chapter 6 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 6 PowerPoint Presentation
Download Presentation
Chapter 6

Loading in 2 Seconds...

play fullscreen
1 / 49

Chapter 6 - PowerPoint PPT Presentation


  • 177 Views
  • Uploaded on

Chapter 6. Microbial Growth. Microbial growth = increase in number of cells, not cell size. What are. Populations Colonies. The Requirements for Growth. Physical requirements Temperature pH Osmotic pressure Chemical requirements Carbon Nitrogen, sulfur, and phosphorous Trace elements

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 6' - tevin


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
chapter 6

Chapter 6

Microbial Growth

what are
What are
  • Populations
  • Colonies
the requirements for growth
The Requirements for Growth

Physical requirements

Temperature

pH

Osmotic pressure

Chemical requirements

Carbon

Nitrogen, sulfur, and phosphorous

Trace elements

Oxygen

Organic growth factor

the requirements for growth physical requirements
The Requirements for Growth: Physical Requirements
  • Temperature
    • Minimum growth temperature
    • Optimum growth temperature
    • Maximum growth temperature
temperature
Temperature

Figure 6.1

psychrotrophs
Psychrotrophs
  • Grow between 0°C and 20-30°C
  • Cause food spoilage
psychrotrophs8
Psychrotrophs

Figure 6.2

the requirements for growth physical requirements9
The Requirements for Growth: Physical Requirements
  • pH
    • Most bacteria grow between pH 6.5 and 7.5
    • Molds and yeasts grow between pH 5 and 6
    • Acidophiles grow in acidic environments
the requirements for growth physical requirements10
The Requirements for Growth: Physical Requirements
  • Osmotic Pressure
    • Hypertonic environments, increase salt or sugar, cause plasmolysis
    • Extreme or obligate halophiles require high osmotic pressure
    • Facultative halophiles tolerate high osmotic pressure
the requirements for growth chemical requirements
The Requirements for Growth: Chemical Requirements
  • Carbon
    • Structural organic molecules, energy source
    • Chemoheterotrophs use organic carbon sources
    • Autotrophs use CO2
slide13
Nitrogen
    • In amino acids, proteins
    • Most bacteria decompose proteins
    • Some bacteria use NH4+ or NO3
    • A few bacteria use N2 in nitrogen fixation
  • Sulfur
    • In amino acids, thiamine, biotin
    • Most bacteria decompose proteins
    • Some bacteria use SO42 or H2S
  • Phosphorus
    • In DNA, RNA, ATP, and membranes
    • PO43is a source of phosphorus
slide14
Trace Elements
    • Inorganic elements required in small amounts
    • Usually as enzyme cofactors
toxic forms of oxygen
Toxic Forms of Oxygen
  • Singlet oxygen: O2 boosted to a higher-energy state
  • Superoxide free radicals: O2
  • Peroxide anion: O22
  • Hydroxyl radical (OH)
biofilms
Biofilms

Microbial communities

Form slime or hydrogels

Bacteria attracted by chemicals via quorum sensing

Figure 6.5

the requirements for growth chemical requirements18
The Requirements for Growth: Chemical Requirements
  • Organic Growth Factors
    • Organic compounds obtained from the environment
    • Vitamins, amino acids, purines, pyrimidines
culture media
Culture Media
  • Culture Medium: Nutrients prepared for microbial growth
  • Sterile: No living microbes
  • Inoculum: Introduction of microbes into medium
  • Culture: Microbes growing in/on culture medium
slide20
Agar
  • Complex polysaccharide
  • Used as solidifying agent for culture media in Petri plates, slants, and deeps
  • Generally not metabolized by microbes
  • Liquefies at 100°C
  • Solidifies ~40°C
culture media21
Culture Media
  • Chemically Defined Media: Exact chemical composition is known
  • Complex Media: Extracts and digests of yeasts, meat, or plants
    • Nutrient broth
    • Nutrient agar
culture media22
Culture Media

Table 6.2 & 6.4

anaerobic culture methods
Anaerobic Culture Methods
  • Reducing media
    • Contain chemicals (thioglycollate or oxyrase) that combine O2
    • Heated to drive off O2
anaerobic culture methods25
Anaerobic Culture Methods
  • Anaerobic jar

Figure 6.5

capnophiles require high co 2
Capnophiles require high CO2
  • Candle jar
  • CO2-packet

Figure 6.7

biosafety levels
1: No special precautions

2: Lab coat, gloves, eye protection

3: Biosafety cabinets to prevent airborne transmission

4: Sealed, negative pressure

Exhaust air is filtered twice

Biosafety Levels
selective media
Selective Media
  • Suppress unwanted microbes and encourage desired microbes.

Figure 6.9b, c

differential media
Differential Media
  • Make it easy to distinguish colonies of different microbes.

Figure 6.9a

enrichment media
Enrichment Media
  • Encourages growth of desired microbe
  • Assume a soil sample contains a few phenol-degrading bacteria and thousands of other bacteria
    • Inoculate phenol-containing culture medium with the soil and incubate
    • Transfer 1 ml to another flask of the phenol medium and incubate
    • Transfer 1 ml to another flask of the phenol medium and incubate
    • Only phenol-metabolizing bacteria will be growing
slide32
A pure culture contains only one species or strain
  • A colony is a population of cells arising from a single cell or spore or from a group of attached cells
  • A colony is often called a colony-forming unit (CFU)
streak plate
Streak Plate

Figure 6.10a, b

preserving bacteria cultures
Preserving Bacteria Cultures
  • Deep-freezing: -50°to -95°C
  • Lyophilization (freeze-drying): Frozen (-54° to -72°C) and dehydrated in a vacuum
reproduction in prokaryotes
Reproduction in Prokaryotes
  • Binary fission
  • Budding
  • Conidiospores (actinomycetes)
  • Fragmentation of filaments
binary fission
Binary Fission

Figure 6.11

phases of growth
Phases of Growth

ANIMATION Bacterial Growth Curve

Figure 6.15

direct measurements of microbial growth
Direct Measurements of Microbial Growth
  • Plate Counts: Perform serial dilutions of a sample

Figure 6.15, top portion

plate count
Plate Count
  • Inoculate Petri plates from serial dilutions

Figure 6.16

plate count43
Plate Count
  • After incubation, count colonies on plates that have 25-250 colonies (CFUs)

Figure 6.15

direct measurements of microbial growth45
Direct Measurements of Microbial Growth
  • Multiple tube MPN test
  • Count positive tubes and compare to statistical MPN table.

Figure 6.18b