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mollyrf2023

How Many Types of Bacteria Are There? - 0 views

www.typesofbacteria.co.uk/-types-bacteria-are-there.html

bacteria APChemProject types bacteriatypes

shared by mollyrf2023 on 14 Jun 14 - No Cached
  • Cocci are spherical cells, bacilli are rod-shaped. Bacteria of either shape that have thick cell walls are termed gram positive because of the way they take up the Gram stain. Those with thin cell walls are termed gram negative
  • Spirochaetes: corkscrew-shaped bacteria that fall into three species, all of which cause specific diseases
  • Rickettsia: bacteria from the Rickettsiaceae family, which can only live and survive inside other living cells
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  • Mycoplasma: bacteria that have no cell wall
mollyrf2023

Bacterial Resistance to Antibiotics - 0 views

textbookofbacteriology.net/resantimicrobial_3.html

APChemProject resistance how

shared by mollyrf2023 on 14 Jun 14 - No Cached
  • chemically modify the antibiotic,  render it inactive through physical removal from the cell, or modify target site so that it is not recognized by the antibiotic.
  • Efflux pumps are high-affinity reverse transport systems located in the membrane that transport the antibiotic out of the cell.
  • A specific enzyme modifies the antibiotic in a way that it loses its activity. In the case of streptomycin, the antibiotic is chemically modified so that it will no longer bind to the ribosome to block protein synthesis.
  • ...8 more annotations...
  • An enzyme is produced that degrades the antibiotic, thereby inactivating it. For example, the penicillinases are a group of beta-lactamase enzymes that cleave the beta lactam ring
  • In fact, within 8-12 years after wide-spread use, strains resistant to multiple drugs become widespread.
  • Bacteria may be inherently resistant to an antibiotic. For example, an organism lacks a transport system for an antibiotic; or an organism lacks the target of the antibiotic molecule
  • the modification of existing genetic material or the acquisition of new genetic material from another source.
  • one in every every 108- 109  bacteria in an infection will develop resistance through the process of mutation
  • Once the resistance genes have developed, they are transferred directly to all the bacteria's progeny during DNA replication.
  • genetic material contained in small packets of DNA can be transferred between individual bacteria of the same species or even between different species
  • Conjugation occurs when there is direct cell-cell contact between two bacteria (which need not be closely related) and transfer of small pieces of DNA called plasmids takes place
mollyrf2023

Antibiotic-Resistant Bacteria Have Evolved a Unique Chemical Mechanism, New Discovery R... - 0 views

science.psu.edu/...Booker4-2011

APChemProject resistance how helpful

shared by mollyrf2023 on 14 Jun 14 - No Cached
  • methylation -- a process by which enzymes add a small molecular tag to a particular location on a nucleotide -- a molecule that is the structural unit of RNA and DNA
  • facilitates the proper functioning of the bacterial ribosome -- a gigantic macromolecular machine that is responsible for making proteins that bacteria need to survive
  • antibiotics bind to the ribosome, disrupting its function and thereby killing the bacteria
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  • The Cfr protein performs an identical function as the RlmN protein, but it adds the molecular tag at a different location on the same nucleotide. The addition of the tag blocks binding of antibiotics to the ribosome without disrupting its function
mollyrf2023

How antibiotics kill bacteria: from targets to networks - 0 views

www.ncbi.nlm.nih.gov/...PMC2896384

howantibioticswork APChemProject antibiotic

shared by mollyrf2023 on 14 Jun 14 - No Cached
  • Most current bactericidal antimicrobials, which are the focus of this review, inhibit DNA synthesis, RNA synthesis, cell wall synthesis, or protein synthesis
  • Quinolones are derivatives of nalidixic acid, which was discovered as a byproduct of chloroquine (quinine) synthesis
  • Nalidixic acid and other first generation quinolones (i.e., oxolinic acid) are rarely used today owing to their toxicity17. Second (i.e., ciprofloxacin), third (i.e., levofloxacin) and fourth (i.e., gemifloxacin) generation quinolone antibiotics (Table 1) can be classified based on their chemical structure along with qualitative differences in how these drugs kill bacteria
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  • quinolone class of antimicrobials interferes with the maintenance of chromosomal topology by targeting DNA gyrase (topoisomerase II) and topoisomerase IV (topoIV), trapping these enzymes at the DNA cleavage stage and preventing strand rejoining
  • DNA strand breakage occurs after the drug has bound the enzyme
  • quinolone treatment is to generate double-stranded DNA breaks that are trapped by covalently (yet reversibly) linked topoisomerases whose functions are compromised
  • eads to bacteriostasis and eventually cell deat
  • DNA replication machinery becomes arrested at blocked replication forks, leading to inhibition of DNA synthesis, which immediately leads to bacteriostasis and eventually cell death
  • inhibition by quinolones induces the DNA stress response (SOS response), in which RecA is activated by DNA damage and promotes auto-cleavage of the LexA repressor protein, inducing expression of SOS-response genes including DNA repair enzymes
  • Preventing induction of the SOS response has also been shown to reduce the formation of drug-resistant mutants by blocking the induction of error-prone DNA polymerases34, homologous recombination20, and horizontal transfer of drug-resistance elements
  • ifamycin drugs inhibit DNA-dependent transcription by stable binding, with high affinity, to the subunit (encoded by the rpoB gene) of a DNA-bound and actively-transcribing RNA polymerase enzyme
  • a recently discovered class of RNA polymerase inhibitors (based on the compound CBR703) may inhibit elongation by allosteric modification of the enzyme
  • requirement of rifamycins is that RNA synthesis has not progressed beyond the addition of two ribonucleotides
  • bacterial cell is encased by layers of peptidoglycan (PG, or murein), a covalently cross-linked polymer matrix composed of peptide-linked β-(1–4)-N-acetyl hexosamine
  • β-lactams and glycopeptides are among the classes of antibiotics that interfere with specific steps in homeostatic cell wall biosynthesis
  • Successful treatment with a cell wall synthesis inhibitor can result in changes to cell shape and size, induce cellular stress responses, and culminate in cell lysis
  • penicillins, carbapenems and cephalosporins
  • inhibiting the peptide bond formation reaction catalyzed by transpeptidases, which are also known as penicillin-binding proteins
  • the β-lactam drug molecule (containing a cyclic amide ring) is an analog of the terminal D-alanyl-D-alanine dipeptide of PG, and acts a substrate for the enzyme during the acylation phase of cross-link formation –- which disables the enzyme due to its inability to hydrolyze the bond created with the now ring-opened drug
  • reduce cellular mechanical strength
  • chemically-modified glycopeptides have been shown to directly interact with the transglycosylase enzyme
  • lipopeptides (e.g., daptomycin) which affect structural integrity via their ability to insert into the cell membrane and induce depolarization
  • Filamentation can occur, following activation of the DNA damage responsive SOS network of genes
  • mRNA translation occurs over three sequential phases (initiation, elongation and termination) involving the ribosome
  • The ribosome organelle is composed of two ribonucleoprotein subunits, the 50S and 30S
  • Drugs that inhibit protein synthesis are among the broadest classes of antibiotics and can be divided into two subclasses: the 50S inhibitors and 30S inhibitors
  • 0S ribosome inhibitors work by physically blocking either initiation of protein translation
  • or translocation of peptidyl-tRNAs, which serves to inhibit the peptidyltransferase reaction that elongates the nacent peptide chain
  • 30S ribosome inhibitors
  • work by blocking the access of aminoacyl-tRNAs to the ribosome
  • LysisRupture of the cell envelope leading to the expulsion of intracellular contents into the surrounding
  • interferes with the stability of peptidyl-tRNA binding to the ribosome by inhibiting elongation factor-catalyzed translocation
  • promoting tRNA mismatching which can result in protein mistranslation
mollyrf2023

How bacteria become resistant - 0 views

www.abc.net.au/...resistance.htm

APChemProject resistance how

shared by mollyrf2023 on 14 Jun 14 - Cached
  • ncreased production of the antibiotic’s target enzyme so that there are too many of them and the antibiotics cannot inactivate them all
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