Environmental Microbiology Chapter 26 Environmental Microbiology

Figure 26.01: Populations Lacking Access to Safe Drinking Water. 26.1 Water Pollution Includes Biological Changes Harmful to Water Quality Potability is water that is safe to drink Figure 26.01: Populations Lacking Access to Safe Drinking Water. Modified from The World’s Water 1998–1999 by Peter H. Gleick. © 1998 Island Press. Reproduced by permission of Island Press, Washington, D.C.

Unpolluted and polluted water contain different microbial populations. Unpolluted water contains low organic nutrients, thus low numbers of microbes. Water can be polluted with sewage. agricultural runoff. industrial pollutants. Polluted water is high in organic matter. coliform and noncoliform bacteria. Figure 26.02A: Microorganisms in Water Environments. © Eric Grave/Photo Researchers, Inc.

Figure 26.03: The death of a river. Accumulated phosphates cause algal blooms. The blooms supply nutrients to other microbes, which use up oxygen. Aquatic animals and plants die. They accumulate on the bottom where anaerobic bacteria thrive. Figure 26.03: The death of a river.

Halophiles, psychrophiles, and barophiles thrive in the ocean. Diatoms and dinoflagellates are integral parts of food chains in the ocean. Some dinoflagellates produce blooms called red tides. Their toxins can kill many fish species. Courtesy of GSFC/LaRC/JPL, MISR Team/NASA Figure 26.04B: Satellite photo of red tide. Figure 26.04A: Marine microorganisms. Courtesy of Professor Gordon T. Taylor, Stony Brook University/NSF Polar Programs/NOAA

There are three types of water pollution. Physical pollution occurs when sand and soil or cyanobacterial blooms cloud the water. Chemical pollution occurs when inorganic and organic waste enter the water. Biological pollution occurs when microorganisms enter the water from anthropogenic sources. The biological oxygen demand (BOD) of water is the amount of water microbes need to decompose organic matter.

Figure 26.05A: Legionella in the environment. Diseases can be transmitted by water. Diseases spread by contaminated water consumption include typhoid fever cholera shigellosis Legionnaires’ disease Erysipeloid is an infection caused by the marine pathogen Erysipelothrix rhusiopathiae. Figure 26.05B: Legionella. Courtesy of Don Howard/CDC Figure 26.05A: Legionella in the environment. Courtesy of CDC

Vibrio vulnificus can cause: Mycobacterium marinum can cause a lesion (granuloma) at the site of a wound called Fish Handler’s Disease. Vibrio vulnificus can cause: intestinal illness if consumed in raw oysters wound infections involving gangrene and necrotizing fasciitis. Courtesy of Chau Nguyen, M.D., Memorial University of Newfoundland Figure MF26.01: Nodules resulting from infection by Mycobacterium marinum.

Water can also transmit: Viruses such as hepatitis A rotavirus gastroenteritis polio virus Eukaryotic microorganisms like Entamoeba histolytica Giardia lamblia Crytosporidium Toxin-producing dinoflagellates, which cause ciguatera poisoning in humans. For example, Gambierdiscus toxicus

26.2 Proper Treatment of Water and Sewage Ensures Safe Drinking Water Water purification is a three-step process. Sedimentation removes large objects and particles through flocculation. Filtration removes microorganisms by passing water through a layer of: sand Gravel microbe biofilm Chlorination involves adding chlorine gas to kill remaining organisms. Figure 26.06: Steps in the Purification of Municipal Water Supplies.

Sewage treatment can be a multistep process. Domestic human waste usually empties into a cesspool or septic tank. Dried Bacillus subtilis is added to accelerate digestion Septic tanks must be periodically pumped out Sewage (and livestock waste) can be collected in oxidation lagoons. Natural digestion occurs.

Figure 26.07: A sewage treatment facility. Sewage treatment plants can treat large amounts of domestic wastewater. Primary treatment screens out large particles Waste is sent to sedimentation tanks Sludge is flocculated Figure 26.07: A sewage treatment facility.

Figure 26.08: A Trickling Filter. Secondary treatment Aerobic bacteria metabolize organic matter and produce CO2 and H2O Activated sludge system Trickling filter Tertiary treatment May need chlorine added May need to remove Pesticides fertilizers phosphates Figure 26.08: A Trickling Filter. © Jonathan A. Meyers/Photo Researchers, Inc.

Figure 26.09: Biofilm contamination. Biofilms are prevalent in the environment. A biofilm is an immobilized population of microbes tangled together in fibers adhering to a surface. Microbes in a biofilm work together for nutrient storage production predator protection communicate with each other by quorum sensing Biofilms are used in bioremediation to degrade toxic wastes. Biofilms can form in the human body and on medical instruments. Figure 26.09: Biofilm contamination. Courtesy of Dr. Rodney M. Donlan and Janice Carr/CDC

Figure 26.10: Collection of Water for Analysis. The bacteriological analysis of water tests for indicator organisms. Presence of indicator organisms shows that water has been contaminated by feces. Coliform bacteria live in mammalian intestines but can survive in water. The membrane filter technique and standard plate count (SPC) are used to determine numbers of bacteria in a water sample. The most probable number (MPN) test determines number of bacteria by observing carbon dioxide gas production. Figure 26.10: Collection of Water for Analysis. Courtesy of Scott Bauer/USDA

26.3 Microbes Are Indispensable for Recycling Major Chemical Elements The carbon cycle is influenced by microorganisms. Photosynthetic organisms convert CO2 into carbohydrates, called carbon fixation. Decomposers convert dead organic matter to release CO2 for reuse by plants. Figure 26.11: A simplified carbon cycle.

Figure 26.12: The Sulfur Cycle. The sulfur cycle recycles sulfate molecules. Microbes break down proteins and amino acids to yield compounds like hydrogen sulfide. Several bacterial genera transform hydrogen sulfide to sulfate. Plants use the sulfate in amino acids. Figure 26.12: The Sulfur Cycle.

The Nitrogen Cycle Is Dependent on Microorganisms Many microbes release nitrogen from urea, amino acids and nitrogenous organic matter. In mineralization organic compounds are converted to inorganic other microbes convert nitrogen compounds to other forms of nitrogen. Figure 26.13: A simplified nitrogen cycle.

Nitrogen-fixing microbes live symbiotically with legume roots. They provide the plant and surrounding soil with usable nitrogen. Crops should be rotated each year to take advantage of this natural fertilizer Figure 26.14A: Nitrogen fixation, root nodules on cowpeas. Figure 26.14B: Rhizobium leguminosarum. © Medical-on-Line/Alamy Images © DS70/iStockphoto