Diversity of prokaryotes

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Diversity of prokaryotes In morphology In
habitat In metabolism Basics of
metabolism energy source (of electrons,
ultimately used for ATP synthesis) electrons
are eventually transferred to a terminal
electron acceptor (oxygen for us) many
prokaryotes can use different terminal electron
acceptors
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Where does the energy (i.e., electrons) come
from? Some organisms use sunlight can use
CO2 to make sugar phototrophs Other organisms
use organic sources (like sugar!)
heterotrophs Prokaryotes can be classified
further based on carbon source and energy source
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Aerobes- terminal electron acceptor is
oxygen most efficient Anaerobes- inorganic
molecule is terminal electron acceptor (e.g.,
S, SO4-, NO3- or NO2-) less efficient than
aerobic respiration Fermenters- use organic
molecule as terminal electron acceptor least
efficient
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Some organisms use organic material for energy
organotrophs Some use inorganic material
lithotrophs Anaerobic lithotrophs may have been
among the earliest on Earth
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Where do anaerobic environments exist
today? Soils aerobes consume existing
oxygen Aquatic environments Various internal
environments Obligate anaerobes are killed by
oxygen
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Anaerobic chemolithotrophs Oxidize inorganic
molecules like hydrogen gas (and produce
what?) Use carbon dioxide or sulfur as electron
acceptor Methanogens- produce methane and
water grow in sewage, intestinal tracts,
etc. Hard to culture, but may be a significant
alternative energy source
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Anaerobic chemoorganotrophs Eubacteria-
high-sulfur-content mud often found in
communities with other bacteria help cycle
sulfur- what is its use in the environment? how
do we know when sulfur is being
metabolized? Archaea hyperthermophiles
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Anaerobic chemoorganotrophic fermenters Do NOT
use Krebs cycle or electron transport in ATP
synthesis End products vary among
species Clostridium- ferment many compounds and
produce many different end products obligate
anaerobes Lactic acid bacteria- OBLIGATE
fermenters produce lactic acid even if oxygen
is present Streptococcus, Lactobacillus, etc.
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Lactobacillus, Lactococcus important
in commercial fermentation processes Yeast-
bread, beer, wine Lactose fermenters- cheese,
yogurt Propionibacterium- also used in
cheese produciton makes CO2 (like yeast)
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anoxygenic phototrophs Usually found in
aquatic habitats shallow enough to obtain light
for energy do NOT use water as electron source
therefore do not produce oxygen Bacteriochlorop
hyll absorbs wavelengths of light that
penetrate water Purple sulfur bacteria use
H2S Purple nonsulfur bacteria do not more
diverse metabolically (and in habitat) Pigments
contained within cell membrane
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Green bacteria pigments contained within
chlorosomes sulfur and non-sulfur forms Can
also grow in the dark Other such organisms have
been found, but are harder to observe Winogradsk
y columns are useful
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Oxygenic phototrophs cyanobacteria Essential as
primary producers Morphologically diverse-
shapes, mobility, presence of sheaths,
etc. Contain chlorophyll and psychobiliproteins
to harvest energy from light Nitrogen-fixing
cyanobacteria fix N2 as well as CO2 from the
atmosphere Enzyme is contained within a
protective heterocyst
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Heterocyst protects enzyme from oxygen
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Overgrowth of cyanobacteria can produce nuisance
blooms
Algae can do this, too
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Aerobic chemolithotrophs Oxidize sulfur,
nitrogen, hydrogen Sulfur oxidizers generate
H2SO4 may be filamentous or unicellular contribu
te to acid runoff (Thiobacillus) some can
oxidize other metals Nitrifiers- help cycle
nitrogen in soil oxidize ammonium, nitrite
(nitrate is less toxic, can be taken up by
plants)
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Aerobic chemoorganotrophs some are ubiquitous,
some are specialized May be obligate aerobes or
facultative anaerobes Obligate aerobes cannot
ferment molecules for energy Micrococcus,
Mycobacterium, Pseudomonas Thermus-
extremophile Deinococcus- radiation- resistant
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Facultative anaerobes Corynebacterium
(genus) Enterobacteriaceae (family)
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How do bacteria survive in so many
different environments? Resistance
stages endospores (Clostridium, Bacillus) soil
bacteria cysts (Azotobacter) nitrogen
fixers fruiting bodies (Myxobacteria) decompose
rs filaments (Streptomyces) produce antibiotics
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Aquatic bacteria- nutrients are scarce Sheathed,
swarmers attachment movement to a more
favorable location Caulobacteria,
Hyphomicrbium- specialized attachment
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Parasitic bacteria Bdellovibrio
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Bioluminescent bacteria Emit light- when enough
bacteria are present WHY?? Symbiotic?- host
provides nutrients it provides some advantage
(squid, flashlight fish) Legionella- can inhabit
protozoa found in ventilation systems
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Bacteria and their animal hosts On skin-
Staphylococcus On mucous membranes respiratory-
Streptococcus, Lactobacillus many reside in GI
tract (How do they get there?) Many organisms of
diverse morphology and microenvironment
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Obligate intracellular parasites Lack full
biosynthetic capacity Rickettsia (vector-borne
ticks, lice) Coxiella (shed by one animal,
inhaled by another). May also be
vector-borne Chlamydia (person-to-person
contact) unusual physical and growth features
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Archaea- extreme bacteria Euryarchaeota-
methanogens extreme halophiles (salt-loving
bacteria) membranes contain bacteriorhodopsin (e
nables them to obtain energy from sunlight) Cren
archaeota- both groups contain extreme thermophil
es some generate methane some reduce
sulfur some are thermophilic acidophiles
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Summary bacteria can be found just about
anywhere on Earth! we sue this information to
help identify microorganisms Questions
about evolution (when did they appear what can
they tell us about conditions on
ancient Earth?) their role in maintaining
ecological balance metabolic products of
interest colonization of living organisms
pathogenesis treatment