MicroLecE2Ch6

Question 1

What are the physical requirements for Microbial growth?

Answer 1

1) Temperature: minimum growth temp, maximum growth temp, optimal growth temp
2) pH: most bacteria grow btwn 6.5 & 7.5
3) Osmotic Pressure: salt concentration

Question 2

Psychrophile

Answer 2

0-10 C
Found in ocean floor, polar regions
Can grow below freezing

Question 3

Psychotroph

Answer 3

20 C

Causes food spoilage

Question 4

Mesophile

Answer 4

37 C
Most of pathogens
Found on other living organisms

Question 5

Thermophile

Answer 5

60 C

Found in sunlit soil

Question 6

Hyperthermophile

Answer 6

90 C
Survives in very hot environments
Deep sea thermal vents

Question 7

Neutrophile

Answer 7

Bacteria that prefer neutral pH

Most pathogens

Question 8

Acidophile

Answer 8

Grow in acidic environments

Exs: molds & yeasts grow btwn pH 5-6

Question 9

Halophile

Answer 9

Bactera that like to live in high salt environment

Exs: S. Epidermidis, S. Aureus

Question 10

What are the chemical requirements for Microbial growth?

Answer 10

1) Carbon: structural organic molecules, energy source, used in all 4 chemical groups; from organic carbon sources or CO2
2) Nitrogen: amino acids and proteins; from ammonia, nitrogen fixation, and atmospheric nitrogen
3) Sulfur: amino acids, thiamine, biotin; get from sulfate, hydrogen sulfide
4) Phosphorus: DNA, RNA, ATP, membranes, nucleic acids; get from recycling broken down nucleic acids
5) Trace Elements: inorganic elements required in small amounts, usually as enzyme cofactors; get from the environment
6) Oxygen
7) Organic Growth Factor: organic compounds obtained from environment; vitamins, amino acids, purines, pyrimidines

Question 11

Sterile

Answer 11

No living microbes

Question 12

Inoculum

Answer 12

Introduction of microbes into medium

Question 13

Culture

Answer 13

Microbes growing in and on culture medium

Question 14

Agar

Answer 14

Complex polysaccharide from seaweed used as solidifying agent for culture media
Better than gelatin b/c stays solid at 37 C and is not broken down by microbes

Question 15

Chemically Defined Media

Answer 15

Exact chemical composition is known

Question 16

Complex Media

Answer 16

Pre-prepared media, most of the media used in Micro lab

Exs: nutrient broth, nutrient agar

Question 17

Reducing Media

Answer 17

Specialized media containing thioglycollate or oxyrase that removes oxygen, typically has an oxygen gradient

Question 18

Anaerobic chamber

Answer 18

Obligate anaerobes must be grown within here where all the oxygen has been removed

Question 19

Obligate Aerobe

Answer 19

Must have presence of oxygen to grow

Growth on the surface of the thioglycollate broth

Question 20

Facultative Anaerobe

Answer 20

Can use oxygen but does not require it

Growth throughout tube with concentration on the surface of broth

Question 21

Obligate Anaerobe

Answer 21

Cannot grow in presence of oxygen

Growth at bottom of tube where there is least oxygen in the broth

Question 22

Microaerophile

Answer 22

Prefer less oxygen than aerobes; halfway btwn aerobe and anaerobe
Grows in a band in the middle of thioglycollate broth

Question 23

Capnophile

Answer 23

Requires higher level of CO2

Grows in a Candle Jar so when the candle flame goes out it raises the level of CO2 in the jar

Question 24

BSL 1

Answer 24

No special precautions

Question 25

BSL 2

Answer 25

Lab coat, gloves, eye protection

Question 26

BSL 3

Answer 26

Known pathogenic bacteria that is contagious | BSL 2 + biosafety cabinets to prevent airborned transmission

Question 27

BSL 4

Answer 27

Extremely contagious, very pathogenic microorganisms | BSL 3 + sealed negative pressure, exhaust air filtered twice, maybe govt security clearance

Question 28

Selective Media

Answer 28

Has a chemical that will inhibit growth of some bacteria but select for growth of some bacteria Ex: salt For ID-ing a bacteria

Question 29

Differential Media

Answer 29

Test built into the media that has a color change; makes it easy to distinguish colonies of different microbes Ex: mannitol (sugar) For ID-ing a bacteria Most of the time media will be both selective and differential

Question 30

Enriched Media

Answer 30

Has a molecule in it that encourages the growth of the deried microbe, enriching for the target bacteria For isolating a bacteria

Question 31

Colony

Answer 31

Population of cells arising from a single cell or spore or from a group of attached cells Often called a colony-forming unit (CFU)

Question 32

Streak Plate Method

Answer 32

Used to isolate pure cultures Every time original streak is streaked to another quadrant of the dish it is diluted until eventually the bacteria will be isolated

Question 33

Preserving Bacteria

Answer 33

1) Deep Freezing | 2) Lyophilization (freeze drying)

Question 34

Binary Fission

Answer 34

1) cell elongates and DNA is replicated 2) cell wall and plasma membrane begin to constrict 3) cross-wall forms, completely separating the two DNA copies 4) cells separate

Question 35

Phases of Growth

Answer 35

1) Lag phase: bacteria sensing its environment once introduced in it, prepare for binary fission 2) Log phase: highest rate of growth, population dramatically increases, binary fission happens 3) Stationary phase: no active growth; bacteria has run out of nutrients and space 4) Death phase: bacteria die off at exponential rate; waste products have built up becoming toxic to the bacteria cells

Question 36

Direct vs. Indirect Count

Answer 36

Direct count - directly/actually counting | Indirect count - estimating

Question 37

Direct Count Methods

Answer 37

1) Serial Dilutions: several dilutions done and each one is plated; # of colonies x dilution factor 2) Plate Counts: pour plate method and spread plate method (count colonies on plates that have 25-250 colonies or 30-300 colonies) 3) Membrane Filtration (non-viable direct count) 4) Direct Microscopic count

Question 38

Indirect Count Methods

Answer 38

1) Turbidity: estimate by cloudiness using Spectrophotometer that shines light through it and measures the amount of light coming out the other side 2) Metabolic activity: measure amount of ATP and use that to estimate # of bacteria 3) Dry Weight: dehydrate a culture, weight resulting powder, estimate how much bacteria in it

Question 39

Turbidity

Answer 39

Scientific term for cloudiness | Higher the concentration of bacteria, the more turbid it is

Question 40

Generation Time

Answer 40

Time it takes for one bacteria to divide into two, or for the population to double. Bacterial growth is logarithmic