Exercise 28

Question 1

Biofilm

Answer 1

Community of microorganisms that thrive on solid surfaces exposed to water

Question 2

Not just layers of cells

Answer 2

Have structural components that allow water to bring nutrients and take away waste products

Question 3

Protection of microbes in biofilm

Answer 3

Extracellular polysaccharides that they synthesize

Question 4

Quorum sensing

Answer 4

Process of modifying gene expression of bacterial cells as they grow which allows them to communicate and coordinate behavior

Question 5

Inducer

Answer 5

Quorum sensing, signaling chemical

Question 6

Human biofilm example

Answer 6

Teeth

Question 7

Biofilm forming strains

Answer 7

Streptococcus mutans, streptococcus sobrinus, Lactobacillus acidophilus

Question 8

Dextran

Answer 8

Dental plaque, highly branched polysaccharide that is sticky and allows the bacteria to stick to the surface of the tooth, traps Food particles and ferments sucrose creating an acid byproduct that eats at enamel causing cavities

Question 9

Cavity testing

Answer 9

Testing for acid producing bacteria in the saliva called cariogenic bacteria

Question 10

Agar used

Answer 10

Snyder agar

Question 11

Components of Snyder’s agar

Answer 11

Low pH to inhibit non acidophiles, contains dextrose, bromcresol green as pH indicator, pH 4.8

Question 12

Snyder agar media classification

Answer 12

Selective and differential
Selective for pH and color change green to yellow

Question 13

Positive control

Answer 13

Lactobacillus acidophilus

Question 14

Negative control

Answer 14

TSB