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Biodegradation of Chemicals
• Natural organics typically degraded quickly
• Most xenobiotics not as easily broken down
– Synthetic chemicals are often recalcitrant
• Chemicals leaching into ground water is a growing problem
– Sources are landfills, pesticides and illegal dumps
– Bioaccumulation
Small differences in structure can make a big difference in biodegradability
• Bioremediation
– use of microbes to detoxify
or degrade pollutants
– Oil spills provide a
dramatic example
– Bioaugmentation
• Solid municipal waste (garbage) is frequently placed in
landfills
– 150 million tons annually in US
– Mostly anaerobic conditions not conducive to the
biodegradation of organic material
– Promotes activity of methanogens
– Composting may reduce amount of organic material
entering landfills
• May be used as organic fertilizer depending on
origin
Aquatic Microbiology
• Bacteria don’t often exist as single species in isolated
colonies
• Often form biofilms attached to a surface or less often as
floating floc
• Essential in proper sewage treatment
• Important health factor
– Prevention involves incorporation of anti-bacterial agents into
potential colonization surfaces
• Benefits of biofilm formation:
– Cell-to-cell communication
– Share nutrients
– sheltered from harsh environmental conditions
– Easier sharing of genetic information
•Form pillar-like structures with channels
•Primitive circulatory system
•Individual bacteria and clumps of slime break away
• Establish new biofilms
• Large numbers of microbes in a body of water
indicate high nutrient levels
– Sewage or agricultural contamination
– Estuaries
• Aquatic microbes in nutrient poor systems may
have appendages or holdfasts for attachment
– Increases contact with nutrients
– Caulobacter and Hyphomicrobium
• Freshwater Microbiota
– Populations affected by light and oxygen availability
– Oxygen does not diffuse into water well
• movement increases availability
– Littoral zone
– Limnetic zone
– Profundal zone
– Benthic zone
• Seawater Microbiota
– Divides into zones based on light and O2 availability
– Includes abyssal zone dominated by archaea
– Phytoplankton
• microscopic photosynthetic organisms
• Mostly cyanobacteria and single-cell algae
• Form basis of oceanic food chain
– food source for increasingly larger consumers
(Protozoa, zooplankton, fish)
– Bioluminescence
• Luminescent bacteria have luciferase enzyme
• Picks up electrons and emits energy as photon of light
• Symbiotic relationships with deep water fish
– Aids fish in capturing prey
– Benefit to microbe?
Luminous organ
Water Pollution
• Chemical contamination
– Industrial wastes may leach chemicals resistant to
biodegradation
– Agricultural runoff may have excess nitrates and
phosphates, as well as pesticide contamination
Algal Blooms
• Biodegradable
detergents and
agricultural runoff
can lead to algal
blooms
• May lead to
eutrophication
Red tide
• Industrial water pollution includes mercury from
paper production
– 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
• Biosensors may be used
to detect pollutants
Luciferase
FMNH2
FMN + photon
Vibrio fisheri
• 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
quality
• Fecal contamination is the most dangerous form
of water pollution
– Many diseases are spread through oral-fecal route
Water Purity Tests
• Monitored to determine the safety of water
– potability
• Aimed at detecting indicator organisms
• Criteria include:
– Present in human feces in high numbers
– Survive in water as well as pathogens would
– Detectable by simple tests
• Coliforms commonly used to detect contamination
of drinking water
– Aerobic or facultatively anaerobic, gram-negative, non–
endospore forming rods
– Ferment lactose to acid & gas within 48 hr, at 35°C
– Not all are limited to intestinal tract of animals
– Most tests specific for fecal coliforms
• E. coli is dominant fecal coliform
MPN - most probable number/100 ml of water
Quantitative
but looks at
total coliforms
ONPG/MUG Test
-galactosidase
ONPG
MUG
yellow indicates coliforms
- glucuronidase
Blue indicates fecal coliforms
Qualitative only but
distinguishes fecal coliforms
Membrane filtration, utilizing
differential media like Eosin
Methylene Blue Agar (EMB), is
quantitative and specific for
fecal coliforms
• PCR utilizing gene specific primers may also be
used to detect microbes present due to sewage
contamination
• Specific group of fecal Streptococci (Enterococci)
used as indicators in recreational waters