Environmental Conditions affecting the Oral Environment

Question 1

process by which bacteria re-produce

Answer 1

binary FISSION- divide into 2 daughter cellsp

Question 2

process by which yeasts re-produce

Answer 2

binary FUSION/ budding

Question 3

how can cell GROWTH be measured

Answer 3

1. cell no.
2. cell mass (dry weight)
3. cellular constituents (ATP, endotoxin)

Question 4

how can cell POPULATIONS be measured

Answer 4

total cell count OR
viable counts (cfu, serial dilution)

Question 5

disadvantage of total cell count

Answer 5

doesn’t differentiate between living and dead cells

Question 6

phases of the bacterial growth curve

Answer 6

lag phase
log/exponential
stationary
death/decline

Question 7

list all the environmental factors in the mouth that affect bacterial growth

Answer 7

1. host defences
2. availability of nutrients
3. temperature
4. o2/ redox potential
5. pH
6. antimicrobial compounds

Question 8

how does inflammation effect the temperature

Answer 8

increases T from 35- 39 … alters gene expression…changes the bacteria community found at site

Question 9

categorise the bacteria depending on their optimum temperatures

Answer 9

psycrophile= 20 °C
mesophile= 40 °C
thermophile= 70 °C

Question 10

obligate aerobe

Answer 10

only o2

Question 11

facultative anaerobe

Answer 11

prefers o2 but can grow without

Question 12

micro-aerophile

Answer 12

sub-atomic o2 concentrations

Question 13

aero-tolerant anaerobe

Answer 13

prefers no oxygen but can tolerate o2 at low levels

Question 14

obligate anaerobe

Answer 14

only grows in NO o2- highly sensitive to it

Question 15

list examples of reactive oxygen species

Answer 15

molecular oxygen 
singlet oxygen
peri-oxide anion (o2^2-)
super-oxide anion (o2-)
hydroxyl free radical (°OH)

Question 16

what is the redox potential

Answer 16

the tendency of a solution to take up OR give electrons

Question 17

what is the role of de-toxifying enzymes

Answer 17

they convert ROS into o2/ h20

Question 18

give example of 3 de-oxifying enzymes used by bacteria for their growth

Answer 18

1. superoxide dismutase: o2- —> H202 + o2
2. catalase: 2H2O2 —> 2H2o + o2

3.peroxidase: h2o2 —> 2H2o
(also need NADH and H+ for this reaction)

Question 19

what is the redox potential of a fresh bacteriological medium

Answer 19

+100 to +200 mV

Question 20

what is the redox potential of anaerobic growth

Answer 20

less than -100mV

Question 21

during plaque development there is a change in the bacterial population to anaerobic bacteria which decreases the redox potential of the GINGIVA from ___ to ___

Answer 21

from +73 mV
to -48 mV

gingivitis= -48 mV

Question 22

what is meant by aciduric

Answer 22

organisms which can SURVIVE AND GROW at low pH

Question 23

what is meant by homo-fermentation

Answer 23

when carbohydrate is in excess and LACTATE is formed

Question 24

what is meant by hetero-fermentation

Answer 24

when carbohydrate is limited and ACETATE, FORMATE, ETHANOL is made

Question 25

mircobes within dental plaque utilise endogenous mucin and exogenous sucrose. what is the difference in the utilisation

Answer 25

endogenous mucin= slow rate of acid production, small fall in pH

exogenous sucrose= rapid rate of acid production, low terminal pH less than 5

Question 26

pH and microbes.

Answer 26

resting pH= strep. sanguinis, actinomyces neaslundii, neisseria

acidic pH= strep. mutans, lactobacilli
NB. acidic growing bacteria inhibit health associated species

high pH= anaerobes are found linked with Periodontitis
porphyromonas gingivalis

Question 27

name antibiotics and the pathways they target to inhibit or kill bacteria

Answer 27

penicillins, cephalosporins, vancomycin= cell wall synthesis

quinones, rifampin= DNA replication/ transcription

polymyxin B, nystatin= membrane function

metranidazole= activity against ANAEROBES

trimethoprin= synthesis of essential metbaolites