GOALS: Review characteristics of prokaryotic cells Describe how prokaryotic cells are classified Explain ecological roles & significance of prokaryotes Compare prokaryotic binary fission to eukaryotic mitosis Explain 4 mechanisms for how bacteria create new genetic combinations Describe shape and cell wall structure of bacteria

Characteristics of Prokaryotic Cells Lack nucleus -->have ‘nucleoid region’ Have one, circular piece of DNA with all genes Contain a cell wall made of peptidoglycan Have ribosomes Lack membrane-bound organelles May have a flagellum, but it’s not made of microtubules like those of eukaryotes What else?

Classification of Prokaryotes- 1 million species(est)-4,000 named There are two domains of prokaryotic cells A domain is more inclusive than a kingdom Prokaryotic domains: –BACTERIA- Kingdom Eubacteria (true bacteria) –ARCHAEA- Archaea consists of Kingdom Archaea Figure 27.2

LIFE IN EXTREME ENVIRONMENTS ARCHAEA Most of us have the tendency to think of life a a rather cozy affair, taking place at a pressure of one atmosphere, in an atmosphere of oxygen, at approximately neutral pH and temperature near that of our own bodies (37 oC). Indeed, most organisms have uniquely adapted to growth in this common environment. What is an extreme environment? a. Environments that usually contain physical or chemical factors that have traditionally used to kill microorganisms that spoil food and clothing and cause disease of animals and plants. b. An environment in which some organisms can \grow, whereas others cannot. thus, an extreme environment has a low species diversity with whole taxonomic groups missing. Extremophiles are microorganisms that have been shown to exist(growth) in more stringent conditions than do other organisms.

WHY STUDY THEM? Anatomically related to bacteria but possess biochemical and genetic properties similar to those of Eukaryotes. Extant hyperthermophiles live in environments that are thought to be similar to those that existed on earth 3.9 billion years ago (when life could have originated). a. Hot b. Reducing atmosphere (no oxygen) c. High levels of hydrogen and sulfurous compounds Paleobiological evidence that 400-million-year-old rocks contain chemical, physical, and anatomical imprints of ancient hydrothermal ecosystems (similar to todays hyperthermophiles).

Classification of Prokaryotes Domain Archaea consists of Kingdom Archaea –Bacteria of Kingdom Archaea are called extremophiles because they live in harsh environments –ACIDOPHILES: live in highly acidic environments –HALOPHILES: live in extremely salty environments –THERMOPHILES: live in extremely hot environments( C)(0-10 C) Thermus aquaticus lives in hot springs of Yellowstone National Park –METHANOGENS : derive energy by using CO 2 to oxidize H 2 to make CH 4 (methane)

MOST RESEARCH HAS BEEN CARRIED OUT WITH THERMOPHILIC MICROORGANISMS WHY HAS MOST OF THE RESEARCH FOCUSED ON THIS GROUP OF MICROORGANISMS? 1. Identify the clever biochemical and genetic ways that these organisms have found to adapt to high temperature environment.. gene regulation. unique protein structure 2. Direct utilization of these organisms and their products for industrial purposes.. Enzymes used in research (molecular cloning)TAQ. Enzymes used in medical diagnostic kits. Enzymes used for production of ethanol. Enzymes used for commercial purposes 3. Hyperthermophiles may be the oldest organisms still around. their natural habitats (associated with volcanic activity) have existed throughout most of the time in which organisms have been evolving on earth.

Domain Bacteria consists of Kingdom Eubacteria (true bacteria)

Ecology of Bacteria- Eubacteria Bacteria obtain energy in a variety of ways (table 27.1) Bacteria can be autotrophs –Photoautotrophs –Chemoautotrophs Bacteria can be heterotrophs –Photoheterotrophs –Chemoheterotrophs Chemo- = use inorganic chemicals as energy source CYANOBACTERIA: –First photoautotrophic organisms on Earth which produced oxygen as waste product and changed conditions of life on Early Earth

Ecology of Bacteria Bacteria interact with other organisms within their community –SAPROBES: C, N element cycling Denitrifying: NO > N 2 Pseudomonas Nitrifying: NH > NO 2 or NO 3 Nitrosomonas –PARASITES Pathogens - cause disease / illness in plants, animal, fungi –MUTUALISTIC Nitrogen fixing: N 2 --> NH 4 + Rhizobium –BIOREMEDIATION Metabolize petroleum from oil spills Sewage treatment –PHYTOPLANKTON & ZOOPLANKTON: base of food chains & food webs –BIOTECHNOLOGY & BIOCHEMICAL USES Copy human genes, make human proteins, make alcohol

Bacteria Morphology There are three main shapes of bacteria cells (fig 27.3) –Coccus = spherical –Bacillus = rod-shaped –Spirillum = helical Cells can be grouped: –Staphylo = clusters –Strepto = chains

Bacteria Morphology Prokaryotes have cell wall made of peptidoglycan (27.5) Peptidoglycan is composed of CHO & proteins There is >> variation in structure & composition of bacteria cell walls between Eubacteria & Archaea Some bacteria also possess a capsule & a pilus which allow bacteria to bind to substrates, swap genetic info, or block immune responses of hosts What is the function of the cell wall?

Peptidoglycan Molecular Structure

Bacteria Reproduction Bacteria reproduce asexually by BINARY FISSION. In ideal environments, bacteria can divide every 20 minutes! What is the selective advantage to such rapid reproduction? How does prokaryotic binary fission differ from eukaryotic mitosis?

Bacteria Reproduction Bacteria may swap genes and therefore alter their genetic make up What is selective advantage for obtaining new genes? CONJUGATION –Obtain plasmid or swap plasmid with another cell thru sex pilus TRANSFORMATION –Pick up naked DNA from environment TRANSDUCTION –Obtain new genes from viruses

ROLE OF BACTERIA 1. Responsible for creating properties of atmosphere and soils 2. Are autotrophic, photosynthetic and chemosynthetic, contribute to world carbon balance 3. Are heterotrophic and break down organic compounds 4. Few genera of bacteria are capable of fixing atmospheric nitrogen 5. Involved in industrial processes and chemical syntheses a.Produce acetic acid, vinegar, amino acids, enzymes b.Production of various milk products, bread and ethanol c.Antibiotics derived from bacterial sources 6. Genetic engineering applications

ROLE OF BACTERIA 1. Responsible for creating properties of atmosphere and soils 2. Are autotrophic, photosynthetic and chemosynthetic, contribute to world carbon balance 3. Are heterotrophic and break down organic compounds 4. Few genera of bacteria are capable of fixing atmospheric nitrogen 5. Involved in industrial processes and chemical syntheses a.Produce acetic acid, vinegar, amino acids, enzymes b.Production of various milk products, bread and ethanol c.Antibiotics derived from bacterial sources 6. Genetic engineering applications

III. PROKARYOTES( "before nucleus") VERSUS EUKARYOTES A. Structural Differences 1. Multicellularity: bacteria are fundamentally single-celled a.May adhere within matrix, some form filaments b.Few integrated activities between cells 2. Cell size: extremely small individual cell size 3. Chromosomes: non-membrane bound DNA is circular and lacks proteins 4. Cell division and genetic recombination a.Simple division via binary fission b.True sexual reproduction absent, genetic recombination irregular 5. Internal compartmentalization: Lack membrane-bound organelles a.Enzymes are bound to cell membrane b.Only organelles present are ribosome's B. Metabolic Diversity: 1. Eukaryotes exhibit only one form of photosynthesis 2. Bacteria exhibit several patterns of photosynthesis, aerobic and anaerobic 3. Bacteria undergo chemosynthesis and fix atmospheric nitrogen