Bacteria Flashcards
what are the different structural components of bacteria?
- capsule
- cell wall
- nucleoid
- plasmids
- plasma membrane
- ## ribosomes
what can certain bacteria produce?
endospores (allow bacterial genome protection - in a dormant state when the environmental conditions are unfavourable) inclusion bodies (bacteria in unstable environments store excess nutrients within inclusion bodies)
what are bacterial sizes
0.5 micrometer to 5
what are the shapes of bacteria
coccus, bacillus, vibrio, coccobacillus, spirilli, spirochete
what is the capsule?
organisational layer located outside cell wall and composed of polysaccharides or proteins (glycoalyx)
Can get capsulated or non capsulated bacteria
Capsuled produce smooth colonies
Non capsulated produce rough colonies
what do capsules protect the cell from?
drying
attachment of phages
antibacterials
phagocytic cells
what is bacterial mode of nutrition?
absorptive
what cellularity is bacteria?
multicellular, prokaryotic
how do bacteria reproduce?
binary fission
what is the major component of the bacterial cell wall
peptidoglycan
or murein
what are the layers of peptidoglycan composed of?
long chains of alternating molecules of N-acetylglucosamine, and N-acetylmuramic acid
how are tetra peptide chains linked in gram positive and negative?
gram positive = linked by pentaglycine cross bridges
Gram negative = directly cross linked
what do antibiotics do to bacterial cell wall?
as peptidoglycan is unique to bacteria it is a good target - interfere with PG synthesis - weaken the cell wall and make cells more susceptible to effects of osmotic pressure
what is the cell wall like in gram positive?
simple - thick layer of peptidoglycan with embedded teichoic acid external to the plasma membrane
What is the cell wall like in gram negative?
complex- 3 layers -
thin layer of peptidoglycan
inner membrane
outer membrane containing lipopolysaccharides
what are teichoic acids?
the PG layers are embedded with these TAs (CHO chains that extend - they stabilise PG by increasing its rigidity)
what is embedded in the PG layers that increase its rigidity?
teichoic acids
what is mycobacteriaceae?
have PG and TAs but also an additional external layer of waxy mycolic acids in the cell wall. - They’re called acid fast bacteria
why are mycobacteriaceae called acid fast bacteria?
Because acid fast stains are used to penetrate the mycolin acid during staining - stain red by carbolfuschin
what is the nucleoid?
DNA and DNA proteins are in the nucleoid. DNA interacts with nucleoid associated proteins that assist in the organisation and packaging of chromosome
what are plasmids?
sometimes bacteria have extra chromosomal DNA which isn’t part of the chromosome - they are in plasmids which are small, circular dsDNA. - carry genes that confer advantageous traits
what is the plasma membrane?
selectively permeable bilayer of mainly phospholipids formed with ester linkages, and proteins. The phospholipids and proteins move laterally within the plane as well as between phospholipid layers
name and describe 3 types of membrane transport
- Simple diffusion (passive) - high concentration to low - small molecules
- Faciliated - uses selective protein carriers channels - charged and large molecules
- Active transport - when cells move across a membrane against concentration gradient - requires ATP
What are the colours of gram positive and negative on gram staining with crystal violet?
positive- purple
negative-pink
what is the primary stain for the acid fast staining of mycobacteria?
carbolfuschin
what is the order of reagents used in gram stain?
crystal violet, iodine, decolourizer, safranin
the process of gram staining is based on the ability of the bacterial cell wall to what?
retain crystal violet dye during solvent treatment
why do bacteria store nutrients in inclusion bodies in a polymerised form?
It reduces the build up of osmotic pressure as the cell accumulates solutes
what are:
volutin granules
sulfur granules
volutin granules - inclusions that store polymerised inorganic phosphate that can be used in metabolism and assist in biofilm formation
sulfur - in sulfur bacteria (thiobacillus) - store elemental sulfur for metabolism
What are the characteristics of endospores?
- resistant to extreme temps and radiation
- dont absorb gram stain - only endospore stain
- dehydrated, no metabolic activity
- dormant
outline sporulation
Formation of septum in vegetative cell, septum divides.- DNA replicates. = foreshore
- Membrane forms around the forespore
- Protective cortex forms around forespore by laying down layers of calcium and dipicolinic acid between membranes
- protein spore coat forms around cortex and mother DNA disintegrates
- Maturation forming the outermost exosporium
- Mother cell disintegrates and the endospore is released
what is sporulation and why does this happen?
process of a vegetative cell turning into an endospore - this happens when nutrients are depleted or the conditions in environment are unfavourable
what happens to endospores once living conditions improve?
undergo germination to re-enter a vegetative state
name gram positive bacteria that produce endospores (5)
- B.anthracis (anthrax)
- C.tetani = tetanus
- C.botulinum = botulism
- C.difficile
- C.perfrinogens = gas gangrene
what are filamentous appendages and what do they do?
protein appendages embedded within cell envelope - extend outward and allow interaction with environment - attach to other surfaces, transfer DNA or aid in movement
what are 3 types of appendages
fimbriae
pili
flagella
what are fimbriae
short, bristle like proteins projecting from the cell surface by the hundreds - enable cell to attach to surfaces e.g on host cell or for biofilm production
what are pili
what is F pilus
longer, less numerous protein appendages aiding in attachment to surfaces.
F pilus = sex pilus for transfer of DNA between cells - physical
what are flagella
stiff, spiral filaments composed of flagellin protein subunits - move in aqueous environment and have propellers to dictate direction of bacteria
what are the 4 types of flagella arrangements
- monotrichous - singular flagellum at end of cell (polar) - vibrio cholera
- amphitrichous - flagellum at each end - spirillum minus
- lophotrichous- tuft at 1 end - pseudomonas aeruginosa
- Peritrichous - cover entire surface - E.coli
how do bacteria achieve directional movement?
by changing the rotation of their flagella
flagella rotations
1- bundle when they rotate anti-clockwise resulting in a run
- Rotate clockwise they are no longer bundled resulting in tumbles
describe bacterial cell division (binary fission)
- genome attached to membrane (by mesosomes)
- chromosomes replicate and separate
- septum formation
- septum divides - 2 daughter cells separate that are identical to parent (diplococci, chains)
describe gram staining
- Crystal violet - primary stain added to specimen - stains cells purple or blue (pink)
- Iodine - mordant makes dye less soluble so adheres to cell walls - they remain blue or purple
- Alcohol - decolourizer washes away stain from gram negative cell wall. Gram pos remain their colour
- Safranin - counterstain allows dye adherence to gram negative walls - gram negative appear pink
