Microbial Metabolism & Nutrition

Energy Production• Phototrophs convert light to ATP energy• Chemotrophs convert chemicals to ATP energy• Lithotrophs use inorganic chemicals - S, N, Fe

Carbon Source• Autotrophs use CO2 to make organic compounds• Heterotrophs use organic chemicals

ONLY some prokaryotes are lithotrophs.

Basic groups of organisms

Chemoheterotrophic Microbial ReactionsES = electron source; EA = electron acceptor

Aerobic ExampleMANY body-associated microbes - like usGlucose (ES) + O2 (EA) yields CO2 + H2O

Anaerobic ExampleOther body-associated microbes - not like usGlucose (ES) + SO4 (EA) yields CO2 + H2SBasis for an important Salmonella ID test - LAB

Chemolithotrophic Microbial ReactionsES = electron source; EA = electron acceptor

Aerobic ExampleAmmonia (ES) + O2 (EA) yields nitrate + H20 River pollution problem - creates acid, toxins

Anaerobic ExampleH2 (ES) + CO2 (EA) yields CH4 + H2OMethanogen - natural gas from decomposition

Microbial GrowthSpending of ATP to build cell parts for growthGrowth - increase in the number of organismsSingle bacterium multiplies to make a colony

Physical Requirements

• Oxygen• Carbon dioxide• Temperature• pH• Salt concentration

Atmospheric Requirements

• Aerobic– use O2– Obligate– Microaerophiles (5%

O2)• Anaerobes– do not

require O2– Obligate– Aerotolerant– Facultative– Capnophiles (higher

CO2)

Toxic forms of Oxygen

• Superoxide O2-

• Hydrogen Peroxide H2O2

• Superoxide dismutase• Catalase

Temperature

Categories

ExamplesPsychrophile

Thermophile

pH

• Acid• Basic

Figure 6.6a

Water and Salt

• Osmotic • Salt water• Halophiles

A Strange Phenomenon Caused By Red Halobacteria