bacterial cell structure Flashcards
morphology of bacteria
shape
morphology:
coccus
coccobacilllus
bacillus
vibrio
spirillum
spirochete
pleomorphic
coccus- spherical
coccobacilllus
bacillus- rod shaped
vibrio- curved rod
spirillum- stiff sinusoid
spirochete- flexible sinusoid
pleomorphic- abnormal
binary fission steps in bacteria
- chromosome replication begins
- replication continues
- replication finishes
- two daughter cells results
2 copies of origin in chromosome get separate to either side then membrane pinches so that daughter both have organ of replication (the DNA sequence that makes copies of DNA)
bacterial reproduction via snapping division
cell wall outer portion remains in tact
inner portion snaps and splits into two cells
bacterial reproduction vis spores of actinomycetes
spores on filaments break off and create new filaments
bacterial reproduction via budding
DNA is replicated –> one daughter DNA molecules is moved into bud –> young bud forms –> pinches off into daughter cell
arrangement of bacteria in cocci
- plane of cell division
- do cells stick together after dividing?
diplococci- pairs
streptococci- line
–> both 1 plane of division
tetrads- split into flat 4; 2 planes
sarcinae; 3 planes creates 8 cell cube
staphylococci; many random planes creates big clump
arrangement of bacteria in bacilli
only can divide in one plane along short axis (rod shape)
single bacillus
diplobacilli
streptobacilli
palisade and v shape are weird snapping division
glycocalyces (external structure of bacterial cell)
glyocalyx could be tightly packed capsule or slime layer
made of polysaccharide sugar and protein
flagella (bacterial cell external structure)
protein rings allow for it to whip around
tail that is made of flagellin protein
peritrichous: flagella everywhere
single polar flagellum: 1 at 1 end
tuft of polar flagella: clump at 1 end
how do flagellated bacteria move: biased random walk
- tumble
- run
eventually move toward chemotaxis, phototaxis (attractants)
fimbriae (bacterial cell external structure)
adhere to other substances (short little projections)
pili (bacteria cell external structures)
conjugation pilus –> specialized fimbria
let bacterial cells connect and have “sex” and exhcngae nucleic acid genetic material;
= conjugation -transfer genes
roles of bacterial cell wall
-protection (many antimicrobial drugs target cell walls)
-attachment to other bacteria or cells
-resistance to osmotic forces
-give shape to the cell
what are cells walls made of?
peptidoglycan: polysaccharide comprised of repeating N-acetylglucoasmine (NAG) and N-acetylmuramic acid (NAM)
these sugar backbones are connected by a chain of amino acids and a tetra peptide amino acid cross bridge
gram negative vs gram positive cell wall
gram negative has a cytoplasmic membrane then the peptidoglycan layer of the cell wall then the outer membrane of the cell wall
in the gram negative cell wall there is lipopolysaccharide (LPS) which has lipid A which is very toxic
in a gram positive cell wall there is only the inner membrane and then a thick cell wall (no outer membrane)
gram stain
Hans Christian Gram-
- primary stain; crystal violet to stain all cells
- mordant (iodine) to make crystal violet less soluble and make it stick better to all cells
- decolorize: flood with ethanol and acetone
–> Et and Ac destroy cell wall- gram + have a thicker cell wall so they will remain purples
gram negative are now colourless - counter-stain: safranin to stain everything
-gram positive remain purple
-gram negative become pink
what does gram stain fail to identify?
mycobacterium and nocardia bacteria
–>gram positive; they have very waxy cell walls that reject crystal violet
so use Ziehl-Neelsen acid-fast staining technique
-turn acid fast bacteria pink and the others will be blue
cytosol of bacteria
cytosol has ions, carbs, proteins (enzymes), lipids, waste products
and nucleoid region (DNA compartmentalizes even though there’s no nucleus)
cytosol
- inclusion
- inclusions; deposits of lipids, starch, nitrogen, sulphur, phosphorus, contained by protein membrane (polyhydroxybutyrate PHB in inclusion bodies)
endospores
hibernate from harsh environment and are able to survive
-after binary fission
1. membrane grows and enfolds foreshore within a second membrane
2. cortex of calcium and dipicollnic acid is deposited between memrbanes
3. form spore coat
4. maturation and get outer spore coat
4. endospore is released from original cell
… many membrane layers
