growth parameters (chapter 7)

temperature, pH, osmotic pressure

name the physical requirements of growth parameters

oxygen

name the chemical requirements of growth parameters

- minimum growth temperature (less than this is freezing)

- optimum growth temperature

- maximum growth temperature (more than this is denaturing)

describe temperature ranges

- psychrophiles

- psychrotrophs

- mesophiles

- thermophiles

- hyperthermophiles

state the 5 temperature lifestyles

very cold loving

describe psychrophiles

cold loving; cause food spoilage in fridge

describe psychrotrophs

moderate temperature loving; nearly all pathogenic bacteria

describe mesophiles

heat loving; optimum growth temperature of 50 C to 60 C

found in hot springs and organic compost

describe thermophiles

extreme heat loving; optimum growth temperature >80 C

describe hyperthermophiles

- destroy most pathogenic microbes

- lower temps on this scale take more time to completely kill

- bacterial cytol

food preservation temperatures:

explain temperatures above 60 C

cause very slow bacterial growth of pathogenic microbes

food preservation temperatures:

explain temperatures between 50 C and 60 C

- DANGER ZONE

- cause rapid growth of pathogenic bacteria (some may produce toxins)

food preservation temperatures:

explain temperatures between 15 C and 50 C

cause many bacteria to survive and some may grow

food preservation temperatures:

explain temperatures between 5 C and 15 C

- refrigerator temperature

- may allow slow growth of bacteria but very few pathogens

- bacterial static

food preservation temperatures:

explain temperatures between 0 C and 5 C

cause no significant growth of pathogens (below freezing)

food preservation temperatures:

explain temperatures below 0 C

- located at the Galapagos rift; where lava meets cool oceanic water

- nourish chemoautotrophs living within Riftia worms (heterotrophic)

- 3 species live inside the Riftia tubeworms and all are hyperthermophilic

describe the deep sea hypothermal vents

- temperature and microbial growth rates

- blue = minimum temperature

- pink = optimum temperature

- green = maximum temperature

describe this growth curve; name what each colored section is representing

6.5 to 7.5 (neutrophils)

what pH do most pathogenic bacteria grow at

5-6

what pH do molds and yeast grow at

microbes that grow in acidic environments

define acidophiles

microbes that grow in basic environments

define alkalinophiles/basophiles

- pathogenic neutrophils cannot survive in the acidic pH so cannot contaminate

- e.g. pickles, sauerkraut, kim chi, and some types of cheeses

describe pH as a food preserving process

they cannot fold properly and make enzymes correctly, therefore cannot function

what happens if you put microbes in the wrong pH

- diagram is showing charge distributions at different pH

- a: pH around 2, inside of cell will have a charge of about -2.1

- b: pH around 7, inside of cell will have charge of about -7.1

- c: pH around 12, inside of cell will have charge of about -12.1

cell cytoplasm is slightly negative compared to outside environment

describe this diagram; state what is occurring at a, b, and c

require high osmotic pressure (30%-40% salt concentration); many archaeans

describe extreme or obligate halophiles

tolerate high osmotic pressure; includes many opportunistic pathogens (don't need salt but can tolerate it)

describe facultative halophiles

0.8%

what salt concentration are humans

- Staphylococcus epidermidis

- Staphylococcus aureus (MRSA)

give two examples of facultative halophiles

- if a cell if hypertonic (more solute, less water) to the environment and the bacterial PG cell wall cannot withstand the influx of water then the cell lyses

- bacterial cytol

describe osmotic lysis

gram + bacteria exposed to penicillin

what kind of bacteria does osmotic lysis typically cause an issue with

- cell is hypotonic (less solute, more water) to the environment and there is a net efflux of water

- increase in extracellular salt or sugar can cause this

- bacterial static

describe plasmolysis

causes prokaryotic PM to withdraw from PG cell wall

what does plasmolysis cause

- cell doesn't have enough water to live (tertiary structures are not properly formed within cytosol)

- less movement of water and less water inside the cell

- enzymes are not fully hydrated which means they cannot metabolize and shape change (form = function)

describe how plasmolysis causing the PM to detach from the PG cell wall is dangerous for that cell

- salting foods as preservation

- why honey acts as a food preservative (high sugar instead of salt)

what is plasmolysis the basis for regarding pathogenic microbes

creatures that require oxygen

define obligate aerobes

creatures that grow via fermentation or anaerobic respiration when oxygen is not available (e.g. Bacillus spp.)

define facultative anaerobes

unable to use oxygen and are harmed by it (e.g. Clostridium spp.)

define obligate anaerobes

tolerate but cannot use oxygen (don't us O2 as terminal e- acceptor)

define aerotolerant anaerobes

require oxygen at a concentration lower than air

define microaerophiles

- Thioglycollate assay; shows oxygen growth requirements

- fluid in tubes in thiglyicid

- thiglycollate is a chemical that chelates (binds) O2 gas

what is this type of experiment called

- obligate aerobes

- growth occurs where high concentrations of oxygen have diffused into the medium

name what kind of microbe in the test tube and describe the growth pattern

- facultative anaerobes

- growth is best where most oxygen is present, but occurs throughout tube

- top of tube is aerobic respiration, bottom of tube is fermentation

name what kind of microbe in the test tube and describe the growth pattern

- obligate anaerobes

- growth occurs only where there is no oxygen

- top and middle of tube may have endospores, bottom is the vegetative cells

name what kind of microbe in the test tube and describe the growth pattern

- aerotolerant anaerobes

- growth occurs evenly, oxygen has no effect

name what kind of microbe in the test tube and describe the growth pattern

- microaerophiles

- growth occurs where a low concentration of oxygen has diffused into medium

name what kind of microbe in the test tube and describe the growth pattern

highly reactive oxygen species, will steal electrons from random molecules starting a lethal chain reaction

describe toxic oxygen or free radicals

- singlet oxygen (O): super-reactive free radical

- superoxide free radicals (O2-): dangerous, denatures DNA

- peroxide anions (ionized H2O2 --> O2^2-): dangerous

- hydroxyl radical (OH)

name the 4 toxic oxygen or free radical types

O2- + O2- + 2 H+ (protons) --> superoxide dismutase (SOD) --> H2O2 + O2 --> catalase (CAT) or peroxidase (PER) --> H2O (+ O2 if using CAT)

state the reaction that occurs to neutralize superoxide free radicals

- 2 H2O2 --> catalase (CAT) --> 2 H2O + O2

- H2O2 + 2 H+ (protons) --> peroxidase (PER) --> 2 H2O

state the 2 reactions that can occur to neutralize peroxide anions

- Superoxide dismutase (SOD) neutralizes superoxide

- Catalase (CAT) neutralizes peroxide ions

- Peroxidase (PER) catalyzes peroxide ions

name the 3 enzymes that can neutralize the toxic oxygen or free radical types

obligate anaerobes

which types of microbe will never have the enzymes that neutralize toxic oxgyen or free radicals

those are the conditions they need to survive in humans

why are most pathogenic microbes mesophilic as well as neutrophilic