Degradation of Chemicals in Soil and Water

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Degradation of Chemicals in Soil and Water

• Natural organics are degraded quickly
• Many xenobiotics are not as easily broken down
• Synthetic chemicals are very resistant
• New research looks at producing plastics from
  natural plant chemicals
• Small differences in structure can make a big
  difference in biodegradability
• Chemicals leaching into ground water is a growing
  problem
• Sources are landfills, pesticides and illegal
  dumps

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Decomposition by Microbes
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• Bioremediation is the use of microbes to detoxify
  or degrade pollutants
• Microbes will degrade petroleum under aerobic
  conditions and high nutrients
• Bioaugmentation is the addition of genetically
  modified bacteria

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• Solid municipal wastes (garbage) is frequently
  placed in landfills
• Mostly anaerobic
• Promote activity of methanogens
• methane may be harvested to generate electricity
  or purified into natural gas
• Composting is the process of microbial digestion
  of plant materials converting them into organic
  fertilizer

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Aquatic Microbiology

• Bacteria do not often exist as isolated colonies
• They form slime-like communities called biofilms
• Cell-to-cell communication allows bacteria to
  organize into coordinated, functional communities
• Usually attached to a surface
• Some are floating particulate groups
• Floc
• Share nutrients
• somewhat sheltered from harsh environmental
  conditions
• allows for easier sharing of genetic information

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Biofilms
Form pillar-like structures with
channels Primitive circulatory system
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• Bacteria in biofilms work together to perform
  tasks
• 5 species are required to digest cellulose in
  ruminants
• Essential in proper sewage treatment
• Important health factor
• 1000X more resistant to antimicrobials
• CDC estimates 65 of infections caused by
  biofilms
• Preventative measures
• Incorporate antibiotics into potential biofilm
  surfaces
• Addition of lactoferrins which sequester iron
  need for bacteria mobility

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• Large numbers of microbes in a body of water
  indicate high nutrient levels
• Most aquatic microbes have appendages or
  holdfasts that attach to various surfaces
• Increases contact with nutrients to grow on
  stationary surface

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• Freshwater Microbiota
• Littoral zone along shore light penetrates
  throughout
• Limnetic zone- surface of open water away from
  shore
• Profundal zone deep water under limnetic zone
• Benthic zone- bottom (sediment)
• Populations are affected by the amount of light
  and availability of oxygen

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• Primary producers are found in the littoral and
  limnetic zones
• photosynthetic bacteria, protozoa and algae
• Oxygen does not diffuse into water well
• movement of water increases availability of
  oxygen
• Anaerobic photosynthetic bacteria metabolize
  hydrogen sulfide in the profundal zone
• Purple and green anoxygenic bacteria
• Benthic zone houses anaerobic sulfur reducing
  organisms
• Clostridium, Desulfovibrio and various methanogens

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• Seawater Microbiota
• Phytoplankton microscopic photosynthetic
  organisms
• Form basis of oceanic food chain
• Mostly cyanobacteria and single-cell algae
• Fix carbon dioxide into organic matter (sugar)
• Serve as food source for increasingly larger
  consumers
• Protozoa, which are prey for zooplankton, then
  fish
• Bioluminescence- light emission
• Some bioluminescent bacteria have developed
  symbiotic relationships with deep water fish
• Aid in capturing prey
• Have an enzyme called luciferase
• Picks up electrons from the electron transport
  chain
• Emits some of the electrons energy as a light
  photon

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Bioluminescence
Luciferase
FMNH2
FMN photon
Figure 27.13
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Role of Microbes in Water Quality

• Microbial water pollution is of primary interest
• especially pathogens
• Moving water below the surface is filtered
• water from deep springs and wells is usually good
  
• Fecal contamination is the most dangerous form of
  water pollution
• Many diseases are spread through oral-fecal route

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• CDC estimates 900,000 people contract water-borne
  illnesses yearly in the US
• 2 million annual deaths globally mostly children
• Diseases like typhoid fever and cholera are only
  spread through contaminated water

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• Chemical water contamination is also a concern
• Agricultural and industrial chemicals leach
  chemicals that are resistant to biodegradation
• Rural waters often have excess nitrates and
  phosphates from agricultural runoff, as well as
  pesticide contamination

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• Examples of industrial water pollution are
  mercury from paper production and synthetic
  detergents
• Mercury is converted to a soluble compound by
  microbes and accumulates in fish
• Coal mining wastes are high in iron and sulfur
• Microbes convert sulfur to sulfates lowering pH
  which causes insoluble iron hydroxide to form and
  precipitate

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Algal Blooms

• Biodegradable detergents and agricultural runoff
  can lead to algal blooms
• May lead to eutrophication or red tide

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• Most of the concern for water purity has been
  related to the transmission of disease
• Tests have been developed to determine the safety
  (potability) of water
• Tests are aimed at detecting indicator organisms
• Criteria for indicators include
• Present in human feces in high numbers
• Survive in water as well as pathogens would
• Detectable by simple tests

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Waterborne Diseases
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Coliforms

• Aerobic or facultatively anaerobic,
  gram-negative, nonendospore forming rods
• ferment lactose to acid gas within 48 hr, at
  35C
• Indicator organisms
• Used to detect fecal contamination in food or
  water
• Coliforms embedded in biofilms may not be
  detected
• Some pathogens, like protozoa, produce cysts that
  are more resistant than coliforms
• MPN
• Most probable number/100 ml of water

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MUG Test

• ONPG causes E. coli to make ?-galactosidase
• Indicates presence of coliforms (E. coli)

?- galactosidase
MUG
fluorescent compound