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
• 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
• Chemical contamination– Industrial wastes may leach chemicals resistant to
biodegradation
– Agricultural runoff may have excess nitrates and phosphates, as well as pesticide contamination
Water Pollution
• Biodegradable detergents and agricultural runoff can lead to algal blooms
• May lead to eutrophication
Algal Blooms
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
• 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
• 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
Water Purity 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
-galactosidase
ONPG yellow indicates coliforms
ONPG/MUG Test
MUG Blue indicates fecal coliforms- glucuronidase
Qualitative only but distinguishes fecal coliforms
Membrane filtration, utilizing differential media like Eosin Methylene Blue Agar (EMB), is quantitative and specific for fecal coliforms
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