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Micro Exam 2 > 4: Microbial Growth III > Flashcards

4: Microbial Growth III Flashcards

1
Q

Binary Fission

A

parent cell spits into 2

each daughter has one old and one new strand of DNA

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2
Q

Division time

A

can take 20 minutes to over 24 hrs

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3
Q

type of growth caused by binary fission

A

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

each new cell becomes 2 new cells and so on

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4
Q

if unchecked at this rate… e coli could

A

exceed earth’s weight in 2 days

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5
Q

why haven’t bacteria eaten the world?

A

they eventually run out of food

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6
Q

Growth phases of bacteria

A

Lag phase
Log Phase
Stationary Phase
Death Phase

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7
Q

Lag phase

A

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

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8
Q

Log phase

A

2^n
binary fission
growth unchecked

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9
Q

Stationary Phase

A

Running low on nutrients… only metabolize to stay alive

not growth, just maintenance of numbers

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10
Q

Death phase

A

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

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11
Q

Division time depends on…

A

Nutrient Source!

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12
Q

how nutrients affect bacterial growth

A

glucose is favored carbon source, bacteria grow quickly

lactose less preferred carbon source

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13
Q

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

A

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

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14
Q

Ways to measure bacterial growth

A

Optical Density

Serial Dilution and Plating

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15
Q

Optical Density (OD)

A

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

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16
Q

Drawback of OD

A

doesn’t tell you a number

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17
Q

Serial Dilution and Plating

A

gives you an actual number

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18
Q

DNA replication… the strands

A

are not identical
are complementary: matched by base pairing

know the sequence of 1 strand? figure out the other

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19
Q

DNA in bacteria

A

is a closed circle

2 replication forks, 2 leading and 2 lagging strand

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20
Q

the genetic info is carried…

A

on a single strand

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21
Q

base pairing

A 
hydrogen bonds connect bases
3 bonds (GC) means more stable
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22
Q

sugar backbones of antiparallel strands

A

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

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23
Q

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

A

hydrolysis of the phosphate bonds

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24
Q

how many DNA strands are around during replication

A

4… 2 parent, 2 new

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25
Q

DNA polymerase

A

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
Q

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

A

3’ end
needs a primer
must be a free hydroxyl

27
Q

helicase

A

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
Q

where MUST the new nucleotide be added

A

3’ END!!!!!!!

29
Q

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

A

RNA polymerase

30
Q

bacteria: EACH replication fork as a leading and lagging strand

A

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
Q

Leading/Lagging with 2 forks

A

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

32
Q

what is PCR?

A

tool for targeting and amplifying specific DNA sequences

33
Q

what is required for PCR

A

single stranded DNA “primers”

34
Q

types of Horizontal Transfer of DNA

A

Recombination
Conjugation
Transduction
Transposition

35
Q

Horizontal DNA transfer

A

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

36
Q

What enzyme does PCR use?

A

DNA Polymerase

37
Q

verticle DNA transfer

A

DNA replication linked to cell division

38
Q

why use PCR

A

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
Q

what do the DNA Primers do in PCR

A

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

40
Q

how are copies made using PCR (equation)

A

2^n

41
Q

what does PCR do?

A

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

42
Q

Recombination

A

(transformation)
uptake SIMILAR DNA sequence

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

NO VECTOR needed

“naked” DNA

43
Q

Conjugation

A

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
Q

Transduction

A

uptake of DNA by phage

movement by viruses

45
Q

Transposition

A

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
Q

Conjugation… cell “types”

A

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

donor replicates the plasmid then moves it into the recipient

47
Q

Why does F+ make pili and F- doesn’t

A

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
Q

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

A

SPLIT THE CELL

49
Q

how do baccili grow?

A

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

50
Q

How does it know how to grow?

A

growth is a function of increased cell mass

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

51
Q

what else grows during DNA growth?

A

plasma membrane and cell wall

52
Q

Contractile rings

A

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

53
Q

Ring Scars

A

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

54
Q

2 main proteins of contractile rings

A

FtsZ: like tublin
MreB: like actin

both PROTEINS

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

55
Q

FtsZ

A

like tublin

56
Q

MreB

A

like actin

57
Q

DNA segregatin

A

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

replication and division are tightly linked

58
Q

Antibotic Resistance Transfer

A

conjugation plasmids

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

59
Q

what is a main way antibiotic resistance genes are transferred?

A

plasmids

60
Q

how transduction works

A

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

Micro Exam 2 (8 decks)

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