Lecture 5: Microbial Growth Flashcards Preview

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Flashcards in Lecture 5: Microbial Growth Deck (40)
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1

What is Cell growth?

Increase in cell number
-Growth = reproduction

2

What is binary fission?

Division of 1 cell into 2 cells
-Divides through elongation and septum formation

3

What is generation time?

Time required for binary fission
-30min to 6hrs typically

4

What factors affect generation time?

Environmental Factors
-Nutrient availability and temperature

Genetic Factors
-Specific to different microbial species

5

What is the Divisome?

Collection of FTS Proteins embedded in cytoplasmic membrane that direct cell division in prokaryotes

6

What does FTS stand for?

Filamenting Temperature Sensative

7

What proteins make up the Divisome?

FtsZ
ZipA
FtsA
Ftsl

8

What does the FtsZ protein do?

Forms ring around center of the dividing cell
-Related to tubulin

9

What does the ZipA protein do?

Connects FtsZ ring to Cytoplasmic Membrane
-The "Anchor"

10

What does the FtsA protein do?

Attracts the other Fts proteins to form the divisome
-The "Recruiter"

11

What does the Ftsl Protein do?

Peptidoglycan synthesis
-Synthesizes peptidoglycan for the newly formed cell walls in order to complete separation

Good for new antibiotics or Drug design
-Target this (Or any) protein = prevent bacterial growth

12

What is the MreB protein?

Part of cell morphology
-Forms cellular cytoskeleton

Absent in Coccoid bacteria
Present in Rod-shaped bacteria

13

What kind of growth does a microbial population experience? What are the applications of this?

Exponential growth
-Cells double EACH generation (1->2->4->8 etc)
-So the rate increases each generation

Applicable to standards for bacterial counts in food

14

What are the different phases of the growth cycle for a bacterial population in a CLOSED SYSTEM (No nutrients in and No waste products out)?

Lag Phase
Exponential Phase
Stationary Phase
Death Phase

15

What is the lag phase of microbial growth?

Low (but positive) growth rate
-Recovering from transfer to nutrient agar (lab conditions but also wild)

16

What is the Exponential Phase of Microbial Growth?

Big jump in growth rate
-Maximal rate, all cells dividing

17

What is the Stationary Phase of Microbial growth?

Net Growth rate = 0
-Nutrients begin depleting and waste products accumulating

Also known as "Cryptic Growth"
-# of cells dividing = # of cells dying

18

What is the death phase of microbial growth?

Growth Rate Negative

19

What is a Continuous Culture? What is an Example?

Continuous Culture is an open system

Example is Chemostat
-Nutrient Rich broth in
-Waste products out

20

What are some controls and applications of a continuous culture?

Controls
-Dilution rate (How fast in/out)
-Nutrient concentration

Applications
-Ecology and physiology

21

What are the methods for measuring microbial growth?

Microscopic Counts
-Cell counts (Both living/dead)

Viable Counts
-Plate counts (living)
-# of colonies that form = # of cells in sample

22

What are the advantages/disadvantages of Microscopic Counts for measuring microbial growth?

Advantages
-Simple method

Disadvantages
-Counts living/dead
-Difficult with low cell number and/or motile cells

23

What are the advantages/disadvantages of Viable Counts for measuring microbial growth?

Advantages
-High sensitivity
-Counts only viable cells

Disadvantages
-Possible errors (Cell clumps, plating inconsistencies)

24

What is the Turbidimetric Method for measuring Microbial growth?

Using light shined through vials with sample and measuring with spectrophotometer
-Cell mass = Cell Number

25

What are the advantages/disadvantages for using the Turbidimetric method for measuring microbial growth?

Advantages
-Simple method
-Non-destructive (don't have to throw away sample)

Disadvantages
-Possible errors (cell clumps + Biofilms)

26

What are the cardinal temperatures?

Minimum: below this temp = no growth
Optimal: at this temp = fastest growth
Maximum: above this temp = cell death

Differ for each species of microorganism
-Limited Temp (25-40 degrees Celsius)
-Proteins within each microbe function at specific temp

27

What are the different temperature classifications for microbes that live in different environments?

Psychrophile = (< 15 degrees C)
Mesophile = Moderate
Thermophile = (> 45 degrees C)
Hyperthermophile = (>80 degrees C)

Anything that isn't a Mesophile = Extremophile

28

What kind of Microbe lives in the cold? Where are they found?

Psychrophiles
-Slow growing in pockets of water
-Deep Oceans, Glaciers, Polar Regions

29

What kinds of molecular adaptations have Psychrophioles developed for their environment?

Cytoplasmic membrane contains much more Unsaturated/Short Chain Fatty Acids
-This causes the membrane to be more loosely packed and fluid at low temperatures

Cyroprotectants
-Cold Shock Proteins
-Antifreeze for cell
-Ice that forms inside cell will cause PHYSICAL damage

30

What kinds of Microbes live in hot/very hot temps? Where are they found?

Thermophiles and Hyperthermophiles
-Hot springs, Surface Soils, Water

Throwback to life on early earth