BIOL 112 Lecture 16

« previous | Wednesday, October 3, 2012 | next »

Bacteria (cont'd)

Energy Sources

autotrophs: CO₂ (inorganic carbon) + Energy → is fixed into → organic compound (C-H compounds) → ATP; photoautotrophs: use light as energy (plants, some protists, some prokaryotes); chemoautotrophs: use from inorganic oxidation reactions (prokaryotes only)
heterotrophs: ≥ 1 organic compound (from somewhere else) → ATP; chemoheterotrophs: use the process above exclusively (animals, fungi, some protists, prokaryotes); photoheterotrophs: need light to create ATP (prokaryotes only)

Oxygen and Respiration

aerobic: glucose → (via glycolysis) pyruvate → Kreb's Cyle → NADH, etc. → O₂ electron acceptor (36 ATP)
facultative [anaerobic] repiration: prefer aerobic, but can perform following reaction in absence of O₂; sugars → alcohol, ATP, and CO₂ (2 ATP)
obligate anaerobes: O₂ is toxic; use an alternate electron acceptor.

Nitrogen Fixation

N₂ → NH₄ → organic compounds

For example:

Some species of cyanobacteria
Rhizobium (in roots of legumes.

Metabolic Cooperation

colonies: specialization among a collection of bacterial cells; e.g. cyanobacteria
biofilms: surface-coating colony; connected by adhesion molecules with connecting channels between.; e.g. dental plaque

Domain Bacteria

Endosymbiosis:

Chloroplasts came from cyanobacteria ancestor
Mitochondria came from α-proteobacteria ancestor

Archaea

Prior to 1970s, Whittaker's 5 kingdoms had a single Monera kingdom for all single-celled prokaryotes

Late 1970s, Carl Woese sequenced rDNA genes from many Monera bacteria, and discovered HUGE differences. This led to the modern 3 domain trees we know today.

Extremophiles: live in a particular extreme environmental condition (e.g. thermophile / heat, halophiles / salt) Methanogens: obligate anaerobes, generate methane (CH₄) from carbon and diatomic hydrogen.

Note: Not all Archaea are extremophiles