4: Microbial Growth III Flashcards Preview

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Flashcards in 4: Microbial Growth III Deck (60):
1

Binary Fission

parent cell spits into 2
each daughter has one old and one new strand of DNA

2

Division time

can take 20 minutes to over 24 hrs

3

type of growth caused by binary fission

Logarithmic growth (2^n, where n is number of generations)

each new cell becomes 2 new cells and so on

4

if unchecked at this rate... e coli could

exceed earth's weight in 2 days

5

why haven't bacteria eaten the world?

they eventually run out of food

6

Growth phases of bacteria

Lag phase
Log Phase
Stationary Phase
Death Phase

7

Lag phase

bacteria not growing, but adjusting to environment
preparing to use up food in environment
change protein expression to divide

8

Log phase

2^n
binary fission
growth unchecked

9

Stationary Phase

Running low on nutrients... only metabolize to stay alive
not growth, just maintenance of numbers

10

Death phase

Not enough food to maintain life
bacteria due
some cannibalize each other

11

Division time depends on...

Nutrient Source!

12

how nutrients affect bacterial growth

glucose is favored carbon source, bacteria grow quickly
lactose less preferred carbon source

13

what if you have 2 carbon sources (glucose and lactose)

glucose preferred, so used first, grow fast: steep line
glucose used: lag phase. take time to adapt to new environment (lactose). synthesize metabolites needed to metabolize glucose.
Lactose: another log phase

14

Ways to measure bacterial growth

Optical Density
Serial Dilution and Plating

15

Optical Density (OD)

based on light absorbance... 600 nm wavelength
instant measurement based on absorbancece

if lots of bacteria in the tube, they will scatter the light. more absorption of light, less light is transmitted

16

Drawback of OD

doesn't tell you a number

17

Serial Dilution and Plating

gives you an actual number

18

DNA replication... the strands

are not identical
are complementary: matched by base pairing

know the sequence of 1 strand? figure out the other

19

DNA in bacteria

is a closed circle
2 replication forks, 2 leading and 2 lagging strand

20

the genetic info is carried...

on a single strand

21

base pairing

hydrogen bonds connect bases
3 bonds (GC) means more stable

22

sugar backbones of antiparallel strands

opposite! the double bonded oxygen on the phosphate is on the opposite side
5': oxygen points toward top
3': oxygen points toward bottom

23

what provides the energy for the reaction of adding a base?

hydrolysis of the phosphate bonds

24

how many DNA strands are around during replication

4... 2 parent, 2 new

25

DNA polymerase

adds free nucleotides to 3' end. (copies DNA 5' to 3')
MUST have primer to start (RNA or DNA)
Proofreading ability
Can degrade RNA (RNase activity)

26

whats important about the free hydroxyl and where does it need to be?

3' end
needs a primer
must be a free hydroxyl

27

helicase

opens RNA polymerase to put down primer
other enzymes stabilize the replication fork
lagging strand has to wait for DNA to be unwound to keep going

28

where MUST the new nucleotide be added

3' END!!!!!!!

29

what adds the RNA primer so that DNA replication can start?

RNA polymerase

30

bacteria: EACH replication fork as a leading and lagging strand

1 origin of replication: 2 replication forks
they go in opposite directions
lots of things happen to happen (including unwinding) at the end to put them back together

31

Leading/Lagging with 2 forks

if its leading on one fork, its lagging on the other

32

what is PCR?

tool for targeting and amplifying specific DNA sequences

33

what is required for PCR

single stranded DNA "primers"

34

types of Horizontal Transfer of DNA

Recombination
Conjugation
Transduction
Transposition

35

Horizontal DNA transfer

acquisition of new DNA NOT from parent cell... usually smaller than chromosome

36

What enzyme does PCR use?

DNA Polymerase

37

verticle DNA transfer

DNA replication linked to cell division

38

why use PCR

to study genes... which are much smaller than the total DNA of the cell...
ex. shig toxin: 2,000 bases out of 5 million in e. coli

39

what do the DNA Primers do in PCR

are DESIGNED to direct DNA poly to a particular sequence and copy it a ton of times to make lots of copies

40

how are copies made using PCR (equation)

2^n

41

what does PCR do?

uses DNA polymerase in a very specific way. copy just the small piece you want

42

Recombination

(transformation)
uptake SIMILAR DNA sequence

DNA out there in environment... taken up and put into genome

NO VECTOR needed

"naked" DNA

43

Conjugation

Transfer DNA using type IV secretion (bacterial sex)

plasmid usually used to transfer DNA

DNA transferred BETWEEN bacteria

can carry antibiotic resistance plasmids between cells

44

Transduction

uptake of DNA by phage
movement by viruses

45

Transposition

jumping DNA

usually genes that have sequence on end that allow it to move around

usually within same cell.... but can move out of the crhomosome and become a plasmid

46

Conjugation... cell "types"

need a donor (F+) cell with a plasmid
and a recipient (F-) cell

donor replicates the plasmid then moves it into the recipient

47

Why does F+ make pili and F- doesn't

plasmid of F+ codes for pili
F- doesn't have plasmid (yet)

when injected with pili... F- can get the instructions for making pili

48

What else do we need to do to complete binary fission?

SPLIT THE CELL

49

how do baccili grow?

by elongation. gets to good size, repressors of DNA rep diluted so crhomosomes are copied and cells divide

50

How does it know how to grow?

growth is a function of increased cell mass

have enough cell mass (DNA, RNA, protein) to make a second cell

51

what else grows during DNA growth?

plasma membrane and cell wall

52

Contractile rings

form in middle of cell
directs cell division
scar helps hold bacillus in palce during new round of growth

53

Ring Scars

from where daughters divided previously
made of proteins
help new cell stay together and keep its shape

54

2 main proteins of contractile rings

FtsZ: like tublin
MreB: like actin

both PROTEINS

they may form spirals that may help rod shape stay in place

55

FtsZ

like tublin

56

MreB

like actin

57

DNA segregatin

just before contractile ring closes, DNA segregated into each daughter cell

replication and division are tightly linked

58

Antibotic Resistance Transfer

conjugation plasmids

Bacteriodes fragilis plsamid is a conjucation plasmid (RFT) that has resistance to 4 antibiotics

59

what is a main way antibiotic resistance genes are transferred?

plasmids

60

how transduction works

phage infects cell, puts its genome in bacterial chromosome for replication

sometimes the phage takes some bacterial DNA from the host and puts it into its next host