Antibiotic resistance gene

Their strategy was firstly to identify genes conferring resistance to mitomycin upon the produdng organism, since antibiotic resistance genes are often clustered... 

That bacterial resistance predates the era of clinical use of antibiotics by several hundred millions of years is the recent result of genomic sequence data mining from antibiotic-producing microorganisms. These are supposed to be the inventors of antibiotic resistance genes which they had developed to protect themselves from the lethal action of their own antibiotics [4]. 

Plasmids have the ability to transfer within and between species and can therefore be acquired from other bacteria as well as a consequence of cell division. This property makes plasmid-acquired resistance much more threatening in terms ofthe spread of antibiotic resistance than resistance acquired due to chromosomal mutation. Plasmids also harbour transposons (section 2.1.3), which enhances their ability to transfer antibiotic resistance genes. 

Fig. 2.1 (A) Structure of the HCV genome, with 5 - and 3 -untranslated regions and individual proteins of the polyprotein indicated Regions of the genome (approximately 3,000 bases) are drawn to scale. Structural protein regions are in light gray, nonstructural proteins in white, and untranslated regions in dark gray. (B) Structure of a typical replicon sequence, with the antibiotic resistance gene (Neo ) in place of the structural region and the second IRES (EMCV) inserted. The NS2 sequence is often rwt present in the replicon.

Bergeron, M. G. Ouellette, M. Preventing antibiotic resistance through rapid genotypic identification of bacteria and of their antibiotic resistance genes in the clinical microbiology laboratory. J. Clin. Microbiol. 1998, 36, 2169-2172. 

Salyers, A. A. Amdbile-Cuevas, C. F. Why are antibiotic resistance genes so resistant to elimination Antimicrob. Agents Chemother. 1997, 41, 2321-2325. 

Pillai SD, Pepper IL (1991) Transposon Tn5 as an identifiable marker in rhizobia survival and genetic stability of Tn5 mutant bean rhizobia under temperature stressed conditions in desert soils. Microbial Ecol 21 21-33 Pote J, Ceccherini MT, Van VT, Rosselli W, Wildi W, Simonet P, Vogel TM (2003) Fate and transport of antibiotic resistance genes in saturated soil columns. Eur J Soil Biol 39 65-71... 

Another requirement for oral delivery is the ability to express foreign proteins in plastids that are present in non-green tissues. One such example is the expression of an antibiotic resistance gene (aadA) in tomato chromoplasts [28]. More recently, stable and highly efficient plastid transformation has been achieved in the non-green... 

Fig. 1 Mechanisms of antibiotic resistance acquisition (a) and spreading in a community over time (b). Arrows indicate horizontal gene transfer processes and R acquired antibiotic resistance gene...

The generalized evidences on the increase of antibiotic resistance, allied with the development of analytical methods and genome exploring tools, motivated numerous studies on the environmental pollution produced by antimicrobials and other anthropogenic substances or on the diversity and distribution of antibiotic resistance genes (e.g. [3, 10, 26, 32]). Overall, these studies showed the complexity of antibiotic resistance dissemination in the environment. For instance, it was revealed that (1) not only bacterial pathogens but, very often environmental bacteria are important reservoirs of antibiotic resistance (2) antibiotic resistance may have a... 

In comparison with culture-dependent procedures, culture-independent methods are more sensitive and have an increased potential to survey the diversity of antibiotic resistance genes in the environment. A weakness of these methods is the impossibility to elucidate about the bacteria in the community that host specific resistance determinants. On the other hand, the possibility to explore the genetic environment (mobile element, associated genes, promoter, etc.) in which the resistance determinant is integrated offers relevant clues about the gene transfer potential and gene acquisition history. 

The vast majority of the smdies on antibiotic resistance in the environment have focussed on the survey of resistance genes. However, the mere detection of the antibiotic resistance genes may be insufficient to get a clear perspective of their function in the environment. If the role of antibiotic resistance genes in the environment is to be assessed, it is also important to determine the factors capable of triggering gene expression and to measure the expression levels [24]. Such an approach requires transcriptomic analyses supported, for instance, by reverse-transcription PCR or microarrays. 

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