Transcript Chapter 27
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