Ch.6 Flashcards Preview

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Flashcards in Ch.6 Deck (30):
1

Mesophiles

* Moderate temperature loving microbes
* Most pathogen's belong to this group

2

Thermophiles

Heat loving microbes

3

Most bacteria grow best in this pH range

6.5-7.5

4

Mold and yeast grow best at this pH range

5.0-6.0

5

Osmotic Pressure

* Microorganisms require 80-90% water for growth.
* Many foods are preserved with salt, the salt draws water out of their cells and prevents growth.

6

Hypertonic

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.

7

Plasmolysis

Shrinkage of the cell cytoplasm

8

Obligate Aerobes

Organisms that requires oxygen (O2) to live.

9

Facultative Anaerobe

Both aerobic and anaerobic growth.

10

Obligate Anaerobe

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

11

Chemical requirements for microbial growth:

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

12

Major physical requirements:

Temperature
pH
Osmotic Pressure

13

Quorum sensing

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

14

Planktonic form of biofilm

* 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.

15

Chemically Defined

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

16

Complex medium

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

17

Nutrient Broth

* Complex medium made beef extract and peptone.
* In liquid form

18

When agar is added to the broth it becomes:

* Nutrient Agar
* Agar itself is not a nutrient

19

Differential

* 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

20

Selective Medium

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

21

Quadrant Streak Plate Method

* 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.

22

Agar comes from?

Brown seaweed

23

Bacterial growth Curve

* Increase in bacterial numbers
* 4 phases

24

Lag Phase

* 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.

25

Log Phase (Exponential Growth Phase)

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

26

Stationary Phase

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

27

Death Phase

* 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.

28

Budding

* 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.

29

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

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

30

Psychrophiles/Psychrotrophs

* Cold loving microbes.
* Food microbiologists favor