Microbiology
86 flashcards by MentisLibrary
Get to know the organisms too small to see: bacteria, viruses, fungi, and protists. Covers growth curves, staining and culture methods, pathogenesis, and how antibiotics work and why resistance spreads.
- What are the three domains of life?
- Bacteria, Archaea, and Eukarya
- Who first observed microorganisms through a microscope and what did he call them?
- Antonie van Leeuwenhoek, who called them animalcules
- What did Louis Pasteur's swan-neck flask experiment disprove?
- Spontaneous generation
- What are Koch's postulates used to establish?
- That a specific microorganism causes a specific disease
- What molecule makes up the bacterial cell wall?
- Peptidoglycan, also called murein
- What is the key structural difference between Gram-positive and Gram-negative bacteria?
- Gram-positive have a thick peptidoglycan layer; Gram-negative have a thin layer plus an outer membrane
- What color do Gram-positive and Gram-negative cells appear after a Gram stain?
- Gram-positive appear purple and Gram-negative appear pink or red
- What are the four steps of the Gram stain in order?
- Crystal violet, iodine mordant, alcohol decolorizer, safranin counterstain
- Which stain is used for Mycobacterium species and why is it needed?
- The acid-fast stain, because their waxy mycolic acid wall resists the Gram stain
- What is an endospore and which genera form them?
- A dormant, highly resistant survival structure formed by Bacillus and Clostridium
- What are the three basic bacterial cell shapes?
- Coccus, which is spherical, bacillus, which is rod-shaped, and spiral forms
- What is a bacterial capsule and what does it do?
- A sticky outer polysaccharide layer that resists drying and helps evade phagocytosis
- What are pili or fimbriae used for?
- Fimbriae attach bacteria to surfaces; the sex pilus transfers DNA during conjugation
- How do bacteria reproduce?
- By binary fission, splitting into two identical daughter cells
- What are the three mechanisms of horizontal gene transfer in bacteria?
- Transformation, transduction, and conjugation
- What are the four phases of a bacterial growth curve?
- Lag, exponential or log, stationary, and death phase
- What is generation time?
- The time it takes for a bacterial population to double
- What is an obligate aerobe?
- An organism that requires oxygen for growth
- What is a microaerophile?
- An organism that needs oxygen but only at concentrations lower than in air
- What is a thermophile?
- An organism that grows best at high temperatures, roughly 45 to 80 degrees Celsius
- What is a halophile?
- An organism that requires high salt concentrations to grow
- What is the difference between a selective and a differential medium?
- Selective media suppress unwanted organisms; differential media make colony types visually distinguishable
- What does blood agar reveal about a bacterium?
- Its pattern of red blood cell breakdown: beta is complete clearing, alpha is greenish partial, gamma is none
- What is the purpose of the streak plate technique?
- To dilute a sample across the plate so single cells grow into isolated colonies
- What is the difference between sterilization and disinfection?
- Sterilization destroys all microbial life including spores; disinfection only reduces harmful microbes on surfaces
- What autoclave conditions are standard for sterilization?
- 121 degrees Celsius at 15 pounds per square inch for 15 to 20 minutes
- Why is 70 percent alcohol a better disinfectant than 95 percent?
- Water is needed to help the alcohol penetrate the cell and denature proteins
- What is pasteurization?
- Brief controlled heating that reduces spoilage organisms and pathogens without sterilizing
- What are the main structural parts of a virus?
- A nucleic acid genome and a protein capsid, sometimes with a lipid envelope
- Why are viruses generally not considered living?
- They have no metabolism and cannot reproduce without a host cell