THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• HOW DID LIFE ORIGINATE?
– SPONTANEOUS GENERATION
• LIFE ARISING FROM NON-LIVING MATTER
• LONG BELIEVED AS THE ACCEPTED EXPLANATION OF
ORIGINATION OF LIFE
• EXPERIMENTS EVENTUALLY SHOWED IT TO BE
IMPOSSIBLE
– ORIGINATION OF LIFE HAD TO BE A STEP-WISE
PROCESS
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• MILLER AND
UREY’S
EXPERIMENT
– ATTEMPTED TO
EXPLAIN/SHOW
HOW EARLY
EARTH COULD
HAVE GIVEN RISE
TO ORGANIC
COMPOUNDS
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• THE FIRST POLYMERS FORMED ON HOT ROCKS
OR CLAY
– EXPERIMENTS HAVE SHOWN HEAT ENERGY ON
HOT SURFACES PROVIDES SUFFICIENT ACTIVATION
ENERGY FOR DEHYDRATION SYNTHESIS
REACTIONS
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• THE FIRST GENETIC MATERIAL WAS PROBABLY
RNA
– WHY?
– RIBOZYMES
• RNA THAT ACTED AS
ENZYMES
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• MOLECULAR COOPERATIVES ENCLOSED BY
MEMBRANES PROBABLY PRECEDED THE FIRST
REAL CELLS
– EXPERIMENTS HAVE SHOWN THAT IN AQUEOUS
ENVIRONMENTS, CERTAIN KINDS OF MOLECULES,
INCLUDING LIPIDS AND POLYPEPTIDES, CAN SELFASSEMBLE INTO MICROSCOPIC SPHERES FILLED
WITH FLUID
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• PROKARYOTES WERE PROBABLY THE FIRST
FORMS OF LIFE BECAUSE…
– SIMPLEST FORM OF LIFE (UNICELLULAR
PROKARYOTE)
– HAVE INHABITED EARTH FOR BILLIONS OF YEARS
– IMMENSE NUMBER OF PROKARYOTES EXIST
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• TWO MAIN FORMS OF PROKARYOTES
– ARCHAEA VS. BACTERIA (EUBACTERIA)
– EXTREMELY DIFFERENT FORMS OF BACTERIA
– GENETIC DATA SUPPORTS 3 DOMAIN SYSTEM
– BACTERIAL CELL WALLS CONTAIN
PEPTIDOGLYCAN; NOT FOUND IN ARCHAEA
– BACTERIAS COME IN A VARIETY OF
SHAPES/STRUCTURES
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• BACTERIAS
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• PROKARYOTES OBTAIN NOURISHMENT IN A
VARIETY OF WAYS
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• PROKARYOTIC NOURISHMENT
– “HETEROTROPH HYPOTHESIS” VS
CHEMOAUTOTROPHIC HYPOTHESIS
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• ARCHAEA CAME FIRST BECAUSE
– THRIVE IN EXTREME ENVIRONMENTS AND THE
OCEAN
• EXTREME HALOPHILES  SALT LOVERS
• EXTREME THERMOPHILES  HEAT LOVERS
• METHANOGENS  LIVE IN ANAEROBIC
ENVIRONMENTS AND GIVE OFF METHANE AS A WASTE
PRODUCT
– JUST BECAUSE THEY CAME FIRST, DOESN’T MEAN
THEY ARE SO OLD THEY ARE EXTINCT!! (ANCIENT
DOES NOT EQUAL EXTINCT)
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• DIVERSE STRUCTURAL FEATURES HELP
PROKARYOTES THRIVE ALMOST ANYWHERE
– PROKARYOTIC FLAGELLUM
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• DIVERSE STRUCTURAL FEATURES HELP
PROKARYOTES THRIVE ALMOST EVERYWHERE
– PILI  TINY APPENDAGES THAT HELP BACTERIA
ATTACH TO EACH OTHER AND SURFACES
– ENDOSPORES  SPECIALIZED
“INNER CELL” THAT CAN
SURVIVE HARSH
CONDITIONS, MAY
REMAIN
DORMANT FOR
CENTURIES
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• CYANOBACTERIA (A.K.A. BLUE-GREEN ALGAE)
– SPECIFIC TYPE OF
BACTERIAL CELL THAT
CAN PERFORM
PHOTOSYNTHESIS
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• SOME BACTERIA CAUSE DISEASE
– PATHOGENS  DISEASE-CAUSING AGENTS
– EXOTOXINS  TOXIC PROTEINS SECRETED BY
BACTERIAL CELLS
– ENDOTOXINS  COMPOUNDS OF THE CELL WALLS OF
CERTAIN BACTERIA
• SANITATION, ANTIBIOTICS, EDUCATION ARE WAYS
TO DEFEND AGAINST BACTERIAL DISEASE
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• DISEASE CAUSING BACTERIA
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• BACTERIA CAN BE USED AS BIOLOGICAL
WEAPONS
• **PATHOGENIC PROKARYOTES ARE IN THE
MINORITY, MOST PROKARYOTES ARE VITAL TO
OUR WELL BEING
– EXAMPLES:
• NITRIFYING BACTERIA,
DECOMPOSERS, ETC…
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• THE EUKARYOTIC CELL PROBABLY ORIGINATED
AS A COMMUNITY OF PROKARYOTES
– MEMBRANE INFOLDING  THE ORGANELLES
(NOT MITOCHONDRIA AND CHLOROPLAST) ARISE
FROM THE INWARD FOLDS OF THE PLASMA
MEMBRANE OF A PROKARYOTIC CELL
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• THE EUKARYOTIC CELL
PROBABLY ORIGINATED AS A
COMMUNITY OF
PROKARYOTES
– ENDOSYMBIOSIS  ONE
SPECIES LIVING WITHIN
ANOTHER
– EXAMPLES??
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• PROTISTS
– A DIVERSE GROUP OF MOSTLY
UNICELLULAR EUKARYOTES;
SOME PROTISTS ARE
PHOTOSYNTHETIC, OTHERS
ARE HETEROTROPHIC
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
TWO GENERIC TYPES OF PROTISTS
• ANIMAL-LIKE PROTISTS
•
• A.K.A. PROTOZOA
•
• PROTISTS THAT LIVE
•
PRIMARILY BY INGESTING
FOOD, A HETEROTROPHIC
MODE OF NUTRITION THAT
IS “ANIMAL-LIKE”
PLANT-LIKE PROTISTS
A.K.A. ALGAE
PROTISTS THAT LIVE BY
SYNTHESIZING FOOD FROM
CARBON DIOXIDE AND
WATER, AN AUTOTROPHIC
MODE OF NUTRITION THAT
IS “PLANT-LIKE”
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• GROUPS OF PROTISTS
– FLAGELLATES
– PSEUDOPODIA
– CILIATES
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• PHOTOSYNTHETIC PROTISTS ARE CALLED
ALGAE
– ALGAE  DEF??
– DINOFLAGELLATES
– DIATOMS
– GREEN ALGAE
• PROBABLY MOST INTERESTING EVOLUTIONARILY,
BECAUSE IT IS PROBABLY THE ANCESTOR OF LAND
PLANTS
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• SEAWEEDS ARE MULTICELLULAR MARINE
ALGAE
– THREE TYPES OF SEAWEED
• BROWN ALGAE
– EXAMPLE: KELP  CAN GROW
ABOUT 100 METERS)
• RED ALGAE
– SEE PICTURE TO RIGHT
• GREEN ALGAE
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• MULTICELLULAR LIFE MAY HAVE EVOLVED
FROM COLONIAL PROTISTS
THE ORIGIN AND EVOLUTION OF
MICROBIAL LIFE
• SO THE SIMPLE
LIFE CAME
FIRST…BUT
WHAT CAME
NEXT??
• THAT’S WHAT
NEXT CHAPTER
IS ALL ABOUT