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© 2012 Pearson Education Inc.
Lecture prepared by Mindy Miller-Kittrell North Carolina State University
Chapter 22
Applied and
Environmental
Microbiology
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Food Microbiology
• Microorganisms are involved in producingmany foods and beverages
• Fermentation produces desirable
characteristics of various foods• Microbial metabolism has other functions
– Acts as a preservative
– Destroys many pathogenic microbes and toxins
– Can add nutritional value in form of vitamins or other nutrients
• Microbes are used in food production
• Microbes can help control food spoilage
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Food Microbiology
• The Roles of Microorganisms in Food
Production
– Fermentation
– Any desirable change to a food or beverage thatoccurs as a result of microbial growth
– Spoilage is unwanted change to a food due to
various reasons
– Undesirable metabolic reactions – Growth of pathogens
– Presence of unwanted microorganisms in the food
© 2012 Pearson Education Inc.
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Food Microbiology
• The Roles of Microorganisms in Food
Production
– Use starter cultures in commercial food and
beverage production – Composed of known microorganisms
– Consistently perform specific fermentations
– Many common products result from fermentation
of vegetables, meats, and dairy products
© 2012 Pearson Education Inc.
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Figure 25.1 The cheese-making process
Pasteurization kills
unwanted microorganisms
Addition of starter
bacterial culture
Coagulation of milk
proteins (curd formation)
Disposal of
liquid whey as
waste product
Production of
unprocessed
cheeses
Cutting
of curds
Production of processed
cheeses through pressing,
addition of secondary
microbial cultures, and
aging (ripening)
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Food Microbiology
• The Roles of Microorganisms in Food
Production
– Products of alcoholic fermentation
– Alcoholic fermentation – Microorganisms convert simple sugars into alcohol
and carbon dioxide
– Specific starter cultures used in commercial
applications of alcohol fermentation – Various alcoholic products made through
fermentation
© 2012 Pearson Education Inc.
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Figure 25.2 The wine-making process
Preparation of must by stemming
and crushing of grapes (or other fruit)
Addition of starter cultureof yeast and bacteria
Fermentation
of must
(crushed
fruit) or of
juice alone
into wine
Clarification
of wine
Aging
of wine
Bottling
of wine
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Figure 25.3 The beer-brewing process
Barley is moistened and germinated,
producing enzymes that convert
starch into sugars. Barley is then dried
to halt germination, and crushed to
produce malt.
Mashing malt and
adjuncts with warm
water allows
enzymatic activity
to generate moresugars. Solids are
removed to
produce wort. Mashing kettle
Addition of hops for flavoring
Cooking of wort halts enzymatic
activity, extracts flavor from hops,
and kills the microorganisms present.
Removal
of hops
Addition of yeast culture
Wort fermentsinto beer.
Aging, filtering
or pasteurization,
and bottling
finish the
process.
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Food Microbiology
• The Causes of Food Spoilage
– Food spoilage results from intrinsic or
extrinsic factors
– Intrinsic factors are inherent properties of thefood itself
– Extrinsic factors involved with processing or
handling of food
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Table 25.2 Factors Affecting Food Spoilage
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Food Microbiology
• The Causes of Food Spoilage
– Classifying foods in terms of potential for spoilage
– Three categories based on likelihood of spoilage
– Perishable – Nutrient rich, moist, and unprotected by coverings
– Semi-perishable
– Can store sealed for months without spoiling
– Many fermented foods are semi-perishable
– Nonperishable
– Dry or canned foods that can be stored indefinitely
– Often nutrient poor, dried, fermented, or preserved
© 2012 Pearson Education Inc.
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Food Microbiology
• The Causes of Food Spoilage
– The prevention of food spoilage
– Food-processing methods
– Industrial canning – Eliminates mesophilic bacteria and endospores
– Pasteurization
– Lowers microbe numbers, but some microbes survive
– Lyophilization – A vacuum draws off ice crystals from frozen foods
– Gamma radiation
– Can achieve complete sterilization
© 2012 Pearson Education Inc.
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Figure 25.4 Industrial canning
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Food Microbiology
• The Causes of Food Spoilage
– The prevention of food spoilage
– Use of preservatives
– Salt and sugar remove water from the food – Garlic contains allicin, which inhibits enzyme function
– Benzoic acid interferes with enzymatic function
– Certain spices and herbs interfere with the functions of
membranes of microorganisms – Chemical preservatives can be purposely added to
foods
© 2012 Pearson Education Inc.
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Food Microbiology
• The Causes of Food Spoilage
– The prevention of food spoilage
– Attention to temperature during processing and
storage – High temperatures desirable to prevent food
spoilage
– Proteins and enzymes become denatured
– Low temperatures are desirable for food storage
– Cold slows metabolism and retards microbial growth
– Listeria monocytogenes can grow in cold storage
– Found in certain dairy products
© 2012 Pearson Education Inc.
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Food Microbiology
• Foodborne Illnesses
– Consumption of spoiled foods or foods containing
harmful microbes or their products
– Two categories of food poisoning – Food infections
– Consumption of living microorganisms
– Food intoxications
– Consumption of microbial toxins rather than themicrobe
– Symptoms include nausea, vomiting, diarrhea,
fever, fatigue, and muscle cramps
© 2012 Pearson Education Inc.
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Industrial Microbiology
• Important field within the microbiological
sciences
• Industrial microbiology used in various
applications – Microbes in fermentation
– Microbes in the production of several industrial
products
– Treatment of water and wastewaters
– Disposal and cleanup of biological wastes
– Treatment of mine drainage
© 2012 Pearson Education Inc.
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Industrial Microbiology
• The Roles of Microbes in Industrial
Fermentations
– Industrial fermentations
– Large-scale growth of particular microbes for producing beneficial compounds
– Examples include amino acids and vitamins
© 2012 Pearson Education Inc.
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Industrial Microbiology
• The Roles of Microbes in Industrial
Fermentations
– Primary metabolites
– Produced during active growth and metabolism – Required for reproduction or are by-products of
metabolism
– Secondary metabolites
– Produced after the culture has entered stationarygrowth
– Substances are not immediately needed for growth
© 2012 Pearson Education Inc.
Figure 25 5 Fermentation vats
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Figure 25.5 Fermentation vats
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Industrial Microbiology
• Industrial Products of Microorganisms
– Microorganisms produce array of industrially
useful chemicals
– Recombinant organisms add to this diversity – Produce substances not normally made by
microbial cells
© 2012 Pearson Education Inc.
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Industrial Microbiology
• Industrial Products of Microorganisms
– Enzymes and other industrial products
– Microbial products used as food additives and
supplements – Include vitamins, amino acids, organic acids, dyes
– Alternative fuels
– Some microbes produce carbohydrates used as fuels
– Other microbes convert biomass into renewable fuels
– Pharmaceuticals
– Includes antimicrobials, recombinant hormones, and
other cell regulators
© 2012 Pearson Education Inc.
Figure 25 6 Burning methane gas released from a landfill
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Figure 25.6 Burning methane gas released from a landfill
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Industrial Microbiology
• Industrial Products of Microorganisms
– Pesticides and agricultural products
– Microbes used to help crop management
– Biosensors and bioreporters – Use of microorganisms to solve environmentalproblems
– Biosensors
– Bacteria or microbial products combined with
electronic measuring devices
– Bioreporters
– Composed of microbes with innate signalingcapabilities
© 2012 Pearson Education Inc.
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Industrial Microbiology
• Water Treatment
– Water pollution
– Water pollution can occur three ways
– Physically – Chemically
– Biologically
– Polluted waters support a greater than normal
microbial load
© 2012 Pearson Education Inc.
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Industrial Microbiology
• Water Treatment
– Waterborne illnesses
– Consuming contaminated water can cause
various diseases – Diarrheal diseases occur worldwide
– Waterborne diseases rare in the United States
– Outbreaks are point-source infections
– Water treatment removes most waterbornepathogens
© 2012 Pearson Education Inc.
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Industrial Microbiology
• Water Treatment
– Treatment of drinking water
– Potable water is water considered safe to drink
– Water is not devoid of microorganisms and chemicals – Levels are low enough that they are not a health
concern
– Presence of coliforms in water indicates fecal
contamination
– Increased likelihood that disease-causing microbes
are present
– Treatment of drinking water involves four stages
© 2012 Pearson Education Inc.
Figure 25.7 The treatment of drinking water-overview
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Industrial Microbiology
• Water Treatment
– Water quality testing
– Majority of waterborne illnesses caused by fecally
contaminated water – Indicator organisms signal possible presence of
pathogens
– E. coli or other coliforms used as indicator organisms
– E. coli is a good indicator organism – Consistently found in human waste
– Survives in water as long as most pathogens
– Easily detected by simple tests
© 2012 Pearson Education Inc.
Figure 25.8 Two water quality tests-overview
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g q y
i i i
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Industrial Microbiology
• Water Treatment
– Treatment of wastewater
– Wastewater
– Water that leaves homes or businesses after use – Wastewater contains a variety of contaminants
– Treatment intended to remove or reduce
contaminants
– Processed to reduce the biochemical oxygendemand (BOD)
– Oxygen needed by aerobic bacteria to metabolize
wastes
– Levels reduced so unable to support microbial growth© 2012 Pearson Education Inc.
Figure 25.9 Traditional sewage treatment-overview
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Figure 25.10 A home septic system
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House
Sedimentation in septic tank Filtration in leach field
Sludge
(must be pumped out eventually)
Pipes beneath ground distribute
water through leach field
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E i t l Mi bi l
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Environmental Microbiology
• Studies the microorganisms as they occur intheir natural habitats
• Microbes flourish in every habitat on Earth
• Microbes are important to the cycling of chemical elements
© 2012 Pearson Education Inc.
E i t l Mi bi l
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Environmental Microbiology
• Microbial Ecology
– Study of the interrelationships among
microorganisms and the environment
– Two aspects to consider – Levels of microbial associations in the
environment
– Role of adaptation in microbial survival
© 2012 Pearson Education Inc.
Figure 25.12 The basic relationships among microorganisms and between microorganisms and the environment
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Biosphere
Heterogeneous
microbial communities
(all guilds together)
Guilds of related
populations
(e.g., photosynthetic
microorganisms at surface)
Populations of microbes
inhabit microhabitats
(e.g., cyanobacteria, algae)
Soil
ecosystem
Soilhabitats
Soil particlemicrohabitats
E i t l Mi bi l
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Environmental Microbiology
• Microbial Ecology
– Role of adaptation in microbial survival
– Most microorganisms live in harsh environments
– Microbes must be specially adapted to survive
– Microbes must adapt to constantly varying
conditions
– Extremophiles
– Adapted to extremely harsh conditions
– Can survive only in these habitats
© 2012 Pearson Education Inc.
E i t l Mi bi l
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Environmental Microbiology
• Microbial Ecology
– Role of adaptation in microbial survival
– Biodiversity held in balance by various checks
– Competition – Antagonism
– Cooperation
© 2012 Pearson Education Inc.
Environmental Microbiology
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Environmental Microbiology
• Bioremediation
– Uses organisms to clean up toxic, hazardous,
or recalcitrant compounds by degrading them
to harmless compounds
– Most known application is use of bacteria to
clean oil spills
© 2012 Pearson Education Inc.
Industrial Microbiology
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Industrial Microbiology
• Two Types of Bioremediation
– Natural bioremediation
– Microbes “encouraged” to degrade toxic
substances in soil or water
– Addition of nutrients stimulate microbe growth
– Artificial bioremediation
– Genetically modified microbes degrade
specific pollutants
© 2012 Pearson Education Inc.
Industrial Microbiology
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Industrial Microbiology
• The Problem of Acid Mine Drainage
– Drainage results from exposure of certain metal
ores to oxygen and microbial action
– Resulting compounds are carried into streamsand rivers
– Causes decrease in pH
– Can kill fish, plants, and other organisms
– Acidic water unfit for human consumption – Some microbes flourish in these acidic conditions
© 2012 Pearson Education Inc.
Figure 25.13 The effects of acid mine drainage
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Figure 25.14 An acid-loving microbe
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Figure 25.15 Simplified carbon cycle
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Fungi, bacteria
Methane
Dead organisms
Animals
Fossil fuels
Plastics and
other artificial
products
Atmospheric CO2 and CO2
dissolved in water
Fixation
(into organic carbon)
Decomposition Respiration Combustion
Consumption
Autotrophs (plants, algae,
photosynthetic bacteria, protozoa,
chemoautotrophic bacteria)
Figure 25.16 Simplified nitrogen cycle
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DeaminationWastes,
dead cells
Organisms
(proteins, nucleic
acids, etc.)
N2 in atmosphere
NO2
NO3 NO2
NH4
NH3
Nitrification
Ammonification
Denitrification
Nitrogen fixation
A n a m m o x r
e a c t i o n s
Figure 25.17 Simplified sulfur cycle
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Dissimilation
Reduction Oxidation
Oxidation
SO42
S0 H2S
Plant, algal, and
prokaryotic proteins
Animal
proteins
Proteins from
dead organismsAmino
acids
Environmental Microbiology
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Environmental Microbiology
• Role of Microorganisms in BiogeochemicalCycle
– Phosphorus cycle
– Environmental phosphorus undergoes little changein oxidation state
– Phosphorus converted from insoluble to soluble
forms
– Becomes available for uptake by organisms – Conversion of phosphorus from organic to inorganic
forms
– Occurs by pH –dependent processes
© 2012 Pearson Education Inc.
Environmental Microbiology
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Environmental Microbiology
• Role of Microorganisms in BiogeochemicalCycle
– The cycling of metals
– Metal ions are important microbial nutrients – Primarily involves transition from insoluble to
soluble forms
– Allows trace metals to be be used by organisms
© 2012 Pearson Education Inc.
Environmental Microbiology
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Environmental Microbiology
• Soil Microbiology
– Examines the roles played by organisms
living in soil
– Nature of soils – Soil arises from the weathering of rocks
– Soil also produced through the actions of
microorganisms
© 2012 Pearson Education Inc.
Figure 25.18 The soil layers and the distributions of nutrients and microorganisms within them
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Topsoil
Subsoil
Bedrock
Organics,nutrients
Numbers of microorganisms
Decrease
with depth
Decrease
with depthbut stillpresent inbedrock
Environmental Microbiology
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Environmental Microbiology
• Soil Microbiology
– Environmental factors affecting microbial
abundance in soils
– Moisture content
– Moist soils support microbial growth better than
dry soils
– Oxygen
– Moist soils are lower in oxygen than dry soils
– Oxygen dissolves poorly in water
– pH
– Highly acidic and highly basic soils favor fungi
© 2012 Pearson Education Inc.
Environmental Microbiology
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Environmental Microbiology
• Soil Microbiology
– Environmental factors affecting microbial
abundance in soils
– Temperature
– Most soil organisms are mesophiles
– Nutrient availability
– Microbial community size determined by how
much organic material is available
© 2012 Pearson Education Inc.
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Table 25.7 Selected Soilborne Diseases of Humans and Plants
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Environmental Microbiology
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Environmental Microbiology
• Aquatic Microbiology – Study of microbes living in freshwater and marine
environments
– Water ecosystems support fewer microbes
than soil – Due to dilution of nutrients
– Types of aquatic habitats
– Freshwater systems – characterized by low salt
content – Marine systems – characterized by a salt content
of ~3.5%
– Specialized aquatic systems – salt lakes, iron
springs, and sulfur springs© 2012 Pearson Education Inc.
Environmental Microbiology
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v o e c ob o ogy
• Aquatic Microbiology – Types of aquatic habitats
– Freshwater systems
– Characterized by low salt content
– Marine systems
– Characterized by a salt content of ~3.5%
– Specialized aquatic systems
– Salt lakes, iron springs, and sulfur springs
© 2012 Pearson Education Inc.
Figure 25.19 Vertical zonation in deep bodies of water-overview
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Biological Warfare and Bioterrorism
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g
• Microbes can be fashioned into biologicalweapons
• Bioterrorism
– Uses microbes or their toxins to terrorize humanpopulations
• Agroterrorism
– Uses microbes to terrorize human populations by
destroying the food supply
© 2012 Pearson Education Inc.
Biological Warfare and Bioterrorism
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• Assessing Microorganisms as PotentialAgents of Warfare or Terror
– Not all organisms have potential as biological
weapons
– Governments have criteria to assess biological
threats to humans
– Evaluate the potential of microorganisms to be
“weaponized” – Help focus research and defense efforts where
needed
© 2012 Pearson Education Inc.
Biological Warfare and Bioterrorism
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• Assessing Microorganisms as Potential Agentsof Warfare or Terror
– Criteria for biological threats to humans based on:
– Public health impact
– Ability of hospitals and clinics to handle the casualties
– Delivery potential
– How easily agent can be introduced into the population
– Public perception
– Effect of public fear on ability to control an outbreak
– Public health preparedness
– Existing response measures
© 2012 Pearson Education Inc.
Biological Warfare and Bioterrorism
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• Assessing Microorganisms as PotentialAgents of Warfare or Terror
– Criteria for assessing biological threats to livestock
and poultry
– Criteria similar to those used to evaluate potential
human threats
– Include agricultural impact, delivery potential, and
plausible deniability
© 2012 Pearson Education Inc.
Biological Warfare and Bioterrorism
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• Assessing Microorganisms as PotentialAgents of Warfare or Terror
– Criteria for assessing biological threats to
agriculture crops
– Plant diseases generally not as contagious as
animal or human diseases
– Criteria based on several factors
– Predicted extent of crop loss
– Delivery and dissemination potential
– Containment potential
© 2012 Pearson Education Inc.
Biological Warfare and Bioterrorism
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• Known Microbial Threats – Various microorganisms considered threats
as agents of bioterrorism
– Three types
– Human pathogens
– Animal pathogens
– Plant pathogens
© 2012 Pearson Education Inc.
Table 25.8 Bioterrorist Threats to Humans in Order of Concern
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Biological Warfare and Bioterrorism
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• Known Microbial Threats – Animal pathogens
– Divided into categories based on level of danger
– Some agents could potentially amplify an outbreak – Infect wild animal populations in addition to livestock
– Foot-and-mouth disease is most dangerous of the
agents
– It affects all wild and domestic cloven-hoofed animals
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Biological Warfare and Bioterrorism
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• Known Microbial Threats – Plant pathogens
– Most potential agents are fungi
– Dissemination could easily result in
contamination of soils
– All agents are naturally present
– Detecting difference between a natural outbreak
and an intentional attack would be difficult
© 2012 Pearson Education Inc.
Biological Warfare and Bioterrorism
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• Defense Against Bioterrorism – Much can be done to limit impact of an attack
– Key is coupling surveillance with effective
response protocols
© 2012 Pearson Education Inc.
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Biological Warfare and Bioterrorism
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• Defense Against Bioterrorism – Agroterrorism
– Little security protecting nation’s agricultural
enterprises
– Livestock and poultry often moved without being
tested for disease
– Many agricultural facilities are open to the public
– Methods to help defend against agroterrorism
– Screening of animals
– Restricting public access to agricultural facilities
© 2012 Pearson Education Inc.
Biological Warfare and Bioterrorism
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• The Roles of Recombinant GeneticTechnology in Bioterrorism
– Could use to create new or modify biological
threats
– Traits of various agents could be combined to
create novel agents
– No immunity would exist in the population
– Terrorists theoretically could make their own
microbes
© 2012 Pearson Education Inc.
Biological Warfare and Bioterrorism
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• The Roles of Recombinant GeneticTechnology in Bioterrorism
– Could be used to thwart bioterrorism
– Scientists can identify unique genetic sequences
– May aid in tracking biological agents and
determining their source
– Genetic techniques could help develop vaccines,
treatments, and pathogen-resistant crops