Microbiology chapter 6/11

Phycobilins (Photosynthetic pigments)

(cyanobacteria, red algae)

Bacteriochlorophylls (Photosynthetic pigments)

(in anoxygenic bacteria) -Absorb different wavelengths than chlorophylls

Chlorophylls (Photosynthetic pigments)

(in plants, algae, cyanobacteria)

Carotenoids (Photosynthetic pigments)

(many photosynthetic prokaryotes and eukaryotes)

•Cyclic photophosphorylation

-Photosystem I alone -Produces ATP (using energy from the proton motive force) -Reaction-center chlorophyll is the electron donor and the terminal electron acceptor

Photosystems

capture and use light energy

Methanogens

chemolithotrophs; Archaea that use CO2 and hydrogen gas to release methane, a greenhouse gas.

Reaction-center pigments

excited by radiant energy (=energy of light); emit electrons that are passed to the electron transport chain

Antennae pigments

funnel light energy to the reaction-center pigments

sulfur

if the chemoorganotroph is a anaerobe, it will use what as its electron acceptor?

Purple bacteria

in cytoplasmic membrane

Green bacteria

in specialized structures called chlorosomes attached to cytoplasmic membrane

Plants, algae:

in thylakoids in chloroplast

Enterococcus (lactic acid bacteria)

inhabit human, animal intestinal tract

photosystems

located within photosynthetic membranes

Archaea

most anaerobic chemolithotrophs are in the domain ...

anoxygenic photosynthesis

non-oxygen producing; bacteriophylls

oxygenic photosynthesis

oxygen producing; chlorophyll a

Green bacteria

photosystem similar to photosystem I

Cyanobacteria

photosystems in membranes of thylakoids (inside cell)

Over 1 million species; Only ~6,000 described •950 genera

prokaryotes estimated

anaerobic habitats

•Aerobes contribute by depleting O2 •Mud, tightly packed soil limit diffusion of gases •Aquatic environments can become limiting •Human body (especially intestinal tract, anaerobic microenvironments in skin, oral cavity)

•Six "turns" of cycle: net gain of one fructose-6-phosphate

•Consumes 18 ATP, 12 NADPH per fructose molecule

carbon fixation

•In photosynthetic organisms: light-independent reactions •Consumes lots of ATP, reducing power (Reverse process of oxidizing compounds to CO2 liberates a lot of energy!) •Calvin cycle most commonly used •Three essential stages •Six "turns" of cycle: net gain of one fructose-6-phosphate

•Three essential stages carbon fixation

•Incorporation of CO2 into organic compounds •Reduction of resulting molecule Regeneration of starting compound

Anaerobic Chemoorganotrophs - Fermentation

•Many anaerobic bacteria ferment • ATP via substrate-level phosphorylation • Many different organic energy sources, end products

Light-dependent reactions: anoxygenic photosynthetic bacteria

•Only one photosystem •Cannot use water as electron donor, so anoxygenic •Use electron donors such as hydrogen gas (H2), hydrogen sulfide (H2S), organic compounds

Methanogens (Archaea)

•are group of methane-producing archaea •Oxidize H2 gas to generate ATP. •CO2 as terminal electron acceptor: smaller energy yield than other electron acceptors. •Very sensitive to O2 •Sewage, swamps, marine sediments, rice paddies, digestive tracts. •Cows produce ~10 ft3/day

Chemoorganotrophs

•oxidize organic compounds (for example, glucose) to obtain energy

Chemolithotrophs

•oxidize reduced inorganic chemicals to obtain energy. • Ex: H2 (gas)

purple bacteria

•photosystem similar to photosystem II

Non-cyclic photophosphorylation

-Produces both ATP and reducing power -Electrons from photosystem II drive photophosphorylation -Electrons are then donated to photosystem I -Photosystem II replenishes electrons by splitting water -Generates oxygen (process is oxygenic) -Electrons from photosystem I reduce NADP+ to NADPH

Light-independent reactions (dark reactions)

-Use ATP to synthesize organic compounds -Involves carbon fixation

Genus Propionibacterium

Anaerobic Chemoorganotrophs - Fermentation •Produce propionic acid via fermentation • Can also ferment lactic acid • Swiss cheese (propionic acid for taste, CO2 for holes) • Obligate anaerobe

Clostridium

Anaerobic Chemoorganotrophs - Fermentation •are Gram-positive rods (obligate anaerobes) • Common in soils; vegetative cells live in anaerobic microenvironments created by aerobes consuming O2 • Endospores tolerate O2 • Some cause diseases (tetanus, gas gangrene, botulism...)

Lactic Acid Bacteria (aerotolerant anaerobes)

Anaerobic Chemoorganotrophs - Fermentation •produce lactic acid • Most can grow in aerobic environments; but only ferment • Lack catalase • S. thermophilus used to make yogurt • Streptococcus inhabit oral cavity Some pathogens (ex: S. pyogenes, strep throat)

anoxic

Atmosphere ____ for first ~1.5 billion years that prokaryotes inhabited earth.

Light reactions (light-dependent reactions)

Capture energy and convert it to ATP

carbon fixation

Chemolithoautotrophs and photoautotrophs use CO2 to synthesize organic compounds:

anaerobic respiration; fermentation

Early chemotrophs likely used ____ and ___

pigments

are located in protein complexes

Colors of photosynthetic organisms

are those of wavelengths reflected by pigments

Co2 and sulfur

Anaerobes use alternative electron acceptor like

Light dependent reactions: cyanobacteria and eukaryotes

Two distinct photosystems (I and II) 1. Cyclic Photophosphorylation 2. Non-cyclic photophosphorylation

Desulfovibrio

What bacteria is the most studied in the anaerobic chemoorganotrophs group?

Its a green house gas that forms layer on top of the atmosphere and keeps heat and trap it in environment.

Why is methane important for environment?

1. Antennae pigments and 2. Reaction center pigments

Within the photosystems, pigments can function as:

Lactobacillus (lactic acid bacteria)

rod-shaped, common in mouth and vagina

Anaerobic Chemolithotrophs

some are bacteria that inhabit aquatic environments

Chemolithoautotrophs and photoautotrophs

use CO2 to synthesize organic compounds: carbon fixation

Lactococcus species (lactic acid bacteria)

used to make cheese

Sulfur- and Sulfate-Reducing Bacteria

• Important in sulfur cycle - sulfur is used as a terminal electron acceptor • Produce hydrogen sulfide (rotten-egg smell) • H2S is corrosive to metals • At least a dozen recognized genera of bacteria (Desulfovibrio) and some archaea