Prokaryotes

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Prokaryotes

• Bacteria and Archaea
• Chapter 27

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Small Size
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Two Domains
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Phylogeny of Domains
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Bacteria include every mode of nutrition and
metabolism
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Archaea

• Single celled microorganisms
• Reproduce asexually
• Identified as separate Domain in 1977
• First archaea were discovered in extreme
  conditions. Called extremophiles

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Halophiles salt lovers
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Thermophiles
Live at very high temperatures
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Methanogens

• Use CO2 to Oxidize H2 release CH4
• Release methane
• O2 is toxic to them
• Found in anoxic conditions such as swamps, deep
  caves, and intestines of animals

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Bacteria
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Peptidoglycan Cell Walls
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Movement
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Internal Membranes
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Endospores

• Dormant tough but not reproductive structures
• Ensures survival of bacterium. Resistant to
  ultraviolet, gamma radiation, temperature
  fluctuation, household disinfectants...
• found in soil, and water

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Bacterial DNA
Bacteria have circular DNA
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Bacteria Plasmids

• Extra-chromosome DNA that is separate from the
  bacterial chromosomal DNA
• Separate self replication
• can be transfered to other bacteria and other
  bacteria species

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Symbiotic relationships
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Bioluminescent bacteria
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Human symbiotic relationships
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Termites have specialized bacteria that helps
them digest celluloseTermites comprise 50 of
the animal biomass in Africa
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Humans have a long history of using prokaryotes
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Commercial use of prokaryotesWastewater Treatment
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Commercial use of prokaryotesBioremediation
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Ecosystem Services
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Protists

• Chapter 28

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Aquatic Producers are often Protists
Green Algae Diatoms
Diatoms
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What are Protists

• They are not plants, animals or fungi
• Diverse assortment of eukaryotes
• Most are unicellular with complex cells
• Found in damp soil, oceans and even human bodies

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Nutritional Diversity

• Autotrophs
• Heterotrophs
• Mixitrophs

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Asexual Reproduction
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Sexual Reproduction
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Ciliates
Cillated Pellicle
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Paramecium
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Diatoms 10,000 species
Photosynthetic with golden accessory pigments
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Diatom
Silica in Cell Wall
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Psuedopod-equipped Protists

• Heterotrophic
• Psuedopods or axopods
• With or without cell walls
• Ameoba is a well known psuedopod

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Slime Molds

• Mycetozoans were thought to be fungi
• Now understood to be case of evolutionary
  convergence
• Two main branches
• Plasmodial slime molds
• Cellular slime molds

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Plasmodial slime moldone super cell
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Multicellular Brown Algae Phaeophyta

• May grow up to 60 meters
• Provide 3 demensional habitats for marine species
• Plant like structures, holdfast, stipe, and
  blades
• Pneumatocysts are gas-filled bladders, located at
  the base of blades provides Boyance

Blade
Stipe
Hold -fast
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Laminaria at low tide
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Kelp Forest
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Chlorophyta

• Green algae
• Autotrophic
• Plant-like chloroplasts and pigments
• Cellulose cell walls
• Red and Green algae are the closest relatives to
  plants

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Cladophora form large filamentous mats
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• http//www.youtube.com/watch?vPoiAKcIls6sfeature
  related

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Fungi and nutrient cycling

• Chapters 31 and 54

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Fungi

• Heterotrophic Decomposers or Symbionts

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Fungal Characteristics

• Heterotrophic
• Decomposers
• Opportunistic parasites
• Many produce mycotoxins as metabolic by-products
• Aerobic or facultative anaerobes
• Cell wall composed of chitin
• more closely related to animals than plants
• Grow best in warm, moist environments

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Dimorphic

• Found in two physical forms
• Unicellular Yeasts
• Multicellular Molds and Mushrooms
• Hyphae
• Mycelium hyphal mass

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Reproduction by Spore Formation

• Asexual
• Haploid spores formed on hyphae
• Fragmentation
• Broken fragments of hyphae
• Sexual
• Two mating hyphae types fuse and produce spores

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Penicillium (Blue-green Mold)
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Basidiocarps
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Fig. 31-20
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• http//www.youtube.com/watch?vJeF952Xfz4feature
  relmfu

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Lichens (Fungal-Algal Symbiosis)
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Lichen Structure
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Mycorrhizae

• Plant roots and symbiotic fungi
• Increased nutrient (P) absorption
• Greater surface area
• Enzyme excretions
• Increased plant bimass
• may have originally started as parasitism
• Most plants have Mycorrhizae infections

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Mycorrhizae
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The Nation that Destroys Its Soil Destroys
Itself F.D.R.

• Farmland productivity often suffers from chemical
  contamination, mineral deficiencies, acidity,
  salinity, and poor drainage
• Healthy soils improve plant growth by enhancing
  plant nutrition

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Soil is a living, finite resource

• Plants obtain most of their water and minerals
  from the upper layers of soil
• Living organisms play an important role in these
  soil layers
• This complex soil ecosystem is fragile
• Topsoil contains bacteria, fungi, algae, other
  protists, insects, earthworms, nematodes, and
  plant roots
• These organisms help to decompose organic
  material and mix the soil

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Rocks Contribute Minerals

• Weathering
• Erosion
• Transportation
• Sedimentation

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Grain Size

• Sand
• 2.1 mm to .05 mm
• Silt
• Less than .05 mm but greater than .002 mm
• Clay
• Less than .002 mm

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Soil Texture

• Soil particles are classified by size from
  largest to smallest they are called sand, silt,
  and clay
• Soil is stratified into layers called soil
  horizons
• Topsoil consists of mineral particles, living
  organisms, and humus, the decaying organic
  material

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Soil

• Minerals
• Water
• Air
• Dead Organic material
• Organisms

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Water and soil interact

• Soil particle size influences
• water transport nutrients
• soil moisture
• Water flows through and evaporates quickly from
  sandy soils
• Clay soils bind water which prevent plants from
  absorbing

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Litter and Topsoil

• Most plant root biomass
• Most nutrient turnover
• Most decomposer biomass
• Most microbial activity

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Litter Decomposers
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2. Global C sources and sinks (CO2)
Atmosphere 750
Net deforestation 0.9
3.2/yr
Combustion 6
GPP 120
Plant R 45
Soil R 75
560
92
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Rivers .8
Soils 1500
Oceans 38000
Values are 1015 g C, fluxes are annual
Schlesinger 1997
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3. Nutrient cycling
Litterfall
Decomposition
Nutrient uptake
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Decomposition over Time
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Litter and Topsoil Organisms
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Size of Soil Microorganisms
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Soil Protozoa

• Decomposers
• Consumers

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Producers
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Soil Fungi

• Decomposers
• Symbionts

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Soil Actinomycetes

• Fungus-like bacteria
• Some are symbiotic with plants
• Some produce antibiotics

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Soil Bacteria

• Producers
• Decomposers
• Mineralizers

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Soil Bacteria and Plant Nutrition

• The layer of soil bound to the plants roots is
  the rhizosphere
• The rhizosphere has high microbial activity
  because of sugars, amino acids, and organic acids
  secreted by roots

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Rhizobacteria

• Free-living rhizobacteria thrive in the
  rhizosphere, and some can enter roots
• Rhizobacteria can play several roles
• Produce hormones that stimulate plant growth
• Produce antibiotics that protect roots from
  disease
• Absorb toxic metals or make nutrients more
  available to roots

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Bacteria in the Nitrogen Cycle

• Nitrogen is often an important limiting nutrient
  for plant growth
• The nitrogen cycle transforms nitrogen and
  nitrogen-containing compounds
• Most soil nitrogen comes from actions of soil
  bacteria

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Nitrogen-Fixing Bacteria A Closer Look

• N2 is abundant in the atmosphere, but unavailable
  to plants
• Nitrogen fixation is the conversion of nitrogen
  from N2 to NH3
• Symbiotic relationships with nitrogen-fixing
  bacteria provide some plant species with a
  built-in source of available N
• Most commonly legumes beans, peas

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N2
N2
Atmosphere
Atmosphere
Nitrate and nitrogenous organic compounds exported
in xylem to shoot system
Soil
Nitrogen-fixing bacteria
N2
Denitrifying bacteria
H (from soil)
NH4
Soil
NO3 (nitrate)
NH3 (ammonia)
NH4 (ammonium)
Ammonifying bacteria
Nitrifying bacteria
Organic material (humus)
Root
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Nitrogen Cycle
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Nitrogen Fixation

• N2 NH4
• Nitrogen gas is fixed as ammonium ion.

• Photosynthetic
• Nitrogen Fixing
• Nostoc and Anabaena
• Specialized cells
• heterocysts

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Non-Photosynthetic Nitrogen Fixers

• Free-living heterotrophic bacteria
• Azotobacter
• Azomonas
• Symbiotic heterotrophic bacteria
• Rhizobium
• Mesquite Trees are Facultative N-Fixers

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Ammonification
C2H2O2 NH4
Amino acid

• Carried out by many heterotrophic microbes.

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Nitrification

• NH4 -gt NO2- -gt NO3-2
• Oxidation carried out by aerobic,
  chemoautotrophic (mineralizing) bacteria

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Denitrification

• NO3-2 NO2- N2
• Pseudomonas and Paracoccus
• Carried out by anaerobic, heterotrophic microbes
• How can we measure denitrification?

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Nitrogen cycle summary

• Nitrogen fixation
• (Gas) N2 ? NH4
• Ammonification
• (organism) Amino Acid ? NH4
• Nitrification
• NH4 ? NO2 ? NO3 (Mineral)
• Denitrification
• (Mineral) NO3 ? NO2 ? N2 (Gas)
• Carried out by cyanobacteria, Rhizobium,
  heterotrophs, bacteria, fungi