Microbiology Chapter 6

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Microbiology
Chapter 6
Micorbiology Chapter 6 powerpoint notes
updated 8 years ago by jenkarmata
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College: Second year
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1

Microbial Growth refers to

Increase in number of cells, not cell size.
*Populations
*colonies

2

The requirements for growth

* Physical requirements (there are 3)

1. Temperature
2. pH
3. Osmotic pressure

3

The requirements for growth

* Chemical Requirements (there are 5)

1. Carbon

2. Nitrogen, sulfur & phosphorous

3. Trace elements

4. Oxygen

5. Organic growth factor

4

Physical Requirements

Temperature
* MINIMUM growth temp
* OPTIMUM growth temp
* MAXIMUM growth temp

5

Psychrotrophs

* Grow between 0°C & 20-30°C
* Cause food spoilage

6

Food preservation temperatures

What temperatures is the danger zone?

Between 20°C to 50°C

* Rapid growth of bactera; some may produce toxins.

7

pH

Most bacteria grow between pH

6.5 & 7.5

8

pH

Molds and yeasts grow between pH

5 & 6

9

pH

Acidophile grow in _____ environments

acidic

10

Osmotic Pressure

Hypertonic environments, or an increase in salt or sugar, cause

Plasmolysis

11

Osmotic Pressure

_____ or ______ require high osmotic pressure

Extreme / obligate halophiles

12

Obligate →

requires

13

Facultative →

tolerate

14

Osmotic Pressure

_______ tolerate high osmotic pressure

Facultative halophiles

*(notice the word tolerate in the question)

15

Chemical Requirements

Carbon

* Structural organic molecules, energy source
* Chemoheterothrophs use organic carbon sources
* Autotrophs use CO2

16

Chemical Requirements

Nitrogen

* In amino acids & proteins
* Most bacteria decompose proteins
* Some bacteria use NH4+ or NO-3 (ammonia / Nitrates)
* A few bacteria use N2 in NITROGEN FIXATION

17

Chemical Requirements

Sulfur

* In amino acids, thiamine, & biotin
* Most bacteria decompose proteins
* Some bacteria use SO2-4 or H2S

18

Chemical Requirements

Phosphorus

* In DNA, RNA, ATP & membranes
* PO3-4 is a source of phosphorus

19

Chemical Requirements

Trace elements

* Inorganic elements required in small amounts
* Usually as enzyme cofactors

20

The effect of Oxygen on the growth of various types of bacteria

Obilgate Aerobes

card image

* Only aerobic growth; oxygen required.
* Growth occurs on where high concentration of oxygen have diffused into the medium.
example: 1st tube at the left

21

The effect of Oxygen on the growth of various types of bacteria

Facultative Anaerobes

card image

*Both aerobic & anaerobic growth; greater growth in presence of oxygen.
* Growth is best where most oxygen is present, but occurs through out tube.
example: 2nd tube from left

22

The effect of Oxygen on the growth of various types of bacteria

Obilgate Anaerobes

* Only anaerobic growth ceases in presence of oxygen.
* Growth occurs only where there is no oxygen
(bacteria clumped at bottom of tube)

23

The effect of Oxygen on the growth of various types of bacteria

Aerotolerant Anaerobes

card image

*Only anaerobic growth, but continues in presence of energy.
*Growth occurs evenly; oxygen has no effect
example: 2nd to the last tube on right

24

The effect of Oxygen on the growth of various types of bacteria

Microaerophiles

*Only aerobic growth; oxygen required in low concentration.
*Growth occurs only where a low concentration of oxygen has diffused into medium.
example: very last tube on the right.