Week 2 Review Flashcards
What are the chemical requirements for growth?
Nutrients: substances used in biosynthesis (build)
- Macronutrients
- Trace elements
Organic growth factors
- Vitamins, amino acids
What are the most common macronutrients and trace elements needed for growth?
Macronutrients:
carbon, nitrogen, phosphorus, sulfur
Trace elements:
copper iron, molybdenum, zinc
What are organic growth factors?
Organic growth factors are organic compounds that we cannot synthesize ourselves such as vitamins and amino acids
How are nutrients taken up in prokaryotes and eukaryotes? What is the role of diffusion, osmosis, facilitated diffusion, and active transport?
Nutrients are taken up in prokaryotes through passive diffusion, osmosis, facilitated diffusion, and active transport.
- Passive diffusion: smaller molecules moving from an area of higher concentration to an area of lower concentration in a concentration gradient
- Osmosis: water will move from the more hypotonic (low concentration) solution to a more hypertonic solution (high concentration)
- Facilitated diffusion: using proteins to facilitate the movement of larger molecules from a higher concentration to a lower concentration in a concentration gradient
- Active transport: The use of ATP to move molecules across the membrane from an area of low concentration to a high concentration
Nutrients are taken up in eukaryotes through endocytosis.
- The cell membrane surrounds the nutrient with pseudopods, encloses it, and engulfs it in the cell
How do bacteria acquire nutrients?
Bacteria acquire nutrients through exoenzymes.
- Bacteria and fungi have a cell wall that acts as a barrier so the cell membrane can’t extend pseudopods to engulf nutrients
- So, the cell walls excrete exoenzymes outside the cell wall which hydrolyzes the bonds on nutrients
- Smaller molecules (nutrients) are transported across the wall and cell membrane into the cytoplasm
What are the physical requirements for growth?
Temperature
pH
Osmotic pressure
Oxygen requirements
What are the major types of organisms based on temperature, pH, and osmotic pressure?
Temperature:
Psychrophiles grow at -10C, peak at 10C and stop growing at 20C
Psychrotrophs grow at 0C, peak at 25C, stop at 30C
Mesophiles grow at 10C, peak at 40C, stop at 50C
Thermophiles grow at 40C, peak at 65C, stop at 71C
Hyperthermophiles grow at 65C, peak at 95C, stop at 110C
pH:
Acidophiles (lower pH)
Neutrophils (pH of 7)
Alkolophiles (higher pH)
Osmotic pressure:
Barotolerant: adversely affected by high pressure, but will survive
Barophilic: needs high pressure to grow
Do all organisms require oxygen? If not, what enzymes do all the different types of organisms possess?
Not all organisms require oxygen, oxygen can be toxic because it forms superoxide free radicals (O2-) that steal our electrons
- Organisms that can live with oxygen can create superoxide dismutase which converts superoxide free radicals into H2O2 and O2
- Organisms that can further break down H2O2 have a better chance of living in an oxygen environment
- Some organisms can make Catalase that breaks down H2O2 into H2O and O2
- Some organisms can make Perooxidase that breaks H2O2 into H2O
Enzymes that all the types of organisms possess:
Obligates aerobe: superoxide dismutase and catalase
Facultative aerobe: superoxide dismutase and catalase
Aerotolerant anaerobe: superoxide dismutase and NOT catalase
Strict anaerobe: NO superoxide dismutase and Catalase
Microaerophile: superoxide dismutase and +/- (low) levels of Catalase
How do the growth of obligate aerobe, facultative aerobe, strict (obligate) anaerobe, aerotolerant anaerobe, and microaerophile differ in media?
Obligates aerobe: growth is on top of media
Facultative aerobe: growth is on top of media and some at the bottom
Strict (obligate) anaerobe: growth is at the bottom of the media
Aerotolerant anaerobe: growth is spread evenly across media
Microaerophile: growth is at a fixed point of media
What are the six I’s, including definitions and examples?
Inoculation: introducing bacteria into a sterile media
Isolation: getting a bacteria colony by itself
Incubation: growth at 37C
Inspection: observation
Information gathering: looking at colony morphology
Identification: dichotomous key
What is the difference in the composition of broth vs solid media? Why would one use one over the other?
Broth media (liquid composition):
Allows the growth of larger volumes of bacteria and saves space
Solid media (solid composition):
Allows the isolation of bacteria and allows you to determine the colony morphology
What is the purpose of agar? What are some characteristics of agar? Why is agar used in media and not gelatin?
The purpose of agar is to solidify media
Agar IS NOT digested by microbes, explaining why gelatin cannot be used as an alternative solidifying agent as gelatin IS digested by microbes
Agar liquefies at 100C and solidifies at about 40C
What is the difference between chemically defined and complex media?
Chemically defined media
- The exact chemical composition is known
Complex media
- The exact chemical composition is not constant
How are pure cultures isolated?
- Streak plate method (diluting bacteria on an agar plate)
- Dip the loop in broth and inoculate one part of the plate using the streak plating method, then flame and kill the loop
- Drag a little bit of the inoculated part into another section, then flame and kill the loop
- Then drag a little bit of the second inoculated part into another section
How do bacteria grow? Explain the role of binary fission.
Bacteria grow in population number, not in size
Prokaryotic Cell Division: Binary Fission
- The cell elongates, then DNA replicates
- The cell wall and membrane constrict and a cross wall forms and separates the cells
- The cells separate, forming two daughter cells from one parent cell
