voca



  • Antibiotic: a chemical substance from one microorganism that inhibits or kills another microorganism.

  • Bactericidal: drug that kills bacteria.

  • Bacteriostatic: drug that inhibits bacterial growth but does not kill bacteria.

  • selective toxicity: killing microbial cells but not the host’s own cells (skin, muscle, nerves, etc.).

  • broad spectrum antibiotic: drug that is effective against a wide range of microbes.

  • narrow spectrum antibiotic: drug that is effective against a limited range of microbes. 

  • beta-lactam antibiotic: inhibit penicillin binding proteins, thus interfering with peptidoglycan synthesis.

  • acquired resistance: resistance due to mutation or acquisition of new genes.

  • Penicillin: from Penicillium chrysogenum. Discovered by Alexander Fleming. Interferes with peptidoglycan synthesis by inhibiting penicillin binding proteins, which normally cross-links the short peptides in the cell wall.

  • minimum inhibitory concentration: the lowest concentration of a drug that will inhibit the microorganism from growing.

  • minimum bactericidal concentration: lowest concentration of a drug that will kill 99.9% of the population of a particular bacterium.

  • disc diffusion test: “Kirby-Bauer Test” — plate a lawn of bacteria and add antibiotic discs.Then, determine susceptibility or resistance to antibiotics. Clear zones around the disc means bacteria are killed and the antibiotic is effective. No clear zone means the antibiotic is not effective, and that the bacteria can grow normally.

  • R plasmid: “Resistance (R) Factor” — plasmid carrying one or more genes for antibiotic resistance.

  • therapeutic index (TI#): lowest dose toxic to the patient divided by the dose used to treat the disease. The higher the therapeutic index, the less toxic the drug.

  • intrinsic resistance: resistance due to an inherent characteristic of the microbe.

  • site of action: antibiotic target—anything that is an essential process in the bacteria. Include:

  • cell membrane, cell wall, DNA, mRNA, and proteins.

  • vertical gene transfer: moving genes, including antibiotic resistant genes, through reproduction. Passing the genes to the daughter cells.

  • horizontal gene transfer: moving genes, including antibiotic resistant genes, through conjugation, transduction, and transformation. Can pass genes to the same and different species of bacteria.

  • DNA: genetic material that carries heritable information. Has a sugar-phosphate chain with nitrogen bases (adenine, thymine, guanine, and cytosine). Double stranded. Deoxyribose sugar. Can self-replicate.

  • mRNA: messenger RNA. Used as a template for translation. Type of RNA molecule translated during protein synthesis.

  • tRNA: transfer RNA. Type of RNA molecule involved in interpreting the genetic code; each tRNA molecule carries a specific amino acid.

  • rRNA: ribosomal RNA. Type of RNA molecule present in ribosomes.

  • nucleotide: contains a 5-carbon sugar (deoxyribose or ribose), a phosphate group, and one of four different nucleobases (A, T/U, G, or C).

  • adenine: nucleobase; paired with thymine.

  • thymine: nucleobase in DNA; paired with adenine.

  • guanine: nucleobase; paired with cytosine.

  • cytosine: nucleobase; paired with guanine.

  • uracil: nucleobase in RNA; paired with adenine.

  • promoter: Nucleotide sequence to which RNA polymerase binds to start transcription.

  • RNA polymerase: Enzyme that synthesizes RNA using one strand of DNA as a template.

  • DNA polymerase: Enzyme that synthesizes DNA, using an existing strand as a template to make a new complementary strand.

  • DNA replication: Duplication of a DNA molecule.

  • template: The RNA sequence made during transcription is complementary and antiparallel to the DNA template. The DNA strand that serves as the template for transcription is called the minus (-) strand.

  • haploid: a single set of unpaired chromosomes.

  • diploid: two complete sets of chromosomes, one from each parent.

  • transcription: The process by which the information encoded in DNA is copied into RNA.

  • translation: The process by which the information carried by mRNA is used to synthesize the encoded protein.

  • codon: A series of three nucleotides that code for a specific amino acid.

  • start codon: Codon at which translation is initiated; it is typically the first AUG after a ribosome-binding site.

  • stop codon: Codon that terminates translation, signaling the end of the protein; there are three stop codons.

  • intron: non-coding regions that must be removed from pre-mRNA to create functional mRNA.

  • constitutive gene expression: gene is always expressed (mRNA transcription always occurs)

  • inducible gene expression: gene is only expressed under certain conditions (transcription of mRNA only occurs under these conditions)

  • repressible gene expression: gene is usually expressed, but transcription is blocked under certain conditions.

  • co-repressor: attaches to the repressor, the co-repressor-repressor complex can then bind to the operator, blocking transcription.

  • inducer: attaches to the repressor, the shape of the repressor changes so that it can no longer attach to the operator.

  • repressor protein: a regulatory protein that blocks transcription (negative regulation). It does this by binding to an operator, a specific DNA sequence located immediately downstream of a promoter

  • operator: a specific DNA sequence located immediately downstream of a promoter.

  • lac operon: RNA polymerase transcribes lacZ, lacY, and lacA when lactose is being used by the cell.

  • Ames test: tests for potential mutagenic chemicals. Create a control plate: bacteria with an auxotroph, liquid without suspected mutagen, and notice the amount of random mutations that fix the auxotroph. Then make a test plate: bacteria with an auxotroph, liquid containing suspected mutagen, and if there are many random mutations that fix the auxotroph (chemical is a mutagen), if the number of random mutations is comparable to the control (chemical is not a mutagen).

  • mutant: organism that bears a mutation and may exhibit an altered phenotype.

  • wild-type: organism that exhibits the normal (non-mutant) phenotype.

  • mutation: any permanent, inheritable change in the genetic information of the cell. (Change of ATGC).

  • frameshift: caused by insertions or deletions that shift the reading frame of the mRNA so that codons are not read in the correct register.

  • transposon: “Jumping genes.” Transposable elements can move from one location in the genome to another (chromosomes, plasmids). Contain inverted repeat sequences at the ends of a transposes gene. Can create genetic recombination. Can cause mutations in genes where they are inserted.

  • plasmid: small circular double stranded DNA. Can have antibiotic resistant genes, or numerous, and has the potential to transfer those via sex pilus (conjugation).

  • F plasmid: Fertility plasmid. Can form a sex pilus needed for conjugation.

  • donor cell: F+, contains F plasmid originally.

  • recipient cell: F-, then F+. Receives F plasmid from donor through conjugation.

  • conjugation: transfer of the F (fertility) plasmid using a sex pilus (most common method). Donor cell (F+) makes contact with the recipient cell (F-), a single strand of the F plasmid is transferred to the recipient cell, its complement is synthesized. The recipient cell that was F- is now F+ and can also synthesize the pilus.

  • R plasmid: “Resistance (R) Factor” — plasmid carrying one or more genes for antibiotic resistance.

  • Hfr cell: high frequency recombination. F plasmid integrates into the bacterial chromosome, donor cell (Hfr) makes contact with the recipient cell (F-), a single strand of the donor chromosome is transferred to the recipient cell, its complement is synthesized, the DNA transfer is interrupted. The donor DNA is integrated into the recipient cells chromosome; the recipient is still F-. Rare.

  • generalized transduction: phage mistake. During construction of viral particles, bacterial DNA can mistakenly enter a protein coat. This creates a transducing particle that carries bacterial DNA instead of phage DNA. When the transducing particle attaches to another bacterial cell, the original bacterial DNA is injected into the cell. The injected bacteria, DNA integrates into the chromosome and replaced host DNA is degraded.

  • specialized transduction: when viral genome of prophage is excised from bacterial chromosome it takes a piece of adjacent bacterial DNA with it. Replication and assembly produces defective phage particles that carry certain bacterial DNA in place of some phage DNA. The DNA of the defective phage is injected into the new host, but cannot cause a productive infection, thus the phage DNA is degraded. The bacterial DNA integrates into the host genome.

  • transformation: bacterial uptake of small fragment of DNA rom the surrounding environment. Usually non-specific — any DNA fragment can be taken up. DNA fragment is incorporated into the bacterial chromosome. Cells that are capable of being transformed are called “competent.” Double stranded DNA binds to the surface of a competent cell. Single strand enters the cell; the other strand is degraded. The strand integrates into the recipient cells genome. One daughter cell will have the resistance gene, one will not.

  • mitosis: in which each daughter cell receives the same number of chromosomes as the parent cell.

  • meiosis: in which diploid cells give rise to haploid cells. These haploid cells can develop into haploid organisms, or they can be used as haploid sex cells called gametes that are involved in sexual reproduction. Contains Meiosis I and II. Also contains crossing-over. Diploid cell undergoes two sequential divisions resulting in 4 cells, each with a single set of chromosomes. Homologous chromosomes (member of a pair) pair up and crossing-over may occur. Sexual reproduction and meiosis result in increased genetic recombination.

  • crossing-over: occurs in Meiosis I. The exchange of chromosome segments between non-sister chromatids during the production of gametes