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Microbiology
| Question | Answer |
|---|---|
| What is RuBisCO? | Is an enzyme involved in the first major step of carbon fixation |
| Louis Pasteur 1822-1895 | Invented pasteurization which kills microbes and prevents spoilage in beer |
| Lactic acid fermentation | Yeast is responsible for forming alcohol from sugar. |
| Archaea | ancient “bacteria” unicellular like bacteria also simple cell structure (prokaryote – no nucleus) distinct metabolism |
| Bacteria | unicellular prokaryote found everywhere |
| Eukarya | unicellular to multicellular complex and organized cells with nuclei and organelles (mitochondria) |
| What is a Eukaryotic cell? | • They possess a true nucleus along with membrane-bound organelles • Have 80S ribosomes composed of 40S and 60S subunits • Fungi and parasites are eukaryotes |
| What is a Prokaryotic cell? | • A prokaryotic cell is a primitive type of cell that is characterized by the absence of a nucleus, they do not possess membrane-bound cellular organelles • Have 70S ribosomes composed of 30S and 50S subunits. |
| Three of the DNA viruses have envelopes: | Herpes Hepadna Pox |
| Three of the DNA viruses are naked: | Papova Adeno Parvo |
| Filamentous bacteria: | Nocardia and Actinomyces |
| Fragmentation is... | Also known as splitting, is a form of asexual reproduction in which an organism splits into fragments. It is seen in organisms such as filamentous cyanobacteria, molds. |
| Generation time | The log of a number is the number that a fixed base has to be raised to in order to yield the number. Is important when you want to study the ability of an agent to inhibit the microbe. |
| Lag Phase of bacterial growth curve: | Period of little or no cell division |
| Log Phase of bacterial growth curve: | Period of growth also known as logarithmic increase |
| Stationary Phase of bacterial growth curve: | Period of equilibrium |
| Chemostat : | continuous culture used in industrial fermentation |
| Death Phase of bacterial growth curve: | Also known as Logarithmic Decline Phase Continues until a small fraction of the population is diminished Some population dies out completely Others retain surviving cells indefinitely while others only retain for a few days |
| Single oxygen (O2) in oxygen detoxification: | Is in high energy state & extremely reactive; exists in phagocytes |
| Superoxide free radical (O2-) & hydrogen peroxide (H2O2) in oxygen detoxification: | Very toxic to cells; formed in small amount in cellular respiration |
| Peroxide anion (O2 -2) in oxygen detoxification: | Used as antimicrobial agent |
| Hydroxyl radical (OH-) in oxygen detoxification: | The most active and is formed in the cytoplasm from respiration |
| A Chemically defined Medium for Growing: | Nutrient Broth/Agar Tryptic Soy Broth/Agar Blood agar |
| Undefined medium for growing: | is composed of mixtures of yeast cell extracts or enzymatic digests of protein: MacConkey |
| Complex Media: | Mannitol Salt Agar and MacConkey |
| Heterotrophs: | Are a group of microorganisms (yeast, moulds & bacteria) that use organic carbon as food. |
| Selective agents: | Bismuth sulfite and brilliant green |
| Eosin methylene blue (EMB): | Eosin methylene blue is a selective stain for Gram-negative bacteria |
| Tellurite Glycine Agar: | Tellurite Glycine Agar Base is used for quantitative detection of coagulase -positive staphylococci from foods and other sources like skin, mucous membranes, faeces, air and soil. |
| Mannitol Salt agar: | Mannitol Salt agar inoculated with Staphylococcus aureus, Staphylococcus epidermidis and Micrococcus |
| Classic Method of Pasteurization: | • Milk was exposed to 65o C for 30 minutes. High Temperature Short Time (HTST) • Milk is exposed to 72o C for 15 seconds. Ultra High Temperature (UHT): Milk is treated at 140o C for 3 seconds and then cooled very quickly in a vacuum chamber. |
| Filtration | • Different sizes: 0.22 and 0.45um Pores: Used to filter most bacteria. Don’t retain spirochetes, mycoplasmas and viruses. 0.01 um Pores: Retain all viruses and some large proteins. |
| Radiation | Radiation in various forms, from high-energy radiation to sunlight, can be used to kill microbes or inhibit their growth. Ionizing radiation includes X-rays, gamma rays, and high-energy electron beams. |
| Gamma irradiation | for food preservation Petri dishes and disposable plastic inoculating loops great care must be taken when using X-rays and gamma irradiation. These types of ionizing irradiation cannot penetrate thick layers of iron or lead |
| UV radiation | causes the formation of thymine dimers in DNA, leading to lethal mutations in the exposed microbes. (b) Germicidal lamps that emit UV light are commonly used in the laboratory to sterilize equipment. |
| Bactericidal: B-lactams | Most of the cell wall–active antibiotics are classified as β-lactam antibiotics. Streptococcal infections Meningococcal infections, Syphilis, Tetanus, gas gangrene. |
| Bactericidal: Cephalosporins | • They have the same mechanism of action as the penicillin; • They have a wider antibacterial spectrum, • They bind to different proteins than those which bind to penicillin. |
| Bacteriostatic: Tetracyclines | Inhibit protein synthesis in bacteria by binding reversibly to the 30S ribosomal subunits, thus blocking the binding of aminoacyl-transfer RNA (tRNA) to the 30S ribosome–mRNA comple |
| Bacteriostatic: Tetracyclines | Used against: • All types of Gram-positive and negative cocci are sensitive • Most gram positive bacilli • Chlamydia, Mycoplasma, and Rickettsia species • Enterobacteria are now largely resistant |
| Bacteriostatic: Choramphenicol | ✓ Gram positive and negative bacteria, ricketsiae. ✓ Highly active against the Salmonella thypi • Meningitis & variety of bacterial infections, including gram positive, gram negative and anaerobic bacteria. • Mainly for eye infections |
| Amphotericin B | • Amphotericin B remains for years the gold-standard drug of choice in defense in the treatment of life-threatening systemic fungal infections because of its uncanny ability to outwit antibiotic resistance in spite of widespread therapeutic application. |
| Ergosterol | is a sterol found in cell membranes of fungi and protozoa, serving many of the same functions that cholesterol serves in animal cells. |
| AUG | START codon as it the first codon in the transcribed mRNA that undergoes translation. AUG is the most common START codon and it codes for the amino acid methionine (Met) in eukaryotes and formyl methionine (fMet) in prokaryotes. |
| UAG, UAA, and UGA | There are 3 STOP codons in the genetic code. These codons signal the end of the polypeptide chain during translation. These codons are also known as nonsense codons or termination codons as they do not code for an amino acid. |
| The central Dogma | The central dogma of molecular biology describes the flow of genetic information in cells from DNA to messenger RNA (mRNA) to protein. It states that genes specify the sequence of mRNA molecules, which in turn specify the sequence of proteins. |
| DNA Replication | • DNA is made up of a double helix of two complementary strands. • DNA polymerase synthesizes the new strands by adding nucleotides that complement. • The separation of the two single strands of DNA creates a 'Y' shape called a replication 'fork’ |
| Lagging strand | The lagging strand is synthesized in short, separated segments. A DNA polymerase extends the primed segments, forming Okazaki fragments. The RNA primers are then removed and replaced with DNA, and the fragments of DNA are joined together by DNA ligase. |
| DNA Replication | • The semiconservative: after one round of replication, every new DNA double helix would be one that consisted of one strand of old DNA bound to one strand of new DNA • DNA is added to the leading strand continuously, one complementary base at a time. |
| Plasmids: | • usually small, closed circular DNA molecules • exist and replicate independently of chromosome • not required for growth and reproduction • carry the genetic material for a variety of genes |
| Prokaryotic Gene exchange: | Vertical gene transfer : • is the transfer of genetic information, including any genetic mutations, from a parent to its offspring. • bacteria reproduce by binary fission, where the cell divides into two identical daughter cells. |
| Horizontal gene transfer - Three mechanisms known in prokaryotes: | • Transformation: Free DNA released by one cell is taken up by the other; • Transduction: Gene transfer is mediated by a virus • Conjugation: DNA exchange requires cell to cell contact and the presence of a conjugative plasmid in the donor cell |
| Transformation: | • DNA (released from dead cells) is taken up. • Newly introduced DNA is generally linear, • The linear DNA is then stabilized by homologous recombination. |
| oriT (origin of transfer) | where a single strand break in the DNA will be made and then oriT begins the transfer of one strand of the double helix. |
| Transduction: | A generalized transducing phage is produced when the phage with a lytic life cycle puts a piece of bacterial DNA into its head. • Specialized transduction can occur when an error is made in the life cycle of a temperate (lysogenic) phage. |
| Non-homologous [Illegitimate]: | • Bacteriophage will insert its genetic material into a bacteria in order to have it inserted into the bacterial genome. • Duplication mutations of a genome: In this case a portion of the parental genome is inserted multiple times into the genome. |
| At a DNA level: | Insertion: • Results in a shortened protein that may function improperly, be nonfunctional, or get broken down. |
| At a DNA level: | Deletion: • Point mutation example is cystic fibrosis |
| Types of Mutations : | -conditional mutations: by light, temperature or the presence of certain chemicals -Null mutation: In a gene that usually encodes a specific enzyme leads to the production of a nonfunctional enzyme or no enzyme at all |
Created by:
elenatz
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