biodegradation of chemicals

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

• 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

• Biosensors may be used to detect pollutants

Vibrio fisheriFMNH2

LuciferaseFMN + photon

• 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

MPN - most probable number/100 ml of water

Quantitative but looks at total coliforms

-galactosidaseONPG 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

• 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