lecture 3 bacteria 2 Flashcards
what are glycocalyces
umbrella name for other structures that have a similar function like capsule and slime
describe the features of capsules
Tightly attached, tight matrix; visible if treated with India ink
describe the structure and functions of the slime layer
- loosely attached, easily deformed (e.g., Leuconostoc)
- assist in attachment to surfaces
- role in development and maintenance of biofilms
- virulence factors: protect against phagocytosis
- prevent dehydration/desiccation
what are the similarities between capsules and slime layer
- both are sugars, capsule is more structured and tighter, whereas slime is more soft loose and less well defined
- both protective and adhere to different surfaces which can help the bacteria
what is the s-layer and where is it found. what does it help the cell with
an additional protective layer commonly found in free-living Gram positive and Gram negative bacteria and archaea
may contribute to cell shape and help protect the cell from osmotic stress
what is the s-layer composed of
crystalline layer of thick subunits consisting of protein or glycoprotein
what are fimbriae and pili
filamentous protein structures ~2-10 nm wide
what is the function of fimbriae
Fimbriae enable organisms to stick to surfaces or form pellicles (thin sheets of cells on a liquid surface).
name the two types of pili and what they do
conjugative/sex pili facilitate genetic exchange between cells (conjugation).
type IV pili adhere to host tissues and support twitching motility (e.g., Pseudomonas and Moraxella).
how many fimbriae are found per cell, how many pili are found
many fimbriae, only 1/a few pili
what are 9 structural features of the cytoplasm . which are the 3 not usually found in eukaryotes
- nucleoid
- extra chromosomal dna
- enzymes
- regulatory factors
- ribosomes
- cell inclusions
- gas vesicles
- magnetosomes
- cytoskeleton
7,8,9
what kind of shape does FtsZ give the cell
spherical
what shape does MreB give the cell
rod
what shape does crescentin give the cell
virbroid shape
what is the ParM protein and how does it help chromosomes divide
at the origin of replication, theres a protein called Par, binds on to origin, as chromosome divides, the two proteins are dragged to poles of cells. doing that bc between it is a build of cytoskeletal protein, and pushes the two proteins that are bound to the origin to the poles of cells, thereby segregating them to split them up
do bacteria undergo mitosis and meiosis
no
how do bacteria cells divide and what does it require
through fission
bacterial cell division, or fission, requires highly coordinated growth and formation of all the cell’s parts
what is the bacterial DNA replication coordinated with
bacterial DNA replication is coordinated with the cell wall expansion and ultimately the separation of the two daughter cells
explain how the process of septation works. what does it form?
as DNA synthesis terminates, the cell divides by a process called septation, the formation of the septum
the septum grows inward from the sides of the cell, at last constricting and sealing off the two daughter cells
how does FtsZ direct septal growth in the bacterial cell
FtsZ subunit assembly circles around the septum in a treadmilling pattern, stepwise around the cell, that directs septal growth
what does septation require? what is it managed by
Septation requires rapid biosynthesis of all envelope components, including membranes and cell wall.
the overall process of septation is managed by a protein complex called the divisome
what is the difference in dna organization between eukaryotic and prokaryotic cells
Eukaryotic cells have a well-defined nucleus delimited by a nuclear membrane
prokaryotic cells have a nucleoid region that extends throughout the cytoplasm and is not enclosed by a membrane
what is dna attached to in bacterial cells
in most bacterial species, the DNA is attached to the envelope at the origin of replication, on the cell’s equator
explain how translation is prokaryotes is coupled to transcription
the ribosomes bind to mRNA and begin translation even before the transcription of the mRNA strand is complete
explain the four steps of cell division in bacterial cells
- in prokaryotes, a circular chromosome begins to replicate at its origin, or ori site
- two replication forks are generated, which proceed outward in both directions. at each fork, DNA is synthesized by DNA polymerase, with the help of accessory proteins, this protein complex is called the replisome.
- as the termination site is replicated, the two forks separate from the DNA
- completion of replication triggers Z-ring formation
what is the name of the protein complex that helps synthesize dna in bacterial cells
replisome
how do bacterial cells efficiently divide
it starts to replicate again, before it divides in the 4th picture. so this happens if the bacteria is in a nutrient rich environment, its an efficient system to divide rapidly. they havent finished replicating the whole genome buy they have already started a new replication.
what are the two types of daughter cells bacteria can generate
some bacteria generate two kinds of daughter cells: one stationary (sessile) and one mobile (swarmer)
what form does the cell have to be in to divide? how can a swarmer cell divide?
in order to be able to divide, this cell has to be in the sessile form. swimmers can go to good areas to divide, ditch its flag, grow a stalk, stick itself to a surface, then on the top side of the bacteria it will grow a whole new cell that is a swarmer cell (with a flagella)
what is polar agining increased by
stress
what is a major form of asymmetrical growth
endospore formation
what does the process of cell division determine about the poles in bacteria
the actual process of cell division itself determines that the poles of each daughter cell differ chemically from each other
what are the 3 functions of vesicles
- attractors of partner hetertrophs
- phage decoys
- vehicles for DNA transfer
what are contained in the membrane vesicles that microbial cells export
surprisingly, isolated microbial cells continually export bits of cytoplasm in membrane vesicles. these carry proteins and nucleic acids
what are nanotubes? what do they allow for
nanotube have cell membrane that connects two cells. allows for cells to contain protein and mra, a way to exchange information between the two
these nanotubes allow bacteria to directly share proteins and mRNA useful under hostile conditions, such as when exposed to antibiotics
what are thylakoids
thylakoids: extensively folded intracellular membranes found in photosynthetic bacteria
what are carboxysomes
carboxysomes: polyhedral bodies packed with the enzyme Rubisco for CO2 fixation
what are gas vesicles
Gas vesicles: protein-bound gas-filled structures that increase buoyance
what are magnetosomes
allow bacteria to orient themselves across a magnetic gradient
what is an inclusion body and what is their function
inclusion bodies come out of the bacteria is because their are being produced in too high volumes
inclusions function as energy reserves, carbon reservoirs, and/or have special functions
what are inclusion bodies enclosed by, what do they reduce
thin membrane, osmotic stress
what kind of storage polymers do cell inclusions have
glycogen: glucose polymer
poly-β-hydroxybutyric acid (PHB): lipid polymer, stored as lipid droplets
what are the 4 arrangements of flagella in bacteria
polar, lophotrichous, amphitrichous, peritrichous
describe the structure of flagella
helical in shape
consists of several components
filament composed of flagellin
increase or decrease rotational speed relative to strength of proton motive force
what does ccw rotation of the flagella result in? what is this movement called? what is it caused by?
- CCW rotation
- flagella bundle together
- push cell forward
- “run”
what does cw rotation of the flagella result in? what is this movement called? what is it caused by?
- repellents (or absence of attractants) cause CW rotation
- flagellar bundle falls apart
- “tumble”
- bacterium briefly stops, then changes directions
what is a biased random walk
biased random walk is when you are moving towards a signal
what is a random walk
random walk is when they are moving not with a signal and not towards a attractant
what are the 5 types of taxis
- chemotaxis: response to chemicals
- phototaxis: response to light
- aerotaxis: response to oxygen
- osmotaxis: response to ionic strngth
- hydrotaxis: response to water
what does an endospore do?
endospores essentially protect the bacterial genome in a dormant state when environmental conditions are unfavorable
what are 4 characteristics of endospores
- resistant to extreme temperatures and radiation
- do not absorb gram stain, only special endospore stains
- dehydrated; no metabolic activity
- dormant; no growth or metabolic activity
what are 5 structural features of an endospore
- many layers: exosporium (outermost), spore coats, cortex, core wall
- contains dipicolinic acid and is enriched in Ca2+ both form the calcium-dipicolinic acid (DPA) complex
- DPA complex help the cells to cope with dehydration and stabilize DNAdehydration and stabilize DNA
- Core contains small acid-soluble spore proteins (SASP), which bind and protect DNA and function as carbon and energy source for outgrowth.
- Core also contains the cytoplasmic membrane, cytoplasm, ribosomes and other cellular essentials.
when are endospores formed
Formed during endosporulation or sporulation
where are endospore present? where are they not present?
Present only in some gram-positive bacteria, (e.g., Bacillus and Clostridium), none in archaea, suggesting this process evolved in bacteria after split.
what kind of dispersal are endospores ideal for?
Ideal for dispersal via wind, water, or animal gut
name the 6 steps from dna from forming to releasing an endospore
- dna replicates
- membranes form around the dna
- forespore forms additional membranes
- protective cortex forms around the spore
- protein coat forms around the cortex
- spore is released.
