OBJECTIVETo review the research progress on Type IV secretion system (T4SS) in Helicobacter pylori.

DATA SOURCESThe data used in this review were identified by searching of PUBMED (1995 - 2007) online resources using the key terms 'Type IV secretion system' and 'Helicobacter pylori'.

STUDY SELECTIONMainly original articles and critical reviews written by major pioneer investigators of this field were selected.

RESULTSThe research progress on T4SS in Helicobacter pylori was summarized. The structure and function was discussed.

CONCLUSIONST4SS is not only involved in toxin secretion and injection of virulence factors into eukaryotic host target cells, but also involved in horizontal DNA transfer to other bacteria and eukaryotic cells, through DNA uptake from or release into the extracellular milieu. It provides a new insight into the pathogenicity of Helicobacter pylori and a novel target for antimicrobials development. However, many challenges remain for us in understanding the biological role of T4SS in Helicobacter pylori.

A new class of RNA regulatory genes known as microRNAs (miRNAs) has been found to introduce a whole new layer of gene regulation in eukaryotes. The intensive studies of the past several years have demonstrated that miRNAs are not only found intracellularly, but are also detectable outside cells, including in various body fluids (e.g. serum, plasma, saliva, urine and milk). This phenomenon raises questions about the biological function of such extracellular miRNAs. Substantial amounts of extracellular miRNAs are enclosed in small membranous vesicles (e.g. exosomes, shedding vesicles and apoptotic bodies) or packaged with RNA-binding proteins (e.g. high-density lipoprotein, Argonaute 2 and nucleophosmin 1). These miRNAs may function as secreted signaling molecules to influence the recipient cell phenotypes. Furthermore, secreted extracellular miRNAs may reflect molecular changes in the cells from which they are derived and can therefore potentially serve as diagnostic indicators of disease. Several studies also point to the potential application of siRNA/miRNA delivery as a new therapeutic strategy for treating diseases. In this review, we summarize what is known about the mechanism of miRNA secretion. In addition, we describe the pathophysiological roles of secreted miRNAs and their clinical potential as diagnostic biomarkers and therapeutic drugs. We believe that miRNA transfer between cells will have a significant impact on biological research in the coming years.
Animals ; Diagnosis ; Extracellular Space ; genetics ; Gene Transfer, Horizontal ; Humans ; MicroRNAs ; genetics ; metabolism ; Therapeutics

Paclitaxel (taxol) has long been used as a potent anticancer agent for the treatment of many cancers. Ever since the fungal species Taxomyces andreanae was first shown to produce taxol in 1993, many endophytic fungal species have been recognized as taxol accumulators. In this study, we analyzed the taxol-producing capacity of different Colletotrichum spp. to determine the distribution of a taxol biosynthetic gene within this genus. Distribution of the taxadiene synthase (TS) gene, which cyclizes geranylgeranyl diphosphate to produce taxadiene, was analyzed in 12 Colletotrichum spp., of which 8 were found to contain the unique skeletal core structure of paclitaxel. However, distribution of the gene was not limited to closely related species. The production of taxol by Colletotrichum dematium, which causes pepper anthracnose, depended on the method in which the fungus was stored, with the highest production being in samples stored under mineral oil. Based on its distribution among Colletotrichum spp., the TS gene was either integrated into or deleted from the bacterial genome in a species-specific manner. In addition to their taxol-producing capacity, the simple genome structure and easy gene manipulation of these endophytic fungal species make them valuable resources for identifying genes in the taxol biosynthetic pathway.
Biosynthetic Pathways ; Colletotrichum* ; Fungi ; Gene Transfer, Horizontal ; Genome ; Genome, Bacterial ; Methods ; Mineral Oil ; Paclitaxel*

Horizontal gene transfer (HGT) is the movement of genetic material between kingdoms and is considered to play a positive role in adaptation. Cryptosporidium parvum is a parasitic protozoan that causes an infectious disease. Its genome sequencing reported 14 bacteria-like proteins in the nuclear genome. Among them, cgd2_1810, which has been annotated as CysQ, a sulfite synthesis pathway protein, is listed as one of the candidates of genes horizontally transferred from bacterial origin. In this report, we examined this issue using phylogenetic analysis. Our BLAST search showed that C. parvum CysQ protein had the highest similarity with that of proteobacteria. Analysis with NCBI's Conserved Domain Tree showed phylogenetic incongruence, in that C. parvum CysQ protein was located within a branch of proteobacteria in the cd01638 domain, a bacterial member of the inositol monophosphatase family. According to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, the sulfate assimilation pathway, where CysQ plays an important role, is well conserved in most eukaryotes as well as prokaryotes. However, the Apicomplexa, including C. parvum, largely lack orthologous genes of the pathway, suggesting its loss in those protozoan lineages. Therefore, we conclude that C. parvum regained cysQ from proteobacteria by HGT, although its functional role is elusive.
Apicomplexa ; Bacteria ; Communicable Diseases ; Cryptosporidium ; Cryptosporidium parvum ; Eukaryota ; Gene Transfer, Horizontal ; Genome ; Humans ; Inositol ; Phosphoric Monoester Hydrolases ; Proteins ; Proteobacteria

Cationic liposome-mediated gene transfection is a promising method for gene therapy. In this study, the transfection efficiency and histological patterns were evaluated in rat lung after intravenous administration via femoral vein of naked plasmid DNA, naked plasmid DNA with pretreatment of DOTAP, and DOTAP-cholesterol-plasmid DNA complex. Plasmid DNA encoding bacterial LacZ gene was used. For quantification of LacZ gene expression, -galactosidase assay was performed. For histologic examination, X-gal staining and immunohistochemical staining for transfected gene products were performed. Pretreatment of DOTAP prior to the infusion of naked plasmid DNA increased transfection efficiency up to a level comparable to DOTAP-cholesterol-plasmid DNA complex injection. Transfected genes were mainly expressed in type II pneumocytes and alveolar macrophages in all animals. We conclude that the high transfection efficiency is achievable by intravenous administration of naked plasmid DNA with pretreatment of DOTAP, to a level comparable to DOTAP-cholesterol-plasmid DNA complex. In this regard, naked plasmid DNA administration with pretreatment of DOTAP could be a more feasible option for intravenous gene transfer than DOTAP-cholesterol-plasmid DNA complex, in that the former is technically easier and more cost-effective than the latter with a comparable efficacy, in terms of intravenous gene delivery to the lung.
Animal ; DNA/*administration & dosage/metabolism ; Galactosides/analysis ; *Gene Therapy ; Gene Transfer, Horizontal ; Immunohistochemistry ; Indoles/analysis ; Injections, Intravenous ; Lung/*metabolism ; Male ; *Plasmids ; Rats ; Rats, Inbred F344 ; *Transfection

With the proceeding of the human genome program(HGP), new genes related to male reproduction have been cloned continuously by different methods. However, investigation of the gene function is still at the rudimentary stage. In spite of the advances in the common methods of studying gene function, some special methods have yet to be developed concerning the study of the genes related to male reproduction. This paper summarizes the current methods of study on gene function relevant to male reproduction.
Animals ; Gene Targeting ; Gene Transfer, Horizontal ; Genes ; physiology ; Genetic Vectors ; genetics ; Humans ; Male ; Models, Animal ; Oligonucleotides, Antisense ; therapeutic use ; Reproduction ; genetics ; Reverse Transcriptase Polymerase Chain Reaction

The liberal use of antibiotics in human medicine and animal husbandry has promoted the spread of multiple antibiotic resistance. Molecular mechanisms for the acquisition of resistance genes by integron-mediated recombination was discovered recently during an intensive study of antibiotic resistance. Integrons are best known as the genetic agents responsible for the capture and spread of antibiotic resistance determinants among diverse Gram-negative clinical isolates. These DNA elements, mobilized by broad-host-range conjugative plasmids, have the ability of horizontal transfer of antibiotic resistance genes between interspecies of bacteria. The association of integrons with mobile elements promotes their vertical transmission from plasmids to the bacterial chromosome and among different replicons, contributing to the dissemination of resistance genes. Integrons have been found widely distributed among resistant bacteria circulating in hospitals and in the community and have been reported from all continents. The evolution of multi-drug resistance seems to proceed continuously through the acquisition and clustering of dispersed resistance genes by integrons. For public health, proper strategies should be instituted to reduce the potential for dissemination of these genes.
Animal Husbandry ; Anti-Bacterial Agents ; Bacteria ; Chromosomes, Bacterial ; DNA ; Drug Resistance, Microbial ; Drug Resistance, Multiple* ; Epidemiology ; Gene Transfer, Horizontal ; Humans ; Integrons* ; Plasmids ; Public Health ; Recombination, Genetic ; Replicon

Knowledge of the evolution of pathogens is of great medical and biological significance to the prevention, diagnosis, and therapy of infectious diseases. In order to understand the origin and evolution of the SARS-CoV (severe acute respiratory syndrome-associated coronavirus), we collected complete genome sequences of all viruses available in GenBank, and made comparative analyses with the SARS-CoV. Genomic signature analysis demonstrates that the coronaviruses all take the TGTT as their richest tetranucleotide except the SARS-CoV. A detailed analysis of the forty-two complete SARS-CoV genome sequences revealed the existence of two distinct genotypes, and showed that these isolates could be classified into four groups. Our manual analysis of the BLASTN results demonstrates that the HE (hemagglutinin-esterase) gene exists in the SARS-CoV, and many mutations made it unfamiliar to us.
Amino Acid Motifs ; Amino Acid Substitution ; Base Composition ; Codon ; genetics ; Computational Biology ; DNA Mutational Analysis ; Evolution, Molecular ; Gene Transfer, Horizontal ; Genetic Variation ; Genome, Viral ; Phylogeny ; SARS Virus ; genetics

Throughout human history, pandemic bacterial diseases such as the plague and tuberculosis have posed an enormous threat to human beings. The discovery of antibiotics has provided us with powerful arsenal for the defense against bacterial infections. However, bacteria are acquiring more and more resistance genes to shield off antibiotics through mutation and horizontal gene transfer. Therefore, novel antibiotics must be produced and the arms race between bacterial pathogens and antibiotics is becoming increasingly intense. Recently, researchers have found that plasmids carrying a new metallo-beta-lactamase gene, blaNDM-1, and many other antibiotics resistance genes can easily spread through bacterial populations and confer recipient stains resistance to nearly all of the current antibiotics. It is a threat to the human health and a great challenge for our medical science, which we are facing. We need to find new ways to fight and win this arms racing.
Anti-Bacterial Agents ; pharmacology ; Bacteria ; drug effects ; genetics ; Drug Resistance, Bacterial ; genetics ; Gene Transfer, Horizontal ; Mutation ; Plasmids ; genetics ; beta-Lactamases ; genetics

Antibacterial drugs are one of the most important therapeutic agents of bacterial infections but multidrug resistant Escherichia coli (MDREC) is an increasing problem worldwide. Major resistance mechanism of MDREC is horizontal gene transfer of R plasmids harboring integrons, which the integron integrase (IntI) catalyzes gene cassette insertion and excision through site specific recombination. In this study, resistance profiles of integron harboring E. coli isolated in Korea and the genetic environments of integron gene cassettes were analyzed by PCR and direct sequencing to clarify the mechanisms of spread of integron harboring E. coli. Resistance rates of integron harboring E. coli, including β-lactams, aminoglycosides, and fluoroquinolones and MDR frequencies were significantly higher than that of E. coli without integron (p < 0.01). Majority (80%) of integron harboring E. coli showed resistance transfer by conjugation. Most (80%) of E. coli had dfrA17-aadA5 cassette array and PcH1 hybrid promoter; 16.7% of E. coli had dfrA12-orfF-aadA2 cassette array and PcW promoter. The higher prevalence of weak Pc variants among most (96.7%) of integron harboring MDREC suggests that a flexible cassette array is more important than enhanced expression. All the integrons had LexA binding motif suggests that SOS responses control the expression of these integrons. In conclusion, the genetic bases of integrons were diverse, and the spread and the expression of prevalent gene cassette arrays may be deeply related with strengths of Pc promoters in integrons. These informations will provide important knowledge to control the increase of integron harboring MDREC.
Aminoglycosides ; Bacterial Infections ; Escherichia coli ; Escherichia ; Fluoroquinolones ; Gene Transfer, Horizontal ; Integrases ; Integrons ; Korea ; Polymerase Chain Reaction ; Prevalence ; R Factors ; Recombination, Genetic ; SOS Response (Genetics)