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Biology Ch. 27 (27.2 - 27.3 (Genetic Recombination (Conjugation (The F…

- - - - A process where a prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment
    - - Is the movement of genes between bacteria by phages (from bacteriophages, viruses that infect bacteria)
    - - DNA is transferred between two prokaryotic cells that are temporarily joined.
      - A donor cell attaches to a recipient by a pilus and transfers DNA through a structure called the mating bridge
      - A piece of DNA called the F factor is required for the production of pili
      - DNA donors have the F plasmid and DNA recipients dont
      - F factor is transferable during conjugation
      - Provided some of the F plasmid's DNA is transferred, the recipient cell becomes a recombinant cell
      - The F Factor in the Chromosome
        
        A cell with the F factor built into its chromosome functions as a donor during conjugation
        
        Such cells are called Hfr cells (for high frequency of recombination)
        
        The recipient becomes a recombinant bacterium, with DNA from two different cells
    - - R plasmids carry genes for antibiotic resistance
      - Antibiotics kill sensitive bacteria, but not bacteria with specific R plasmids
      - Through natural selection, the fraction of bacteria with genes for resistance increases in a population exposed to antibiotics
  - - - Phototrophs obtain energy from light
      - Chemotrophs obtain energy from chemicals
      - Autotrophs require CO2 or related compounds as a carbon source
      - Heterotrophs require an organic nutrient to make organic compounds
      - Energy and carbon sources are combined to give 4 major modes of nutrition
        
        Photoautotroph
        
        Chemoautotroph
        
        Photoheterotroph
        
        Chemoheterotroph
  - - - Obligate aerobes require O2 for cellular respiration
      - Obligate anaerobes are poisoned by O2 and live by fermentation or use substances other than O2 for anaerobic respiration
      - Facultative anaerobes can use O2 if it is present or carry out fermentation or anaerobic respiration if it is not
    - - essential for production of amino acids and nucleic acids in all organisms
      - For example, some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3) in a process called nitrogen fixation
      - Prokaryotes can metabolize nitrogen in a variety of ways
- - - - include vast majority of prokaryotic species familiar of most people
      - diverse nutritional types
      - Proteobacteria
        
        Gram-negative bacteria include photoautotrophs, chemoautotrophs, and heterotrophs
        
        some are anaerobic and others aerobic
        
        five subgroups of proteobacteria recognized by molecular systematists
        
        Subgroup: Alpha Proteobacteria
        
        many species closely associated with eukaryotic hosts
        
        Scientists hypothesize that mitochondria evolved from aerobic alpha proteobacteria through endosymbiosis
        
        ex Rhizobium and Agrobacterium
        
        Subgroup: Beta Proteobacteria
        
        nutritionally diverse
        
        Example: the soil bacterium Nitrosomonad converts NH4+ to NO2–
        
        other members include aquatic species and pathogens
        
        Subgroup: Gamma Proteobacteria
        
        Autotrophic members include sulfur bacteria such as Thiomargarita namibiensis
        
        Some heterotrophs are pathogenic, such as Legionella, Salmonella, and Vibrio cholerae
        
        Escherichia coli resides in the intestines of many mammals and is not normally pathogenic
        
        Subgroup: Delta Proteobacteria
        
        Example: the slime-secreting myxobacteria, which produces drought-resistant “myxospores”
        
        Example: bdellovibrios, which mount high-speed attacks on other bacteria
        
        Subgroup: Epsilon Proteobacteria
        
        Most species in this subgroup are pathogenic
        
        Examples include Campylobacter, which causes blood poisoning, and Helicobacter pylori, which causes stomach ulcers
      - Chlamydias
        
        are parasites that live within animal celss
        
        Ex: Chlamydia trachomatis causes blindness and nongoncoccal urethritis by sexual transmission
      - Spirochetes
        
        Are helical gram-negative heterotrophs
        
        Some are parasites, including Treponema pallidum, which causes syphilis, and Borrelia burgdorferi, which causes Lyme disease
      - Cyanobacteria
        
        These are gram-negative photoautotrophs that generate O2
        
        Plant chloroplasts likely evolved from cyanobacteria by the process of endosymbiosis
        
        Cyanobacteria are abundant components of freshwater and marine phytoplankton
      - Gram-positive bacteria
        
        Colony-forming groups, such as actinomycetes, many of which help decompose organic matter
        
        Solitary species including Bacillus anthracis, the cause of anthrax; Clostridium botulinum, the cause of botulism; and various Staphylococcus and Streptococcus species
        
        Mycoplasmas, the smallest known cells, lack cell walls
  - - - Don't have nuclear envelope
      - Don't have membrane enclosed organelles
      - Has peptidoglycan in cell wall
      - Membrane lipids unbranched hydrocarbons
      - One kind of RNA polymerase
      - Initiator amino acid for protein synthesis: formyl-methionine
      - Introns in genes is very rare
      - Response to the antibiotics streptomycin and chloramphenicol: growth usuall inhibited
      - Doesn't have Histones associated with DNA
      - has circular chromosome
      - Doesnt have growth at temperature >100 degree c
    - - Don't have membrane enclosed organelles
      - Don't have membrane enclosed organelles
      - Don't have peptidoglycan on cell wall
      - Membrane lipids some unbranched hydrocarbons
      - Several kinds of RNA polymerase
      - Initiator amino acid for protein synthesis is Methionine
      - Introns in genes present in some genes
      - Response to the antibiotics streptomycin and chloramphenicol: Growth not inhibited
      - Histones associated with DNA present in some species
      - has circular chromosome
      - growth at temperature >100 degree c: Some species
    - - Has Nuclear envelope
      - Membrane enclosed organelles
      - Don't have peptidoglycan on cell wall
      - membrane lipids are unbranched hydrocarbons
      - Several kinds of RNA polymerase
      - Initiator amino acid for protein synthesis is Methionine
      - Introns in genes present in many genes
      - Response to the antibiotics streptomycin and chloramphenicol: Growth not inhibited
      - Histones associated with DNA present
      - Don't have Circular chromosome
      - Doesnt have growth at temperature >100 degree c
- - - - Some chemoheterotrophic prokaryotes function as decomposers of dead organisms and waste products
      - can convert some molecules to forms that can be taken up by other organisms
      - Can also immobilize or decrease the availability of nutrients by using them in their own cells
  - - - Human intestines are home to about 500–1,000 species of bacteria
      - Many of these are mutualists and break down food that is undigested by our intestines
    - - Bacteria cause about half of all human diseases
      - Some bacterial diseases are transmitted by other species
      - For example, Lyme disease is caused by a bacterium and carried by ticks
      - typically cause disease by releasing exotoxins or endotoxins
      - Exotoxins are secreted and cause disease even if the prokaryotes that produce them are not present
      - Endotoxins are released only when bacteria die and their cell walls break down
- - - - Bacteria
      - Archaea
    - - Spiral: loose coils
      - Bacillus: rod-shaped
      - Coccus: spherical shape
    - - Prokaryotic cells usually lack complex compartmentalization
      - Some prokaryotes do have specialized membranes that perform metabolic functions
      - These are usually infoldings of the plasma membrane
      - The prokaryotic genome has less DNA than the eukaryotic genome
      - Most of the genome consists of a circular chromosome
      - The chromosome is not contained in a nucleus; it is located in the nucleoid region with no surrounding membrane
      - Typical prokaryotes also have smaller rings of independently replicating DNA called plasmids
    - - Prokaryotes reproduce quickly by Binary fission
      - Can divide every 1-3 hours under optimal conditions
      - Key features of prokaryote biology
        
        They are small
        
        They reproduce by binary fission
        
        They have short generation times
  - - - Maintains cell shape
      - Protect the cell and prevent the it from busting in a hypotonic environment
      - Eukaryote
        
        Cell walls are made of cellulose or chitin
      - Most bacterial cell walls
        
        contain peptidoglycan,
        
        A polymer composed of modified surgars cross-linked by short polypeptides
      - Archaea cell walls
        
        Contain polysaccharides and proteins but lack peptidoglycan
    - - classifies bacteria by cell wall composition
      - Gram Positive
        
        Bacteria have simpler walls
        
        Large amount of peptidoglycan
        
        Stains purple
      - Gram negative
        
        Bacteria have complex walls
        
        less peptidoglycan
        
        an outer membrane that contains lipopolysaccharides
        
        Stains pink/red
    - - A sticky outer layer of polysaccharide or protein present in some prokaryotes
      - Allows adherence to the substrate, or other individuals
      - Shields pathogenic bacteria from the host immune system
    - - Many prokaryotes form metabolically inactive endopores
      - Which can remain viable in harsh conditions for centuries
    - - some prokaryotes have this
      - hairlike appendages that allow them to stick to their substrate or other individuals in a colony
    - - longer then fimbrae and allow prokaryotes to exchange DNA
  - - - The ability to move toward or away from a stimulus
      - about half of all prokaryotes exhibit taxis
      - Ex: chemotaxis is the movement toward or away from a chemical stimulus
    - - Most common structures used by prokaryotes for movemonet
      - May be scattered about the surface or concentrated at one or both ends of the cell
      - flagella of prokaryote differ from eukaryotes in structure, mechanism or propulsion, and molecular composition