chapter 6 Flashcards
physical requirements for microbial growth
- temperature
- pH
- osmotic pressure
chemical requirements for microbial growth
- macronutrients (CHONPS)
- trace elements
- oxygen
- growth factors
what does temperature affect?
protein function in a cell (properly folded)
different classes for optimal growth in temperature
- psychrophiles: 0-25 degree celsius (food spoilage)
- mesophiles (normal): 25-40” (37)
- thermophiles: 40-80”
- hyperthermophiles: ober 80”
temperature tolerance vs optimal growth
look at chart in lecture notes
- x: mesophile (sensitive to high temperature)
- y: mesophile (tolerates high temperature to a point and has widest range of thermotolerance)
- z: thermophile (requires higher temperature)
are halophilic in a hypertonic or hypotonic environment and why?
hypertonic since salt is outside the cell (over 5% salt) and it must adapt to high osmotic pressure
*note: hypertonic=shrinkage, hypotonic=swelling
optimal pH range for most microorganisms, acidophiles, alkaliphiles, and fungi
- 6.5-7.5
- acid: less than 6
- alk.: 8-11
- fungi: 5-6
what causes internal pH to drop (acidic)?
weak acid diffuses into cell while partially giving up protons. it also leads to a growth inhibitory effect
what do buffers do?
maintain pH
what are the chemical requirements for growth?
essential nutrients, macronutrients, micronutrients, and growth factors
define essential nutrients
cannot be synthesizes and must be supplied
what are the required macronutrients?
CHONPS, K, Mg, Ca
- C: biggest influence on growth. it is an energy source that can be complex (heterotroph) or CO2 (autotroph)
-cations serve as cofactors or signaling molecules
what are the required micronutrients?
Co, Cu, Mn, Fe, Mo, Ni, Zn
what are the organic growth factors?
vitamins, amino acids, blood, serum
Describe aerotolerance (oxygen tolerance)
- oxygen used by aerobes in cellular respiration to obtain energy (ATP) from the breakdown of nutrients; serves as terminal electron acceptor (used to differentiate between anaerobic and aerobic)
- enzymes react with O2 to for either reactive superoxide or hydroxyl radicals
-damages DNA, RNA, proteins
How are microbes that do not use O2 affected by aerotolerance?
microbes become susceptible to damage and require protection
name and describe the protective enzymes against oxygen radicals
1.) superoxide dismutase (SOD): neutralizes the affect of O2 radicals
2.) catalase and peroxidase: neutralize peroxide anions (O2) in H2O2
locate the growth zones on the tube
i cant put a fucking picture on here bruh. just imagine it i guess
more energy (ATP) in anaerobes lead to…?
more growth
where there are the most enzymes in test tubes represent what?
where growth is at optimal oxygen
describe the tubes of O2 effect on growth (i cant put a picture so just look at lecture slide)
describe obligate aerobe and microaerophile
- obligate: (atmospheric) oxygen at 21% (highest)
- microaerophile: oxygen is 5-10% (less)
describe obligate anaerobe and aerotolerant
- both do not use O2 and either ferment or respire anaerobically
- obligate: O2 is TOXIC because it lacks protective enzymes
- aerotolerant: O2 is NOT toxic
describe facultative anaerobe
- can use or not use O2, can ferment or respire aerobically/anaerobically (process taken depends on what’s available)
- O2 is NOT toxic
growth medium is formed by a combination of what?
macro- and micro-nutrients
complex vs defined media
- complex (rich): pre-formed, nutrients cells can readily assimilate (proteins, yeast extract, beef extract)
- defined (minimal): chemical composition is known and cells must synthesize all required molecules (requirement for fastidious (longer list) bacteria)
*prob should look at a pic
liquid vs solid culture media
- liquid: growth studies, harvest DNA, protein isolation
- solid: agar, formation of colonies, need for pure culture
selective vs differential media
- selective: add inhibitory agents
- differential: see metabolic differences between types
define generation time of bacterial growth
- length of time for a cell to divide
- Generation time (or doubling time) = minutes/generation
growth formulas (represents population size):
N0 x 2n = NT ; n = # of generations; NT = # cells after n generations; N0 = # cells at start
list and describe the phases of the bacterial growth curve
1.) lag phase: no growth, acclimation, syntehsis, turn on/off genes
- factors affecting it: inoculum age and size, media composition, and physical factors
2.) log phase: most active, fastest growth, cell size increases
-mid: most active and biggest
-late: slow down of growth begins
3.) stationary phase: growth rate=death rate, stress response (nutrient limited) leads to cell size decreasing and conserving energy, endospores start forming
4.) death phase: lack of nutrients and pH changes lead to exponential death
describe the fed-batch culture
it feeds additional nutrients (glucose) at mid-log phase leading to extra growth
biofilm formation occurs in what? what part of the cell has biofilm?
- disease and the environment (ex: catheters)
- fimbriae/pili
describe the stages of biofilm development
- via chemical and environmental signals
- originally planktonic cells or “swimmers” (motile form)
1.) attachment monolayer
- seeks a favorable environment
2.) microcolonies
- kinda lose its flagellum
3.) expopolysacc. (EPS) production
- sugar covers cells
- synthesis
- “stickers”
4.) mature biofilm
- biofilm towers
- sustained with the flowing nutrients supply
5.) dissolution and dispersal
- flow in and out to feed everyone, and dissolve if not enough food available
- return to motile form and reseek favorable environment
