directed by two orthogonal processes—vertical transfer through cell division and horizontal transfer through conjugation. When considered individually, improvements in either mode of transfer can promote how well a plasmid spreads and persists. Together, however, the metabolic cost of conjugation could create a tradeoff that constrains plasmid evolution. Here we present evidence for the presence, consequences, and molecular basis of a conjugation-growth tradeoff across 40 plasmids derived from clinical E. coli pathogens. We discover that most plasmids operate below a conjugation efficiency threshold for major growth effects, indicating strong natural selection for vertical transfer. Below this threshold, E. coli demonstrates a remarkable growth tolerance to over four orders of magnitude change in conjugation efficiency. This tolerance fades as nutrients become scarce and horizontal transfer attracts a greater share of host resources. Our results provide insight into evolutionary constraints directing plasmid fitness and strategies to combat the spread of antibiotic resistance.
Project description:In present, interspecies cloning and interspecies-pregnancy were studied for endangered species rescue. However, the low implantation and survival ratio, spontaneous abortion, and unknown reason embryos absorption are the common and difficult problems of interspecies-pregnancy. In order to discover the mechanism of interspecies-pregnant failure and find ways to overcome the xeon-pregnant obstacles, we chosen the rat embryos pregnant in mouse uterus as a interspecies-pregnancy model. Three groups were set, mouse embryos to mouse recipients (MM) as control group, rat embryos to mouse recipients (RM), and rat and mouse embryos to mouse recipients together (RMM) as experiment groups. The former studies showed that rat embryos live no longer than day 7 of mouse pregnancy (D7). Our results showed that rat embryos survived to D7, and still existed to day 9 of mouse pregnancy (D9) in RM group. Surprisingly, the rat embryos survived to day 13 of the mouse gestation (D13) in RMM group. Microarray analysis was used to detect the global-gene expression profile changes of the whole implantation sites among the three groups at D7 and D9. By this way, we screened out the genes promoting the implanted rat embryos development in a mouse uterus which helped the rat embryos survive to D13 in RMM group compared with RM group, and the genes hindering the rat embryos development in a mouse uterus which prevented rat embryos living longer than D7 in RM group and D13 in RMM group compared with MM group. These findings provide insights into the mechanism of interspecies pregnant failure and new idea for interspecies pregnant studies. Experiment Overall Design: microarray was use to screen the genes among the day 7 and day 9 implantation sites of rat embryos implantation sites in a mouse uterus between rat embryos transfer to mouse recipients and rat embryos transfer to mouse recipients with mouse embryos. The mouse day7 and day 9 embryos implantation sites were use as control. Experiment Overall Design: totally 6 samples were analyzed, each samples two replications (one of them had three replications).