6.3 Microbial metabolism and nutrition

Phototrophs use ___ as an energy source

Light

Chemotrophs use ____ stored in ____ as an energy source (electron chemicals)

potential energy; chemical compounds

(Chemo) Lithotrophs need

inorganic chemicals

(Chemo) organotrophs need

organic compounds

Autotrophs

make their own carbon compounds starting with CO₂

• “carbon fixation”

Heterotrophs

Obtain carbon compounds from other organisms

• food web consumers

Methanotrophy

CH₄→ CO₂

Methanogensis

CO₂→ CH₄

What needs Nitrogen?

1) amino acid (proteins)

2) Nucleic acids (DNA/RNA)

Denitrification

NO₃^- (nitrate) → N₂ (gas)

Nitrogen fixation

N₂ → NH₄⁺

Nitrification

NH₄⁺ → NO₃^- (nitrate)

Assimilation

How useful forms of nitrogen are taken up by other organisms

Decomposition

How nitrogen is released back into the cycle

Nitrogenase

Enzyme that catalyzes Nitrogen Fixation and is VERY sensitive to O₂

Nitroblast

newly discovered organelle in an Algae for Nitrogen Fixation

Strict Anaerobe

Must have NO O₂

Strict Aerobe

Must have O₂

Microaerophile

Prefer lower [O₂]

facultative Anaerobe

Prefers O₂, but has the “option” to grow without

Aerotolerant Anaerobe (Obligate fermenters)

Doesn’t use O₂, but tolerates it

Reactive oxygen species (ROS)

Produced as byproducts of aerobic metabolism

• damages DNA, proteins, membrane, etc

Superoxide dismutase (SOD) and catalse

Enzymes that break down ROS

Essential nutrients

compounds a microbe cannot make itself but must gather from its immediate environment

Auxotrophy

When a microbe cannot synthesize an essential nutrient, it must be added to culture media for the organism to grow and divide

• aka growth factors

Complex media (rich medium)

often “dead” things (yeast, , plant, or tissue extract)

Chemically Define Media (aka synthetic meium)

All the chemical components are known