Bacterial Morphology Flashcards
name the 3 basic bacterial shapes
coccus
bacillus
spirillum
thickness of gram-positive cell walls
thick
thickness of gram-negative cell walls
thin
why should antibiotics be avoided when treating gram-negative bacteria?
would release lipid A endotoxin when cell dies
all gram positive cell walls contain ____
teichoic acid (stabilizer)
what are the primary components of bacterial cell walls?
peptidoglycans: proteins & sugars
in bacterial cell walls, repeating units of ____ are held together by ____
sugars
peptide chains
gram negative cell walls contain the endotoxin ____
lipid A
what does teichoic acid do to the cell?
- protrudes above cell wall thus imparting negative charge to cell (like rebar in concrete)
- positive charge allows for stronger bonding with stains which are negatively charged
M protein is only required for infection by ____ species
streptococcus
function of M protein
- protrudes from cell wall making cell too large to phagocytize
- highly susceptible to mutation
mycolic acid is only found in gram _____ cell walls of _____ species
positive
mycobacterium
what is mycolic acid and its function?
- waxy lipid inside cell wall structure
- barrier against antibiotics & host defenses
what makes up the unique outer later of gram negative cell walls?
lipopolysaccharide
what are O polysaccharides used as?
diagnostic marker in gram negative wall
(E. coli O157:H7)
what is gram stain?
differential stain based on components of the bacterial cell wall
gram positive stains ____, while gram negative stains ____
purple
red/pink
describe the 4 steps of the gram stain procedure
- apply crystal violet (1 min), drain, rinse
- add grams iodine (1 min), drain, rinse
- decolorize w alcohol, (1 short rinse), wash immediately w water
- apply safranin (1 min), drain, rinse, blot
what are the components of the gram stain?
- primary stain: crystal violet
- mordant: gram’s iodide
- decolorizer: 95% ethanol
- secondary stain: safranin
name 7 bacterial structures
glycocalyx
fimbraie
pili
flagella
axial filaments
plasmids
endospores
many organisms are not infectious without a ____
capsule
a capsule inhibits ____
phagocytosis
glycocalyx: slime layer
- associated w dental decay
- very loose adherence to surface
- genes are transferrable
fimbraie
- sticky projections for adherence (like velcro)
- found on gram neg organisms
- genes are transferrable
pili
- bacterial conjugation
- motility through twitching
- involved in development of biofilms
flagella
- motility
- movement from one area of body to another (e. coli to bladder)
name 4 flagellar arrangements
- monotrichous
- amphitrichous
- lophotrichous
- peritrichous
what type of flagellar arrangement has one flagella at one end and allows movement in one direction, with inability to turn around?
monotrichous
what type of flagellar arrangement allows movement in a rolling pattern, typically in liquids where currents can be used?
amphitrichous
what type of flagellar arrangement has several flagella at one end and allows movement in one direction?
lophotrichous
what type of flagellar arrangement has flagella all along the periphery, allowing movement in any direction by running and tumbling, giving it the ability to turn around?
peritrichous (best flagellar arrangement)
describe the characteristics of axial filaments
- endoflagella (located inside bacteria)
- rotate like corkscrew (found in spirochetes)
- ability to bore through tissue
- very slow moving (latent diseases not recognized by immune system for years)
clinical significance of flagella and axial filaments
- opportunistic infections (normal flora, wrong place)
- escape from host defenses (out run neutrophils)
- systemic infection (into bloodstream to rest of body)
describe the characteristics of plasmids
- extra-chromosomal pieces of DNA (DNA “doughnuts”; not within nucleus)
- carry genes for toxins and antibiotic resistance
- transferred via pili during conjugation
describe the factors for endospore formation
- response to environmental stress (too hot/cold/wet/etc)
- only soil-dwelling gram positive rods have ability to form spores
- extremely resistant to heat, desiccation, toxic chemicals, UV radiation, and antibiotics
name 3 examples of spore formers
- clostridium tetani (tetanus)
- clostridium botulinum (nerve block)
- bacillus anthracis (anthrax: natural in skin & GI, lab-made bioweapon in pulmonary form)
what are the 2 major categories of bacterial growth requirements?
physical
chemical
physical requirements of bacterial growth
- temperature (~37*)
- pH (acidic foods)
- osmotic pressure
what does increased temperature do to bacterial growth?
breaks chemical bonds
human pathogens fall into the ____ temperature range
mesophile (moderate)
(33-37*C)
majority of bacteria grow best at what pH?
neutral (7.0)
pathogens prefer the pH of ____
blood (7.34, slightly alkaline)
what effect does alkaline or acidic pH have on bacterial growth?
break bonds thus altering protein structure = lethal event
what is the major agent of osmotic pressure for bacterial growth?
water
(pressure exerted on bacteria by environment)
high salt concentrations create a ____ environment leading to ____
hypertonic
plasmolysis
obligate halophilic bacteria
requires high salt concentration
extreme halophilic bacteria
requires very high levels of salt
facultative halophilic bacteria
can grow with or without salt in the environment
name 2 types of bacteria that can grow in the presence of oxygen
- aerobes (require O2)
- facultative anaerobes (with or without O2)
obligate aerobes
must have O2
obligate anaerobes
die in presence of O2
facultative anaerobes
grow with or without O2
definition of bacterial generation
each division of a bacteria
binary fission
process whereby bacteria increase their numbers by splitting
the time between bacterial divisions is the ____
generation time
lag phase
entry: bacteria are adjusting to their environment
log phase
- bacteria double exponentially
- constant minimum doubling time
- lasts until resources depleted
- most metabolically active
during which phase are bacteria most susceptible to antibiotics?
log phase
(preoccupied with division)
stationary phase
- number of cells dividing equals number of cells dying
- caused by decreasing availability of resources
death phase is also known as ____
logarithmic decline phase
death phase
- continuous decline in number of dividing cells
- caused by exhaustion of resources
- cause by toxicity of environment
