Ch.6

Question 1

Mesophiles

Answer 1

• Moderate temperature loving microbes

* Most pathogen’s belong to this group

Question 2

Thermophiles

Answer 2

Heat loving microbes

Question 3

Most bacteria grow best in this pH range

Answer 3

6.5-7.5

Question 4

Mold and yeast grow best at this pH range

Answer 4

5.0-6.0

Question 5

Osmotic Pressure

Answer 5

• Microorganisms require 80-90% water for growth.

* Many foods are preserved with salt, the salt draws water out of their cells and prevents growth.

Question 6

Hypertonic

Answer 6

Cell is in a solution whose concentration of solute is higher than in the cell, The cellular water passes out through the plasma membrane to high solute concentration.

Question 7

Plasmolysis

Answer 7

Shrinkage of the cell cytoplasm

Question 8

Obligate Aerobes

Answer 8

Organisms that requires oxygen (O2) to live.

Question 9

Facultative Anaerobe

Answer 9

Both aerobic and anaerobic growth.

Question 10

Obligate Anaerobe

Answer 10

Organism that does not use oxygen (O2) to live.

Question 11

Chemical requirements for microbial growth:

Answer 11

Carbon, Nitrogen, Sulfur Phosphorus, Trace Elements (Small mineral requirements)

Question 12

Major physical requirements:

Answer 12

Temperature
pH
Osmotic Pressure

Question 13

Quorum sensing

Answer 13

Cell-to-cell communication, bacteria coordinate their activity
Attracts other microbes to Biofilm

Question 14

Planktonic form of biofilm

Answer 14

• Free swimming bacterium attaches to a surface.
• Form pillar like structures with channels between them so water can flow through, the water carries nutrients and takes away waste.

Question 15

Chemically Defined

Answer 15

• Exact chemical composition is known
• Must contain organic growth factors that serve as a source of carbon and energy
• e. Coli

Question 16

Complex medium

Answer 16

• Medium in which the exact chemical composition not know.
• Growth of most chemoheterotrophic organisms.
• consist of tone, beef extract, sodium chloride, agar, and water

Question 17

Nutrient Broth

Answer 17

• Complex medium made beef extract and peptone.

* In liquid form

Question 18

When agar is added to the broth it becomes:

Answer 18

• Nutrient Agar

* Agar itself is not a nutrient

Question 19

Differential

Answer 19

• A solid culture medium that makes it easier to distinguish colonies of the desired organisms from other colonies growing on the same plate.
• Ex: Blood Agar

Question 20

Selective Medium

Answer 20

• Cultural medium designed to suppress the growth of unwanted bacteria and encourage the growth of the desired microbes.
• Mannitol Salt Agar

Question 21

Quadrant Streak Plate Method

Answer 21

• Isolation method to obtain a pure culture.
• Grows into isolated communities and then maybe transferred to a test tube of nutrient medium to form a pure culture containing only one type of bacterium.

Question 22

Agar comes from?

Answer 22

Brown seaweed

Question 23

Bacterial growth Curve

Answer 23

• Increase in bacterial numbers

* 4 phases

Question 24

Lag Phase

Answer 24

• Last one hour to several days, period of little or no cell division
• Not dormant, metabolic activity, synthesis of enzymes and molecules.
• Intense activity preparation for population growth.

Question 25

Log Phase (Exponential Growth Phase)

Answer 25

* Cells begin to divide and enter a period of growth | * Reproduction is most active by binary fission (bacteria) or mitosis (yeast),

Question 26

Stationary Phase

Answer 26

Period of equilibrium, microbial deaths balance production of new cells.

Question 27

Death Phase

Answer 27

* Population decreasing at a logarithmic rate. * Cells are swimming in their own waist and have nothing to eat * Number of deaths exceeds the number of new cells formed.

Question 28

Budding

Answer 28

* Few species reproduce this way. * They form a small initial outgrowth, that enlarges until it's size approaches that of the parent cell, and then it separates.

Question 29

* The time required for a sale to divide in the population to double. * The population doubles with each generation.

Answer 29

* Generation time (doubling time) | * Ex.: 2^4= 16 cells

Question 30

Psychrophiles/Psychrotrophs

Answer 30

* Cold loving microbes. | * Food microbiologists favor