Microbes

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  • Created by: Gina
  • Created on: 22-05-16 10:18

Archaea

1. Crenarchaeota

  • Many hyperthermophilic species- live at v.high temperatures
  • Often chemolithotrophic

2. Euryarchaetota

  • Physiologically diverse
  • Many are extremophiles

3. Hyperthermophiles

  • Isolated from geothermal springs and soils
  • Temperature of 100'C or more
  • Found in sulphur-rich springs with pH from mildly alkaline or pH1
  • Found in Hydrothermal vents where water is under pressure and temperatures are above 100'C
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Archaea 2

4. Sulfolobales

  • Sulfolobus acidocaldarius
  • Grows in sulfur-rich hot springs
  • Aerobic chemolithotrophs that oxidise reduced sulfur to iron
  • Live at 90'C, pH1-5, spherical, adheres to sulfur crystals
  • S-layer of proteins, anchored to the membrane

5. Desulfurococcales 

  • Pyrolobus fumarii
  • Optimum growth at 106'C, lives in walls of black smokers
  • S layer composed of protein, membrane composed of diglycerol tetraethers
  • Autotrophic
  • Faculative aerobe, obligate H2 chemolithotroph
  • NO3- used as terminal electron acceptor in anaerobic conditions
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Nonthermophilic Crenarchaeota

  • Found in nutrient poor marine environments
  • Can survive in very cold seawater and ice
  • Planktonic
  • Identified by SSU rRNA sampling
  • Can fix inorganic carbon
  • Plays key role in carbon cycle
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Haplophilic archaea

  • Halobacterium salinarum
    • Extreme halophile
    • have a requirement for high salt concentrations, at least 1.5M, NaCL needed for growth
    • Found in sea salt evaporation ponds
  • Adaptations to high salt
    • High solute levels in cells lead to high osmotic pressure, maintain a positive water balance by pumping K+ into cells
    • Higher K+ inside than Na+ outside
    • Glycoprotein cell wall stabilised by Na+
    • Cellular protiens composed of more acidic amino acids so they are more soluble at higher solute concentrations
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Methanogens

  • Produce Methane
    • severalcarbon substrates can be used
    • ATP produced
  • Unique to Archaea
    • Important in degradation of organic matter
  • Found in
    • Sediments with low O2
    • Animal digestive tracts
    • Hydrothermal vents
  • Obligate anaerobes
  • Pseudomurin in cell wall
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Bacillus anthracis

  • causes anthrax
  • >80% mortality is untreated
  • Growth in lymph nodes and lymphatic tissue of lungs
  • death from septisemia, haemorrhagic and menigitis
  • Endospore structure:
    • Many layers
    • Contains dipicolinic acid with Ca2+ which dehydrates endospore and stabalises DNA
    • Core contains small acid-soluble proteins that bind to DNA and protect from damage are used as a carbon and energy source for germination
  • Toxic parasporal chrystal
    • BT toxin toxic to inset larvae
    • help make insect resistant crops
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Staphylococcus

  • Nonsporulating 
  • aerobic
  • produces cocci
  • resistant to reduced water potential
  • tolerate high salt
  • many species are pigmented
  • E.g. Staphylococcus aureus is yellow
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Mycoplasma

  • Lacks a cell wall
  • key components of peptodoglycan abscent
  • membranes contain sterols and lipoglycans which stabalise the membrane
  • Pleomorphic
    • cells may be cocci or filamentous of various lengths
  • capable of autonomous growth
  • inhabit animal and plant hosts
  • often defective in several biosynthetic pathways 
  • E.g Mycoplasma genitalium
    • host associated
    • genome 580bp
    • 470 genes

Actinobacteria

  • Rod-shaped
  • Obigate aerobe
  • Faculative intracellular parasite with complex cell wall,
  • E.g Mycobacterium tuberculosis
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Streptomyces

  • Branching filaments
  • produces spores called conida
  • Important secondary metabolites
    • produce antibiotics and extracellular enzymes
  • strict aerobes
  • genomes large
  • soil dwelling
  • role in carbon cycling: produce hydrolytic exoenzymes
  • spores form when colony ages
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Pseudomonas

  • Pseudomonas aeruginosa
    • infects urinary and respiratory tract
    • infects burn wounds
    • resistant to antibiotics
  • Capable of breaking down many components including oil so can be used in bioremediation, however, may turn pathogenic
  • Can infect plants, causes hypersensitivity in TMV
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Enteric bacteria

  • Includes E. coli
    • Inhabit intestinal tract
    • may synthesize vitamins for host
    • can be pathogenic
    • salmonella and shigles closely related, usually pathogenic
  • Faculative aerobes
    • Ferments sugars produces a mixture of acids, H2 and CO2
  • May be motile
  • Nonsporulating
  • Simple nutrient requirements
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Vibrio

  • Cells are motile, straight or curved rods
  • Faculative aerobes/ fermentative metabolism
  • inhabit aquatic environments
  • E.g. Vibrio cholerae
  • Some can cause biolumenescence
    • catalysed by luciferase
    • regulated by population density via quorem sensing
    • Associated with fish- host provides nutrients and shelter, luminescence can be used for communication and hide host from predators
    • Requires luciferae, long chain aliphaitc aldehyde, flavin and oxygen
    • Lux operon
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Bdevellovibrio

  • Prey on other bacteria
  • small genome
  • highly motile
  • obligate aerobes
  • widespread in soil and water
  • Cycle:
    • attachment and penetration of host
      • resides in periplasm
      • breaks down peptiglycan
      • assimilates organic compounds from prey cytoplasm
    • elongates without dividing
    • cell division occurs once nutrients are depleted
      • filament divides
      • differentiation into motile forms
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Camplobacter and Helicobacter

  • Motile
  • Microaerophilic
    • requires small conc of O2
  • Campylobacter causes bloddy diahorrea
  • Helicobacter causes gastritis and peptic ulcers
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Gliding Myxobacteria

  • Long rods or filaments
  • Lack flagella, can move when is contact with surfaces
  • Myxospores
    • nutrients depleted
    • vegetative cells aggregate
    • construct fruiting bodies
    • differentite into myxospores
    • resistant to drying, UV and heat
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Cyanobacteria

  • Oxygenic phototrophs
  • most are obligate phototrophs
  • important in producing oygen in the early atmosphere
  • gave rise to chloroplasts via endosymbiosis
  • Morphologically diverse
    • unicellular and filamentous 
  • many produce potent neurotoxins
  • Found in terrestrial, freshwater and marine habitats
  • peptidoglycan in cell walls
  • outer and cytoplasmic membranes present
  • Mucilagenous envelopes
  • Gas vesicles help maintain buoyancy
  • many display gliding motility
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Lichen

  • Symbiosis between fungi and phototrophic organism
    • algae or cyanobacteria
    • cyanobacteria can fix nitrogen
    • fungus gains organic matter from photosynthesis
    • bacteria gains anchorage, water and inorganic nutrients
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Spirochetes

  • Motile
  • Tightly coiled
  • Treponema- flate wave form
    • host associated- parasites of humans
    • cause syphalis 
    • some are parasites of the mouth
    • some found in rumen
  • others are helical
  • widespread in aquatic environments and animals
  • Cell structure
    • protoplasmic cylinder enclosed by cell wall and membrane
    • outer shealth- flexibke and made of lipid, protein and carbohydrate
    • Endoflagella: located under periplasm
  • Motility
    • Endoflagella anchored at one end
    • Move via flexing or lashing
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Chlamydia

  • Gram negative type cell wall
  • Does not stain
  • Outer lipopolysaccaride membrane
  • lacks peptidoglycan
  • obligate parasites
    • poor metabolic capasities
    • require biosynthetic intermediates
    • simple biochemical capasities
  • Chlamydia trachomatis 
    • small genome
    • missing genes supplied by host
    • genes for peptidoglycan and ATP present
    • some genes acquired by horizontal gene transfer
  • Infections
    • STD
    • Non-specific urethrisis 
    • Trachoma (blindness)
    • Associated with reactive arthritis 
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