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Flashcards in Microb Growth Deck (17)
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0
Q

Binary Fission

A

Asexual reproductive process of bacteria. Results in two daughter cells.

1
Q

Fungal Growth

A

Moulds:

  • Hyphae to Mycelium
  • Apical growth - protoplasm movement into tip.
  • Spores (sexual or Asexual)

Yeast:
-Budding (asexual process)

2
Q

Physical factors affecting microbial growth

A
  • Temperature: Minimun, Maximum, optimum
  • Gas Requirements: Electron receptor - Catalase/Superoxide dismutase
  • Water Activity(Aw): most grow at 1.0Aw, Bacteria unable to grow below 0.9Aw
  • Effects of pH
3
Q

Psycrophile

A

Microbe that growth under cold conditions:
Opt temp below 15C
Capable of growth at 0C
Cannot grow above 20C

4
Q

Psychrotroph

A

Facultative Psycrophile
Grow slowly in cold conditions BUT have opt temp above 20C
CONCERN: Contaminants of food/dairy products

5
Q

Mesophile

A

Opt temp 20-40oC
Capable of growth 10-50C (minor fact)
Group containing HUMAN PATHOGENS (30-37C)!!!!

6
Q

Thermophile

A

Opt temp >45oC
Capable of growth 45-85oC
Incapable of growth at usual body temp
(NOT INVOLVED in HUMAN INFECTIONS)

7
Q

Fungi and Temperature

A

FREE-LIVING STATE
– Mycelial or hyphal form (mold)
– At sub-physiological temperature (25C)

PARASITIC STATE
– Yeast form
– Due mainly to physiologic temperature (37C)

8
Q

Obligate Aerobes

A
  • Uses O2 dependent system for ATP.
  • Have catalase and superoxide dismutase to remove H2O2 and free radicals
  • Can tolerate high [O2]
9
Q

Microaerophiles

A

Grow in presence of O2 BUT tolerate only 4%

Possess superoxide dismutase only, BUT if toxic products incrase, enzyme systems overload INHIBITING GROWTH

10
Q

Facultative Anaerobes

A
Grow in presence or absence of O2 
 Presence: Aerobic respiration  
 Absence:  Fermentation for energy prodn 
 Grow best under AEROBIC CONDITIONS 
**ALL YEASTS
11
Q

Obligate anaerobes

A

Grow ONLY in ABSENCE of O2
Effect of presence: LETHAL
LETHAL - org’s lack enzymes to remove toxic products
Brief exposure will KILL

12
Q

Xerotolerant

A

Ability of microbes to grow with reduced water requirements.
Fungi able to grow Aw 0.60
Yeasts (conc sugar soln’s Aw = 0.60)

13
Q

Halophile

A

Salt-tolerant bacteria (high [solute], low water activity)

14
Q

Chemical Factor Affecting Microbial Growth

A

Nutrient Concentration: CHNOPS, Minterals (Ca++, etc.), trace elements (Zn, Cu, etc.)

  - Autotroph - CO2 primary source of C
  - Heterotroph - organic materials source of C
15
Q

Sabouraud’s Agar

A

Fungal Cultivation for primary: selective isolation
-Peptone (protein hydrolysate)
-pH 5.6 (inhibits faster growing bacteria)
-Antibiotics: Penicillin, Streptomycin, Tetracycline (inhibitbacteria)
Cultivated at 25C and 37C for molds and Yeast

16
Q

Corn Meal Agar

A

Fungal Cultivation for Secondary: species identification
– Incubated at 25C, several days
– Characteristic sexual structures develop– ID based on morphology (microscopy)