Chapter 6 - Microbial Growth Flashcards
Physical Requirements for Growth
-temperature
-pH
-osmotic pressure
Chemical Requirements for Growth
-sources of carbon, nitrogen, sulfur, phosphorus, oxygen
-trace elements
-organic growth factors
True Psychrophiles
-cold-loving microbes
-can grow at 0℃
-optimum: 15℃
-cannot grow in reasonably warm room (20-25℃)
-non-pathogenic (don’t cause diseases)
-ie. bacteria in antarctica or ocean depth
Psychrotrophs (Psychrophile group)
-aka facultative/flexible
-more common than psychrophile
-can grow at 0℃
-optimum: 20-30℃
-cannot grow: 30℃+
-pathogenic: food spoilage (usually in the fridge)
-ie. mold, odour, slime layer
Mesophiles
-moderate-temp-loving microbes
-grow at a large range: 35-40℃
-optimum: 37℃ (human body temp)
-cannot grow: 50℃+
-all pathogenic: common spoilage and disease organisms
Thermophiles
-heat-loving microbes
-cannot grow below 45℃
-optimum: 50-60℃ (hot water)
-max: 70-80℃
Hyperthermophiles (Thermophile group)
-max temp: 110℃ (boiling water)
-optimum temp: 80℃+
-deep sea thermal vents or volcanoes
Minimum Growth Temperature
-lowest temp at which the species will grow
Optimum Growth Temperature
-temp at which the species grows best
Maximum Growth Temperature
-highest temp at which growth is possible
pH
-most bacteria grow best between 6.5 and 7.5
-few grow below 4 (acidic)
Acidophiles
-tolerant of acidity
Osmotic Pressure
-microbes require water for growth
Hypertonic
-concentration of solutes is higher outside the cell (environment is hypertonic to the cell)
-cellular water passes into high solute concentration
-cells cytoplasm shrinks (plasmolysis)
Extreme Halophiles
-adapted to high salt concentrations so they require them for growth
Facultative Halophiles
-do not require high salt concentration but can tolerate up to 2%
Isotonic
-same concentration of salt and water
Hypotonic
-osmotic pressure is unusually low
-water will enter cell
Carbon
-one of the most important requirements for microbial growth
Oxygen
-not essential for bacterial life
-divides bacteria into 5 groups
Obligate Aerobes
-need O₂ to complete ETC and survive
-love oxygen
-extract more energy (ATP)
-most bacteria belong to this group
-grow well
-produce SOD and catalase
Facultative Anaerobes
-flexible
-use O₂ for growth and metabolism when available
-when O₂ not available: goes into anaerobic cell resp or fermentation and growth is slowed
-create a variable # of ATP
-produce SOD and catalase
-ie. Escherichia Coli
Obligate Anaerobes
-unable to use O₂
-harmed by O₂
-undergo glycolysis but not krebs cycle or ETC
-ie. Clostridium
-NO SOD OR CATALASE
Aerotolerant Anaerobes
-tolerate O₂
-fermentative and can’t use O₂ for growth/metabolism
-ie. Lactobacilli
-can tolerate O₂ because they have SOD and catalase
Microaerophiles
-aerobic (require O₂)
-grow only in O₂ concentrations lower than the air
-ie. Helicobacter pylori, Campylobacter jejuni
Helicobacter pylori
-causes stomach ulcers
Campylobacter jejuni
-GI issues
-diarrhea and cramping
Toxic Oxygen
-O₂ starts to generate toxic forms during metabolism
Singlet Oxygen
-normal O₂ that has been boosted to a high energy state ¹O₂⁻
-extremely reactive
Superoxide Radicals
-O₂⁻ is formed in small amounts during normal aerobic respiration
-steal electrons from other molecules
Superoxide Dismutase (SOD)
-an enzyme formed by some organisms attempting to grow in atmospheric O₂
-neutralizes toxic O₂⁻ by converting it into O₂ and hydrogen peroxide (H₂O₂)
Peroxide Anion
-O₂²⁻
-produced from the hydrogen peroxide produced in the SOD reaction
-is toxic because it steals from other dangerous molecules
Catalase
-enzyme used to neutralize the peroxide anion
-converts it to water and oxygen
Perioxidase
-another enzyme that breaks down hydrogen peroxide
-reaction doesn’t produce oxygen
Hydroxyl Radical
-OH﹒
-most reactive intermediate form of oxygen
-no enzyme that can neutralize
-irreversible
Biofilms
-communities of bacteria
-thin slimy layer encasing bacteria that adheres to a surface
-biological systems
-how infection can spread
Quorum Sensing
-cell-to-cell communication
-coordinate activities
Culture Medium
-nutrients prepared for microbial growth
Inoculum
-introduction of microbes to a medium
Culture
microbes growing in (nutrient broth) or on (agar plate) a medium
Sterile
-medium must be sterile and contain no other microorganisms
Agar
-complex polysaccharide
-remains solid and sterile
-not metabolized by many microorganisms
-liquifies at 100℃
-cool down to 45℃
-incubate at 37℃
Pure Culture
-contains only one species or strain
-streak plate method used to isolate cultures
Colony
-population of cells arising from a single cell or spore
Streak Method
-divide petri dish into thirds
-move clockwise and dip some in each section
Selective Media
-used to suppress unwanted microbes and encourage desired microbes
-Bismuth sulfite agar
-ie. growing Salmonella typhus (causes typhoid fever and GI tract hemorrhaging disease)
Differential Media
-make it easy to distinguish colonies if different microbes
-uses blood agar
-a clear ring/empty region will appear around the colonies where hemolysis of the RBCs has occured
-ie. to grow Steptococcus pyogenes (causes strep throat)
Selective and Differential Media
-suppress unwanted organisms
-make it easy to distinguish colonies
-mannitol salt agar
-yellow halo that degraded the mannitol occurs
-ie. Staphylococcus aureus (skin infections, TSS, food poisioning)
Binary Fission
-increase in numbers, not size
-cells divide and grow exponentially
Bacterial Growth Curve
- LAG PHASE: intense activity preparing for growth but no increase in population
- LOG PHASE: exponential population increase, best time to give antibiotics/use radiation
- STATIONARY PHASE: plateau, equilibrium, deaths balance new growth
- DEATH PHASE: population decreases at a logarithmic rate
Generation Time
-time required for a cell to divide (population to double)
-time (in minutes)/number of generations
