Wednesday, July 24, 2024

How Is Antibiotic Resistance Related To Natural Selection

The Spread Of Antibiotic Resistance

Natural Selection | Antibiotic resistance as natural selection example

Antibiotic resistance spreads as bacteria themselves move from place to place via human contact, for example, through coughing, or contact with unwashed hands, as well as animal contact, contaminated materials and in water, food and the wind. You will find resistant bacteria in the same places you find bacteria its just some of them are resistant. For more on this subject visit our Expert FAQs.

Horizontal Gene Transfer In Bacteria

Although bacteria reproduce asexually, they are very promiscuous-they love to share genetic information with their neighbors. In this way bacteria can share their mutations with one another. This sharing of genetic information with neighbors is called horizontal gene transfer and is another reason antibiotic resistance has spread so rapidly among bacteria.

3 different ways bacteria share genetic information.

  • Conjugation: bacteria make physical contact with each other and transfer DNA from a donor bacterium to a recipient bacterium.
  • Transduction: a bacterial virus called a bacteriophage transfers DNA from a donor bacterium to a recipient bacterium.
  • Transformation: transfer of naked DNA from a donor to a recipient bacterium. Some bacteria make DNA binding proteins on their surfaces. These DNA binding proteins can bind naked DNA in the environment, then pass the DNA into the interior of the bacterium. Bacterial cells which can be transformed are called competent cells.
  • Naturalized Escherichia Coli In Wastewater And The Co

    • 1School of Public Health, University of Alberta, Edmonton, AB, Canada
    • 2Antimicrobial Resistance One Health Consortium, Calgary, AB, Canada
    • 3School of Medicine, Ningbo University, Ningbo, China
    • 4The Affiliated Hospital of Medical School, Ningbo University, Ningbo, China
    • 5Human-Environment-Animal Transdisciplinary Antimicrobial Resistance Research Group, School of Public Health, University of Alberta, Edmonton, AB, Canada
    • 6Healthy Environments, Centre for Health Communities, School of Public Health, University of Alberta, Edmonton, AB, Canada

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    Appendix 1 Nucleic Acid Structure Of Cells: Dna And Rna

    DNA structure, nucleotide structure

    The DNA of chromosomes is a beautiful double helix 2 chains of DNA are held together by chemical attractions

    Each chain of DNA is made of nucleotides linked by strong chemical bonds.

    Each nucleotide of DNA consists of 3 parts :

    a. a sugar called deoxyribose

    b. a phosphate group

    c. one of 4 nitrogenous bases:

    -the nitrogenous bases of DNA are adenine , thymine , guanine and cytosine

    -adenine can form hydrogen bonds with thymine A:T and

    guanine can form hydrogen bonds with cytosine G:C

    • the above pairing rules are officially called complementary base pairing rules
    • hydrogen bonds between complementary bases on the 2 sister DNA strands holds the 2 strands or chains of DNA together in the chromosome
    • complementary base pairing also permits the precise replication of DNA, and its transcription

    Figure 2: The* double helix of chromosomal DNA. A single strand of DNA consists of a chain or polymer of individual nucleotides joined by strong chemical bonds. Each nucleotide carries one of 4 bases, the letters of the DNA alphabet. 3 specific bases make up the words of DNA language. Each DNA word or codon specifies one of 20 amino acids the cell uses to build proteins. Therefore the DNA base sequence determines the amino acid sequence of cellular proteins. In turn, the amino acid sequence of proteins determines how the protein will fold and the proteins ultimate shape. The shape/structure of the protein determines its function.

    Contributions Of Evolutionary Forces Under Antibiotic Treatment

    natural selection of antibiotic resistance in bacteria

    Antibiotic treatments are designed to achieve sufficient concentration in vivo to clear the infection and prevent the development of new resistant mutants. However, for several reasons including poor drug pharmacokinetics, poor drug distribution, or poor patient compliance, antibiotic concentrations are often below the MIC in body compartments . It is expected that as drug concentrations increase, the strength of selection relative to other forces also increases. We therefore analyzed resistance phenotypes of the whole population after 3 days of evolution under subinhibitory drug concentration and after 12 days of evolution in increasing drug levels that concluded at four times the MIC. We analyzed population-wide resistance instead of measures of single isolates because heterogeneity can determine the success or failure of an antibiotic treatment in clinical scenarios .

    Effects of history, chance, and selection on the evolution of CAZ or IMI resistance after 3 days at 0.5x MIC.

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    Statistical Analysis Of The Role Of Each Evolutionary Force

    We calculated the phenotypic effect of the evolutionary forces using a nested linear mixed model. By means of this nested linear mixed model including ancestors and replicates as random effects, we estimated the effect of history as the square root of the variance among all propagated populations the effect of chance as the square root of the variance between the replicates propagated from the same ancestor and the effect of selection was calculated as the difference in grand mean of the propagated replicates and their ancestors .

    Percentile bootstrap was employed to compute the confidence intervals of each force at the level of significance = 0.05 by taking 1000 random samples with replacement. In addition, the statistical evidence of each force was assessed adopting a Bayesian approach, which allows to circumvent the issues associated to null hypothesis statistical testing . Specifically, a set of models excluding each force were confronted against the full model including the three forces . Thus, let BIC1 be the Bayesian Information Criterion associated to the alternative model and BIC0 the Bayesian Information Criterion for one of the null models. Then, a Bayes factor can be approximated as follows:

    The roles of the evolutionary forces at the genotypic level were calculated using all identified mutations above a detection threshold of 5% based on the Manhattan distance between populations. For a pair of populations j and k with n genes,

    Dissemination Of Antibiotic Resistance From Wastewater Treatment Plants

    A better understanding of the environmental influences on the rapid growth of antibiotic resistance has led to the identification of environmental hotspots in the current antibiotic resistance crisis. In particular, wastewater treatment plants have received considerable attention as important drivers of antibiotic resistance, especially as a conduit for the dissemination of antibiotic resistance from anthropogenic activities to natural environments . Indeed, antibiotics, antibiotic resistant microbes, and their associated resistance genes are widespread in wastewater matrices , such that their subsequent release via effluent discharge represents an important source of antibiotic pollution in the surrounding environment. As such, despite the recent technological emergence of wastewater treatment plants to manage the sanitary wastes of densely populated societies , wastewater treatment plants have been identified as important hotspots in the dissemination of antibiotic resistance .

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    Modelling The Behavior And Dynamics Of Microswimmers

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    Selection Of Antibiotic Resistance Within Wastewater Treatment Plants

    Natural Selection and Antibiotic Resistance

    The wide range of antibiotic resistance genes and mobile genetic elements that are released following water treatment points to the presence of an extensive and highly mobile resistome in wastewater. With such an accessible reservoir of mobile antibiotic resistance genes, the importance of wastewater treatment plants in the antibiotic resistance crisis may extend well beyond the dissemination of antibiotic resistant-determining contaminants in downstream environments. In fact, the wastewater matrix itself may be particularly hospitable for the acquisition and dissemination of antibiotic resistance.

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    Schools Wikipedia Selection Related Subjects: Evolution And Reproduction

    Galápagos IslandsSee also character displacement, adaptive radiation, divergent evolution.

    Natural selection is the process by which individual organisms with favorable traits are more likely to survive and reproduce than those with unfavorable traits. It works on the whole individual, but only the heritable component of a trait will be passed on to the offspring, with the result that favorable, heritable traits become more common in the next generation. Given enough time, this passive process results in adaptations and speciation .

    Natural selection is one of the cornerstones of modern biology. The term was introduced by Charles Darwin in his 1859 book The Origin of Species, by analogy with artificial selection, by which a farmer selects his breeding stock.

    How Antibiotics Kill Bacteria

    Since the discovery of penicillin, an extensive arsenal of highly effective antibiotics has been derived from both natural and synthetic sources. In the process, weve learned much about the way antibiotics kill bacteria. Unlike humans, plants, and animals, which are made up of trillions of cells, bacteria are single celled organisms. Most antibiotics target basic biological processes necessary for the growth and survival of bacterial cells. Quinolones for instance , are a class of antibiotics that tamper with the cellular apparatus responsible for unwinding and rewinding DNA, which is normally packed away into tight coils. If the DNA cant be unwound, it cannot be replicated or repaired, and its genes cannot be read to produce new cellular components. Quinolone-treated bacteria can thus no longer divide or sustain themselves, and die. Other classes of antibiotics, such as beta-lactams , operate by blocking the construction and maintenance of the bacterial cell wall, a protective mesh made of sugars and proteins. Beta-lactams target the machinery necessary to fuse together components of the cell wall, such that bacteria treated with these antibiotics become fragile and eventually burst . While bacterial cells are in many ways similar to the cells in our body, the machinery our cells employ is different enough that most antibiotics are not toxic to us.

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    Engineering Natural Selection In Microbes Has Implications For Biofuel Production Addressing Antibiotic Resistance

    Scientists who study adaptation or edit the genes of organisms know the limitations inherent in conventional approaches to mutation that offer little opportunity to target individual genes without altering others as well.

    So many other things change around a gene at the same time, you cant focus on how a single gene changes, said Michael Travisano, a professor in the University of Minnesota College of Biological Sciences Department of Ecology, Evolution, and Behavior and the BioTechnology Institute. This was a major limitation for understanding evolutionary biology and leveraging it to make products.

    University researchers have now developed a tool that makes it possible to mutate a single gene at a time opening the door not only to a better understanding of evolution, but also better ways to modify the genes of microbes to give them the ability to mass-produce molecules, such as biofuel-generating enzymes, for human use.

    The approach called Experimental Designed Genic Evolution, or EDGE makes it possible to mutate a single, specific gene in E. coli bacteria without altering others. The study was published recently in PLOS ONE.

    Travisano developed EDGE in collaboration with Romas Kazlauskas, professor in the Department of Biochemistry, Molecular Biology, and Biophysics, and postdoctoral fellow Xiao Yi, both also affiliated with the BioTechnology Institute.

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    Selection And Genetic Variation

    How does natural selection act on individuals?

    A portion of all genetic variation is functionally neutral i.e., it produces no phenotypic effect or significant differences in fitness. Previously, this was thought to encompass most of the genetic variation in non-coding DNA, but recent studies have shown that large parts of those sequences are highly conserved and under strong purifying selection i.e. they do not vary as much from individual to individual, indicating that mutations in these regions have deleterious consequences). When genetic variation does not result in differences in fitness, selection cannot directly affect the frequency of such variation. As a result, the genetic variation at those sites will be higher than at sites where selection does have a result.

    Genetic linkage

    Genetic linkage occurs when two alleles are in close proximity to each other. During the formation of the gametes, recombination of the genetic material results in reshuffling of the alleles. However, the chance that such a reshuffle occurs between two alleles depends on the distance between those alleles the closer the alleles are to each other, the less likely it is that such a reshuffle will occur. Consequently, when selection targets one allele, this automatically results in selection of the other allele as well through this mechanism, selection can have a strong influence on patterns of variation in the genome.

    Mutation-selection balance

    Selective sweep

    Background selection

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    An Example: Antibiotic Resistance

    Figure 1

    A well-known example of natural selection in action is the development of antibiotic resistance in microorganisms. Antibiotics have been used to fight bacterial diseases since the discovery of penicillin in 1928 by Alexander Fleming. However, the widespread use and especially misuse of antibiotics has led to increased microbial resistance against antibiotics, to the point that the methicillin-resistant Staphylococcus aureus has been described as a ‘ superbug’ because of the threat it poses to health and its relative invulnerability to existing drugs.

    Natural populations of bacteria contain, among their vast numbers of individual members, considerable variation in their genetic material, primarily as the result of mutations. When exposed to antibiotics, most bacteria die quickly, but some may have mutations that make them a little less susceptible. If the exposure to antibiotics is short, these individuals will survive the treatment. This selective elimination of maladapted individuals from a population is natural selection.

    Recently, several new strains of MRSA have emerged that are resistant to vancomycin and teicoplanin. This is an example of what is sometimes called an ‘ arms race’, in which bacteria continue to develop strains that are less susceptible to antibiotics, while medical researchers continue to develop new antibiotics that can kill them. A similar situation occurs with pesticide resistance in plants and insects.

    What Is Antibiotic Resistance

    Overuse of antibiotics is creating stronger germs. Some bacteria are already “resistant” to common antibiotics. When bacteria become resistant to antibiotics, it is often harder and more expensive to treat the infection. Losing the ability to treat serious bacterial infections is a major threat to public health.

    Antibiotics are designed to fight bacteria by targeting specific parts of the bacterias structure or cellular machinery. However, over time, bacteria can defeat antibiotics in the following ways:

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    Antibiotic Use And Antibiotic Resistance

    When an antibiotic is used, bacteria that can resist that antibiotic have a greater chance of survival than those that are susceptible, and those that are not killed quickly multiply. Some resistance occurs without human action, as bacteria can produce and use antibiotics against other bacteria, leading to a low-level of natural selection for resistance to antibiotics. However, the current higher-levels of antibiotic-resistant bacteria are attributed to the overuse and abuse of antibiotics.

    Some bacteria are naturally resistant to certain types of antibiotics. Some mutate to either produce enzymes that deactivate antibiotics while other mutations change or close the target area on the bacteria that the antibiotic would normally attack. Some even create mechanisms to push the antibiotic back out of the cell when it attacks. Bacteria can acquire antibiotic resistance genes from other bacteria in several ways. They can transfer genetic material through a simple mating process, or through plasmids that reprogramme other bacteria to be resistant to antibiotics. They can also pick up stray DNA in their environment or can be infected by viruses.

    Naturalized Wastewater Microbes And The Co

    natural selection of antibiotic resistance in bacteria

    Characterization of the resistomes found in wastewater treatment plants suggest that naturalized microbes adapted to wastewater matrices may represent an important source of resistance genes contributing to the dissemination of antibiotic resistance in the microbial world. Unfortunately, the majority of the research has focused on clinical microbes in wastewater, even though clinical subpopulations are only transiently present in wastewater matrices due to their removal during the course of water treatment . In contrast, naturalized wastewater microbes may represent a persistent source of resistance genes driving the evolution of antibiotic resistance within the wastewater treatment plant.

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    Characterization Of Naturalized Wastewater Escherichia Coli As A Model For The Co

    A series of studies conducted by Zhi et al. have characterized novel clonal strains of E. coli that appear to have evolved to survive and replicate in wastewater and sewage environments as their primary niche. These findings point to an interesting prospect concerning the life history of naturalized microbes and their role in the evolution of antibiotic resistance. Typically, natural microbial populations are conventionally understood as ancient microbial lineages that predate the existence of human or animal hosts however, the characterization of naturalized wastewater E. coli suggests that host-derived bacterial populations may also evolve toward the adaptation and colonization of newly engineered environments. Notably, naturalized wastewater strains of E. coli have been primarily isolated from wastewater treatment plants and appear to be globally distributed . Considering that large-scale engineered wastewater treatment systems are a relatively new technology for sanitary management , it can be argued these naturalized wastewater strains represent a recently emerged subpopulation of E. coli that evolved to exploit a new engineered environment for its growth and survival.

    a. DNA repair systems linked to damage caused by UV irradiation

    b. type I and III restriction-modification systems, which cleave foreign DNA and are likely critical for survival in a sewage/wastewater environment that is abundant in diverse bacteriophages and conjugative plasmids

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