MB 351 - Lecture 14 & 15 (Requirements for growth) Flashcards
(49 cards)
Obligate Aerobe
require O2 as final e- acceptor in aerobic respiration. air is 21% Ox
Obligate anaerobes (aerophobes)
do not need O2. O2 is toxic, and can kill or inhibit growth. Live by fermentation, anaerobic respiration, bacterial photosynthesis. (Marshes, deep subsurfaces)
Facultative anaerobes
can switch between aerobic and anaerobic types of metabolism
Microaerophile
requires oxygen to survive, but requires environments containing lower levels of oxygen than are present in the atmosphere
Aerotolerant anaerobe
Don’t use O2 for growth, but tolerate it. Exclusively anaerobic metabolism.
The medium that may be used to grow microorganisms under aerobic conditions, or to test for the oxygen requirements of a bacterium.
Thioglycollate - medium that serves as a reducing agent to remove traces of O2 by reducing it to water. Pink dye when oxidized and colorless when reduced
Toxic oxygen: Normal molecular O2 that has been boosted into a higher energy state and is extremely reactive
Singlet Oxygen
Toxic oxygen: Formed in small amounts during normal respiration of microbes that use oxygen as the final e- acceptor. These radicals are toxic to cellular components. Toxicity is caused by their great instability, which leads them to steal an electron from a neighboring molecule, and this repeats itself.
Superoxide free radicals or superoxide anions
Toxic oxygen: Peroxide anions
Produced as part of Hydrogen peroxide
Toxic oxygen: Formed in the cytoplasm by ionizing radiation. Most reactive intermediate form of oxygen.
Hydroxyl radical (OH.)
Toxic oxygen: Cells contain several enzymes that aid when exposed to the peroxidation of lipids:
superoxide dismutase, catalase, peroxidase, as well as cellular antioxidants which are able to scavenge oxygen free radicals and repair peroxidized lipids. Able to convert theses toxic oxygen radicals to something less damaging, like water.
Chemical Requirements for growth: macromolecules
Elements: CHNOPS Mineral ions: K+, calcium, sodium, magnesium, iron (Fe2+, Fe 3+), chlorine -mineral ions play an important role in enzymes and macromolecules
Sources of Carbon: Heterotrophs
Rely on other organisms to form the organic compounds (such as glucose, proteins, lipids) that they use as carbon sources. -Carbon source also typically supplies H and O -Carbon source supplies energy (glucose)
Sources of Carbon: Autotrophs
-Use inorganic CO2 as sole or principal carbon source -Carbon source does not supply energy -CO2 fixation
Autotroph: Chemoauto(litho)trophs
inorganic chemicals as energy (ammonia, nitrite, iron, hydrogen sulfide, hydrogen).
Autotroph: Phototrophs
light as an energy source
Sources of N
required as proteins and nucleic acids. Acquired from Amino acids, NH4+, NO3-, also N2- fixation (cyanobacteria)
Sources of S
required for S-amino acids (cysteine and methionine), vitamins Acquired from inorganic sulfate (SO4^2-)
Sources of P
required in nucleic acids, phospholipids, ATP, proteins. Acquired from PO4^2-
Micronutrients
Trace Elements and Growth Factors
Trace Elements
-Inorganic transition metals (Mn, Fe, Mo, Cu, B, Co). -typically required in microgram quantities -serve structural/catalytic roles in specific enzymes -Key trace element: Fe for cellular respiration (redox center), or functions as cofactors in enzymes involved in e- transport rxns
Growth Factors
-Small organic compounds: amino acids, purines/pyrimidines, vitamins (enzyme cofactors) -required in varying concentrations -some organisms satisfy their own requirements for growth factors
Physical requirements for growth:
Temperature, pH, and water availability
Effects of temperature on growth: temperature affects microbes in two opposing ways
As temperature rises, the rate of enzymatic rxns increases, and growth becomes faster. However, above certain temperatures, proteins may become denatured or damaged.
