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Molecular cell > prokaryotic cell biology > Flashcards

prokaryotic cell biology Flashcards

1
Q

organisation of a prokaryote

A
  • cell wall
  • plasma mem.
  • cytoplasm
  • ribosomes
  • pili
  • nucleoid
  • flagellum
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2
Q

what are plantomycetes

A

true bacteria that contain a nuclear envelope

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3
Q

members of planctomycetes show

A

true compartmentalisation

–> DNA is surrounded by a double lipid bilayer–> like the nuclear envelope of eukaryotes

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4
Q

organelle

A

a structure or part that is enclosed with its own mem., inside a cell and has a particular function

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5
Q

organelles are found only in

A

eukaryotic cells and are absent from he cell of prokaryotes such as bacteria

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6
Q

magnetosomes

A
  • navigate along magnetic filed

- can detect magnetic field and contain a ‘compass’ that detects the magnetic field of earth

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7
Q

magentosomes are found wihtin

A

gram negative bacyeria

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8
Q

first bacteria discovered two have magentosomes

A

Magnetospirilium magnetotacticum found by richard blakemore

-contains iron mineral and crystal that are magnetic and are called magnetosomes

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9
Q

bacteria use the magnetosomes for

A

mangnetotaxis

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10
Q

formation of magentosomes is a stepwise process

A

step 1: invagination of cytoplasmic men
stem 2: accumulation of ferrous iron
step 3: nucleation of magnetosome formation

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11
Q

what shows a similar fold in eukaryotes and prokaryotes

A

F-actin and prokaryotic actin-like protein filaments

  • same fold , but only 15% identity between MreB and eukaryotic actin
  • Both bind ATP and both polymerise
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12
Q

which structures are very similar

A

ParM, MreB and actin

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13
Q

Actin

A
  • eukaryotes
  • cytoskeleton
  • 100% identical between humans and chickens
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14
Q

MreB

A
  • prokaryotes
  • cell shape
  • <15% sequence identity with actin
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15
Q

ParM

A
  • Prokaryotes
  • DNA partitioning
  • <12% sequence identity with actin and 11% with MreB
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16
Q

ParM and MreB are

A

actin like protein filaments

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17
Q

functions of actin-like proteins in prokaryotes

A

1) organelle assembly
- plasmid segregation
- cell shape

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18
Q

MamK

A

is an actin like protein which forms filaments and organises the magentosome chain

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19
Q

how do we know MamK organises the magentosome chain

A

using GFP-the wild type shows an ordered chain, whereas mutated MamK shows disordered magentosomes

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20
Q

MreB and Mdl1 are involved in

A

bacterial morphogenesis

e.g. the cocci shape is lost if either no MreB or no MbI

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21
Q

FtsZ is a

A

distant prokaryotic tubular homologue.

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22
Q

common features of FtsZ and tubulin

A
  • GTPase activity that controls polymerisation
  • formation of protofilaments
  • simlar fold
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23
Q

FtsZ forms

A

in vitro-cell free and in vivo -in cell

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24
Q

where does FtsZ form

A

a ring at the cell cleavage site- functions in cytokinesis in prokaryotes

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25
Q

ParM filaments are

A

dynamic

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26
Q

what makes ParM filaments dynamic

A

polymerisation of ATP bound ParM at both ends. ATP hydrolysis occurs spontaneously

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27
Q

when is the ParM filaments unstable

A

when ParM-ADP is at an end

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28
Q

ParM filaments function in

A

plasmid segregation

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29
Q

process of plasmid segregation

A

1) ParR binds to the centromeric DNA sequence (ParC)
2) ParM polymerises and binds to ParR
3) filament elongation separates the plasmid
- replisome involved

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30
Q

random brownian motion is not sufficient to move

A

prokaryotic cells around

-bacteria and archaea actively moe through liquids or over most surfaces

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31
Q

models of prokaryotic motility include

A

swimming, swarming, gliding, twitching

32
Q

swimming behaviour of bacteria

A

prokaryotes are too small to sense a nutrient gradient along their cell, they need to swim to find their food

33
Q

flagella-based motility involves

A

swimming and swarming

34
Q

swarming occurs

A

on surfaces

35
Q

swimming

A
  • bacteria swim at a rate of 25-160 micrometers per second

- several flagella cooperate in propelling the cell forward

36
Q

what is used to rotate the flagellum

A

a basal “motor” that uses a proton gradient to rate the flagellum

37
Q

what doe she basal motor use to rotate the flagellum

A

a proton gradient

38
Q

how many rotations per s in a flagellum

A

100-300

39
Q

F0F1-ATPase

A

found in eukaryotic mitochondria- also a rotation motor- induced by a proton gradient producing ATP

40
Q

what is secretion based motility

A

where the action of secretion propels the bacteria along

41
Q

secretion based motility

A
  • surface-attached motility at around 2-5 micrometers per sec
  • some cells rate over secreted adhesion proteins in flavobacterium spp
42
Q

pili-based motility

A

twitching

  • 100-1000 per cell, 1-2 micrometers long and 2-6 nm wide.
  • pili are dynamic and can retract and grow
  • pili function in DNA exchange between cells and surface adhesion
43
Q

what do pili do to cause movement

A

they change in length and this can be used for gliding over surfaces

44
Q

twitching motility in pili is used to

A

form colonies

45
Q

structure of a pilus

A

thin polymers made of one protein- Pilin

46
Q

which proton is used in the formation of pili

A

Pilin

47
Q

how do bacteria force the host cell to take them up

A

many bacteria inject proteins into the human host cell to manipulate the actin cytoskeleton, thereby forcing uptake

48
Q

how many different secretion systems known

A

6

49
Q

type 3 secretion system

A

injects proteins
-the needle-like structure is used as a sensory probe to detect the presence of eukaryotic organisms and secrete proteins that help the bacteria infect them. The secreted effector proteins are secreted directly from the bacterial cell into the eukaryotic (host) cell, where they exert a number of effects that help the pathogen to survive and to escape an immune response.

50
Q

types 6 secretion system

A

injects proteins
is molecular machine used by a wide range of Gram-negative bacterial species to transport proteins from the interior (cytoplasm or cytosol) of a bacterial cell across the cellular envelope into an adjacent target cell. The T6SS was first identified in 2006 in Vibrio cholerae, which causes cholera.

51
Q

how many proteins injected in the type 3/6 secretory system

A

15-30

52
Q

which bacteria have complex protein translocation machines?

A

gram negative bacteria e.g. Shigella spec. and Yersinia enterocolitica

53
Q

there are similarities between the

A

rotation motor of the flagellum and type 3 secretion system

54
Q

TTSS

A

type three secretory system

55
Q

what occurs when bacteria inject components into host cells>

A

the components interfere with cellular processes and suppress host defences

56
Q

process of bacterial cell injecting components and interfering with cellular processes

A

1) secretion system attaches to hot cell
2) needle and translocon attaches to the host cell
3) components from the bacterial cell pass through the basal body and needle into the host cell
4) damaging the cytoskeleton, cell cycle, apoptosis, transcription and

57
Q

engulfed bacteria escape the vacuole, multiply and start intracellular movement

A

to avoid attack of the host cell

58
Q

why do bacteria continuously move around inside cells

A

impossible to form outer phagosome around the bacteria and therefore cannot be killed

59
Q

what causes acute inflammation

A

the bacteria infect the epithelial lying of the colon, causing acute inflammation by entering the host cell cytoplasm and spreading

60
Q

bacteria… into the neighbouring cell

A

rocket themselves

61
Q

what moves the bacteria inside the host cell

A

actin–> during movement bacteria form cytoskeleton tails at the rear
–> E microscopy indicates the tails consists of actin

62
Q

what sort of actin is added to the tail to allow movement

A

G actin

63
Q

proof that G actin is added to the tails

A

• G actin (fluorescentand not polymerized) added to bacteria and if the tail is actin, then the bacteria will start moving

64
Q

what triggers Actin polymerisation

A

Listeria ActA resembles a host protein and triggers actin polymerisation

65
Q

how do bacterium make an actin “comet tail”

A

uses endogenous machinery

66
Q

how can we prove ActA mediates motility

A

add it to bacteria and they should start moving

67
Q

what shoots the bacteria through the cell and across another cell mem.

A

polar polymerisation

68
Q

life cycle of a cytosolic bacterium

A

engulfment, proliferation and motility, which involves being shot into a neighbouring cell

69
Q

MamK

A

organelle assembly

70
Q

ParmM

A

plasmid segregation

71
Q

MreB

A

cell shape

72
Q

three actin like proteins that make up the cytoskeleton of prokaryotes

A

MamK, ParM, MreB

73
Q

MreB and Mdl1 involved in

A

bacterial morphogenesis

74
Q

FtsZ

A

a distant prokaryotic tubular homologue

75
Q

which protein helps with cytokinesis

A

FtsZ

Molecular cell (21 decks)

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