Lab 3 - Ubiquity

Question 1

where are microbes found?

Answer 1

everywhere - soil, water, organisms, etc.

Question 2

why don’t microbes take over the world?

Answer 2

because they have to be given the right chemical (nutrients) and physical (temperature, pH) conditions.

Question 3

what happens if the microbes have the right chemical and physical conditions?

Answer 3

The microbes can increase in number rapidly (example, 1 E. coli cell multiplies to form a million cells in less than 8 hours)

Question 4

what are good and bad cases of rapid growth of microbes?

Answer 4

bad - in case of pathogens/food spoilage microbes.
good - in case of culturing microbes in lab for studies.

Question 5

what is broth? and an example?

Answer 5

liquid growth medium, example: nutrient broth (NB)

Question 6

growth of microbes in broth is called…?

Answer 6

growth in broth can be visualized as cloudiness or turbidity

Question 7

when can turbidity be seen?

Answer 7

when microbes reach a density of 1 million cells per ml

Question 8

what does a lack of turbidity mean?

Answer 8

means absence of growth

Question 9

what is agar? and an example?

Answer 9

a solid growth medium, example: nutrient agar (NA)

Question 10

how do you convert a broth growth medium to an agar growth medium?

Answer 10

when you add a thickening agent called agar to a broth, it turns into agar

Question 11

what did they used to add instead of agar to make a broth an agar?

Answer 11

gelatin

Question 12

what are the two advantages of agar over gelatin?

Answer 12

1. It is enzyme-resistant (it is a polysaccharide that microbes can’t eat)
   and
2. it is heat-stable (it is liquid when hot and solid when it cools down)

Question 13

who discovered agar?

Answer 13

Angelina Fanny Hesse

Question 14

what is growth on agar called? how is it visualized?

Answer 14

growth on agar can be visualized as colonies

Question 15

what is a colony?

Answer 15

a cluster of microbes

Question 16

why are the vast majority of microbes non-culturable?

Answer 16

because the growth requirements are unknown; we know they exist because we can detect their DNA using techniques like PCR

Question 17

we interact with microbes by what two things?

Answer 17

transient exposure and colonization

Question 18

what is a normal microbiota - mutualistic?

Answer 18

a mutualistic relationship in which both the partners benefit - the host and the microbe (+/+)

Question 19

what is a parasitic relationship?

Answer 19

a harmful relationship when the parasite benefits but the host is harmed (+/-)

Question 20

what happens when the microbiome is displaced?

Answer 20

if displaced to another location, the normal microbiota can become parasitic

Question 21

what is an example of a displaced microbiota?

Answer 21

when E. coli is the colon is displaced to the bladder causing a UTI

Question 22

what is a commensal relationship?

Answer 22

displays a type of relationship where one partner benefits and one remains unaffected (+/o)

Question 23

how would you turn a yeast extract broth to a yeast extract agar?

Answer 23

by adding agar

Question 24

is it possible for a single bacterial species to have 2 different ecological relationships with people?

Answer 24

yes, it can be mutualistic in one part of the body but parasitic in a different part of the body.

Question 25

T/F: we use a variety of different agars in the lab to provide different sources of nutrition to bacteria

Answer 25

False; the agar isn’t different. the liquid is