Download The Evolution of Microbial Life: Prokaryotes, Protista - Jocha

The Evolution of Microbial Life: Prokaryotes, Protista
The Evolution of Life
Major Episodes in the History of Life
 Earth was formed about 4.6 billion years ago.
 Prokaryotes
(1) Evolved by 3.5 billion years ago
(2) Began oxygen production about 2.7 billion years ago
 Lived alone for almost 2 billion years
 Continue in great abundance today
(1)
(2)
(3)
(4)
(5)
(3) Single-celled eukaryotes first evolved about 2.1 billion years ago.
(4) Multicellular eukaryotes first evolved at least 1.2 billion years ago.
(5) Modern humans appeared about 200,000 years ago!
Prokaryotes: Bacteria & Archaea
 Are the simplest, single celled, organisms living on Earth today…
 the most abundant…
 and the most diverse!
Domain
Domain
 It has been calculated that the
collective biomass of all
prokaryotes is at least 10 times
that of Eukaryotes
Domain
Kingdoms
1
The Evolution of Microbial Life: Prokaryotes, Protista
 Prokaryotes live deep within the Earth and in habitats too cold, too hot,
too salty, too acidic, or too alkaline for any eukaryote to survive.
Deep Sea chimneys (12,000 feet deep)
Temperature above 170F!
Extremophile Archaea
Hot springs
Head of a pin
Extremophile Archaea
Halophiles
(Extremely salty
Environments)
Salt-producing ponds,
San Francisco bay, 5-8
times more salty than sea
water!
Main Prokaryotic characteristics
1) Prokaryotes lack nuclei
2) Have cell walls exterior to their
plasma membranes
3) Cell size: Much smaller than
Eukaryotes: Bacteria <1μm,
Eukaryotes >10 μm
4) DNA: No chromosomes in Prokaryotes
5) Cell division: Asexual by binary fission in bacteria, variable in Eukaryotes
6) Internal compartmentalization: Lack other membrane-enclosed
organelles, only ribosomes
7) Metabolic diversity: Cellular respiration and synthesis of organic
compounds can be done in different ways in prokaryotes
2
The Evolution of Microbial Life: Prokaryotes, Protista
Prokaryotic Nutrition
 We can group all organisms in four major modes of nutrition based on…
 Energy source (phototroph versus chemotroph) and
 Carbon source (autotroph versus heterotroph)
Prokaryotes
Plants
Algae
Cyanobacteria
Photosynthesis
All
Eukaryotes
Prokaryotes
Prokaryotes
Cellular
Respiration
Why are prokaryotes so diverse?

Two strains of Escherichia Coli are genetically
more different than you and a platypus!
Binary fission

Genetic variability ultimately depends on…
(1) How fast reproduction takes place
More reproduction means more DNA replication,
which means high mutational rates (glitches
while copying the DNA)
 Prokaryotes reproduce by binary
fission at very high rates if conditions
are favorable.
A few antibiotic resistant individuals in the
“population” can rapidly increase in a short
time and be transferred from one host to
another
3
The Evolution of Microbial Life: Prokaryotes, Protista
(2) Ways of shuffling the DNA between organisms
Transformation is a process by which bacterial
cells “scavenge” DNA from their environment
(usually from bacteria that have died)

Conjugation
allows
prokaryotes to
directly exchange
DNA between
individuals (similar
to crossing over in
eukaryotes!)

Transduction
is when a virus
containing
bacterial DNA
passes it to
another
bacterium when
infecting it

Many prokaryotes form endospores
 Some prokaryotes
 Form endospores, thick-coated, protective cells that are produced within
the cells when they are exposed to unfavorable conditions
 Can survive very harsh conditions for extended periods, even centuries
 Most endospores can survive in boiling water

What prevents a prokaryotic colony to grow indefinitely?

Nutrient supply

Accumulation of metabolic wastes

Predation by other organisms
4
The Evolution of Microbial Life: Prokaryotes, Protista
Main Prokaryotic Roles in Ecosystems
Ch 5
Nitrogen fixation & Nitrification
 Nitrogen is needed for
proteins and nucleic
acids (DNA, RNA)
 Prokaryotes are the
only living things that
can convert
atmospheric N2 to a
form that can be used
by other organisms,
such as NH3
(Ammonia)
Decomposition
Prokaryotes
Prokaryotes
Prokaryotes
 Is a chemical recycling
 Prokaryotes and fungi are
the main decomposers in
all ecosystems
Trichodesmium, also called sea sawdust, is a genus
of filamentous cyanobacteria (photosynthetic) that
also fixes nitrogen. They are found in nutrient poor
tropical and subtropical ocean waters
5
The Evolution of Microbial Life: Prokaryotes, Protista
Photosynthesis
 Together with eukaryotic microscopic
algae (phytoplankton)…
 Cyanobacteria (colonial blue-green
bacteria) are producers that release
more than 60% of the O2 present in out
atmosphere
Mutualistic symbionts
 Are very important in the deep sea by producing
bioluminescence in specific organs of many deep
sea organisms. This in turn is used for…
 Avoiding predators
 Attracting prey
 Signaling potential mates
 Herbivores that house bacteria in their digestive system that
help break down the cellulose
 Bacteria in humans’ large intestine produce vitamins
Opportunistic pathogens

Some bacteria that are normal flora can also cause disease if the
person’s resistance is low, e.g. pneumonia
Harmful (Pathogenic) bacteria


Alteration of normal physiology: Bacteria cause
the destruction of the tissue, e.g. strep throat,
pneumonia, tuberculosis, leprosy
Leprosy
Bacteria produce endotoxins or exotoxins:
 Endo: chemical components of cell wall
 Exo: proteins secreted by bacteria
Human diseases:
 botulism (toxins present in food or drinks)
 tetanus and diphtheria (bacteria grow
inside the host)

Plant diseases: e.g. Apples: tree branches are killed, Citrus
plants (lemon, orange, etc.): cancer-like growths. Fruit
production is lowered
6
The Evolution of Microbial Life: Prokaryotes, Protista
Kingdom Protista
 What is a protist?
 Whatever thing that is alive, is a eukaryote, and does not fit inside the other
groups!
 they can be single celled (protozoa, algae) or multicellular (more than 180
feet in some seaweeds)
ECOLOGICAL CLASSIFICATION
Plant-like: autotrophic
phytoplankton
Seaweeds 
Animal-like: heterotrophic
(phagotrophic or ingestive)
protozoa
Fungus-like: heterotrophic
(absorptive)
24
Slime molds and water molds
13
Differences between Animal-like and Fungus-like
 Both are heterotrophs (cannot make their own food)
 An animal like protist or protozoa (and
real animal cells as well)
 Has only a flexible cell membrane
 Will move big molecules inside the
cell by means of phagocytosis
(endocytosis)
Food!
(bacterium)
phagocytosis
 A fungus like protist (and real fungi cells
as well)
 Has a rigid cell wall that prevent any
change in shape
 Will move big molecules inside the
cell by means of absorption of pre
digested food (using exoenzymes)
Food! (bacterium)
(1) exoenzymes
(2) Extra
cellular
digestion
(3) Absorption
to the cell
24
14
7
The Evolution of Microbial Life: Prokaryotes, Protista
Algae:
Algae
Plant-like Protists
 Most algae have a cellulose cell wall. They
have chlorophyll inside chloroplasts and carry
on photosynthesis.
 Plankton: small floating organisms 
Phytoplankton photosynthetic algae that forms
the basis for most aquatic food chains.
Microscopic
(Phytoplankton)
Others
Multicellular
(Seaweeds)
Red
algae
Diatoms
1) Microscopic algae
Dinoflagellates
Microscopic: Phytoplankton
Green
algae
Brown
algae
Diatoms
Diatoms the most common eukaryotic
producers in marine and
freshwater ecosystems
 With a unique two-part, glass-like wall of
hydrated silica
 Provides protection from predators
 Can withstand pressure up to 1.4
million kg/m2
24
15
Dinoflagellates
 Aquatic photoautotrophs that prefer warmer waters
 (2nd) components of both marine and freshwater “net” phytoplankton
 Shape is reinforced by internal plates of cellulose
 Two flagella, make them spin as they move through the water
Mutualism with coral polyps
 Dinoflagellates photosynthetic output
 Is food for reef communities
Bioluminescence
ATP driven chemical reaction
 Creates a glow when water is
agitated and dinoflagellates are
in great number
Corals provide
raw materials
algae need in
order to make
photosynthesis
Polyp’s tentacles
with symbionts
Dinoflagellates
Coral body
Red Tides
 Rapid growth of some dinoflagellates and other
microbes
 Is responsible for causing “red tides,” some
of which can be toxic to humans
 Color appears red because of carotenoids
24
Red tide
16
8
The Evolution of Microbial Life: Prokaryotes, Protista
2) Multicellular algae
 Macroscopic: Seaweeds
Color depends on the type
 Brown, red, and green seaweeds and amount of
photosynthetic pigments
Economic importance
 Some “red” species are important commercially
because they produce agar, used to grow bacteria
in a laboratory, and also carrageenin, which is
used in paint, cosmetics, and baking
 Some “brown” species produce alginates, used
as stabilizers in frozen desserts, emulsifiers in
salad dressings, etc.
Brown algae
(biggest of all:
kelps)
Green algae
Red algae
24
(mostly
macroscopic)
17
Protozoa: Animal-like Protists
 Unicellular and Heterotrophs (ingestive or phagotrophic, like us!)
 Most of them are free-living, some are parasites, some mutualists
Some
Protozoa
Flagellates
Move by flagella
Amoebozoans
Sporozoans
Move by pseudopods
all are parasites
Amoeba
Some are parasites
Entamoeba histolytica, is
spread by means of
contaminated water or
food: causes amebic
dysentery. 100,000 people
die worldwide every year
3rd most importance
disease for humans
Ciliates
Move by cilia
Paramecium
Babesiosis (Babesia)
Malaria (Plasmodium)
Cryptosporidiosis
(Cryptosporidium)
Coccidian diseases
(Coccidian parasites infect
the intestinal tracts of
animals)
Ciliates are the most structurally
protozoan
24complex
Tintinnids
18
9
The Evolution of Microbial Life: Prokaryotes, Protista

The protozoa plasmodium causes malaria (1st disease in importance for humans)
Up to 300 million people become sick with malaria per year and 2 to 4
million die.

Malaria is transmitted
by mosquitoes (vectors)

Sexual stage of the
life cycle takes place in
the mosquito.

Malaria in red blood cells
24
Fungus-like Protists
19
Fungus-like
 Heterotrophs (absorptive)
 Spores for asexual reproduction
Slime molds
(myxomycota)
Water molds
(Oomycota)
 Were previously included in
Fungi
 But these guys…
 Are 2N (Fungi are
N=haploid)
 Cell wall of cellulose
(Fungi is chitin)
 Amoeboid reproductive
stage (different in fungi)
Parasitic water molds damage
fish and many crop plants
• An example is the Irish potato
famine in 1845 and 1847,
which destroyed the potato
crops.
 Decomposers or
parasites
 A “Giant amoeba”, whose
nucleus and organelles
have divided repeatedly
within a single large cell
 Unicellular and
multicellular stages
•Water molds can be
saprophytes and
parasites in aquatic
and terrestrial
ecosystems
24
20
10
The Evolution of Microbial Life: Prokaryotes, Protista
Oomycota - Peronosporales
 Late blight of potato caused by Phytophthora infestans
 Turns the stalk and stem to black slime
 Irish famine of 1847
1 million people died
1 million (at least) had to leave
Ireland
 Today
 15% of losses in North America
Phytophthora infestans - people preparing to
leave Ireland forever during the potato famine
1847
 70% in some areas of Russia
where pesticides are not available
24
21
11