Download presentation
Presentation is loading. Please wait.
1
BIO 205 – Microbiology Chapters 8, 9, end of Ch. 3
2
Chapter 8 - Growth of Microorganisms
Key words / concepts doubling / generation time binary fission the growth phases of a population lag, exponential, stationary, death colony biofilm trance elements vs. growth factors temperature “requirements” oxygen requirements pH and salt “requirements” bacterial counts dilution plating / spread plate technique
3
How do most bacteria replicate?
4
Some do it a bit different . . .
Listeria monocytogenes
5
Generation time
6
Growth Phase
7
Continuous culture in a chemostat
8
Types of Growth
9
Streak plate technique
10
Biofilms
11
Biofilms and quorum sensing
12
Biofilms
13
Microbial nutrition
14
Microbial nutrition Trace elements Growth factors
15
Nutritional classes of microorganisms
carbon from CO2
16
Culture media Defined media Complex media Selective media
Produced from pure chemicals Complex media Extracts of natural sources Beef, blood, milk, protein, yeast, soybeans Precise composition not known Selective media Contents select for specific microorganism Differential media Identification of microorganisms
17
Culture media that we will use
Defined media none Complex media Nutrient agar Mueller Hinton agar - antibiotic testing
18
Culture media that we will use
Selective media EMB - inhibit growth of Gram positive bacteria MacConkey - inhibit growth of Gram positive bacteria Mannitol salt - high salt (staph will grow) Differential media Sheep Blood agar - hemolysis EMB - lactose and/or sucrose fermentation - fecal coliforms MacConkey - lactose fermentation Mannitol Salt - mannitol fermentation - pathogenic staph Enterotube - rapid ID of enteric bacteria (15 tests in 1) Synder - dental caries susceptibility - acid producers in saliva
19
How temperature affects growth
20
Oxygen requirements aerobe anaerobe obligate / strict facultative
microaerophile aerotolerant
21
Oxygen culturing conditions
Shaking machines Increase oxygen in the media Candle jars Not anaerobic but reduces available oxygen Anaerobic chambers All oxygen is replaced with other gas Figure 3.25
22
How do we visualize oxygen requirements in the lab? (stab vs. broth)
23
pH and salt and bacterial growth
halophilic
24
How do you know how much bacteria there is?
25
How do you know how much bacteria there is? Hemocytometer
26
Viable count = dilutions and plating
27
Pour vs. spread plate technique
28
Plate count
29
plate 1 ml of bacteria onto agar plate
A little math for you! plate 1 ml of bacteria onto agar plate 5348 672 126 28
30
Summary - Growth of Microorganisms
31
Chapter 9 - Controlling Microorganisms
32
How we used to protect ourselves from microbes
33
Sterilization Disinfection / sanitizing Decontamination Antiseptics / antisepsis
34
Bactericide vs. Bacteriostatic
35
Methods of Physical Control
Heat moist heat dry heat cold
36
Preserving cultures Cold storage
Short-term: refrigeration slows growth Must continually transfer Long-term: freezing Add substance to reduce freeze-killing Glycerol, skim milk, dimethyl sulfoxide (DMSO) Lyophilization Long term—freeze drying Frozen and dried under vacuum probiotics
37
Methods of Physical Control
autoclave incineration
38
Sterilization Eliminating all microorganisms
Culture media must be sterilized Heat sterilization Moist heat Autoclave 121oC for 20 minutes Dry heat 170oC for 90 minutes Figure 3.20
39
Methods of Physical Control
pasteurization
40
Thermal Death What? Thermal Death Time Thermal Death Point
41
Methods of Physical Control
Radiation nonionizing (UV) ionizing
42
Methods of Physical Control
43
Methods of Physical Control
Filtration Lyophilization
44
Methods of Chemical Control
germicides - activity classified as high intermediate low Assignment for next week: What do you use (at home or work)? How does it work?
45
Methods of Chemical Control
Phenols / phenolics Alcohol
46
Methods of Chemical Control
Halogens Hydrogen Peroxide
47
Methods of Chemical Control
Heavy metals Surfactants / detergents
48
Testing germicides we will do Nov. 9
49
Testing germicides
50
Preserving Food
51
Preserving Food Fig. 1. Flow diagram of the main routes of spore contamination into foods. A circled Sp indicates possible environments for formation of endospores (sporulation).
Similar presentations
