Chapter 6 Flashcards
Facultative Anaerobes
growth with oxygen or with no oxygen
Plate counts
- Count colonies on plates that have 30-300 colonies (CFUs)
- To ensure the right number of colonies, the original inoculum must be diluted via serial dilution
- Counts are performed on baceria mixed into a dish with agar (pour plate method) or spread on the surface (spread plate method)
Physical Requirements for Growth
- Temperature
- pH
- Osomotic Pressure
Direct measurements count microbial _____.
cells
Bacterial Division
Increase the number of cells, not cell size. (Binary Fission)
Optimum growth temperature for Thermophiles
50-60 degrees C
Carbon
- structural backbone of organic molecules
- Chemoheterotrophs use organic molecules as energy
- Autotrophs use CO2 (think of photoautotrophs)
Microaerophiles
require oxygen concentration lower than air
A pure culture contains…
Only one species or strain
Dry weight
Bacteria are filtered, dried, and weighed; used for filamentous organisms
Streak plate method
used to isolate pure cultures
Colony
A population of cells arising from a single cell or spore or from a group of attached cells
CFU
A colony is often called a colony-forming unit (CFU)
Reducing media
- Used for the cultivation of anaerobic bacteria
- Contain chemicals (sodium thioglycate) that combine O2 to deplete it
- Heated to drive off O2
Aerotolerant anaerobes
tolerate but cannot use oxygen
Log phase
Logarithmic or exponential increase in population
Differential Media
- Allow distinguishing of colonies of different microbes on the same plate
- Some media have both selective and differential characteristics
Agar
- Complex polysaccharide
- Used as a solidifying agent for culture media in Petri plates, slants, and deeps
- Generally not metabolized by microbes
- Liquefies at 100 degrees Celsius
- Solidifies at ~40 degrees Celsius
Minimum growth temperature
BSL-3
Biosafety cabinets to prevent airborne transmission
BSL-2
Lab coat, gloves, eye protection
Optimum growth temperature for Hyperthermophiles
Optimum growth temperature >80 degrees C
Filtration
- Solution passed through a filter that collects bacteria
- Filter is transferred to a petri dish and grows as colonies on the surface
Biofilms
- Microbial communities
- Form slime or hydrogels that dhere to surfaces
- Bacteria communicate cell-to-cell via quorum sensing
- Share nutrients
- Shell bacteria from harmful environmental factors
- Found in digestive system and sewage treatment systems (can clog pipes)
- 10000x resistant to microbicides
- Involved in 70% of infections
- Catheters, heart valves, contact lenses, dentail caries

