共查询到20条相似文献,搜索用时 31 毫秒
1.
Whittle G Shoemaker NB Salyers AA 《Cellular and molecular life sciences : CMLS》2002,59(12):2044-2054
Investigations into the mechanisms of antibiotic resistance gene transfer utilized by Bacteroides species have led to a greater understanding of how bacteria transfer antibiotic resistance genes, and what environmental stimuli promote such horizontal transfer events. Although Bacteroides spp. harbor a variety of transmissible elements that are involved in the dissemination of antibiotic resistance genes, it is one particular class of elements, the conjugative transposons, that are responsible for most of the resistance gene transfer in Bacteroides. The potential for Bacteroides conjugative transposons to transfer antibiotic resistance genes extends beyond those genes carried by the conjugative transposon itself, because Bacteroides conjugative transposons are able to mobilize coresident plasmids in trans and in cis, and also stimulate the excision and transfer of unlinked integrated elements called mobilizable transposons. These characteristics of conjugative transposons alone have significant implications for the ecology and spread of antibiotic resistance genes, and in terms of biotechnology. A novel feature of the most widespread family of Bacteroides conjugative transposons, the CTnDOT/ERL family, is that their transfer is stimulated 100- to 1000-fold by low concentrations of tetracycline. This is significant because the use of antibiotics not only selects for resistant Bacteroides strains, but also stimulates their transfer. Other Bacteroides conjugative transposons do not require any induction to stimulate transfer, and hence appear to transfer constitutively. The constitutively transferring elements characterized so far appear to have a broader host range than the CTnDOT/ERL family of conjugative transposons, and the prevalence of these elements is on the increase. Since these constitutively transferring elements do not require induction by antibiotics to stimulate transfer, they have the potential to become as pervasive as the CTnDOT/ERL family of conjugative transposons. 相似文献
2.
Adams V Lyras D Farrow KA Rood JI 《Cellular and molecular life sciences : CMLS》2002,59(12):2033-2043
Mobilisable transposons are transposable genetic elements that also encode mobilisation functions but are not in themselves
conjugative. They rely on coresident conjugative elements to facilitate their transfer to recipient cells. Clostridial mobilisable
transposons include Tn4451 and Tn4452 from Clostridium perfringens, and Tn4453a and Tn4453b from Clostridium difficile, all of which are closely related, and Tn5398 from C. difficile. The Tn4451 group of elements encodes resistance to chloramphenicol and is unusual in that transposition is dependent upon a large resolvase
protein rather than a more conventional transposase or integrase. This group of elements also encodes the mobilisation protein
TnpZ that, by acting at the RSA or oriT site located on the transposon, and in the presence of a coresident conjugative element, promotes the movement of the nonreplicating
circular intermediate and
of plasmids on which the transposon resides. The erythromycin resistance element Tn5398 is unique in that it encodes no readily identifiable transposition or mobilisation proteins. However, the element is still
capable of intraspecific transfer between C. difficile isolates, by an unknown mechanism. The detailed analysis of these mobilisable clostridial elements provides evidence that
the evolution and dissemination of antibiotic resistance genes is a complex process that may involve the interaction of genetic
elements with very different properties.
RID="*"
ID="*"Corresponding author. 相似文献
3.
Although widely studied in Gram-positive Streptococci and in the Gram-negative Bacteroides, there is a scarcity of information on the occurrence and nature of conjugative transposon-like elements in the well-studied
Enterobacteriaceae. In fact, some of the major reviews on conjugative transposons prior to 1996 failed to mention their occurrence in this group.
Recently, their presence has been reported in Salmonella, Vibrio and Proteus species, and in some cases such as the SXT element in Vibrio and the IncJ group element CTnR391, there has been some molecular characterization. The elements thus far examined appear
to be larger than the common Gram-positive conjugative transposons and to be mosaic in structure, with genes derived from
several sources. Recent evidence suggests that in the Enterobacteriaceae the elements may be related to enteric pathogenicity islands. The evolution, distribution and role of these elements
in the Enterobacteriaceae is discussed. 相似文献
4.
Teuber M 《Cellular and molecular life sciences : CMLS》1999,56(9-10):755-763
This short review summarizes data on antibiotic resistance profiles of common food-borne pathogens like Salmonella sp., Escherichia coli, Campylobacter sp., Listeria monocytogenes, Clostridium perfringens, Staphylococcus aureus, and coagulase-negative staphylococci. As a flashlight on the literature of the last few years, it provides ample evidence that antibiotic resistance traits have entered the microflora of farm animals and the food produced from them. Molecular analysis of the resistance genes, where available, shows that the food microflora is not separated from its human counterpart and conjugative transfer of resistance genes has been demonstrated in vitro and in a few cases in vivo. For example, for Salmonella typhimurium, resistance towards tetracyclines has increased from zero in 1948 to a 98% level in certain epidemic populations of S. typhimurium DT104 in 1998. The high incidence of food-borne pathogens in raw meat and milk together with a high level of therapeutic, prophylactic and nutritional application of antibiotics in agriculture reveals an antibiotic resistance problem of global dimensions. The resistance problem in human medicine will not be solved if there is a constant influx of resistance genes into the human microflora via the food chain. 相似文献
5.
Translocation of conjugative transposons proceeds via excision of the element to generate a circular molecule that can then
integrate into a new site, which can be in the same or a different cell. This review summarises some of the different mechanisms
used for excision and integration of conjugative transposons.
RID="*"
ID="*"Corresponding author. 相似文献
6.
Rice LB 《Cellular and molecular life sciences : CMLS》2002,59(12):2023-2032
Among the more important problems in modern hospitals is the prevalence of bacterial pathogens expressing resistance to multiple
antimicrobial agents. The frequency of multiresistance suggests mechanisms by which bacterial species can concentrate and
efficiently exchange a variety of resistance determinants. Mechanisms by which this occurs include insertion of transposons
within transposons, coalescence through the activity of insertion sequences and the employment of integrons. In some instances,
more than one of these mechanisms is involved in creating large multiresistance genetic elements. The association of the elements
with transferable elements or transposons may promote rapid dissemination among clinical strains, and create further opportunities
for inclusion of additional resistance determinants. 相似文献
7.
Comparison of SXT and R391, two conjugative integrating elements: definition of a genetic backbone for the mobilization of resistance determinants 总被引:10,自引:0,他引:10
Beaber JW Burrus V Hochhut B Waldor MK 《Cellular and molecular life sciences : CMLS》2002,59(12):2065-2070
The SXT element (SXT) is becoming an increasingly prevalent vector for the dissemination of antibiotic resistances in Vibrio cholerae. SXT is a member of a larger family of elements, formerly defined as IncJ plasmids, that are self-transmissible by conjugation
and integrate site-specifically into the host chromosome. Comparison of the DNA sequences of SXT and R391, an IncJ element
from Providencia rettgeri, indicate that these elements consist of a conserved backbone that mediates the regulation, excision/integration and conjugative
transfer of the elements. Both elements have insertions into this backbone that either confer the element-specific properties
or are of unknown function. Interestingly, the conserved SXT and R391 backbone apparently contains hotspots for insertion
of additional DNA sequences. This backbone represents a scaffold for the mobilization of genetic material between a wide range
of Gram-negative bacteria, allowing for rapid adaptation to changing envi
ronments.
RID="*"
ID="*"Corresponding author. 相似文献
8.
9.
D. K. Willis T. M. Barta T. G. Kinscherf 《Cellular and molecular life sciences : CMLS》1991,47(8):765-771
Genes for phytotoxin production have been identified and cloned from several phytopathogenic pseudomonads. These genes comprise physically linked clusters that have been located both on the chromosome and on endogenous plasmids. Contained within these genetic regions are resistance genes specific to those toxins that have a bactericidal component to their activity. DNA sequences required for toxin production are often conserved among bacteria with divergent host specificities, suggesting the ability of toxin genes to be transferred between bacteria. Toxins are usually modulators of plant pathogenicity, their production causing a significant increase in disease severity. In one case, however, toxin production appears to be a major contributor to the basic pathogenicity of a plant pathogenic bacterium. 相似文献
10.
Screening for differentially expressed genes is a straightforward approach to study the molecular basis for changes in gene
expression. Differential display analysis has been used by investigators in diverse fields of research since it was developed.
Differential display has also been the approach of choice to investigate changes in gene expression in response to various
biological challenges in invertebrates. We review the application of differential display analysis of gene expression in invertebrates,
and provide a specific example using this technique for novel gene discovery in the nematode Caenorhabditis elegans. 相似文献
11.
Alicja M. Nogacka Nuria Salazar Silvia Arboleya Marta Suárez Nuria Fernández Gonzalo Solís Clara G. de los Reyes-Gavilán Miguel Gueimonde 《Cellular and molecular life sciences : CMLS》2018,75(1):83-91
The colonization of the neonatal digestive tract provides a microbial stimulus required for an adequate maturation towards the physiological homeostasis of the host. This colonization, which is affected by several factors, begins with facultative anaerobes and continues with anaerobic genera. Accumulating evidence underlines the key role of the early neonatal period for this microbiota-induced maturation, being a key determinant factor for later health. Therefore, understanding the factors that determine the establishment of the microbiota in the infant is of critical importance. Exposure to antibiotics, either prenatally or postnatally, is common in early life mainly due to the use of intrapartum prophylaxis or to the administration of antibiotics in C-section deliveries. However, we are still far from understanding the impact of early antibiotics and their long-term effects. Increased risk of non-communicable diseases, such as allergies or obesity, has been observed in individuals exposed to antibiotics during early infancy. Moreover, the impact of antibiotics on the establishment of the infant gut resistome, and on the role of the microbiota as a reservoir of resistance genes, should be evaluated in the context of the problems associated with the increasing number of antibiotic resistant pathogenic strains. In this article, we review and discuss the above-mentioned issues with the aim of encouraging debate on the actions needed for understanding the impact of early life antibiotics upon human microbiota and health and for developing strategies aimed at minimizing this impact. 相似文献
12.
Antibiotic resistance in microbes 总被引:31,自引:0,他引:31
The treatment of infectious disease is compromised by the development of antibiotic-resistant strains of microbial pathogens. A variety of biochemical processes are involved that may keep antibiotics out of the cell, alter the target of the drug, or disable the antibiotic. Studies have shown that resistance determinants arise by either of two genetic mechanisms: mutation and acquisition. Antibiotic resistance genes can be disseminated among bacterial populations by several processes, but principally by conjugation. Thus the overall problem of antibiotic resistance is one of genetic ecology and a better understanding of the contributing parameters is necessary to devise rational approaches to reduce the development and spread of antibiotic resistance and so avoid a critical situation in therapy--a return to a pre-antibiotic era. 相似文献
13.
Evolution of bacterial pathogenesis 总被引:6,自引:0,他引:6
Ziebuhr W Ohlsen K Karch H Korhonen T Hacker J 《Cellular and molecular life sciences : CMLS》1999,56(9-10):719-728
The evolution of bacteria is associated with continuous generation of novel genetic variants. The major driving forces in this process are point mutations, genetic rearrangements, and horizontal gene transfer. A large number of human and animal bacterial pathogens have evolved the capacity to produce virulence factors that are directly involved in infection and disease. Additionally, many bacteria express resistance traits against antibiotics. Both virulence factors and resistance determinants are subject to intrastrain genetic and phenotypic variation. They are often encoded on unstable DNA regions. Thus, they can be readily transferred to bacteria of the same species or even to non-related prokaryotes. This review article focuses on the main mechanisms of bacterial microevolution responsible for the rapid emergence of variants with novel virulence and resistance properties. In addition, processes of macroevolution are described with special emphasis on gene transfer and fixation of adaptive mutations in the genome of pathogens. 相似文献
14.
Bacterial antibiotic efflux systems of medical importance 总被引:6,自引:0,他引:6
Multidrug efflux systems endow on bacterial cells the ability to limit the access of antimicrobial agents to their targets. By actively pumping out antibiotic molecules, these systems prevent the intracellular accumulation necessary for antibiotics to exert their lethal activity. Drug efflux appears to be one of the most widespread antibiotic resistance mechanisms among microorganisms, since it has been demonstrated to occur in many Gram-positive and Gram-negative bacteria including medically important species like staphylococci, streptococci, enterobacteria and opportunistic pathogens like Pseudomonas aeruginosa. Efflux pumps can be specific for only one substrate or accommodate a more or less wide range of noxious products. Export of structurally unrelated compounds confers a multidrug-resistance phenotype on bacterial cells. Therapeutically critical levels of resistance can be achieved by overexpression of efflux systems, especially in those species such as P. aeruginosa which possess a low outer membrane permeability. It is suspected that the dual physiological function of active efflux systems is both the secretion of intracellular metabolites and the protection against a variety of harmful substances that the microorganism may encounter in its natural environment. 相似文献
15.
16.
Extracellular electron transfer 总被引:23,自引:0,他引:23
Results from several laboratories indicate that extracellular electron transfer may be a general mechanism whereby microoorganisms
generate energy for cell growth and/or maintenance. Specifically, bacteria can use redox-active organic small molecules, generated
outside or inside the cells, to shuttle electrons between reduced and oxidized compounds. Electron shuttling has now been
reported for several different bacterial species, and exchanges of shuttling compounds may even syntrophically link diverse
organisms in nature. Biofilm systems in both geological and clinical settings are likely to be important environments for
metabolisms that employ extracellular electron transfer. Both structural and functional analyses suggest that electron shuttles
and some virulence factors may be related to one another.
Received 21 March 2001; received after revision 10 May 2001; accepted 11 May 2001 相似文献
17.
E. Kellenberger 《Cellular and molecular life sciences : CMLS》1994,50(5):429-437
Genetic ecology is the extension of our modern knowledge in molecular genetics to studies of viability, gene expression and gene movements in natural environments like soils, aquifers and digestive tracts. In such milieux, the horizontal transfer of plasmid-borne genes between phylogenetically distant species has already been found to be much more frequent than had been expected from laboratory experience. For the study of exchanges involving chromosomally-located genes, more has to be learned about the behaviour of transposons in such environments. The results expected from studies in genetic ecology are relevant for considerations of evolution, biodiversity and biosafety. The role of this new field of research in restoring popular confidence in science and in its biotechnological applications is stressed. 相似文献
18.
Molecular basis of autosomal-dominant polycystic kidney disease 总被引:5,自引:0,他引:5
Gallagher AR Hidaka S Gretz N Witzgall R 《Cellular and molecular life sciences : CMLS》2002,59(4):682-693
Autosomal-dominant polycystic kidney disease (ADPKD) is one of the most common monogenetic diseases in humans. The discovery
that mutations in the PKD1 and PKD2 genes are responsible for ADPKD has sparked extensive research efforts into the physiological and pathogenetic role of polycystin-1
and polycystin-2, the proteins encoded by these two genes. While polycystin-1 may mediate the contact among cells or between
cells and the extracellular matrix, a lot of evidence suggests that polycystin-2 represents an endoplasmic reticulum-bound
cation channel. Cyst development has been compared to the growth of benign tumors and this view is highlighted by the model
that a somatic mutation in addition to the germline mutation is responsible for cystogenesis (two-hit model of cyst formation).
Since in vitro polycystin-1 and polycystin-2 interact through their COOH termini, the two proteins possibly act in a common
pathway, which controls the width of renal tubules. The loss of one protein may lead to a disruption of this pathway and to
the uncontrolled expansion of tubules. Our increasing knowledge of the molecular events in ADPKD has also started to be useful
in designing novel diagnostic and therapeutic strategies.
Received 12 September 2001; received after revision 7 November 2001; accepted 7 November 2001 相似文献
19.
The tetracycline resistome 总被引:2,自引:0,他引:2
Maulik Thaker Peter Spanogiannopoulos Gerard D. Wright 《Cellular and molecular life sciences : CMLS》2010,67(3):419-431
Resistance to tetracycline emerged soon after its discovery six decades ago. Extensive clinical and non-clinical uses of this
class of antibiotic over the years have combined to select for a large number of resistant determinants, collectively termed
the tetracycline resistome. In order to impart resistance, microbes use different molecular mechanisms including target protection,
active efflux, and enzymatic degradation. A deeper understanding of the structure, mechanism, and regulation of the genes
and proteins associated with tetracycline resistance will contribute to the development of tetracycline derivatives that overcome
resistance. Newer generations of tetracyclines derived from engineering of biosynthetic genetic programs, semi-synthesis,
and in particular recent developments in their chemical synthesis, together with a growing understanding of resistance, will
serve to retain this class of antibiotic to combat pathogens. 相似文献
20.
To have sex, or not to have sex, is a question posed by many microorganisms. In favor of a sexual lifestyle is the associated
rearrangement of genetic material that confers potential fitness advantages, including resistance to antimicrobial agents.
The asexual lifestyle also has benefits, as it preserves complex combinations of genes that may be optimal for pathogenesis.
For this reason, it was thought that several pathogenic fungi favored strictly asexual modes of reproduction. Recent approaches
using genome sequencing, population analysis, and experimental techniques have now revised this simplistic picture. It is
now apparent that many pathogenic fungi have retained the ability to undergo sexual reproduction, although reproduction is
primarily clonal in origin. In this review, we highlight the current understanding of sexual programs in the Candida clade of species. We also examine evidence that sexual-related processes can be used for functions in addition to mating
and recombination in these organisms. 相似文献