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Chapter 19 Viruses an infectious particle consisting of genes packaged…

- - - - Lytic Cycle/ Virulent Phage
        
        The entire Lytic cycle, from phage's first contact w/cell surface to cell lysis, takes only 20-30 minutes at 37*C.
  - - - Lytic & Lysogenic Cycle of Phage/ Temperate Phage
- - - - Plant Viruses:
        
        most have known RNA Genome
        
        Two major routes:
        
        1 Horizontal Transmission, entering through damaged cell walls
        
        Vertical Transmission, inheriting the virus from a parent
      - Types of Virus Shapes: Rod-shaped, polyhedral, helical, or more complex in shape
        
        Viral Structures:
        
        Viral Envelopes:
        
        derived from the membranes of the host cell, contain host cell phospholipids and membrane proteins
        
        contain proteins and glycoproteins of viral origin
        
        Viral Envelopes
    - - Retrovirus Replicative Cycle
    - - 3 Causes for rapidly emerging Viral Diseases:
        
        mutations of existing viruses into new ones that can spread more easily
        
        spread from a small, isolated human population, like a new road into a remote area
        
        spread of existing viruses from other animals, accounts for 3/4 of emerging viruses
        
        Influenza viruses:
        
        have 9 segments in their genome, leading to many new genetic combos
        
        have high rate of mutations
        
        not emerging because of widely circulated variants
        
        Ex: Influenza A
- - - - CRISPR-Cas System
        
        A bacterial immune system
- - - - ENDOSPORES
    - - Motility
        Taxis a directed movement, or
        the ability to move toward or away from a stimulus
        
        chemotaxis - stimulus is chemical, positive (nutrients or Oxygen), negative (toxic substance)
        
        thermotaxis - stimulus is temp dependent
        phototaxis - light stimulus
        halotaxis - salt stimulus
        autotrophs - CO2 or related compound as a Carbon Source
        Heterotrophs - require at least one organic nutrient, such as glucose, to make other organic compounds
        
        Phototropism - when a plant grows toward or away from light stimulus
        Flagella (singular flagellum): one-tenth the width and typically are not covered by an extension of the plasma membrane, can be scattered over the entire surface of the cell or concentrated at one or both ends
        Cilia:
        Prokaryotes: bacterial and archaeal flagella are similar in size and rotational mechanism, but composed entirely diff and unrelated proteins
        
        Prokaryotic flagellum:
        
        -evolved from: as other proteins were added to an ancestral secretory system
        
        Exaptation: the process in which structures originally adapted for one function take on new functions through descent with modification
        
        Role of Oxygen in Metabolism
        Obligate aerobes: must use O2 for cellular respiration and cannot grow without it.
        Obligate anaerobes: are poisoned by O2, some live exclusively by fermentation, others extract chemical energy
        Anaerobic respiration: in which substances other than O2, such as nitrate ions (NO3-) or sulfate ions (SO4 2-) accept electrons at the downhill end of electron transport chains
        Facultative anaerobes: use O2 if it is present but can also carry out fermentation or anaerobic respiration in an anaerobic environment.
        Nitrogen Fixation: the process by which some cyanobacteria and some methanogens convert atmospheric nitrogen (N2) to Ammonia (NH3)
      - Fimbraie
    - - Gram stain:
        
        technique developed by Hans Gram
        
        can categorize bacterial species according to differences in cell wall composition
        
        Gram-positive: bacteria that have relatively simple walls composed of a thick layer of peptidoglycan.
        (Crystal Violet, stains purple)
        
        Gram-negative: bacteria that have less peptidoglycan and are structurally more complex, with an outer membrane that contains lipopolysaccharides (Safranin, stains pink)
        
        lipopolysaccharides (Carbs bonded to lipids)
        
        Gram staining
        
        a valuable tool in medicine for quickly determining if a patients infection is due to gram-positive or gram-negative bacteria.