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11/15/2011 Chapter 27: Bacteria and Archaea Outline 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 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 11/15/2011 Do prokaryotes have a nucleus Ye Photo courtesy of Margaret McFall-Ngai. The First Cells Are Domain Bacteria and Domain Archaea prokaryotic or eukaryotic? 50% 50% ka ry o tic Microfossils are fossilized forms of microscopic life -Oldest are 3.5 billion years old eu ar yo tic 1. prokaryotic 2. eukaryotic pr ok 50% o 50% s 1. Yes 2. No N Euprymna Scolopes have a symbiotic relationship with luminescent bacteria. 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 11/15/2011 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 species archaeal The three-domain (Woese) system of phylogeny is based on rRNA sequences 3 11/15/2011 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 11/15/2011 Table 27.1 The Role of Oxygen in Metabolism Prokaryotic metabolism varies with respect to O2 – Obligate aerobes require O2 for cellular respiration – Obligate anaerobes are poisoned by O2 and use fermentation or anaerobic respiration – Facultative anaerobes can survive with or without O2 © 2011 Pearson Education, Inc. 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) 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 © 2011 Pearson Education, Inc. Metabolic Cooperation Cooperation between prokaryotes allows them to use environmental resources they could not use as individual cells In the cyanobacterium Anabaena, photosynthetic cells and nitrogen-fixing cells called heterocysts (or heterocytes) exchange metabolic products © 2011 Pearson Education, Inc. 5 11/15/2011 Figure 27.14 Eutrophication Cyanobacteria like Anabaena are nitrogen fixers (use heterocysts) Phosphorus and nitrogen are the main limiting mineral in natural ecosystems Photosynthetic cells Heterocyst Ph & N sources include sewage, agricultural runoff (fertilizers), and industry 20 m Ph & N that enters rivers, lakes and estuaries can produce blooms of cyanobacteria Eutrophication Eutrophication This bloom of bacteria covers the top of the pond, blocking light from reaching the water plants below. Oxygen is depleted by decomposers, and blooms block out light which decreases photosynthesis The water plants are not able to photosynthesize so they can’t produce oxygen End result – oxygen depletion, fish need oxygen and will die. Cyanobacteria have a short life and die, decomposers break them down. Decomposers use oxygen. Photoautotroph - cyanobacteria These organisms use the energy from the sun to fix carbon into a sugar from CO2 25% 25% 25% 25% ut ot ro ph s m oa he C hs Ph ot oa er ot ro p er ot ro p m oh et ot oh et he C Ph 35 ut ot ro ph s Photoheterotrophs Chemoheterotrophs Photoautotrophs Chemoautotrophs hs 1. 2. 3. 4. 6 11/15/2011 These organisms use the energy from inorganic compounds to fix carbon into a sugar from CO2 25% 25% 25% 25% ut ot ro ph s m oa he C hs Ph ot oa er ot ro p er ot ro p m oh et ot oh et he 38 C Ph ut ot ro ph s Photoheterotrophs Chemoheterotrophs Photoautotrophs Chemoautotrophs hs 1. 2. 3. 4. Cell-Surface Structures Cell Wall 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 Prokaryotic cell plasma membranes are usually covered with a cell wall. Keeps cell from bursting in hypotonic solutions Eukaryote cell walls are made of cellulose or chitin 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. 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. 7 11/15/2011 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 44 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 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 8 11/15/2011 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 52 External Layers Motility Capsule A gelatinous layer found in some bacteria Aids in attachment Protects from the immune system 53 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. 9 11/15/2011 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 57 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 10 11/15/2011 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. 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 Clostridium tetanus cause tetanus Borrelia burgdorferi – bacteria that uses deer ticks to move from host to host, causes Lyme disease 11 11/15/2011 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 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 Plasma membrane Table 27.2 12 11/15/2011 Domain Archaea Prokaryotic – no nucleus Extreme bacteria 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 74 Thermophile example Yellowstone NP Dunaliella salina 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 13 11/15/2011 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) How does bacteria cause disease Antibiotic resistance Understand eutrophication, including the causes and effects 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 14