Bacterial Morphology

Question 1

name the 3 basic bacterial shapes

Answer 1

coccus
bacillus
spirillum

Question 2

thickness of gram-positive cell walls

Answer 2

thick

Question 3

thickness of gram-negative cell walls

Answer 3

thin

Question 4

why should antibiotics be avoided when treating gram-negative bacteria?

Answer 4

would release lipid A endotoxin when cell dies

Question 5

all gram positive cell walls contain ____

Answer 5

teichoic acid (stabilizer)

Question 6

what are the primary components of bacterial cell walls?

Answer 6

peptidoglycans: proteins & sugars

Question 7

in bacterial cell walls, repeating units of ____ are held together by ____

Answer 7

sugars
peptide chains

Question 8

gram negative cell walls contain the endotoxin ____

Answer 8

lipid A

Question 9

what does teichoic acid do to the cell?

Answer 9

• 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

Question 10

M protein is only required for infection by ____ species

Answer 10

streptococcus

Question 11

function of M protein

Answer 11

• protrudes from cell wall making cell too large to phagocytize
• highly susceptible to mutation

Question 12

mycolic acid is only found in gram _____ cell walls of _____ species

Answer 12

positive
mycobacterium

Question 13

what is mycolic acid and its function?

Answer 13

• waxy lipid inside cell wall structure
• barrier against antibiotics & host defenses

Question 14

what makes up the unique outer later of gram negative cell walls?

Answer 14

lipopolysaccharide

Question 15

what are O polysaccharides used as?

Answer 15

diagnostic marker in gram negative wall
(E. coli O157:H7)

Question 16

what is gram stain?

Answer 16

differential stain based on components of the bacterial cell wall

Question 17

gram positive stains ____, while gram negative stains ____

Answer 17

purple
red/pink

Question 18

describe the 4 steps of the gram stain procedure

Answer 18

1. apply crystal violet (1 min), drain, rinse
2. add grams iodine (1 min), drain, rinse
3. decolorize w alcohol, (1 short rinse), wash immediately w water
4. apply safranin (1 min), drain, rinse, blot

Question 19

what are the components of the gram stain?

Answer 19

• primary stain: crystal violet
• mordant: gram’s iodide
• decolorizer: 95% ethanol
• secondary stain: safranin

Question 20

name 7 bacterial structures

Answer 20

glycocalyx
fimbraie
pili
flagella
axial filaments
plasmids
endospores

Question 21

many organisms are not infectious without a ____

Answer 21

capsule

Question 22

a capsule inhibits ____

Answer 22

phagocytosis

Question 23

glycocalyx: slime layer

Answer 23

• associated w dental decay
• very loose adherence to surface
• genes are transferrable

Question 24

fimbraie

Answer 24

• sticky projections for adherence (like velcro)
• found on gram neg organisms
• genes are transferrable

Question 25

pili

Answer 25

- bacterial conjugation - motility through twitching - involved in development of biofilms

Question 26

flagella

Answer 26

- motility - movement from one area of body to another (e. coli to bladder)

Question 27

name 4 flagellar arrangements

Answer 27

- monotrichous - amphitrichous - lophotrichous - peritrichous

Question 28

what type of flagellar arrangement has one flagella at one end and allows movement in one direction, with inability to turn around?

Answer 28

monotrichous

Question 29

what type of flagellar arrangement allows movement in a rolling pattern, typically in liquids where currents can be used?

Answer 29

amphitrichous

Question 30

what type of flagellar arrangement has several flagella at one end and allows movement in one direction?

Answer 30

lophotrichous

Question 31

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?

Answer 31

peritrichous (best flagellar arrangement)

Question 32

describe the characteristics of axial filaments

Answer 32

- 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)

Question 33

clinical significance of flagella and axial filaments

Answer 33

- opportunistic infections (normal flora, wrong place) - escape from host defenses (out run neutrophils) - systemic infection (into bloodstream to rest of body)

Question 34

describe the characteristics of plasmids

Answer 34

- extra-chromosomal pieces of DNA (DNA "doughnuts"; not within nucleus) - carry genes for toxins and antibiotic resistance - transferred via pili during conjugation

Question 35

describe the factors for endospore formation

Answer 35

- 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

Question 36

name 3 examples of spore formers

Answer 36

- clostridium tetani (tetanus) - clostridium botulinum (nerve block) - bacillus anthracis (anthrax: natural in skin & GI, lab-made bioweapon in pulmonary form)

Question 37

what are the 2 major categories of bacterial growth requirements?

Answer 37

physical chemical

Question 38

physical requirements of bacterial growth

Answer 38

- temperature (~37*) - pH (acidic foods) - osmotic pressure

Question 39

what does increased temperature do to bacterial growth?

Answer 39

breaks chemical bonds

Question 40

human pathogens fall into the ____ temperature range

Answer 40

mesophile (moderate) (33-37*C)

Question 41

majority of bacteria grow best at what pH?

Answer 41

neutral (7.0)

Question 42

pathogens prefer the pH of ____

Answer 42

blood (7.34, slightly alkaline)

Question 43

what effect does alkaline or acidic pH have on bacterial growth?

Answer 43

break bonds thus altering protein structure = lethal event

Question 44

what is the major agent of osmotic pressure for bacterial growth?

Answer 44

water (pressure exerted on bacteria by environment)

Question 45

high salt concentrations create a ____ environment leading to ____

Answer 45

hypertonic plasmolysis

Question 46

obligate halophilic bacteria

Answer 46

requires high salt concentration

Question 47

extreme halophilic bacteria

Answer 47

requires very high levels of salt

Question 48

facultative halophilic bacteria

Answer 48

can grow with or without salt in the environment

Question 49

name 2 types of bacteria that can grow in the presence of oxygen

Answer 49

- aerobes (require O2) - facultative anaerobes (with or without O2)

Question 50

obligate aerobes

Answer 50

must have O2

Question 51

obligate anaerobes

Answer 51

die in presence of O2

Question 52

facultative anaerobes

Answer 52

grow with or without O2

Question 53

definition of bacterial generation

Answer 53

each division of a bacteria

Question 54

binary fission

Answer 54

process whereby bacteria increase their numbers by splitting

Question 55

the time between bacterial divisions is the ____

Answer 55

generation time

Question 56

lag phase

Answer 56

entry: bacteria are adjusting to their environment

Question 57

log phase

Answer 57

- bacteria double exponentially - constant minimum doubling time - lasts until resources depleted - most metabolically active

Question 58

during which phase are bacteria most susceptible to antibiotics?

Answer 58

log phase (preoccupied with division)

Question 59

stationary phase

Answer 59

- number of cells dividing equals number of cells dying - caused by decreasing availability of resources

Question 60

death phase is also known as ____

Answer 60

logarithmic decline phase

Question 61

death phase

Answer 61

- continuous decline in number of dividing cells - caused by exhaustion of resources - cause by toxicity of environment