Chp. 6 Flashcards
What is the minimum, optimum, and maximum growth temperature?
Minimum: lowest temp a microbe can grow and have metabolism
Maximum: highest temp that a microbe can grow and have metabolism
Optimum: Promotes fastest rate of growth and metabolism (~37 degrees celsius)
TRUE OR FALSE: Psychrophiles grow best under cold temperatures under 15 degrees celsius
TRUE
Where are psychrophiles normally found?
Permanently cold environments like the polar regions and glaciers
Which organism is responsible for food spoilage at refrigerator temperature?
Listeria monocytogenes
What happens to microbial reproductive rates at low temperature?
It inhibits or slows down reproductive rates
What is the optimum growth temperature for:
- mesophile
- extreme thermophile
- thermophile
- psychrophile
- psychotrophs
Mesophile: 20-40 degrees celsius
Extreme thermophile: >80 degrees celsius
Thermophile: 50-60 degrees celsius
Psychrophile: <15 degrees celsius
Psychotrophs: between 0 and 20-30 degrees celsius
The pH that most bacteria grow best is ______
6-8
Mold and yeast grow best at which pH?
5-6
Organisms that grow at extreme acid pH are known as ______
Acidophiles
Organisms that grow at extreme basic pH are known as _____
Alkalinophiles
Organisms that require a high concentration of salt to survive are known as ____
Halophiles
Organisms that can tolerate high osmotic pressure but is not ideal to live in are known as ______
Facultative halophiles
Organisms that get their energy from chemical compounds are known as _____
Chemotrophs
Organisms that rely on consuming other organisms for energy are known as ______
Chemoheterotrophs
What happens to bacteria when put into hypertonic or hypotonic solutions?
- Hypertonic solutions can cause plasmolysis due to high osmotic pressure, causing the cell to shrivel
- Hypotonic solutions can cause the bacteria to swell and lyse due to low osmotic pressure
What are the 10 chemical requirements for growth?
- carbon
- hydrogen
- nitrogen
- phosphorus
- oxygen
- sulfur
- potassium
- calcium
- magnesium
- trace elements like iron and zinc
*Why is water required for growth?
Why is carbon needed for growth?
- It is the structural backbone of organic molecules
- Chemoheterotrophs use organic molecules as energy
- Autotrophs use CO2
Why is nitrogen needed for growth?
- It is a component of proteins, DNA, and ATP
- Most bacteria decompose protein material for the nitrogen source
- Some bacteria use NH4+ or NO3- from organic material and a few use N2 for nitrogen fixation
Why is sulfur needed for growth?
- It is used in amino acids, thiamine, and biotin
- Most bacteria decompose protein for the sulfur source
- Some bacteria use SO42- or H2S
Why is phosphorus needed for growth?
- Used in DNA, RNA, and ATP
- Found in membranes
- PO43- is a source of phosphorus
What is nitrogen fixation?
When bacteria convert the N2 in the atmosphere to nitrates and nitrites and incorporate it into their DNA and ATP as usable nitrogen
What does it mean when organisms are symbiotic? What are different types of symbiotic relationships?
When organisms live in close nutritional relationships, required by one or both members
- Mutualism: both members benefit
- Commensalism: one member benefits but the other member is not harmed
- Parasitism: Parasite is dependent and benefits but host is harmed
What does it mean when organisms are non symbiotic? What are different types of non symbiotic relationships?
Organisms are free living relationships are not required for survival
- Synergism: members cooperate and share nutrients
- Antagonism: some members are inhibited or destroyed by others
Which chemicals are usually required as cofactors for enzymes?
Trace elements (iron, copper, zinc, molybdenum)
Organisms that CANNOT grow without oxygen are known as _____
What does their oxygen growth look like?
Obligate aerobes
Growth at the top due to places with high concentrations of oxygen
Organisms that utilize oxygen but can also grow without it are known as ______.
What does their oxygen growth look like?
Facultative aerobes
Growth best where oxygen is present, but can still grow throughout the tube
Organisms that require only a small amount of oxygen are known as ____
What does their oxygen growth look like?
Microaerophiles
Growth where a low concentration of oxygen is found
Organisms that CANNOT SURVIVE in oxygen due to lacking enzymes that detoxify oxygen are known as ______
What does their oxygen growth look like?
Obligate anaerobes
Growth only where there is no oxygen (like the bottom)
Organisms that does not utilize oxygen but can survive and grow in its presence are known as _____
What does their oxygen growth look like?
Aerotolerant anaerobes
What does catalase do?
neutralize hydrogen peroxide
Culture media that is used to prepare microbial growth in liquid and solid form respectively are known as ______ and ______
nutrient broth
nutrient agar
Which type of media where the exact chemical composition is known is ________
Chemically defined media
Which type of media is used for cultivating anaerobic bacteria?
Reducing media
Which type of media suppresses unwanted microbes and encourages desired microbes and contain inhibitors to suppress growth?
Selective media
Which type of media allows distinguishing of colonies of different microbes on the same plate?
Differential media
Which organisms need CO2 at higher concentrations than atmospheric CO2?
Capnophiles
What are 3 ways you can preserve bacterial cultures?
- Deep-freezing: -50 to -95 degrees celsius
- Lyophilization (freeze-drying): frozen (-54 to -72 C) and dehydrated in a vacuum
- refrigeration on agar slants
When a single cell divides into two identical daughter cells this is known as _____
Binary fission
The time it takes for a microbe to divide and replicate itself (usually 20 mins to 24 hours) is known as _____
Generation time
*How is generation time determined?
The total number of cells equals 2 generations
How do you calculate the number of bacteria produced after a certain time period?
Initial population x 2 to the power of # of generations
eg. IP: 2, # gen: 3
= 2 x 2^3
= 16
What are the advantages and disadvantages of the plate count method?
Advantages:
- counts viable cells
- can target specific cells within a mixed population
- can detect a wide range of microbial densities even in low cell count samples
Disadvantages:
- does not count dead cells
- difficult to distinguish between bacterial colonies and debris
- Time consuming; results could take weeks
What are the four phases of growth and what happens in each phase?
- Lag phase: bacteria begin growing but slowly
- Log/ exponential phase: bacteria starts growing fast and rapidly
- Stationary phase: the rate of cell growth equals the rate of cell death
- Death phase: more death than growth
What are the 4 direct methods of measuring microbial growth?
- Plate count
- Filtration
- Most probable number (MPN) method
- Direct microscopic count
Describe the plate count method
- Count colonies on plates that have 30-300 colonies
- Dilute original inoculum via serial dilution to ensure the right number of colonies
- counts are then performed on bacteria mixed into a dish with agar (pour plate method) or spread on the surface of a plate (spread plate method)
Describe the filtration method
- Solution is passed through a filter that collects bacteria
- Filter is transferred to a petri dish and grows as colonies on the surface
Describe the direct microscopic count method
- The volume of a bacterial suspension is placed on a slide
- The avg number of bacteria per viewing field is calculated
- Uses a special Petroff- Hausser cell counter
bacteria/ml = # of cells counted/ volume of area counted
What are the indirect methods of estimating the number of bacteria?
- Turbidity
- Metabolic activity
- Dry weight
How does the turbidity method estimate the number of bacteria?
The degree of cloudiness measured with a spectrophotometer shows the relative population size
