Lab 3

Question 1

what is a bacterial colony

Answer 1

a mass of cells derived from a single isolated cell.

Question 2

2 structural differences between Gram-positive and Gram-negative bacteria

Answer 2

1. gram positive bacteria have a thick peptidoglycan layer which appear purple/blue VS gram negative who have a thin peptidoglycan layer appearing red/pink.
2. Gram negative bacteria have an outer membrane while gram positive bacteria do not.

Question 3

bacterial cell shapes?

Answer 3

coccus, bacillus, spirillum.

Question 4

bacterial cell arrangements?

Answer 4

bacillus: single, diplo, strepto
coccus: single, diplo, strepto, staphylo
spirillum: single

Question 5

purpose of flaming in aseptic technique

Answer 5

This ensures that no microorganisms enter the mouth of the vessel to contaminate the culture or the medium.

Question 6

3 experiments done in the bacterial lab?

Answer 6

1. the amylase test. swab bacteria on a starch agar plate. after 48 hours, pour iodine. iodine reacts with starch to form a dark blue colored complex. if the area is clear, it means there is no starch.
2. antibiotic susceptibility test. plate a lawn of bacteria into regular agar plates. place the antibiotics and leave for 48h. see the zone of inhibition (clearings.)
3. plating bacterial communities for comparison. swab bacteria, and leave a control area and then compare the colonies.

Question 7

bacterial Lawn

Answer 7

a uniform and uninterrupted layer of bacterial growth, in which individual colonies cannot be observed

Question 8

Starch-Agar test? what is it testing for? How do you interpret the results?

Answer 8

test the ability of a bacteria to produce amylase
if purple: yes starch, no amylase
if white, no starch, yes amylase

Question 9

mechanism of penicilin

Answer 9

inhibit Cell wall synthesis, peptidoglycan cross linking

Question 10

mechanism of streptomycin

Answer 10

prevent protein synthesis

Question 11

mechanism of cefotaxime

Answer 11

They bind to and block the activity of enzymes responsible for making peptidoglycan, an important component of the bacterial cell wall
cell wall synthesis

Question 12

mechanism of norfloxacin

Answer 12

inhibits bacterial deoxyribonucleic acid synthesis (dna replication)

Question 13

What is the relationship between the Gram stain and the effectiveness of certain antibiotics?

Answer 13

penicillin kills gram positive bacteria, slight effect on gram 0
streptomycin kills all bacteria

Question 14

almost all bacteria are heterotrophs except for the __

Answer 14

photoautotrophic cyanobacteria

Question 15

how do decomposers decompose

Answer 15

They decompose (break down) organic materials through extracellular digestion: that is they secrete exoenzymes that digest the food. Amylase is an exoenzyme released by many bacteria and fungus that hydrolyzes starch and glycogen into disaccharides. The decomposers then simply absorb the digested particles