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
