PROKARYOTES AND THE ORIGINS OF METABOLIC DIVERSITY CHAPTER 27 PROKARYOTES AND THE ORIGINS OF METABOLIC DIVERSITY

I. THE WORLD OF PROKARYOTES THEY’RE (ALMOST) EVERYWHERE! AN OVERVIEW OF PROKARYOTIC LIFE PROKARYOTES WERE THE FIRST ORGANISMS, AND THEY PERSIST TODAY AS THE MOST NUMEROUS AND PERVASIVE OF ALL LIVING THINGS.

B. BACTERIA AND ARCHAEA ARE THE TWO MAIN BRANCHES OF PROKARYOTIC EVOLUTION CLASSIFICATION OF PROKARYOTES IN TWO DOMAINS, BACTERIA AND ARCHAEA, AND ALL EUKARYOTES IN A THIRD DOMAIN, EUKARYA, SIGNIFIES THAT ORGANISMS PROBABLY HAVE BEEN EVOLVING IN THREE INDEPENDENT LINEAGES FOR OVER 1.5 BILLION YEARS.

II. STRUCTURE, FUNCTION, AND REPRODUCTION INTRODUCTION PROKARYOTES ARE GENERALLY SINGLE-CELLED ORGANISMS, ALTHOUGH SOME OCCUR AS AGGREGATES, COLONIES, OR SIMPLE MULTICELLULAR FORMS. MOST PROKARYOTES ARE SPHERICAL (COCCI), ROD-SHAPED (BACILLI), OR HELICAL IN SHAPE.

A. MANY PROKARYOTES ARE MOTILE MOTILE BACTERIA PROPEL THEMSELVES BY FLAGELLA, USE FLAGELLA-LIKE FILAMENTS POSITIONED INSIDE THE CELL WALL (SPIROCHETES), OR GLIDE ON SLIME SECRETIONS.

A.    THE CELLULAR AND GENOMIC ORGANIZATION OF PROKARYOTES IS FUNDAMENTALLY DIFFERENT FROM THAT OF EUKARYOTES THE CELLS OF PROKARYOTES ARE NOT COMPARTMENTALIZED BY INTERNAL MEMBRANES, BUT INFOLDINGS OF THE PLASMA MEMBRANE IN SOME SPECIES PROVIDE INTERNAL MEMBRANE SURFACES. THE GENOME OF PROKARYOTES IS A SINGLE CIRCULAR DNA MOLECULE UNBOUNDED BY A MEMBRANE. SMALLER SEPARATE RINGS OF DNA CALLED PLASMIDS CODE FOR SPECIAL METABOLIC PATHWAYS AND RESISTANCE TO ANTIBIOTICS IN SOME SPECIES.

C. POPULATIONS OF PROKARYOTES GROW AND ADAPT RAPIDLY PROKARYOTES GROW IN NUMBER AND COLONY SIZE BY BINARY FISSION. GENETIC VARIATION OCCURS THROUGH MUTATION AND THROUGH GENE TRANSFER BY TRANSFORMATION, CONJUGATION, OR VIRAL TRANSDUCTION.

III. NUTRITIONAL AND METABOLIC DIVERSITY ALL MAJOR TYPES OF NUTRITION AND METABOLISM EVOLVED AMONG PROKARYOTES, WHICH ARE THE MOST METABOLICALLY DIVERSE ORGANISMS ON EARTH.

A. PROKARYOTES CAN BE GROUPED INTO FOUR CATEGORIES ACCORDING TO HOW THEY OBTAIN ENERGY AND CARBON PHOTOAUTOTROPHS USE LIGHT ENERGY, AND CHEMOAUTOTROPHS USE INORGANIC SUBSTANCES TO SYNTHESIZE THEIR ORGANIC COMPOUNDS FROM CARBON DIOXIDE. PHOTOHETEROTROPHS USE LIGHT ENERGY AND REQUIRE ORGANIC MOLECULES. MOST PROKARYOTES ARE CHEMOHETEROTROPHS, WHICH REQUIRE ORGANIC MOLECULES AS A SOURCE OF BOTH ENERGY AND CARBON. OBLIGATE AEROBES REQUIRE 02 OBLIGATE ANAEROBES ARE POISONED BY IT FACULTATIVE ANAEROBES CAN SURVIVE WITH OR WITHOUT 02.

CLASSIFICATION MODE OF NUTRITION AUTOTROPHS HETEROTROPHS PHOTO-AUTOTROPHS: FROM LIGHT CHEMO-AUTOTROPHS: FROM CHEMICALS HETEROTROPHS PARASITES: FROM HOST SAPROBES (DECOMPOSERS): FROM DECAY OF ORGANIC MATTER

AVAILABILITY OF OXYGEN OBLIGATE AEROBES: MUST HAVE O2 OBLIGATE ANAEROBES: CANNOT HAVE O2 FACULTATIVE ANAEROBE: GROWS WITH O2, BUT DOES NOT REQUIRE O2 TO LIVE

CLASSIFICATION BY SHAPE COCCI (SPHERICAL) BACILLI (ROD SHAPED) SPIRILLA (SPIRAL) CLASSICATION BY MOVEMENT FLAGELLAR GLIDING CORKSCREW CLASSICATION BY POSITION OF FLAGELLA APICAL: “FRONT” POSTERIOR: “BACK” INTERNAL

GROUPS OF ARCHAEBACTERIA METHANOGENS: ANAEROBIC, HETEROTROPHIC, PRODUCE METHANE EXTREME HALOPHILES : “SALT LOVERS” THERMOACIDOPHILES: “HEAT AND ACID LOVERS”

GROUPS OF EUBACTERIA CYANOBACTERIA: PHOTOSYNTHETIC, NITROGEN-FIXING (N2 CONVERTED TO NH3) CHEMOSYNTHETIC: AUTOTROPHS, NITRIFYING (NO2- CONVERTED TO NO3-) NITROGEN-FIXING BACTERIA: HETEROTROPHS, MUTUALISTIC W/PLANTS SPIROCHETES: COILED BACTERIA, CORKSCREW MOTION, INTERNAL FLAGELLA.