Ch 4-5 Microbio

Question 1

Distinguish between macronutrients and micronutrients, giving examples of each

Answer 1

-Macronutrients: CHONPS make up the bulk of all living cells (carbohydrates, lipids, proteins, nucleic acids)
—>Also include enzyme cofactors and signaling molecules like mg, fe, k, ca
-Micronutrients: needed for enzyme function but in small (trace) quantities (Co, cu, mn, mo, ni, zn)

Question 2

Distinguish between heterotrophy and autotrophy

Answer 2

-Heterotrophs: rely on organic (C containing) compounds made by other organisms
-Autotrophs: make their own organic compounds from carbon dioxide

Question 3

Distinguish between photoautotrophy and chemolithoautotrophy

Answer 3

-Photoautotrophs: use light energy to capture and fix CO2 into organic molecules
-Chemo: use eneergy from mineral oxidation to capture and fix CO2 into organic molecules (litho-rock)

Question 4

Distinguish between photoheterotrophy and chemoheterotrophy

Answer 4

-Photoheterotrophs: like chemo but also uses light energy to obtain energy
-Chemoheterotrophs: beak down organic substances to obtain energy and build biomass (humans are this)

Question 5

Define nitrogen fixation in terms of its chemical input and output

Answer 5

Takes nitrogen gas (plus hydrogen) and converts it ammonia and hydrogen

Question 6

Discuss ways to import nutrients into a cell across the cell membrane(s)

Answer 6

Diffusion (passive, facilitated) and active transport

Question 7

Define facilitated diffusion

Answer 7

Occurs when molecules diffuse through membrane-spanning protein channels or pores
–>requires channel or pores as gateways

Question 8

Define coupled transport, symport, and antiport and describe what powers them

Answer 8

-Coupled transport: moves molecule up gradient. Gets energy by coupling the movement of that molecule to a different molecule (ion) typically moving down gradient
-Symport: both molecules are transported in same direction
-Antiport: actively transported molecule moves from the opposite direction of the driving ion

Question 9

Define ABC transporter and their power sources

Answer 9

ATP binding cassette are very large family of energy driven transport system found in all 3 domains of life
–>use ATP to drive transport
–>2 types: Uptake (nutrients in) and Efflux (toxins/drugs out)

Question 10

Define group translocation and how it works

Answer 10

Avoids uphill transport by chemically altering subtrate –> changed subtrate = starting subtrate not moving against concentration gradient any more
–> alteration requires energy

Question 11

Define the function of a siderophore

Answer 11

Binds tightly to tiny amounts of soluble iron around and then imported into the cell

Question 12

Give examples of molecules transported by the above pathways (active)

Answer 12

Glucose, amino acids, ions like Na and K

Question 13

Describe the process of dilution streaking and its utility

Answer 13

A stick or loop carrying bacteria is spread across the agar surface, leaving cells behind

Question 14

Describe how to make an agar Petri plate

Answer 14

A liquid culture or sample with bacteria is repeatedly diluted and spread on agar plates until single colonies are isolated

Question 15

Describe a bacterial colony

Answer 15

A group of bacteria derived from the same mother cell

Question 16

Describe how dilution plates enable bacteria to be counted

Answer 16

Ensures that there are enough spaces on the plate for each bacterial cell to grow into a distinct colony that can be counted individually

Question 17

Define confluent growth

Answer 17

When cells or bacteria cover an entire surface area without gaps

Question 18

Distinguish complex and synthetic media

Answer 18

-Complex: nutrient rich but poorly defined
-Synthetic: precisely defined ingredients

Question 19

Define and distinguish selective and differential media

Answer 19

-Selective: favor the growth of one organism/strain over another
-Differential: highlight phenotypic differences between two species that may grow equally well on the medium

Question 20

Describe a method to detect the presence of unculturable bacteria

Answer 20

Detect presence by extracting and sequencing DNA from the environment

Question 21

Describe and distinguish direct and indirect ways to count bacteria

Answer 21

-Direct: physically counted individual cells with a microscope
-Indirect: estimate bacterial populations based on measurable parameters (light scattering)

Question 22

Define planktonic growth

Answer 22

Growth as isolated cells, often happens in shaking liquid culture

Question 23

Define growth rate and its relationship to population size

Answer 23

-Growth rate: percentage change in a population over specific period of time (average change in population over time)
-Relates to population: positive growth rate = growing population.

Question 24

Define generation time/doubling time

Answer 24

Time required for the population to double

Question 25

Describe some of the culture conditions that can change generation time

Answer 25

Depends on the species and on the growth conditions (medium, temperature, shaking, etc.)

Question 26

Define batch culture and distinguish it from continuous culture

Answer 26

-Batch culture: in a closed system like a flask
-Continuous: fresh medium is constantly added and culture removed, so cells grow indefinately

Question 27

Define and order the 4 phases of bacterial growth in batch culture

Answer 27

1. Lag: bacteria prepares cell machinery for growth (gearing up)
2. Log: growth approximates an exponential curve (sprinting)
3. Stationary: cells stop growing and shut down (stopping/break)
4. Death: cells die with a “half life” similar to radioactive decay (negative exponential curve) (sleep/die)

Question 28

Describe some of the physiological changes that take place in different growth phases

Answer 28

1. Lag: bacteria prepares cell machinery for growth
2. Log: growth approximates an exponential curve
3. Stationary: cells stop growing and shut down
4. Death: cells die with a “half life” similar to radioactive decay (negative exponential curve)

Question 29

Define a biofilm and give an everyday example of a biofilm

Answer 29

Group of cells secretes a sticky extracellular matrix that encases the population of cells. Examples include dental plaque.

Question 30

Describe typical components of a bacterial extracellular matrix

Answer 30

Polysaccharides, proteins, and/or DNA

Question 31

Briefly describe the stages of biofilm formation

Answer 31

1. Attachment to monolayer by flagella
2. Microcolonies
3. Exopolysaccharide production
4. Mature biofilm
5. Dissolution and dispersal

Question 32

Define endospore and mother cell

Answer 32

When species (i.e Bacillus and Clostridium genera) form endospores under starved conditions (survival cell)
–> form inside mother cell
–> complete formation results in mother cell dying

Question 33

Describe the characteristics of spores

Answer 33

-Dehydrated = resistant to all sorts of environmental insults
-Packed with small acid-soluble proteins (SASPs) to further protect their DNA

Question 34

Define extremophile

Answer 34

An organism that thrives in extreme environmental conditions, such as high salinity, temperature, or pressure

Question 35

Explain the relationship between growth rate and relative temperature

Answer 35

Growth rate increases with temperature up to an optimum, beyond which enzyme denature, slowing growth.
–> Below the optimum, enzymes work more slowly, and membranes lose fluidity

Question 36

Distinguish psychrophile, mesophile, thermophile, and hyperthermophile with respect to their growth temperature ranges

Answer 36

-Psychrophiles: 0-20 °C
-Mesophiles: 15-45°C
-Thermophiles: 40-80°C
-Hyperthermophiles: 65-121°C

Question 37

Define barophile/piezophile

Answer 37

Organisms adapted to grow at high pressure (>1,000 atm), often found in deep-sea environments

Question 38

Define osmotic pressure and why it is an issue for bacterial cells

Answer 38

-Pressure exerted by the movement of water across a membrane due to solute concentration differences.
-High osmotic pressure can cause cells to lose or gain water, impacting growth

Question 39

Define halophiles

Answer 39

-Organisms that require high salt concentrations (2-4 M NaCl) for growth
-Counteracts osmotic pressure by importing potassium or producing compatible solutes

Question 40

Distinguish between “philic” and “tolerant” species

Answer 40

-Philic: requires specific conditions for survival
-Tolerant: can survive but does not require extreme conditions

Question 41

Distinguish neutralophiles, acidophiles, and alkaliphiles with respec to their preferred growth pH

Answer 41

-Neutral: 5-8 pH
-Acid: 0-5 pH
-Alkali: 9-12 ph

Question 42

Describe how alkaliphiles deal with having few protons to establish a proton motive force

Answer 42

Use sodium gradients across membranes instead of protons to power processes, as protons are scarce in alkaline

Question 43

Distinguish strict anaerobes, strict aerobes, faculative microbes, and microaerophiles

Answer 43

-Strict aerobes: require oxygen for growth
-Microaerophiles: grow in low oxygen levels
-Strict anaerobes: die in presence of oxygen
-Facultative anaerobes: grow with or without oxygen
-Aerotolerant: doesn’t use oxygen but can tolerate it

Question 44

Distinguish among sterilization, disinfection, antisepsis, and sanitation with respect to controlling microbes

Answer 44

-Sterilization: kills all living organisms
-Disinfection: kills/removes pathogens from inanimate objects
-Antisepsis: kills/removes pathogens from living tissues
-Sanitation: reduces microbial populations to safe levels

Question 45

Define the parameters needed for effective sterilization via autoclaving

Answer 45

-Conditions: 121°C, 15 psi, >20 minutes
-Effective for sterilizing glassware, instruments, and media

Question 46

Distinguish physical and chemical agents for microbrial control and give at least 2 examples of each

Answer 46

-Physical Agents:
–>Autoclaving: High pressure and moist heat.
–>Filtration: Removes microbes using 0.2 µm filters.
Chemical Agents:
–>Ethanol: Damages proteins and membranes.
–>Chlorine: Oxidizes proteins and damages DNA.

Question 47

Distinguish among different methods of pasteurization

Answer 47

-LTLT (Low Temp, Long Time): 63°C for 30 min.
-HTST (High Temp, Short Time): 72°C for 15 sec.
-Both eliminate pathogens like Coxiella burnetii but do not kill spores.

Question 48

Define D-value

Answer 48

Time needed to reduce a microbial population by 90% under specific conditions

Question 49

Briefly describe phage therapy

Answer 49

-Use of bacteriophages (viruses targeting bacteria) to kill pathogenic bacteria
-Phages are narrow-spectrum and specific to certain bacterial species