The Microbial World and You

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• The Microbial World and You

Instructor Dr. Ahmad Saleh
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Microbes in Our Lives

• Microbiology is the study of microorganisms.
• The overall theme of the Microbiology course is
  to study the relationship between microbes and
  our lives.
• Microorganisms (microbes) are organisms that are
  too small to be seen with the unaided eye, and
  usually require a microscope to be seen.
• This relationship involves harmful effects such
  as diseases and food spoilage as well as many
  beneficial effects.
• Germ refers to a rapidly growing cell.
• Microorganisms include
• Bacteria
• Fungi (yeasts and molds)
• Microscopic Algae
• Protozoa
• Viruses, Viroids, Prions
• (Non-living infectious agents)

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Microbes in Our Lives

• These small organisms are usually associated with
  major diseases such as AIDS, uncomfortable
  infections, or food spoilage.
• However, the majority of microorganisms make
  crucial contributions to the to the welfare of
  the worlds inhabitants by maintaining balance of
  living organisms and chemicals in our
  environment.
• Therefore, Microorganisms are essential for life
  on earth.
• They have important beneficial biological
  functions
• Photosynthesis Marine and freshwater MO (Algae
  and some bacteria) capture energy from sunlight
  and convert it to food, forming the basis of the
  food chain in oceans, lakes, and rivers and
  generates oxygen which is critical for life on
  Earth.
• Decomposers Soil microbes break down dead and
  decaying matter and recycle chemical elements
  that can be used by other organisms.
• Nitrogen Fixation Some bacteria can take
  nitrogen from air and incorporate it into organic
  compounds in soil, water, and air.

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Microbes in Our Lives

• Digestion Human and many other animals have
  microorganisms in their digestive tract, that are
  essential for digestion and vitamin synthesis.
• Cellulose digestion by ruminants (cows, rabbits,
  etc.)
• Synthesis of Vitamin K (for blood clotting) and
  Vitamin B (for metabolism) in humans.
• Synthesis of chemical products MOs have many
  commercial applications, such as the synthesis of
  acetone, organic acids, enzymes, alcohols.
• Medicine Many antibiotics and other drugs are
  naturally synthesized by microbes.
• Penicillin is made by a mold.
• Food industry many important foods and beverages
  are made with microbes vinegar, pickles,
  alcoholic beverages, green olives, soy sauce,
  buttermilk, cheese, yogurt, and bread.

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Microbes in Our Lives

• Genetic engineering recombinant microbes produce
  important
• Medical and therapeutic products human growth
  hormone, insuline, blood clotting factor,
  recombinant vaccines, monoclonal antibodies,etc.
• Commercial products cellulose, digestive aids,
  and drain cleaner.
• Medical Research Microbes are well suited for
  biological and medical research for several
  reasons
• Relatively simple and small structures, easy to
  study
• Genetic material is easily manipulated.
• Can grow a large number of cells very quickly and
  at low cost.
• Short generation times make them very useful to
  study genetic changes.
• Though only a minority of MOs are pathogenic
  (disease-producing), practical knowledge of
  microbes is necessary for medicine and related
  heath sciences.
• Ex. Hospital workers must be able to protect
  patients from common microbes that are normally
  harmless but pose a threat to the sick and
  injured.

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Knowledge of Microorganisms

• Today we understand that MOs are almost
  everywhere !
• Yet not long ago, before the invention of the
  microscope, microbes were unknown to scientists
  and
• Thousands of people died in devastating
  epidemics, the causes of which were NOT
  understood.
• Entire families died because vaccinations and
  antibiotics were NOT available to fight
  infections.
• Therefore, knowledge of MOs allows humans to
• Prevent disease occurrence
• Prevent food spoilage
• Led to aseptic techniques to prevent
  contamination in medicine and in microbiology
  laboratories.

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Naming and Classifying Microorganisms

• Linnaeus established the system of scientific
  nomenclature (naming) of organisms in 1735.
• Latin was the language traditionally used by
  scholars.
• Scientific nomenclature assigns each organism two
  names (Binomial)
• The genus is the first name and is always
  capitalized.
• The specific epithet (species name) follows and
  is not capitalized.
• Are italicized or underlined.
• The genus is capitalized and the specific epithet
  is lower case.
• Are Latinized and used worldwide.
• May be descriptive or honor a scientist.

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Naming and Classifying Microorganisms

• Staphylococcus aureus
• Describes the clustered arrangement of the cells
  (staphylo), (coccus) indicates spherical shape,
  and the golden color of the colonies (aur-).
• Escherichia coli
• Honors the discoverer, Theodor Escherich, and
  describes the bacteriums habitatthe large
  intestine or colon.
• After the first use, scientific names may be
  abbreviated with the first letter of the genus
  and the specific epithet
• Staphylococcus aureus and Escherichia coli are
  found in the human body. S. aureus is on skin and
  E. coli in the large intestine.

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Types of Microorganisms BACTERIA (Sing.
Bacterium)

• Relatively Simple, single-celled (unicelluar)
  organisms.
• Prokaryotic (their genetic material is not
  enclosed in nuclear membrane)
• Prokaryotes include the bacteria and archaea
• Bacteria appear in one of several shapes
• Bacillus (rodlike), b. coccus (spherical),
• spiral (corkscrew or curved),
• some are star-shaped or square.
• Individual bacteria may form pairs, chains,
  clusters, or other groupings.
• Enclosed in cell walls largely composed of
  peptidoglycan (carbohydrate and protein complex).
• Reproduce by binary fission (division into two
  equal cells)
• For nutrition, most bacteria use organic
  chemicals derived from dead or living organisms.
• Some bacteria produce their food by
  photosynthesis, and some can derive nutrition
  from inorganic substances.
• Many bacteria can swim by using flagella (moving
  appendages).

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Types of MicroorganismsARCHAEA

• Consists of prokaryotic cells
• If they have cell walls, they lack peptidoglycan
• Archaea are not known to cause disease in humans.
• Live in extreme environments
• Are divided into three main groups
• Methanogens produce methane as waste product
  from respiration.
• Extreme halophiles Salt loving, live in
  extremely salty environments such as the Great
  Salt Lake and the Dead Sea.
• Extreme thermophiles Heat loving, live in hot
  sulfurous water such as hot springs.

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Types of Microorganisms FUNGI (S. Fungus)

• Eukaryotic (have a distinct nucleus containing
  the cells genetic material surrounded by a
  nuclear membrane)
• Organisms in kingdom Fungi may be Unicellular or
  multicellular
• Multicellular fungi, such as mushroom look like
  plants, but can not carry out photosynthesis.
• True fungi have cell walls composed of chitin.
• The unicellular fungi, yeasts, are oval MOs that
  are larger than bacteria.
• The most typical fungi are molds, composed of
  visible masses of filaments (hyphae) called
  mycelia.
• Use organic chemicals for energy, can not carry
  out photosynthesis.
• Fungi can reproduce sexually and asexually
• They obtain nutrients by absorbing solutions of
  organic material from environment soil, sea
  water, fresh water, or animal or plant host.
• Organisms called slime molds have characteristics
  of both fungi and ameobas.

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Types of Microorganisms PROTOZOA (S. Protozoan)

• Unicellular, eukaryotes microbes.
• Protozoa move by
• Pseudopods extensions of the cytoplasm like
  Ameoba.,
• Flagella long appendages for locomotion like
  Trypanosoma.
• Cilia numerous shorter appendages for locomotion
  like Paramecium.
• Protozoa have a variety of shapes.
• Live as free entities or as parasites (organisms
• that derive nutrients from living hosts).
• Absorb or ingest organic compounds from their
• environment)
• Protozoa can reproduce sexually and asexually.

Figure 1.1c
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Types of Microorganisms ALGAE (S. Alga)

• Photosynthetic eukaryotes
• Have wide variety of shapes
• Reproduce sexually and asexually.
• Unicellular and multicelluar.
• The cell walls of many algae, like those of
  plants,
• are composed of cellulose (a carbohydrate).
• Algae are aundant in fresh and salt water, in
  soil, and in association with plants.
• As photosynthesizers, algae need light, water,
  and carbon dioxide for food production and
  growth.
• Produce molecular oxygen and organic compounds
  (carbohydrates) that are used by other organisms,
  including animals.
• They play an important role in the balance of
  nature.

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Types of MicroorganismsVIRUSES

• So small that can be seen only with electron
  microscope.
• Acellular (not cellular).
• Structurally very simple, a virus particle
  contains
• a core made only of one type of nucleic acid,
• either DNA or RNA.consist of DNA or RNA
  core
• The core is surrounded by a protein coat.
• Sometimes the coat is enclosed in a lipid
  envelope.
• Viruses can reproduce only by using the cellular
  machinery of other organisms.
• Obligatory intracellular parasites (replicate
  only when they are in a living host cell)

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Multicellular Animal Parasites

• Multicellular animal parasites are not strictly
  MOs.
• They are of medical importance.
• They are eukaryotic organisms.
• Multicellular animals
• Parasitic flatworms and round worms are called
  helminths.
• During some stages of their life cycles,
  helminths are microscopic in size.

Figure 12.28a
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Classification of Microorganisms

• Before the existence of microbes was known, all
  organisms were grouped into either the animal
  kingdom or the plant kingdom.
• In 1978, Carl Woese, devised a system of
  classification based on the cellular organization
  of organisms.
• It groups all organisms in three domains as
  follows
• Bacteria (cell walls contain a protein-carbohydrat
  e complex called peptidoglycan)
• Archaea (cell walls, if present, lack
  peptidoglycan)
• Eukarya, which includes the following kingdoms
• Protists (slime molds, protozoa, and algae)
• Fungi (unicellular yeasts, multicellular molds,
  and mushrooms)
• Plants (includes mosses, ferns, conifers, and
  flowering plants)
• Animals (includes sponges, worms, insects, and
  vertebrates).

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A Brief History of Microbiology

• The science of Microbiology dates back only two
  hundred years.
• However, microorganisms have been around for
  thousands of years.
• Ancestors of bacteria were the first living cells
  to appear on Earth.
• The first microbes (animalcules) were observed in
  1673 by Leeuwenhoek.
• In 1665, Robert Hooke reported that living things
  were composed of little boxes or cells, with the
  help of a relatively crude
• microscope.
• In 1858, Rudolf Virchow said cells arise from
• preexisting cells.
• Cell theory All living things are composed of
  cells
• and come from preexisting cells.
• 1673-1723 Antoni van Leeuwenhoek described live
• microorganisms (animalcules) that he
  observed in
• teeth scrapings, rain water.

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The Debate Over Spontaneous Generation

• After van Leeuwenhoek discovered the invisible
  world of microorganisms, the scientific community
  of that time became interested in the origins of
  these tiny living things.
• Not much more than 100 years ago, many scientists
  and philosophers believed that some forms of life
  could arise spontaneously from nonliving matter,
  they called this the hypothesis of spontaneous
  generation.
• Therefore, people commonly believed that toads,
  snakes, and mice could be born of moist soil
  that flies could emerge from manure and that
  maggots, the larvae of flies, could arise from
  decaying corpses.
• According to spontaneous generation, a vital
  force forms life.
• The alternative hypothesis, that the living
  organisms arise from preexisting life, is called
  biogenesis.

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Evidence PRO and CONRedis Experiments

• In 1668 A strong opponent of SG, Francisco Redi
  set out to demonstrate that maggots did not arise
  spontaneously from decaying meat.
• Redi filled two jars with decaying meat.
• The first was left unsealed the flies thaid
  their eggs on the meat, and the eggs developed
  into larvae.
• The second jar was sealed and, because the flies
  couldnot lay their eggs on the meat, no maggots
  appeared.
• Redis antagonists were not convinced they
  claimed that fresh air was needed for spontaneous
  generation.
• Redi set up a second experiment, in which
• a jar was covered with a fine net instead of
  being sealed.
• No larvae appeared in the gauze-covered jar, even
  though air was present.
• Maggots appeared only when flies were allowed to
  leave eggs on the meat.
• Redis results blowed the belief that large forms
  of life could arise from nonlife.

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Evidence Pro and ConNeedhams and Spallanzanis
Exp.

• However, many scientists still believed that
  small organisms such as van Leeuwenhoeks
  animalcules were simple enough to be generated
  from nonliving material.
• In 1745 John Needham performed an experiment
  which seemed to strengthen the SG of MOs.
• He heated nutrient fluids (chicken broth)
• Poured them into covered flasks
• The cooled solution were soon teeming with
  microorganisms.
• Needham claimed that microbes developed
  spontaneously from the fluids.
• 20 years later, Lazzaro Spallanzani, suggested
  that MOs from the air probably had entered
  Needhams solutions after they were boiled.
• Spallanzani showed that nutrients fluids heated
  after being sealed in a flask did not develop
  microbial growth.
• Needham responded by claiming the vital force
  was destroyed by heat and kept out of the flasks
  by the seals.

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Evidence Pro and Con

• The vital force principle was strengthened
  when Anton Lavoisier showed the importance of
  oxygen to life.
• Therefore, Spallanzanis observations were
  criticized on the grounds that there was not
  enough oxygen in the sealed flasks to support
  microbial growth.
• In 1858, Rudolw Virchow challenged SG with the
  concept of Biogenesis, the claim that living
  cells can arise only from preexisting living
  cells.
• In 1861 Louis Pasteur demonstrated that
  microorganisms are present in the air and can
  contaminate sterile solutions, but air itself
  does not create microbes.
• He filled several short-necked flasks with beef
  broth and boiled them.
• Some were left open and allowed to cool.
• In a few days, these flasks were found to be
  contaminated with microbes.
• The sealed after-boiling flasks were free of
  microorganisms.
• Pasteur reasoned that microbes in the air were
  the agents responsible for contaminating
  nonliving matter.

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The Theory of Biogenesis

• Pasteur next placed broth in open-ended
  long-necked flasks and bent the necks into
  S-shaped curves.
• The contents of these flasks were then boiled and
  cooled.
• The broth of in the flasks did not decay and
  showed no signs of life.
• Pasteurs S-shaped neck allowed air to pass into
  the flask, but trapped the airborne MOs that
  might contaminate the broth.

Figure 1.3
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Pasteurs Findings

• Pasteur showed that MOs can be present in
  nonliving matter- on solids, in liquids, and in
  the air.
• He demonstrated that microbial life can be
  destroyed by heat and devised methods to block
  access of airborne MOs to nutrients.
• These discoveries forms the basis of aseptic
  techniques (techniques that prevent contamination
  by unwanted MOs.), which are now the standard
  practice in laboratory and many medical
  procedures.
• Pasteurs work provided evidence that MOs can not
  originate from mystical forces preset in
  nonliving materials.
• Scientists now believe that a form of spontaneous
  generation probably did occur on primitive Earth
  when life first began.
• Pasteur showed that microbes are responsible for
  fermentation.

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The Golden Age of Microbiology

• The period from 1857-1914, has been named the
  Golden Age of Microbiology.
• During this period, rapid advances headed by
  Pasteur and Robert Koch, led to the establishment
  of microbiology as a science.
• Beginning with Pasteurs work, discoveries
  included
• The agents of many diseases.
• The role of immunity in the prevention and cure
  of diseases.
• The relationship between microbes and disease.
• Antimicrobial drugs
• Improved the techniques for microscopy and
  culturing microorganisms.
• Development of vaccines and surgical techniques.
• Studying the chemical activities of
  microorganisms.

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Fermentation and Pasteurization

• At that time, many scientists believed that air
  converted the sugars in beverages into alcohols.
• Pasteur found instead that microbes called yeasts
  convert the sugars to alcohols in the absence of
  air in a process called fermentation.
• Fermentation is the conversion of sugar to
  alcohol to make beer and wine.
• Souring and spoilage are caused by different MOs
  called bacteria.
• In the presence of air, bacteria change the
  alcohol in the beverage into vinegar (acetic
  acid).
• Pasteurs solution to the spoilage problem was to
  heat the beer and wine just enough to kill most
  of the bacteria that caused the spoilage in a
  process called pasteurization.
• Pasteurization is now commonly used to reduce
  spoilage and kill potentially harmful bacteria in
  milk as well as in some alcoholic drinks.
• Showing the connection between spoilage of food
  and MOs was a major step towards establishing the
  relationship between disease and microbes.

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The Germ Theory of Disease

• Until relatively recently, the fact that many
  kinds of diseases are related to MOs was unknown.
• Before the time of Pasteur, effective treatments
  for many diseases were discovered by trial and
  error, but the causes of the diseases were
  unknown.
• The realization that yeasts play a crucial role
  in fermentation was the first link between the
  activity of a MO and physical and chemical
  changes in organic materials.
• This discovery alerted scientists that MOs might
  have similar relationships with plants and
  animals- specially, that MOs might cause
  diseases.
• This idea was known as the germ theory of
  disease.
• Many people did not accept this theory at that
  time, because for centuries disease was believed
  to be punishment for individuals crimes and
  misdeeds.
• Most people in Pasteurs time found it
  inconceivable that invisible microbes could
  travel through the air to infect plants and
  animals, or remain on clothing and bedding to be
  transmitted from one person to another.

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The Germ Theory of Disease

• 1835 Agostino Bassi showed that a silkworm
  disease was caused by a fungus.
• 1865 Pasteur found that another recent silkworm
  disease was caused by a protozoan.
• 1840s Ignaz Semmelwise advocated hand washing to
  prevent transmission of childbirth fever from one
  obstetrical patient to another.
• 1860s Joseph Lister used a chemical disinfectant
  (phenol) to prevent surgical wound infections
  after looking at Pasteurs work showing microbes
  are in the air, can spoil food, and cause animal
  diseases.
• 1876 Robert Koch proved for the first time that
  a bacterium causes anthrax and provided the
  experimental steps, Kochs postulates, to prove
  that a specific microbe causes a specific disease.

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Vaccination

• 1796 Edward Jenner found a way to protect people
  from smallpox almost 70 years before Koch
  established that microorganism causes anthrax.
• He inoculated a healthy 8-years-old volunteer
  with cowpox virus. The person was then protected
  from cowpox and smallpox.
• The process was called Vaccination, derived from
  Latine word vacca for cow.
• The protection from disease provided by
  vaccination or by recovery from the disease
  itself is called immunity.
• In about 1880, Pasteur discovered why vaccination
  work by working on cholera vaccination.
• Pasteur used the term vaccine for cultures of
  avirulent microorganisms used for preventive
  inoculation.
• Some vaccines are still produced from avirulent
  microbial strains, others are made from killed
  virulent microbes, from isolated components of
  virulent MOs, or by genetic engineering
  techniques.

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The Birth of Modern Chemotherapy

• Treatment of disease by using chemical substances
  is called chemotherapy.
• Chemotherapeutic agents prepared from chemicals
  in the laboratory are called synthetic drugs.
• Chemotherapeutic agents produced naturally by
  bacteria and fungi to act against other MOs are
  called antibiotics.
• The success of chemotherapy is based on the fact
  that some chemicals are more poisonous to MOs
  than to the hosts infected by the microbes.
• Quinine from tree bark was long used to treat
  malaria.
• 1910 Paul Ehrlich developed the first synthetic
  drug, Salvarsan, to treat syphilis. (the magic
  bullet!)
• 1930s Several other synthetic drugs derived from
  dyes that could destroy MOs were developed.
• Sulfonamides (sulfa drugs) were synthesized at
  about the same time.

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The Birth of Modern Chemotherapy

• 1928 Alexander Fleming discovered the first
  antibiotic.
• On a contaminated plate, around the mold
  (Penicillium) was a clear area where bacterial
  growth had been inhibited.
• He observed that the Penicillium mold made an
  antibiotic, penicillin, that killed S. aureus.
• 1940s Penicillin was tested clinically and mass
  produced.
• Since then, thousands of antibiotics have been
  discovered.
• Antibiotics and other chemotherapeutic drug faces
  many problem
• Toxicity to humans in practical use, specially
• antiviral drugs (why ?)
• The emergence and spread of new varieties
• of MOs that are resistant to antibiotics.
• (due to bacterial enzymes that inactivate
  antibiotics,
• or prevention of Abt. From entering the microbe.)

Figure 1.5
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Modern Developments in MicrobiologyBranches of
Microbiology

• Bacteriology is the study of bacteria.
• Began with the van Leeuwenhoeks first
  examination of tooth scrapings.
• New pathogenic bacteria are still discovered
  regularly.
• Many bacteriologists, look at the roles of
  bacteria in food and environment.
• Mycology is the study of fungi.
• Includes medical, agricultural, and ecological
  branches.
• Fungal infections accounting for 10 of hospital
  acquired infections.
• Parasitology is the study of protozoa and
  parasitic worms.
• Recent advances in genomics, the study of all of
  an organisms genes, have provided new tools for
  classifying microorganisms.
• Previously these MOs were classified according to
  a limited number of visible characteristics.

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Modern Developments in MicrobiologyBranches of
Microbiology

• Immunology is the study of immunity.
• Vaccines and interferons are being investigated
  to prevent and cure viral diseases.
• Vaccines are now available for numerous diseases,
  including measles, rubella (German measles),
  mumps, chickenpox, pneumococcal pneumonia,
  tetanus, tuberculosis, whooping coughs, polio,
  and hepatitis B.
• Smallpox was eradicated due to effective
  vaccination and polio is expected to.
• Interferons, substances produced by the bodys
  own
• immune system, inhibit the replication of
  viruses and
• are used to treat viral diseases and cancer.
• The use of immunology to identify and classify
  some
• bacteria according to serotypes (variants
  within
• a species) based on certain components in
  the cell
• walls of the bacteria, was proposed by
  Rebecca
• Lancefield in 1933.

Figure 1.4 (3 of 3)
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Modern Developments in MicrobiologyBranches of
Microbiology

• Virology is the study of viruses.
• In 1892, Dimitri Iwanowski reported that the
  organism that caused mosaic disease of tobacco
  was so small that is passed the bacterial
  filters.
• In 1935, Wendell Stanely demonstrated that the
  organism , called tobacco mosaic virus (TMV), was
  different from other microbes, so simple, and
  composed of only nucleic acid core and protein
  core.
• In 1940s, the development of electron microscope
  enabled the scientists to observe the structure
  and activity of viruses in detail.

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Modern Developments in MicrobiologyBranches of
Microbiology

• Recombinant DNA Technology
• In the 1960s, Paul Berg inserted animal DNA into
  bacterial DNA and the bacteria produced an animal
  protein.
• Recombinant DNA is DNA made from two different
  sources.
• Recombinant DNA technology, or genetic
  engineering, involves microbial genetics and
  molecular biology.
• Using microbes
• Beadle and Tatum showed that genes encode a
  cells enzymes (1942).
• Avery, MacLeod, and McCarty showed that DNA was
  the hereditary material (1944).
• Lederberg and Tatum discovered that genetic
  material could be transferred from one bacterium
  to another by conjugation (1946).
• Watson and Crick proposed a model for the
  structure of DNA (1953).
• Jacob and Monod discovered the role of mRNA in
  protein synthesis (1961).

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Microbes and Human Welfare

• Only minority of all MOs are pathogenic.
• Microbes that cause food spoilage are also a
  minority.
• The vast majority of microbes benefit humans,
  other animals, and plants in many ways.
• RECYCLING VITAL ELEMENTS
• In 1880s, Beijerinck and Winogradsky showed how
  bacteria help recycle vital elements between the
  soil and the atmosphere.
• Microbial ecology the study of the relationship
  between microorganisms and their environment.
• Microorganisms recycle carbon, nitrogen, sulfur,
  oxygen, and phosphorus into forms that can be
  used by plants and animals.
• Bacteria and fungi, return CO2 to the atmosphere
  when decomposing organic wastes and dead plants
  and animals.
• Algae, cyanobacteria, and plants use CO2 to
  produce carbohydrates.

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Microbes and Human Welfare

• SEWAGE TREATMENT Using microbes to recycle
  water.
• Recycling water and prevent the pollution of
  rivers and oceans
• Bacteria degrade organic matter in sewage (99
  water), producing such by-products as carbon
  dioxide, nitrates, phosphates, sulfates, ammonia,
  hydrogen sulfide, and methane.
• BIOREMEDIATION Using microbes to clean up
  pollutants.
• In 1988, microbes began used to clean up
  pollutants and
• toxic wastes produced by various industrial
  processes.
• Bacteria degrade or detoxify pollutants such as
  oil and
• mercury.
• In addition, bacterial enzymes are used in drain
• cleaners to remove clogs
• Such bioremedial microbes are Pseudomonas and
• Bacillus, their enzymes used in household
  detergents.

UN 2.1
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Microbes and Human Welfare

• INSECT BEST CONTROL BY MOs
• Insect pest control is important for both
  agriculture and the prevention of human diseases.
• Bacillus thuringiensis infections are fatal for
  many insects but harmless to other animals,
  including humans, and to plants.
• The bacteria produce protein crystals that are
  toxic to the digestive systems of the insects.
• The toxin gene has been inserted into some plants
  to make them insect resistant.
• Microbes that are pathogenic to insects are
  alternatives to chemical pesticides in preventing
  insect damage to agricultural crops, disease
  transmission, and avoid harming the environment.

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Microbes and Human Welfare

• MODERN BIOTECHNOLOGY AND RECOMBINANT DNA
  TECHNOLOGY
• Biotechnology, the use of microbes to produce
  foods and chemicals, is centuries old.
• Genetic engineering is a new technique for
  biotechnology. Through genetic engineering,
  bacteria and fungi can produce a variety of
  proteins including vaccines and enzymes.
• Recombinant DNA techniques have been used to
  produce a number of natural proteins, vaccines,
  and enzymes.
• The very exciting and important outcome of
  recombinant DNA techniques is Gene Therapy
  inserting a missing gene or replacing a defective
  one in human cells by using a harmless virus to
  carry the missing or new gene into certain host
  cells.
• Genetically modified bacteria are used to protect
  crops from insects, from freezing, and to improve
  the appearance, flavor, and shelf life of fruits
  and vegetables. (more Drought resistance and
  temperature tolerance)

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Microbes and Human DiseaseNORMAL MICROBIOTA

• We all live in a world filled with microbes, and
  we all have a variety of microorganisms on and in
  our bodies.
• Microbes normally present in and on the human
  body are called normal microbiota, or flora.
• Bacteria were once classified as plants giving
  rise to use of the term flora for microbes.
• This term has been replaced by microbiota.
• The normal microbiota not only harmless, but also
  benefit us.
• Some protect us against disease by preventing the
  over-growth of harmful microbes.
• Others produce useful substances such as vitamine
  K and B.
• Unfortunately, under some circumstances normal
  microbiota can make us sick or infect people we
  contact.

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Microbes and Human DiseaseINFECTIOUS DISEASES

• An infectious disease is one in which pathogens
  invade a susceptible host, such as a human or
  animal.
• The pathogen carries out at least part of its
  life cycle inside the host, and disease
  frequently results.
• When a pathogen overcomes the hosts resistance,
  disease results.
• Many mistakenly believed that infectious diseases
  were under control
• Malaria would be eradicated by killing mosquitoes
  by DDT.
• A vaccine would prevent diphtheria.
• Improved sanitation measures would help prevent
  cholera transmission.
• Recent outbreaks of such infectious diseases
  indicates that not only they are not
  disappearing, but seem to be reemerging and
  increasing.
• In addition, a number of new diseases -Emerging
  infectious diseases (EID)-have cropped up in
  recent years

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Microbes and Human DiseaseEMERGING INFECTIOUS
DISEASES

• Emerging infectious diseases (EID) are diseases
  that are new or changing and are increasing or
  have the potential to increase in incidence in
  the near future.
• Some factors that have contributed to the
  emergence of EIDs
• Evolutionary changes in existing organisms.
• The spread of known diseases to new geographic
  regions or populations by modern transportation.
• Increased human exposure to new, unusual
  infectious agents.
• West Nile encephalitis
• Caused by West Nile virus
• First diagnosed in the West Nile region of Uganda
  in 1937
• Appeared in New York City in 1999
• Bovine spongiform encephalopathy
• Caused by prion
• Also causes Creutzfeldt-Jakob disease (CJD)
• New variant CJD in humans is related to cattle
  feed from infected sheep.

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Emerging Infectious Diseases

• Escherichia coli O57H7
• Toxin-producing strain of E. coli
• First seen in 1982
• Leading cause of diarrhea worldwide
• Ebola hemorrhagic fever
• Caused by Ebola virus
• Causes fever, hemorrhaging, and blood clotting
• First identified near Ebola River, Congo
• Outbreaks every few years.
• Invasive group A Streptococcus
• Rapidly growing bacteria that cause extensive
  tissue damage
• Increased incidence since 1995
• Avian influenza A (H5N1)
• Caused by Influenza A virus (H5N1)
• Primarily in waterfowl and poultry
• Sustained human-to-human transmission has not
  occurred yet

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Emerging Infectious Diseases

• Severe acute respiratory syndrome (SARS)
• SARS-associated Coronavirus
• Occurred in 2002-2003
• Person-to-person transmission
• Cryptosporidiosis
• Caused by Cryptosporidium protozoa
• First reported in 1976
• Causes 30 of diarrheal illness in developing
  countries
• In the United States, transmitted via water
• Acquired immunodeficiency syndrome (AIDS)
• Caused by Human immunodeficiency virus (HIV)
• First identified in 1981
• Worldwide epidemic infecting 44 million people
  14,000 new infections daily
• Sexually transmitted disease affecting males and
  females
• In the United States, HIV/AIDS cases 30 are
  female and 75 are African American