Download Chapter 26: Environmental Microbiology

Chapter 26
Environmental Microbiology
26.1 Water Pollution
• 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
• 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
• Halophiles, psychrophiles, and barophiles thrive in the ocean
• Diatoms and dinoflagellates are integral parts of food chains in the ocean
• Most marine microorganisms live in the littoral zone
• Some can live in the deep benthic and abyssal zones
• 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
• Diseases Can Be Transmitted by Water
• Diseases spread by contaminated water consumption include
• typhoid fever
• cholera
• shigellosis
• Legionnaires’ disease
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Erysipeloid is an infection caused by the marine pathogen Erysipelothrix
rhusiopathiae
Mycobacterium marinum can cause a lesion (granuloma) at the site of a wound
Vibrio vulnificus can cause
• intestinal illness if consumed
• wound infections involving gangrene and necrotizing fasciitis
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 The Treatment of Water and Sewage
• 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
• accumulated microbe biofilm
• Chlorination involves adding chlorine gas to kill remaining organisms
• Sewage Treatment Can Be a Multistep Process
• Domestic human waste usually empties into a cesspool or septic tank
• Sewage (and livestock waste) can be collected in oxidation lagoons
• Natural digestion occurs
• Sewage treatment plants can treat large amounts of domestic wastewater
• 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
• Biofilms are used in bioremediation to degrade toxic wastes
• Biofilms can form in the human body and on
medical instruments
• 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 are used to
determine numbers of bacteria in a water sample
• The most probable number test determines number of bacteria by
observing carbon dioxide gas production
26.3 The Cycles of Elements in the Environment
• The Carbon Cycle Is Influenced by Microorganisms
• The Sulfur Cycle Recycles Sulfate Molecules
• Microbes break down proteins and amino acids to yield compounds like
hydrogen sulfide
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Several bacterial genera transform hydrogen sulfide to sulfate
• Plants use the sulfate in amino acids
The Nitrogen Cycle Is Dependent on Microorganisms
Nitrogen-fixing microbes live symbiotically with legume roots
• They provide the plant and surrounding soil with usable nitrogen