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CAMPBELL BIOLOGY Outline TENTH EDITION Reece • Urry • Cain • Wasserman • Minorsky • Jackson 27 Bacteria and Archaea I. Categories of life A. Domains B. Eukaryote vs Prokaryote II. Domain Bacteria A. B. C. D. cell walls, structure Bacterial reproduction Nitrogen fixation Pathogenic bacteria III. Domain Archaea Lecture Presentation by Dr Burns NVC Biol 120 © 2014 Pearson Education, Inc. Copyright © 2009 Pearson Education, Inc. Why care about the small stuff Bacteria are important “nitrogen fixers” Bacteria and fungi are decomposers Some bacteria and algae can produce oxygen They are everywhere!! Some can produce disease Good website: http://www.bacteriamuseum.org/cms/ Prokaryotes Prokaryotes thrive almost everywhere, including places too acidic, salty, cold, or hot for most other organisms Most prokaryotes are microscopic, but what they lack in size they make up for in numbers There are more in a handful of fertile soil than the number of people who have ever lived Prokaryotes are divided into two domains: bacteria and archaea © 2011 Pearson Education, Inc. Bacteria in our bodies Bacteria are found naturally in our bodies including in our: Nasal cavity (nose) Large intestine On our skin Staphylococcus in the human nasal passage 1 Euprymna Scolopes have a symbiotic relationship with luminescent bacteria. Do prokaryotes have a nucleus 1. Yes 2. No Ye Photo courtesy of Margaret McFall-Ngai. 50% 50% 1. prokaryotic 2. eukaryotic yo ar s 50% N o The First Cells Are Domain Bacteria and Domain Archaea prokaryotic or eukaryotic? ok pr 50% tic eu ka o ry Microfossils are fossilized forms of microscopic life -Oldest are 3.5 billion years old tic The First Cells Stromatolites are mats of cyanobacterial cells that trap mineral deposits -Oldest are 2.7 billion years old Prokaryotes Domain Archaea – live in extreme environments Domain Bacteria (Eubacteria) Microorganisms are any small organism – too small to see with the naked eye include Pathogens – cause disease Most bacteria are not pathogens 2 Prokaryotic Characteristics 1. Unicellular 2. No membrane-bound nucleus, single chromosome and histone-like proteins found in nucleoid region 3. Lack membrane bound organelles 4. Contain ribosomes Prokaryotic Characteristics 5. Many have flagella 6. Cell wall present in many species Prokaryotes No membrane bound organelles including: nucleus, mitochondria, chloroplasts, endoplasmic reticulum, golgi complex, lysosomes. 7. Have plasma membrane 8. Reproduction by prokaryotic fission They do contain small ribosomes, storage granules, plasma membrane may be folded 9. Great metabolic diversity Domain Bacteria Prokarotes Categorized by 1. Shape 2. Cell wall type 3. Where they get their energy and their nutrients from. 4. Motility Molecular Classification Based on these molecular data, several prokaryotic groupings have been proposed Bergey’s Manual of Systematic Bacteriology Contains about 7,000 bacterial and archaeal species The three-domain (Woese) system of phylogeny is based on rRNA sequences 3 Molecular Classification Categories by shape Cocci – spherical (round ball) shaped, may be singly or in groups Bacilli – rod shaped, may occur as a single rod or as chains of rods Spirilla – helical, spiral shaped Prokaryotic Shapes Figure 27.2 Diverse nutritional and metabolic adaptations have evolved in prokaryotes Prokaryotes can be categorized by how they obtain energy and carbon Phototrophs obtain energy from light Chemotrophs obtain energy from chemicals Autotrophs require CO2 as a carbon source Heterotrophs require an organic nutrient to make organic compounds © 2011 Pearson Education, Inc. 1 m 1 m 3 m Most prokaryotes have one of 3 basic shapes Bacillus = Rod-shaped Coccus = Spherical Spirillum = Helical-shaped (a) Spherical (b) Rod-shaped (c) Spiral Diverse nutritional and metabolic adaptations have evolved in prokaryotes Energy and carbon sources are combined to give four major modes of nutrition: Photoautotrophy Chemoautotrophy Photoheterotrophy Chemoheterotrophy © 2011 Pearson Education, Inc. 4 Table 27.1 Nitrogen Metabolism Nitrogen is essential for the production of amino acids and nucleic acids Prokaryotes can metabolize nitrogen in a variety of ways In nitrogen fixation, some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3) © 2011 Pearson Education, Inc. Nitrogen Fixation Some bacteria are able to take nitrogen gas and fix it in the form that can be used by plants Rhizobium fixes nitrogen for plants like legumes. Legumes and Rhizobium live in a mutualistic relationship Rhizobium provide usable nitrogen Legumes provide sugar Rhizobium live inside legume cells in nodules Metabolic Cooperation Figure 27.14 Cooperation between prokaryotes allows them to use environmental resources they could not use as individual cells Photosynthetic cells In the cyanobacterium Anabaena, photosynthetic cells and nitrogen-fixing cells called heterocysts (or heterocytes) exchange metabolic products Heterocyst 20 m © 2011 Pearson Education, Inc. 5 Photoautotroph - cyanobacteria These organisms use the energy from the sun to fix carbon into a sugar from CO2 25% 25% 25% 25% 1. 2. 3. 4. Photoheterotrophs Chemoheterotrophs Photoautotrophs Chemoautotrophs Ph 31 et oh ot p ro ot er C h hs et oh em p ro ot er hs Ph oa ot s ph ro ot ut C h oa em s ph ro ot ut These organisms use the energy from inorganic compounds to fix carbon into a sugar from CO2 25% 25% 25% 25% 1. 2. 3. 4. Photoheterotrophs Chemoheterotrophs Photoautotrophs Chemoautotrophs Ph et oh ot p ro ot er C h hs et oh em p ro ot er hs Ph oa ot s ph ro ot ut C h oa em s ph ro ot ut Cell-Surface Structures An important feature of nearly all prokaryotic cells is their cell wall, which maintains cell shape, protects the cell, and prevents it from bursting in a hypotonic environment Eukaryote cell walls are made of cellulose or chitin 34 Cell Wall Prokaryotic cell plasma membranes are usually covered with a cell wall. Keeps cell from bursting in hypotonic solutions Eubacteria cell walls contain peptidoglycan, a combination of amino acids and sugars. Bacterial cell walls contain peptidoglycan, a network of sugar polymers cross-linked by polypeptides © 2011 Pearson Education, Inc. 6 Cell Wall Some species have a capsule surrounding the cell wall. The capsule can provide protection against immune system cells (phagocytes) Some bacteria have pili – hair like structures made of protein, help bacteria to adhere to surfaces Some pili are involved in transmitting DNA between bacteria Cell Walls Archaea contain polysaccharides and proteins but lack peptidoglycan Scientists use the Gram stain to classify bacteria by cell wall composition Gram-positive bacteria have simpler walls with a large amount of peptidoglycan Gram-negative bacteria have less peptidoglycan and an outer membrane that can be toxic © 2011 Pearson Education, Inc. Cell Wall Types The Bacterial Cell Wall Types There are two main cell wall types. The differences have important implications in treating the bacteria with antibiotics Gram Positive Gram Negative 40 Gram positive Figure 27.3a (a) Gram-positive bacteria: peptidoglycan traps crystal violet. Gram positive cells have thick cell walls, consisting mainly of peptidoglycan. Gram positive cells absorb the violet “gram stain” Cell wall Peptidoglycan layer Plasma membrane 7 Fig. 28.8-1 Gram Negative Gram negative cells have two layers: A thin peptidoglycan layer A thick outer layer made of polysaccharides bound to lipids, similar to plasma membrane Gram negative cells do not retain the gram stain, they counter-stain pink Figure 27.3b (b) Gram-negative bacteria: crystal violet is easily rinsed away, revealing red dye. Carbohydrate portion of lipopolysaccharide Cell wall Outer membrane Peptidoglycan layer Plasma membrane Gram Stain 48 8 External Layers Motility Capsule A gelatinous layer found in some bacteria Aids in attachment Protects from the immune system 49 Most motile bacteria propel themselves by flagella scattered about the surface or concentrated at one or both ends Flagella of bacteria, archaea, and eukaryotes are composed of different proteins and likely evolved independently © 2011 Pearson Education, Inc. Figure 27.6 Flagellum Filament Hook Motor Cell wall Video: Prokaryotic Flagella (Salmonella typhimurium) Plasma membrane 20 nm Rod Peptidoglycan layer © 2011 Pearson Education, Inc. Flagella Motility Most prokaryotes have a flagella Flagella These flagella are not like eukaryotic flagella, they are not composed of microtubules Long, helical structures Composed of the protein flagellin Involved in locomotion Instead it has: Basal body that acts like a motor Hook Filament Protein is flagellin 53 9 Prokaryotic DNA Prokaryotes usually have a single, circular DNA molecule. Most prokaryotes also have plasmids, small circular fragments of DNA. Plasmids can replicate independently or integrate into the main DNA Reproduction in Bacteria Most bacteria undergo asexual reproduction = binary fission Occasionally some bacteria will undergo a form of sexual reproduction – the plasmid of one bacteria will be transferred to another bacteria through the pilus Internal Organization Prokaryotic cells usually lack complex compartmentalization Some prokaryotes do have specialized membranes that perform metabolic functions These are usually infoldings of the plasma membrane © 2011 Pearson Education, Inc. 10 Figure 27.7a Pathogenic bacteria Some E. coli cause health problems 0.2 m Clostridium botulinum bacteria produce the toxin botulism Respiratory membrane (a) Aerobic prokaryote Cause of Disease Disease caused by bacteria are often caused by either a toxin released by the bacteria, or by the response of the host Clostridium tetanus cause tetanus Borrelia burgdorferi – bacteria that uses deer ticks to move from host to host, causes Lyme disease Commercial Uses Lactobacillus – used to make yogurt, pickles, sauerkraut. Bacteria populations can rapidly mutate, antibiotic resistance can result The few bacteria that mutate and are resistant to antibiotics will repopulate the area with antibiotic resistant bacteria Prokaryotic Domains Domain Archaea and Domain Bacteria (Eubacteria) Differences in ribosomes Archaea does not have peptidglycan in cell wall Archaea have isoprene units and ether linkages in the cell membrane. Domain Bacteria have ester linkages in the cell membrane and fatty acids 11 Plasma membrane Domain Archaea Prokaryotic – no nucleus Extreme bacteria Table 27.2 Methanogens example Discovered in 1983 contains methanococcus jannaschii Pacific Ocean thermal vent Methanogens (methane makers) Extreme halophiles (salt loving) Extreme thermophiles (heat lovers) [©Stan Watson, Woods Hole Oceanographic Institute] Halophile example 70 Thermophile example Yellowstone NP Dunaliella salina 12 Important Concepts Know the vocabulary in the lecture What are auto/hetero/photo/chemo-trophs What are the characteristics of prokaryotes Which domains are prokaryotic Know the parts of a prokaryotic cell and their functions Know the structure of prokaryotic cell walls, what they are made of, and the difference between gram negative and positive, understand how the gram stain technique works Important Concepts Know how many chromosomes a prokaryote has and what plasmids are How do prokaryotes reproduce What is nitrogen fixation, why is it important Domain Archaea – three main types What are the differences between Domain Archaea and Domain Bacteria (Eubacteria) To Know for Lab Practical Be able to identify the three shapes of bacteria, know their latin names Be able to identify anabaena. what are the causes and effects of eutrophication, What are heterocysts, be able to identfy them Characteristics of anabaena What domain does it belong in Identify Rhizobium and know what element it fixes, What domain does it belong in Identify lactobacillus and why is it beneficial, What domain does it belong in 13