Microbiology- Chapter 7 ( Microbial Nutrition, Ecology And Growth)

Front 1

Define nutrition.

Back 1

× Nutrition is a process of acquiring chemical substances from the environment
× The absorbed nutrients are transformed and used for energy yielding processes and growth

Front 2

What the chemical elements that are absolutely needed called?

Back 2

essential Nutrients

Front 3

What are the two types of nutrients.

Back 3

- Macronitrients: C, H, O ( Carbon, hydrogen, oxygen)
- Micronutrients: Mn, Zn, Ni ( Nickel)

Front 4

What are the two sources of essential nutrients that are very important.

Back 4

Carbon and Nitrogen

Front 5

Describe Carbon

Back 5

- Structural Backbone of living matter
× 50% of microbial dry weight is Carbon
× Autotrophs derive C from CO2
× Heterotrophs derive C from organic matter

Front 6

Describe Nitrogen.

Back 6

- 14% of microbial dry weights is N
× Required for protien, DNA, RNA, ATP synthesis
- Microorganisms derive N by:
- Breaking down proteins into amino acids (*some can be reused in the metabolism but soemtimes must be broken down)
- NH4- ammonium ions
- NO3- nitrate
- N2- Nitrogen Fixers

Front 7

What are other elements besides Carbon and nitrogen that are essential.

Back 7

× Sulfur is required for the synthesis of sulfur containing amino acids
× Phosphorus is required for the synthesis of DNA, RNA, ATP, and phospholipids of the cell membrane
× Trace elements- minerals needed as enzyme cofactors

Front 8

What are growth factors?

Back 8

× Growth factors- organic chemicals that cannot be synthesized by certain organisms (vitamins, certain amino acids)

Front 9

what are the two nutritional types or sources of energy.

Back 9

× Energy source

- Light (use cabon dioxide): Photoautotrophs: (organic) photoheterotrophs

- Chemical (use carbondioxide): Chemoautotrouphs: (organic) chemoheterotrophs

Front 10

How do Chemoheterotrophs derive energy and carbon?

Back 10

Derive Energy and Carbon source from organic molecules

Front 11

What is a saprobe?

Back 11

derive nutrients from dead organic material

Front 12

What is an Opportunistic pathogen?

Back 12

a saprobe infecting the compromised host

Front 13

What do pathogens do?

Back 13

harm the host (streptococcus)

Front 14

How do microbes eat?

Back 14

- They absorb nutrients that are dissolved
- The molecules need to be small
- The big molecules are degraded by extracellular enzymes
- *they need to pass through a cell membrane, so molecules needs to be small… if its big the extracellular enzymes break down the big molecules into smaller units which can be taken and absorbed by cells

Front 15

What is Osmosis?

Back 15

× Diffusion of water molecules through a selevtively permeable membrane
× Water molecules will move from the side that has more water to the side with less water
× Until equilibrium is reached

Front 16

What is Isotonic, hypotonic and hypertonic?

Back 16

- Isotonic: water concentration is equal inside and out
- Hypertonic: solutions have lower solute concentrations (higher water concentration);thus water rushes into the cell. cells placed in these solutions will swell and burst
- Hypertonic: Higher solute concentration ( lower water concentration) Water rushes out of the cell.Cell shrinks.

Front 17

What is simple diffusion?

Back 17

× Diffusion- movement of molecules from an area of higher concentration to to an area of lower concentration. Cause by random collision caused by heat
× Used for transport of small molecules (O2)

Front 18

What is facilitated diffusion?

Back 18

- Facillitated diffusion
× Substance to be transported combines with the plasma membrane protein- transporter
× This changes the shape of the carrier- substance is moved across the membrane and released
× No energy needed

Front 19

What is active transport?

Back 19

× Brings in molecule against a gradient
× Involves
 membrane proteins- permeases
 pumps (transport of H+, K+, Na+)
× Expenditure of energy (ATP)
× Group translocation (a type of active transport) the substance is chemically altered, remains inside the cell

Front 20

What is endocytosis?

Back 20

engulfing particles and molecules from the outside with the cell membrane

Front 21

What is Pinocytosis?

Back 21

Absorbing liquids (oils)

Front 22

What is phagocytosis?

Back 22

white blood cells can ingest whole cells- bacteria
× *in phagocytosis a white blood cell gives a whole cell a hug and engulfs it

Front 23

What are the physical factors that influence microbes?

Back 23

- Temperature
- pH
- osmotic pressure

Front 24

What are the Chemical factors that influence microbes?

Back 24

- Elements (C,N,S,P)
- Trace elements
- Oxygen
- Growth factors

Front 25

Name the 3 types of growth temperatures bacterial species have.

Back 25

- Minimum
- Optimum
- Maximum

Front 26

What is the psychorophiles temperature range and optimum temp.

HINT: psychorophiles ( love the cold)

Back 26

Ranges: -12-20C
Optimum: -15C

Front 27

What is the psychotrophs
temperature range and optimum temp.

Hint: Psychotrophs ( grows slowly in cold)

Back 27

Ranges: 0-30C
Optimum: 20C

Front 28

What is the mesophiles temperature range and optimum temp.

Hint:intermediate temps

Back 28

Range: 10-50C
Optimum: 20-40C

Front 29

What is the Thermophiles
temperature range and optimum temp.

Hint: Heat loving

Back 29

Range: 45-80C
Optimum: 45-80C

Front 30

What is the hyperthermophiles temperature range and optimum temp.

Back 30

Range: 80-120C
Optimum: 94C

Front 31

List the oxygen requiring and oxygen fearing types of microbes.

Back 31

× Obligate aerobes- require 02 to live
× Facultative anaerobs- can grow in absence of 02
× Obligate anaerobs- killed by 02
× Microearophiles- require O2 at concentrations lower then those in air

Front 32

Why is oxygen deadly for obligate anaerobs?

Back 32

× Superoxide ( TOXIC to microbes and cells) free radical –O2- and H2O2 is formed during the normal metabolism
× Aerobes produce superoxide dismutase (enzyme that turns oxygen into H2O2 then into normal oxygen) to detoxify O2- by reducing it to H2O2
 H2O2—catalase 2H2O+O2
× Anaerobes lack superoxide dismutase

Front 33

Explain the effects of pH.

Back 33

× Most bacteria grow in pH range of 6.5- 7.5
× Low and high pH inhibits growth of bacteria
× Mild acids can help preserve foods by preventing further microbial growth (sauerkraut, pickles)
× Acidophiles: tolerant to acidity (bacteria and fungi)
× Alkalinophiles: live in alkaline soils and water up to pH 11.5

Front 34

Explain the effects of osmotic pressure.

Back 34

× Microorganisms that live in high salt concentration are called Halophyles
× Obligate halophyles- require hgih salt concentrations to survive, grow in up to 30% salt
× Facultative halophyles- tolerate high salt concentrations (up to 2%)

Front 35

Describe the growth of bacterial cultures.

Back 35

× Bacterial culture grows by doubling individual cells (binary fission)
× Growth of bacterial culture is defined by the generation time
× Generation time is the time required for a cell to divide
× For most bacteria generation time is 30- 60 minutes
× E. coli- 20 minutes (1 cell after 20 generations will produce 1 million cells)
× Logarithmic graphing is used to describe the growth of bacterial culture

Front 36

What are the stages in the normal growth curve?

Back 36

× Lag phase- little or no change in cell number. Cells are metabolically active (enzyme, DNA synthesis)
× Log phase- exponential growth phase- active reproduction, high metabolic activity
× Stationary phase- number of microbial deaths= number of new cells metabolic activity slow (*same die as there are newly formed)
× Death phase- the number of deaths greater then number of new cells

Front 37

What are the ways to measure microbial growth.

Back 37

- Direct method
- Indirect methods
- Plate count

Front 38

What are the direct methods to measure microbial growth?

Back 38

- Viable plate counts
× Plate count
- Suspension of cells (water, milk, urine) is inoculated onto agarized medium
- One simgle cell is transformed into a visible single colony
- Only viable cells are detected
- Usually serial dilutions are required



- Direct microscopic count
× Specially designed slide- cytometer
× Slide contains a well with inscribed squared of known area and volume
× The cells are counted under the microscope, multiplied with the facter that gives the count per ml.
× Disadvantages of the method:
- All cells are counted- including dead cells
- Motile cells are difficult to count
- High contentrations of the cell are required
× Advantage of the method
-It is fast- no need for incubation

Front 39

Describe the turbidity methods of measurement.

Back 39

× Turbidity
- Bacterial growth causes turbidity of the liquid
- The number of cells is proportional to the turbidity
- Spectrophotometer measures the amount of light which passes through the suspension