Module 4 pt. 1 Flashcards
increase in the number of cells or microbial
population rather than in the size of
individual cells
To increase the population of
microorganisms, their nutritional and
physical requirements must be provided.
Microbial Growth
Factors affecting microbial growth
biochemical
factors (nutrition)
generation time
physical factors
biochemical
factors (nutrition) (3)
– macronutrients
– micronutrients
– vitamins
physical factors (7)
- pH
– temperature
– oxygen concentration
– moisture
– hydrostatic pressure
– osmotic pressure
– radiation
supplying cells with chemical tools (nutrients) they need to make monomers of macromolecules that mainly comprise microbial cells
Microbial Nutrition
extracellular substances that provide the microbial cell with materials to
➢ build protoplasm
➢ generate energy
Nutrients
nutrients required in relatively larger amounts
nutrients required in lesser quantities
macronutrients
micronutrients
any nutrient material prepared/used for the growth and cultivation of microorganisms in the laboratory
Culture Medium
What are Culture Media for? (3)
- for the growth and maintenance of microbial cultures
- to favor the production of particular compounds
- to study microbial action on some constituents of the medium
Types of Culture Media
(based on physical state or consistency)
liquid
semi-solid
solid
no solidifying agent
Inoculum preparation;
fermentation test
Nutrient Broth;
Lactose Broth
liquid
with 0.1- 0.5% solidifying agent
Motility test
Sulfur Indole Motility (SIM) Medium
semi-solid
with 1.5-2.0% solidifying agent
Colony morphology observation; hemolysis and pigmentation characterization
Nutrient
Agar; Blood Agar
Solid
solid culture medium types (3)
plate
slant
deep
complex polysaccharide (usually derived from
red algae)
- used as solidifying agent for culture media in
Petri plates, slants, and deeps - no nutritive value;
- not affected by growth of bacteria
- Liquefies at 100°C
- Solidifies at ~40°C
Agar
Types of Culture Media
(based on chemical composition) (2)
Synthetic Medium (DEFINED)
ex. Glucose Inorganic Salt Phosphate
Complex Medium (NOT DEFINED)
ex. Nutrient Agar, yeast extract
Types of Culture Media
(based on principal purpose, function, or application) (5)
general purpose
differential
selective
enrichment
assay
- allows the growth of a specific type of
microorganisms only and suppresses the growth of
others - contains selective agents/additives/toxic chemicals
(salts, dyes, antibiotics, and other inhibitors)
extreme pH value or unusual carbon source to favor
growth of a particular organism
Thayer-Martin agar (Neisseria gonorrhoeae); NA
with penicillin (Gram-negative bacteria);
Selective Medium
- can distinguish or differentiate visually one type
of bacterium from another - identifies microorganisms by the appearance of
their colonies and exploits the ability of a particular microorganism to change the appearance
of the medium - with special reagents like pH indicators and dyes
- i.e. blood agar (Streptococcus species); MacConkey agar (E. coli and lactose fermenters)
Differential Medium
contains general nutrients and 5% sheep blood.
It is useful for cultivating fastidious organisms and for determining the hemolytic capabilities of an organism.
Some bacteria produce exoenzymes that lyse red blood cells and degrade hemoglobin; these are called ___.
Blood agar
hemolysins
Types of hemolysin (3)
β-hemolysis (beta hemolysis) -complete
Alpha-hemolysin - partial, has biliverdin
γ-hemolysis (gamma hemolysis) - none
used to increase the number of microorganisms with unusual physiological characteristics
contains special nutrient(s) for the microbe of interest (i.e. cellulose, petroleum, blood) and inhibitory substances to suppress unwanted microorganisms
Blood agar, Cellulose Agar
Enrichment Medium
used for the assay of vitamins, amino acids,
antibiotics, etc.; used for qualitative or
quantitative production of such a compound by
a microorganis
of prescribed composition
fermentation media, Triple Sugar Iron
Agar
Assay Medium
- medium contains an indicator which
changes its color when a bacterium
grows in them - i.e. Blood agar (also a differential
media); Mac Conkey’s medium
Indicator Medium
