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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

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slide1

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

slide2

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

slide3

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

slide4

Some organisms use organic material for

energy: organotrophs

Some use inorganic material: lithotrophs

Anaerobic lithotrophs may have been among the

earliest on Earth

slide5

Where do anaerobic environments exist today?

Soils: aerobes consume existing oxygen

Aquatic environments

Various internal environments

Obligate anaerobes are killed by oxygen

slide6

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

slide7

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

slide9

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.

slide11

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)

slide12

“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

Bacteriochlorophyll 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

slide13

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

Winogradsky columns are useful

slide14

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

slide17

Overgrowth of cyanobacteria can produce

nuisance “blooms”

Algae can do this, too

slide18

Aerobic chemolithotrophs

Oxidize sulfur, nitrogen, hydrogen

Sulfur oxidizers: generate H2SO4

may be filamentous or unicellular

contribute 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)

slide19

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

slide20

Facultative anaerobes

Corynebacterium (genus)

Enterobacteriaceae (family)

slide21

How do bacteria survive in so many different

environments?

Resistance stages

endospores (Clostridium, Bacillus)

soil bacteria

cysts (Azotobacter)

nitrogen fixers

fruiting bodies (Myxobacteria)

decomposers

filaments (Streptomyces)

produce antibiotics

slide22

Aquatic bacteria- nutrients are scarce

Sheathed, swarmers

attachment; movement to a more favorable

location

Caulobacteria, Hyphomicrbium- specialized

attachment

slide24

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

slide25

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

slide26

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

slide27

Archaea- “extreme” bacteria

Euryarchaeota- methanogens; extreme

halophiles (salt-loving bacteria)

membranes contain bacteriorhodopsin

(enables them to obtain energy from

sunlight)

Crenarchaeota- both groups contain extreme

thermophiles

some generate methane

some reduce sulfur

some are thermophilic acidophiles

slide28

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