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Questions and Answers
What is the main purpose of the Krebs Cycle (TCA Cycle)?
What is the main purpose of the Krebs Cycle (TCA Cycle)?
Complete oxidation of a substrate under aerobic conditions
Which type of fermentation turns sugar into ethanol and CO2?
Which type of fermentation turns sugar into ethanol and CO2?
Acidophiles grow best under acidic conditions.
Acidophiles grow best under acidic conditions.
False
The ______ is used to make yogurt and pickles.
The ______ is used to make yogurt and pickles.
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Match the following bacterial morphologies with their descriptions:
Match the following bacterial morphologies with their descriptions:
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Who is considered the 'Father of Bacteriology and Protozoology'?
Who is considered the 'Father of Bacteriology and Protozoology'?
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Louis Pasteur is known for improving the wine-making process.
Louis Pasteur is known for improving the wine-making process.
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The term 'animalcules' was used by Anton van Leeuwenhoek to refer to ___________.
The term 'animalcules' was used by Anton van Leeuwenhoek to refer to ___________.
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Who challenged the doctrine of spontaneous generation with the concept of biogenesis?
Who challenged the doctrine of spontaneous generation with the concept of biogenesis?
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Match the following in microbiology:
Match the following in microbiology:
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What is the purpose of staining in microbiology?
What is the purpose of staining in microbiology?
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What is the function of differential stains in microbiology?
What is the function of differential stains in microbiology?
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Most bacteria cultures are incubated at a temperature of _ °C to _ °C.
Most bacteria cultures are incubated at a temperature of _ °C to _ °C.
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Hemolysis refers to the dissolution or break apart of white blood cells.
Hemolysis refers to the dissolution or break apart of white blood cells.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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What is the purpose of sterilization?
What is the purpose of sterilization?
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What is the function of disinfection?
What is the function of disinfection?
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Sepsis comes from the Greek word meaning 'decay or putrid'?
Sepsis comes from the Greek word meaning 'decay or putrid'?
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_______ radiation includes gamma rays, X rays, and electron beams.
_______ radiation includes gamma rays, X rays, and electron beams.
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Match the following chemical method with its description:
Match the following chemical method with its description:
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What is the active ingredient of bleach?
What is the active ingredient of bleach?
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Alcohols are effective against endospores and naked viruses.
Alcohols are effective against endospores and naked viruses.
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What is the optimum concentration of ethanol for disinfection?
What is the optimum concentration of ethanol for disinfection?
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Silver nitrate is used to protect infants against __________ infections.
Silver nitrate is used to protect infants against __________ infections.
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Match the following Biosafety Levels with their descriptions:
Match the following Biosafety Levels with their descriptions:
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What does BSC stand for in the context of lab safety equipment?
What does BSC stand for in the context of lab safety equipment?
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What level of Biosafety containment is required for work involving minute quantities of toxic chemicals?
What level of Biosafety containment is required for work involving minute quantities of toxic chemicals?
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Staphylococci exhibit GOLDEN YELLOW PIGMENTATION due to the action of the pigment ____________.
Staphylococci exhibit GOLDEN YELLOW PIGMENTATION due to the action of the pigment ____________.
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Enterotoxins produced by Staphylococci are not heat stable.
Enterotoxins produced by Staphylococci are not heat stable.
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What is the principal virulence factor for Enterococci pathogenesis?
What is the principal virulence factor for Enterococci pathogenesis?
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Which bacterial enzyme degrades the surface structure of the host?
Which bacterial enzyme degrades the surface structure of the host?
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Pneumolysin O is an O2 sensitive toxin.
Pneumolysin O is an O2 sensitive toxin.
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Enterococcus grows on bile esculin media and may be weakly ________ (+).
Enterococcus grows on bile esculin media and may be weakly ________ (+).
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Which of the following describes the action of α hemolysin?
Which of the following describes the action of α hemolysin?
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What is the principle of the Lysostaphin susceptibility test?
What is the principle of the Lysostaphin susceptibility test?
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The interpeptide bridge of Micrococcus does not contain ______.
The interpeptide bridge of Micrococcus does not contain ______.
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Match the enzyme with its function:
Match the enzyme with its function:
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Staphylococcus aureus is the former name of Staphylococcus epidermidis.
Staphylococcus aureus is the former name of Staphylococcus epidermidis.
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What does the CAMP test detect?
What does the CAMP test detect?
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Study Notes
History of Microbiology
- Lucretius and Girolamo Fracastoro suggested that diseases were caused by "invisible living creatures" (1478-1553)
- Anton van Leeuwenhoek, the "first true microbiologist" and "Father of Bacteriology and Protozoology", used the term "animalcules" or "beasties" (1632-1723)
- John Needham suggested that organic matter possessed a "vital force" that could give rise to life (1731-1781)
- Francesco Redi invalidated abiogenesis, proving that maggots cannot rise spontaneously from decaying meat (1626-1697)
- Lazzaro Spallanzani improved on Needham's experiments by heating the broth in a sealed jar, observing no growth (1729-1799)
- Rudolf Virchow challenged the doctrine of spontaneous generation with the concept of biogenesis (1821-1902)
- Louis Pasteur disproved the doctrine of spontaneous generation, developed vaccines for anthrax and rabies, and improved the wine-making process (1822-1895)
Germ Theory of Disease
- Ignaz Semmelweis advocated for handwashing to prevent the spread of puerperal fever (1818-1865)
- Joseph Lister used phenol to prevent surgical wound infections (1827-1912)
- Robert Koch discovered Bacillus anthracis and Mycobacterium tuberculosis, showing that bacteria indeed cause diseases (1843-1910)
Exceptions to Koch's Postulate
- Many healthy people carry pathogens but do not exhibit symptoms of the disease
- Some microbes are difficult or impossible to grow in vitro in artificial media
- Introducing a pure culture to the experimental animal, the animal must be susceptible to the pathogen
- Use of human volunteers is difficult to find and has ethical considerations
Vaccination
- Buddhist monks drank snake venom to confer immunity to snake bite
- Variolation was practiced in 17th century China
- Edward Jenner inoculated a person with cowpox virus, resulting in protection against smallpox in 1796
- Louis Pasteur developed the first vaccine against smallpox in 1798
- Paul Ehrlich developed a synthetic arsenic drug, Salvarsan, to treat syphilis in 1910
- Sulphonamides were synthesized in the 1930s
- Alexander Fleming discovered the first antibiotic, Penicillin, in 1928
Cell Envelope Structures
- Contains plasma membrane (PM)
- Contains cell wall and some do not
- Surface polymers: capsule, slime layer, and other surface structures
Division of Microbiology
- Parasitology: study of parasites, their hosts, and the relationship between them
- Mycology: study of fungi, including their genetic and biochemical properties
- Phycology: study of algae
- Virology: study of viruses
- Bacteriology: study of bacteria
Bacterial Genetics
- Mechanisms of gene transfer: transformation, transduction, and conjugation
- Mutation: a change in the original nucleotide sequence of a gene or genes within an organism's genome
- Recombination: exchange of genes between homologous regions on two DNA molecules
Bacterial Metabolism
- Respiration: efficient ATP-generating process in which molecules are oxidized to generate energy
- Fermentation: anaerobic process in which glucose is converted into ATP and other products
- Types of fermentation: alcoholic, homolactic, heterolactic, mixed acid, and butanediol
Microbial Growth and Nutrition
- Major nutritional needs: carbon, nitrogen, and energy
- Oxygen requirements: aerobic, anaerobic, facultative, and microaerophilic
- Temperature requirements: psychrophiles, mesophiles, and thermophiles
- pH requirements: neutrophiles, acidophiles, and alkaliphiles
- Other requirements: halophiles, capnophiles, and osmophiles
Common Stains for Microscopic Visualization
- Gram stain
- Acid-fast stains
- Acridine orange
- Calcofluor white
- Methylene blue
- Lactophenol cotton blue (LPCB)
- India ink
- Endospore stain
Methods of Studying Bacteria
- Goal of the specimen collector: maintain the viability of the organisms with minimal contamination
- Basic principles: select the correct anatomic site, collect the specimen using the proper technique and supplies, and package the specimen in a container or transport medium
- Collection procedures: stool, sputum, and other specimens
- Transportation of specimens: notify the laboratory in advance, and store the specimen in an environment that will not degrade the suspected organism/s### Laboratory Procedures
- Specimen collection:
- Upper respiratory tract, external ear, eye, and genital tract: swab collection systems with transport media to prevent drying and maintain specimen integrity
- Lesions, wounds, and abscesses: clean area, collect from advancing margin, and use needle aspiration instead of swab
- Urine specimen collection:
- Clean-catch midstream urine specimen
- First morning urine preferred
- Sterile container with tight-fitting lid
Preservatives
- Urine and stool specimens can be preserved with:
- Boric acid: maintains accurate urine colony counts at room temperature for 24 hours
- Cary-Blair transport media: for delayed transportation (up to 2 hours) and refrigeration
Anticoagulants
- Used to prevent clotting of specimens (blood, bone marrow, and synovial fluid)
- Sodium polyanethol sulfonate (SPS): most common anticoagulant used for microbiologic specimens (concentration not exceeding 0.025% wt/vol)
- Heparin: often used for viral cultures and Mycobacterium spp. isolation from blood
Transport and Holding Media
- Stuart's or Amie's transport media: commonly used for preserving microorganisms during transportation
- JEMBEC system: contains selective agar and a CO2-generating tablet for N.gonorrhoeae specimens
Unacceptable Specimens and Specimen Rejection
- Reasons for rejection:
- Information mismatch on requisition and specimen label
- Inadequate quantity or specimen transport time exceeding 2 hours without preservation
- Specimen in formalin or dried up
- Leaking or incorrect transport container
Microscopic Examination
- Gram staining: developed by Hans Christian Gram
- Errors in Gram staining: Gram (+) becomes Gram (-) and vice versa, due to acidic Gram's iodine or inadequate decolorization
Culture Media
- Categories: simple, differential, and probe-mediated stains
- Classification according to physical state, composition, and use
- Types: liquid, semisolid, and solid (agar, BAP, TSI)
Isolation Techniques
- General purpose isolation streak: used for initial isolation of microorganisms
- Quantitative isolation technique: used to determine the number of microorganisms in a sample
Culture Incubation
- Most bacteria cultures incubated at 35°C-37°C
- Some bacteria require specific conditions: capnophiles (Candle jar, CO2 incubator), microaerophiles (jars or bags)
Incubation Time
- Most bacterial cultures held for 48-72 hours
- Culture for anaerobes and broth cultures may be held for 5-7 days
Gross Colony Characteristics
- Hemolysis
- Size
- Form/margin
- Elevation
- Color
- Density
- Consistency
- Pigment
- Odor
Microbial Control
- Early civilizations: practiced salting, smoking, pickling, drying, and use of spices to control microbial growth
- Sterilization: killing or removing all forms of microbial life
- Disinfection: reduction of pathogenic microorganisms to prevent disease
- Antiseptics: applied to living tissue to prevent infection
- Degerming: mechanical removal of microbes in a limited area
- Sanitization: use of chemical agents to minimize disease transmission
- Physical methods: heat, radiation, and filtration
- Heat: kills microorganisms by denaturing enzymes and proteins
- Thermal Death Point (TDP): lowest temperature at which all microorganisms in a liquid suspension are killed in 10 minutes
- Thermal Death Time (TDT): minimal length of time in which all bacteria are killed at a given temperature
- Decimal Reduction Time (DRT): time in minutes at which 90% of bacteria are killed at a given temperature### Sterilization Methods
- Ultra High Temperature Pasteurization (UHT): Milk treated at 140°C for 3 seconds and then cooled quickly in a vacuum chamber, allowing storage at room temperature for several months.
- Tyndallization: Intermittent sterilization using free-flowing steam for 30 minutes on each of 3 successive days to kill all vegetative microorganisms and spores.
Radiation Methods
- Ionizing Radiation: Gamma rays, X rays, electron beams, or higher energy rays with short wavelengths (< 1 nanometer), high energy, and penetrating power, used to sterilize pharmaceuticals and medical supplies, and to retard spoilage in food.
- Nonionizing Radiation: Ultraviolet light with wavelengths (> 1 nanometer), used to disinfect operating rooms, nurseries, and cafeterias.
- Microwave Radiation: Wavelengths (1 millimeter to 1 meter), absorbed by water molecules, killing vegetative cells in moist foods, but not bacterial endospores.
Heat Methods
- Dry Heat: Kills by protein oxidation, used to sterilize inoculating loops and needles by direct flaming, and disposable items by incineration.
- Hot Air Sterilization: used to sterilize objects, requiring 2 hours at 170°C, with damages to skin, eyes, and some materials.
Filtration Methods
- Membrane Filters: Uniform pore size, used in industry and research, retaining all viruses and some large proteins.
- High Efficiency Particulate Air (HEPA) Filters: Used in operating rooms and burn units to remove bacteria from air.
Chemical Methods
- Phenols and Phenolics: Damage cell membranes and inactivate enzymes, used as antiseptics, disinfectants, and in mouthwashes and throat lozenges.
- Halogens: Effective against microorganisms, but may cause skin irritation, used to disinfect drinking water, pools, and sewage.
Osmotic Pressure and Desiccation
- Osmotic Pressure: Uses high concentrations of salts and sugars in foods to create a hypertonic environment, inhibiting microbial growth.
- Desiccation: Removes water from microorganisms, creating a static effect, not effective against bacterial endospores.
Gaseous Sterilizers
- Ethylene Oxide: Kills all microorganisms and endospores, requiring 4 to 18 hours, used to sterilize hospital instruments and mattresses.
- Peroxygens (Oxidizing Agents): Oxidize cellular components, disrupting membranes and proteins, used as antiseptics and disinfectants.
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Description
Student notes on the introduction to microbiology, covering the history of microbiology, including Lucretius, Girolamo Fracastoro, and Anton Van Leeuwenhoek.
