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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
ParM filaments are
dynamic
26
what makes ParM filaments dynamic
polymerisation of ATP bound ParM at both ends. ATP hydrolysis occurs spontaneously
27
when is the ParM filaments unstable
when ParM-ADP is at an end
28
ParM filaments function in
plasmid segregation
29
process of plasmid segregation
1) ParR binds to the centromeric DNA sequence (ParC) 2) ParM polymerises and binds to ParR 3) filament elongation separates the plasmid - replisome involved
30
random brownian motion is not sufficient to move
prokaryotic cells around | -bacteria and archaea actively moe through liquids or over most surfaces
31
models of prokaryotic motility include
swimming, swarming, gliding, twitching
32
swimming behaviour of bacteria
prokaryotes are too small to sense a nutrient gradient along their cell, they need to swim to find their food
33
flagella-based motility involves
swimming and swarming
34
swarming occurs
on surfaces
35
swimming
- bacteria swim at a rate of 25-160 micrometers per second | - several flagella cooperate in propelling the cell forward
36
what is used to rotate the flagellum
a basal "motor" that uses a proton gradient to rate the flagellum
37
what doe she basal motor use to rotate the flagellum
a proton gradient
38
how many rotations per s in a flagellum
100-300
39
F0F1-ATPase
found in eukaryotic mitochondria- also a rotation motor- induced by a proton gradient producing ATP
40
what is secretion based motility
where the action of secretion propels the bacteria along
41
secretion based motility
- surface-attached motility at around 2-5 micrometers per sec - some cells rate over secreted adhesion proteins in flavobacterium spp
42
pili-based motility
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
what do pili do to cause movement
they change in length and this can be used for gliding over surfaces
44
twitching motility in pili is used to
form colonies
45
structure of a pilus
thin polymers made of one protein- Pilin
46
which proton is used in the formation of pili
Pilin
47
how do bacteria force the host cell to take them up
many bacteria inject proteins into the human host cell to manipulate the actin cytoskeleton, thereby forcing uptake
48
how many different secretion systems known
6
49
type 3 secretion system
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
types 6 secretion system
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
how many proteins injected in the type 3/6 secretory system
15-30
52
which bacteria have complex protein translocation machines?
gram negative bacteria e.g. Shigella spec. and Yersinia enterocolitica
53
there are similarities between the
rotation motor of the flagellum and type 3 secretion system
54
TTSS
type three secretory system
55
what occurs when bacteria inject components into host cells>
the components interfere with cellular processes and suppress host defences
56
process of bacterial cell injecting components and interfering with cellular processes
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
engulfed bacteria escape the vacuole, multiply and start intracellular movement
to avoid attack of the host cell
58
why do bacteria continuously move around inside cells
impossible to form outer phagosome around the bacteria and therefore cannot be killed
59
what causes acute inflammation
the bacteria infect the epithelial lying of the colon, causing acute inflammation by entering the host cell cytoplasm and spreading
60
bacteria... into the neighbouring cell
rocket themselves
61
what moves the bacteria inside the host cell
actin--> during movement bacteria form cytoskeleton tails at the rear --> E microscopy indicates the tails consists of actin
62
what sort of actin is added to the tail to allow movement
G actin
63
proof that G actin is added to the tails
• G actin (fluorescentand not polymerized) added to bacteria and if the tail is actin, then the bacteria will start moving
64
what triggers Actin polymerisation
Listeria ActA resembles a host protein and triggers actin polymerisation
65
how do bacterium make an actin "comet tail"
uses endogenous machinery
66
how can we prove ActA mediates motility
add it to bacteria and they should start moving
67
what shoots the bacteria through the cell and across another cell mem.
polar polymerisation
68
life cycle of a cytosolic bacterium
engulfment, proliferation and motility, which involves being shot into a neighbouring cell
69
MamK
organelle assembly
70
ParmM
plasmid segregation
71
MreB
cell shape
72
three actin like proteins that make up the cytoskeleton of prokaryotes
MamK, ParM, MreB
73
MreB and Mdl1 involved in
bacterial morphogenesis
74
FtsZ
a distant prokaryotic tubular homologue
75
which protein helps with cytokinesis
FtsZ

Molecular cell (21 decks)

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