Chapter 1 Lecture Outline

1.3 Members of the Microbial world

*Two basic cell structures* *-Prokaryotes* do not have a membrane-bound nucleus *-Eukaryotes* have a membrane-bound nucleus and organelles* *All living things can be classified into one of three groups, or domains* -Bacteria -Archaea -Eukarya *Organisms in each domain share certain important properties*

1.3 Acellular Infectious Agents

*Viroids* -Simpler than viruses -Require host cell for replication -Consist of single short piece of RNA -No protective protein coat -Cause plant diseases -Some scientists speculate they may cause diseases in humans *No evidence yet

1.3 Acellular Infectious Agents

*Viruses* -Nucleic acid packaged in protein coat -Variety of shapes -Infect living cells, termed *hosts* -Multiply using host machinery, nutrients -Inactive outside of hosts: *obligate intracellular parasites* -All forms of life can be infected by different types

1.1 The Scientific Method

-Make an observation -Develop a testable explanation called an hypothesis -Design experiments to test the hypothesis -Do the experiment, collect and analyze data -Draw a conclusion -Communicate methods, results and conclusions -A *scientific theory* is an explanation supported by a large amount of evidence

1.3 Domain Eukary

-Parasitic *helminths* are worms that live at the expense of a host -Adult stage can usually be seen without magnification -Eggs and larvae are microscopic -Helminths include roundworms, tapeworms,and flukes

1.3 Acellular Infectious Agents

-Viruses, viroids, prions *-Acellular infectious agents* -Not alive -Not microorganisms, so general term *microbe* often used to include them

1.2 Host-Microbe Interactions

*-All surfaces of human body populated by microorganisms* *-Beneficial microbes* -Termed normal microbiota or normal flora -Prevent diseases by competing with pathogens -Development of immune system response -Aid in digestion *-Pathogens* -Damage body tissues -----> disease symptoms

1.1 Golden Age of Microbiology

*-As spontaneous generation was disproved, Golden Age of Microbiology was born* *-The principle that microorganisms cause diseases is known as Germ Theory of Disease.* -Most pathogenic bacteria identified (1875-1918) -Work on viruses began -Understanding that microscopic agents could cause disease led to control efforts -Huge improvements in past century in human health *Antibiotics to treat infectious diseases *Vaccines to prevent diseases

1.2 Applications of Microbiology

*-Bacteria synthesize commercially valuable products* *-Examples include:* -Cellulose (stereo headsets) -Hydroxybutyric acid (manufacture of disposable diapers and plastics) -Ethanol (biofuel) -Hydrogen gas (possible biofuel) -Oil (possible biofuel) -Insect toxins (insecticides) -Antibiotics (treatment of disease) -Amino acids (dietary supplements)

1.2 Applications of Microbiology

*-Biotechnology* -Use of microbiological and biochemical techniques to solve practical problems *-Genetic engineering* -Introduction of genes into another organism -Disease-resistant plants -Production of medications (e.g., insulin for diabetes)

1.2 Present and Future Challenges

*-Despite impressive progress, much work remains* -Especially true for viral diseases and diseases associated with poverty -Respiratory infections, diarrheal diseases cause most illness and deaths in world today *-In United States, ~750 million infections* ~200,000 deaths -Cost in tens of billions of dollars

1.1 The Dispute Over Spontaneous Generation

*-Developed swan-necked flask* -Boiled infusions remained sterile despite opening to air -Ended arguments that unheated air or broths contained "vital force" necessary for spontaneous generation *-Biogenesis describes the production of living things from other living things*

1.2 Applications of Microbiology

*-Food production* -Baking bread using yeast *Egyptian bakers as early as 2100 B.C. -Fermentation of grains to produce beer *Egyptian tombs revealed as early as 1500 B.C. -Fermentation of milk---> yogurt, cheeses, buttermilk *-Biodegradation* -Degrade PCBs, DDT, trichloroethylene and others -Help clean up oil spills *-Bioremediation:* using microorganisms to hasten decay of pollutants

1. 1 The Dispute Over Spontaneous Generation

*-French chemist Louis Pasteur* *-Considered "father of modern microbiology"* *-Demonstrated air is filled with microorganisms* *-Filtered air through cotton plug* -Observed trapped microorganisms -Many looked identical to those found in broths

1.1 The Dispute Over Spontaneous Generation

*-In same year (1876), German botanist Ferdinand Cohn discovered endospores* -Heat-resistant form of bacteria *-Extreme heat resistance of endospores explains differences between Pasteur's results and those of other investigators* -Pasteur used broths made with sugar or yeast extract -Highlights importance of reproducing all conditions as closely as possible when conducting research

1.1 The Dispute over Spontaneous Generation

*-Italian biologist and physician Francesco Redi* *-Demonstrated worms on rotting meat came from eggs of flies landing on meat (1668)* -Placed meat in two jars -Covered one jar with gauze -Gauze prevented flies from depositing eggs -No eggs no worms *-Took another 200 years to convincingly disprove spontaneous generation of microorganisms* -One reason: conflicting results between laboratories

1.2 Medical Microbiology

*-Most microorganisms are not harmful* *-Some are pathogens*:Cause disease -Influenza in 1918-1919 killed more Americans than died in WWI, WWII, Korean, Vietnam, and Iraq wars combined -Modern sanitation, vaccination, and effective antimicrobial treatments have reduced incidences of the worst diseases

1.1 The Dispute Over Spontaneous Generation

*-Multiple contributions helped define question *-In 1749, John Needham demonstrated boiled broths still produced microorganisms* *-In 1776, Father Spallanzani contradicted Needham's results* -Boiled broths longer; sealed flasks by melting necks -Broths remained sterile unless neck cracked *-Controversy still unsolved* -Some argued heating destroyed "vital force" necessary for spontaneous generation

1.2 Microorganisms in the Environment

*-Recycling of nutrients* *-Oxygen production through photosynthesis* *-Nitrogen fixation* *-Decomposers of material* -Cellulose degraded in the environment and in the digestive tracts of ruminants

1.1 The Dispute Over Spontaneous Generation

*-Some scientists remained skeptical* *-Pasteur's results not fully reproducible* *-English physicist John Tyndall finally explained conflicting data* -Proved Pasteur correct -Sterilizing broths required different times *Some sterilized in 5 minutes *Others not despite 5 hours! -Realized broths made from hay contained heat-resistant microbes *Labs with contaminations used broths made from hay

1.2 Past Triumphs

*-Viral disease smallpox once a leading killer* *~10 million deaths over 4,000 years *Devastating on unexposed populations (e.g., Aztecs in New World) *Worldwide eradication attempts eliminated disease -No reported cases since 1977 *-Plague another major killer in history* *~1/3 of population of Europe (or ~25 million individuals) died between 1346-1350 *Today, fewer than 100 die worldwide *Control of rodent population harboring bacterium *Antibiotics available

1.2 Microbiology: A Human Perspective

*-We could not survive without microorganisms* *-Numerous benefits* -Examples include nitrogen fixation, oxygen production, degradation of materials (e.g., cellulose, also sewage and wastewater) *-But microorganisms have also killed more people than have ever been killed in war* -Have even been used as weapons and could be used in bioterrorism attacks

Microorganisms as Model Organisms

*-Wonderful model organisms* -Metabolism, genetics same as higher life-forms *All cells composed of same elements *Synthesize structures in similar ways *Replicate DNA *Degrade foods via metabolic pathways *"What is true of elephants is also true of bacteria, and bacteria are much easier to study" (Nobel Prize-winning microbiologist Dr. Jacques Monod)

1.3 Domain Eukarya

*Algae* -Diverse group -Single-celled or multicellular -Photosynthetic *Contain chloroplasts withchlorophyll or other pigments -Primarily live in water -Rigid cell walls -Many have flagella *Cell walls, flagella distinct from those of prokaryotes

1.3 Domain Archaea

*Archaea* -Like Bacteria, Archaea are prokaryotic -Similar shapes, sizes, and appearances to Bacteria -Multiply via binary fission -May move via flagella -Rigid cell walls *However, major differences in chemical composition* -Cell walls lack peptidoglycan -Ribosomal RNA sequences different *Many are extremophiles* -High salt concentration, temperature

1.3 Domain Bacteria

*Bacteria* -Single-celled *prokaryotes* -Prokaryote = "prenucleus" -No membrane-bound nucleus -No other membrane-bound organelles -DNA in *nucleoid* -Most have specific shapes (rod, spherical, spiral) -Rigid cell wall contains *peptidoglycan* (unique to bacteria) -Multiply via *binary fission* -Many move using *flagella*

Micro-assessment

*Describe Pasteur's experiment that disproved the idea that a vital force in air was responsible for spontaneous generation.*

1.2 Present and Future Challenges

*Emerging diseases* -Changing lifestyles increase opportunities to spread *Closer contact with animals (e.g., hantavirus) -Evolution of infectious agents previously unable to infect humans (e.g., HIV/AIDS, SARS, Ebola virus) *Re-emerging diseases* -Vaccination can become victim of own success -Lack of firsthand knowledge of dangers of diseases can lead people to fear vaccines more than the diseases *Diseases such as measles, mumps, whooping cough nearly eradicated from U.S. but could re-emerge with declining vaccination rates

1.2 Present and future Challenges

*Emerging diseases* -Most newly recognized -Multiple examples *Swine flu *Severe acute respiratory syndrome (SARS) *Multidrug-resistant tuberculosis *Lyme disease *Hepatitis C *Acquired immunodeficiency syndrome (AIDS) *Hemolytic uremic syndrome (E coli O157:H7) *Hantavirus pulmonary syndrome *Mad cow disease *West Nile encephalitis *Ebola virus

1.2 Present and Future Challenges

*Emerging diseases* -Pathogens can become resistant to antimicrobial medications (e.g., tuberculosis, malaria) -Increased travel and immigration *Many diseases eliminated from developed countries still exist in many parts of world (e.g., malaria, cholera, plague, yellow fever) -Changes in population *Weakened immune systems (e.g., elderly, HIV/AIDS) -Chronic diseases may be caused by bacteria *E.g., peptic ulcers caused by Helicobacter pylori *Possibly indigestion, Crohn's disease, others

1.3 Members of the Microbial World

*Enormous numbers* -Bacterial species outnumber mammalian species by factor of 10,000! -Present in all environments on Earth -Considerations of biodiversity typically overlook enormous contribution of microbes -Less than 1% of all microbial species can be grown and studied in laboratory

1.3 Domain Eukarya

*Eukarya* *-Eukaryotes* = "true nucleus" -Membrane-bound nucleus and other organelles -More complex than prokaryotes -Microbial members include fungi, algae, protozoa *Algae and protozoa also termed *protists* *Some multicellular parasites including helminths (roundworms, tapeworms) considered as well

1.3 Domain Eukarya

*Fungi* -Diverse group -Single-celled (e.g., yeasts) or multicellular (e.g., molds, mushrooms) -Energy from degradation of organic materials -Primarily live on land

Second Golden Age of Microbiology

*Less than 1% of prokaryotes ever studied* *Most do not grow in lab* *New sequencing approaches revealing enormous biodiversity of microbial world* -E.g., 1,800 new bacterial species found in Sargasso Sea *Major challenges remain* *Exploring microbial world should answer many fundamental biological questions*

Importance of Microorganisms

*Microorganisms are foundation for all life on Earth* *Our life depends on their activities*

1.3 Acellular Infectious Agents

*Prions* -*Infectious proteins:* misfolded versions of normal cellular proteins found in brain -Misfolded version forces normal version to misfold *Abnormal proteins bind to form *fibrils* *Cells unable to function -Cause several neurodegenerative diseases in humans, animals -Resistant to standard sterilization procedures

1.3 Domain Eukarya

*Protozoa* -Diverse group -Single-celled -Complex, larger than prokaryotes -Most ingest organic compounds -No rigid cell wall -Most motile

A glimpse of History

*Science of microbiology born in 1674* *Antony van Leeuwenhoek (1632-1723)* -Fabric merchant -Made simple magnifying glass -Studied lake water -Observed 'animalcules'! *Robert Hooke* -Also credited with discovery -Described 'microscopical mushroom' (common bread mold) in 1665

1.1 The Dispute over Spontaneous Generation

*Spontaneous Generation* -"Life arises spontaneously from non-living material" -Concept had supporters and *detractors Detractors included --Francesco Redi --Louis Pasteur --John Tyndall *Each contributed to disproving the idea