ABSTRACT
Abstract Endogenous viral elements (EVEs) are the result of heritable horizontal gene transfer from viruses to hosts. In the last years, several EVE integration events were reported in plants by the exponential availability of sequenced genomes. Eucalyptus grandis is a forest tree species with a sequenced genome that is poorly studied in terms of evolution and mobile genetic elements composition. Here we report the characterization of E. grandis endogenous viral element 1 (EgEVE_1), a transcriptionally active EVE with a size of 5,664 bp. Phylogenetic analysis and genomic distribution demonstrated that EgEVE_1 is a newly described member of the Caulimoviridae family, distinct from the recently characterized plant Florendoviruses. Genomic distribution of EgEVE_1 and Florendovirus is also distinct. EgEVE_1 qPCR quantification in Eucalyptus urophylla suggests that this genome has more EgEVE_1 copies than E. grandis. EgEVE_1 transcriptional activity was demonstrated by RT-qPCR in five Eucalyptus species and one intrageneric hybrid. We also identified that Eucalyptus EVEs can generate small RNAs (sRNAs),that might be involved in de novo DNA methylation and virus resistance. Our data suggest that EVE families in Eucalyptus have distinct properties, and we provide the first comparative analysis of EVEs in Eucalyptus genomes.
ABSTRACT
Transposable elements (TEs) represent genome’s dynamic component, causing mutations and genetic variations. Transposable elements can invade eukaryotic genomes in a short span; these are silenced by homology-dependent gene silencing and some functional parts of silenced elements are utilized to perform novel cellular functions. However, during the past two decades, major interest has been focused on the positive contribution of these elements in the evolution of genomes. The interaction between mobile DNAs and their host genomes are quite diverse, ranging from modifications of gene structure to alterations in general genome architecture and can be regarded as hidden magicians in shaping evolution of genomes. Some of the prominent examples that impressively demonstrate the beneficial impact of TEs on host biology over evolutionary time include their role in structure and functions of eukaryotic genomes.
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OBJECTIVE To survey the distribution of class Ⅰ integron in extended-spectrum beta-lactamases(ESBLs)-producing Escherichia coli and Klebsiella pneumoniae and its contribution in horizontal transfer of ESBLs genes.METHODS The presence of class Ⅰ integron among 230 ESBLs-producers and 197 non-ESBLs-producers of E.coli and K.pneumoniae were detected by PCR.The correlation and co-transfer between integron and genes coding for SHV,CTX and TEM were studied. RESULTS One hundred and thirty-seven(59.6%) isolates were positive for intⅠ gene among ESBLs-producers,contrasted to 48(24.4%) in non-ESBLs-producers(P
ABSTRACT
OBJECTIVE To investigate the distribution of integron in Gram-negative isolates which are causing nosocomial infection the association with drug resistance,and it′s contribution in horizontal transfer of drug resistance.METHODS Drug resistance test was performed by K-B method.ESBL-positive strains were detected by double-disk synergy test.Integron was determined by PCR assay with integron-specific-primer.Conjugative transfer test,plasmid profile analysis,nested-PCR,and DNA sequence analysis were used to investigate the transferable mechanism of integron mediated.RESULTS 66.4% of Strains were shown to be positive for classes Ⅰ integron,no class Ⅱ and Ⅲ integrons were detected.Profiles of class Ⅰ integron were 11 types,which sized from 700bp to 2300bp,gene cassettes included genes encoding resistance to aminoglycosides(aadA1,aadA2,aadA5 and aacA4),sulfamethoxazole/trimethoprim(dfrA12,dfrA5 and dfrA17) and chloramphenicol(catB8).Strains positive for class Ⅰ integron were highly related to multidrug resistance and ESBLs.Class Ⅰ integron could horizontal transfer along with plasmid among bacteria.CONCLUSIONS Class 1 integron is widespread in Gram-negative isolates which are causing nosocomial infection.Drug resistance is more liable to horizontal transfer via class Ⅰ integron along with plasmid.It implies the necessary for surveillance of horizontal transfer of antibiotic resistance gene among bacteria genus.
ABSTRACT
BACKGROUND: Vancomycin-resistant enterococci (VRE) have been increasingly isolated world-wide as a nosocomial pathogen. To target infection control, epidemiologic investigations of VRE should include analysis of the resistance gene in addition to typing of strains. We performed molec-ular characterization of the vanA resistance gene to evaluate the inter or intraconstitutional spread. METHODS: Twenty isolates of VanA VRE from the Centers for Disease Control and Prevention (CDC) and 17 from Ajou University Hospital (AUH) were investigated. Minimum inhibitory concen-trations of vancomycin, teicoplanin, and ampicillin were tested by the agar dilution method. Pulsed-field gel electrophoresis (PFGE) and long PCR-restriction fragment length polymorphism (long PCR-RFLP) were performed. The long PCR negative strains were typed by ORF1-, vanS-vanH-, vanX-, vanY-vanZ-, vanZ-, and IS1216-specific PCRs. Filter matings were performed by using rifampin-resistant, fusidic acid-resistant E. faecalis J H2-2 as the recipient. RESULTS: The PFGE from the VRE of the CDC showed 15 patterns including 4 clusters and PFGE from isolates of AUH revealed 6 patterns including 3 clusters. Tn1546 amplicons were detected in 18 of 20 (90%) CDC strains and 16 of 17 (94%) AUH strains. RFLP of Tn1546 amplicons revealed 5 different patterns in the VRE of the CDC strains, and 2 patterns in the VRE of the AUH strains. The mean transfer efficiency of the CDC and the AUH strains are 3.0 X 10(-8)and 4.9 X 10(-5)transconju-gant/ donor, respectively. CONCLUSIONS: Molecular typing of isolates from the CDC suggests the horizontal spread of vanA genes among genetically diverse strains. Analysis of the VRE from the AUH shows a mixed pattern with clonal dissemination of strains and horizontal transfer of vanA.