Environmental Microbiology

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Environmental Microbiology
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• INTRODUCTION

Environmental microbiology is the study of the
composition and physiology of microbial
communities in the environment.
The environment in this case means the soil,
water, air and sediments covering the planet and
can also include the animals and plants that
inhabit these areas.
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• Environmental Microbiology
• Study of microbes in their natural habitats
• Microbial Diversity study of the different
  types of microbes in an environment
• Microbial Ecology
• Studies the interactions between microbes their
  environments
• Involving biotic abiotic components
• Distribution
• Abundance numbers of bacteria

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Biogeochemical Cycle
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Mutualism

• Sheep and cattle (ruminants) live off grass
• Lack the digestive enzymes to break down
  cellulose
• Bacteria in intestinal tract break down
  cellulose
• Products of cellulose degradation are converted
  to carbon
• sources that the ruminants can use
• CH4 is also produced in high amounts (belching!)
• Sugars absorbed by animal and used for energy
• Plants unable to fix atmospheric N2,
• Symbiotic bacteria infect roots
• Plant requires nitrogen for proteins

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Biofilms
Antarctica glaciers Hot springs

• Complex aggregation
• Bacteria, archaea, protozoa, algae
• Microbial Mat
• Free floating organism
• Attached organism
• Highly structured
• Extracellular polysaccharide
• Protective adhesive matrix
• Protection from the environment
• Protection from protozoans
• Protection from antibiotics chemicals

Antarctic Sun February 12, 2006
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• Grows by cell division recruitment
• Industrial biofilms
• Pipe corrosion
• Ship corrosion
• Infections
• Dental plaque
• Contact lenses
• Heart valves
• Artificial hip joints

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1. Initial attachment
4. Maturation of Biofilm Architecture
2. Production of EPS
5. Dispersion
3. Early Biofilm Architecture
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Nutrient Cycling

• A glass column that simulates the complex
  interactions of microbial biofilms in an aqueous
  environment
• Upper aerobic zone
• Microaerophilic zone
• Lower anaerobic zone

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• Algae, cyanobacteria, aerobic heterotrophs
• CO2 H2O ? CH2O O2
• Oxygenic photosynthesis
• H2O is a source of electrons
• CH2O O2 ? CO2 H2O
• Aerobic respiration
• H2S oxidizers
• CO2 H2S ? CH2O S H2O
• Anoxygenic photosynthesis
• H2S is a source of electrons

More on anoxygenic and oxygenic photosynthesis is
few moments
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• Purple nonsulfur photoheterotrophs
• May exist as photoheterotrophs, photoautotrophs
  or chemoheterotrophs
• Freely alternate between these metabolic modes
  depending on environmental conditions
• Degree of anaerobiosis
• Availability and types of carbon sources
• CO2 for autotrophic growth
• Organic compounds for heterotrophic growth
• Availability of light for phototrophic growth
• The non-sulfur label was used since it was
  originally thought that these bacteria could not
  use H2S as an electron donor
• Can use H2S in low concentrations

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• Purple non-sulfur bacteria
• CH2O O2 ? CO2 H2O (Chemoheterotrophs)
• CH2O O2 ? CO2 H2O (Photoheterotrophs)
• CO2 H2O ? CH2O O2 (Photoautotrophs)
• Purple Green sulfur bacteria
• Anoxygenic photosynthesis
• H2, H2S or So ? SO42-
• Sulfate reducers
• SO42- ? S2- compound (H2S or FeS)

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Quorum Sensing

• Cell-cell communication in bacteria
• Coordinate behavior/activities between bacterial
  cells of the same species
• Autoinducers trigger a change when cells are in
  high concentration
• Specific receptor for the inducer
• Extracellular concentration of autoinducer
  increases with population
• Threshold is reached
• The population responds with an alteration in
  gene expression
• Bioluminescence
• Secretion of virulence factors
• Biofilm formation
• Sporulation
• Competence

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Energy Nutrient Flow
It is likely that most of the Earth's atmospheric
oxygen was produced by bacterial cells.
 
Plant cell chloroplast and oxygenic
photosynthesis are originated in prokaryotes.
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• Anoxygenic Photosynthesis
• Anaerobic bacterial photosynthesis that does not
  produce O2
• CO2 H2S ? (CH2O)n S H2O
• H2, H2S or So or organic compounds serves as a
  source of electrons
• Need electrons to make fix C and make ATP
• Purple and green photosynthetic sulfur bacteria
• Aquatic anaerobic
• Pigments that absorb different l
• Bacteriochlorophyll (800 - 1000 nm far red)
• Carotenoids (400 - 550 nm)
• Phycobilins are not present
• Only 1 photosystem
• Rhodobacter
• Oxidize succinate or butyrate during CO2 fixation
  
• Hypothesized to be have become an endosymbiont of
  eucaryotes
• Mitochondrion 16S rRNA sequences

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Cyanobacteria purple bacteria Lake Cadagno,
Switzerland
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Cyanobacteria
Tremendous ecological importance in the C, O and
N cycles Evolutionary relationship to
plants Cyanobacteria have chlorophyll a,
carotenoids and phycobilins
Same chlorophyll a in plants and
algae Chlorophyll a absorbs light at 450 nm 650
- 750 nm Pycobilins absorb at 550 and 650 nm
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Some cyanobacteria fix nitrogen in specialized
cells HETEROCYSTS. Provide anaerobic environment
required for nitrogenase.
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Cyanobacteria have membranes that resemble
photosynthetic thylakoids in plant
chloroplasts. Hypothesized that cyanobacteria
were the progenitors of eucaryotic chloroplasts
via endosymbiosis. Cyanobacteria are very
similar to the chloroplasts of red algae
(Rhodophyta).
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Several species of cyanobacteria are symbionts of
liverworts, ferns, cycads, flagellated protozoa,
and algae. The photosynthetic partners of
lichens are commonly cyanobacteria. There is
also an example of a cyanobacterium as
endosymbionts of plant cells. A cyanobacterial
endophyte (Anabaena spp.) fixes nitrogen that
becomes available to the water fern, Azolla.
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Differences between plant and bacterial
photosynthesis
Plant Photosynthesis Bacterial Photosynthesis
Organisms plants, algae, cyanobacteria purple and green bacteria
Type of chlorophyll chlorophyll a  absorbs 650-750 nm bacteriochlorophyll  absorbs 800-1000 nm
Photosystem I (cyclic photophosphorylation) present present
Photosystem II (noncyclic photophosphorylation) present absent
Produces O2 yes no
Photosynthetic electron donor H2O H2S, other sulfur compounds or  certain organic compounds
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Thank
You