Microbiology: History and Key Figures

• Chapter 1 covers the history of microbiology, scientific methods, human perspective of the subject, and members of the microbial world.

Microorganisms

• Microorganisms can be both beneficial and harmful.
• Key terms to know are prokaryotes and eukaryotes.

A Glimpse of History

• Antony van Leeuwenhoek made a simple magnifying glass and studied lake water in 1674.
• He observed "animalcules".
• Robert Hooke is credited with the discovery of microbes.
• Hooke described 'microscopical mushroom' (common bread mold) in 1665.

Chapter Contents

• History, including the dispute over spontaneous generation.
• Various scientists worked to disprove spontaneous generation.
• Chapter includes information on the Golden Age of Microbiology and the scientific process.
• There is a human perspective of microbiology, including its benefits to humans in health, environment, industry, and research.
• Cellular and acellular agents in the microbial world will also be covered.

Spontaneous Generation

• Spontaneous Generation: the belief that life arises spontaneously from non-living material.
• Over 200 years of experiments were conducted to disprove that microorganisms arise by spontaneous generation.

The Dispute Over Spontaneous Generation

• Francesco Redi demonstrated in 1668 that worms on rotting meat came from fly eggs.
• John Needham demonstrated boiled broths could still produce microorganisms in 1749.
• Father Spallanzani contradicted Needham's results in 1776.
• Spallanzani boiled broths longer and sealed flasks by melting necks.
• Spallanzani found that the broths remained sterile unless the neck was cracked.
• Some argued that heating destroyed the "vital force" necessary for spontaneous generation, and the controversy remained.

Work of Louis Pasteur

• Louis Pasteur demonstrated that air is filled with microorganisms.
• He filtered air through a cotton plug and observed trapped microorganisms.
• He found that they looked identical to those in broths.
• When the plug was placed in sterilized broth growth of microorganisms occurred.

Dispute over Pasteur's Results

• Pasteur's results were not fully reproducible.
• English physicist John Tyndall explained the conflicting data and showed Pasteur to be correct.
• Sterilizing broths required different times.
• Some sterilized in 5 minutes, others not sterilized after 5 hours.
• It was realized broths made from hay contained heat-resistant microbes. Labs that could not reproduce Pasteur's results used broths made from hay.
• In 1876, German botanist Ferdinand Cohn discovered endospores.
• The extreme heat resistance of endospores explains differences between Pasteur's results and those of other investigators.
• He used broths made with sugar or yeast extract.
• It is important to reproduce all conditions as closely as possible when conducting research.

The Golden Age of Microbiology

• Refer to the timeline provided in the image.
• In 1674, van Leeuwenhoek observed microorganisms.
• In 1928, Griffith discovers DNA-mediated transformation.
• In 1929, Fleming discovers penicillin.
• In 1953, Watson, Crick, Franklin, and Wilkins discover the structure of DNA.

Scientists to Remember

• Antony van Leeuwenhoek invented the first microscope in 1674.
• Edward Jenner invented the first vaccine against smallpox in 1796.
• Ignaz Semmelweis showed handwashing reduces childbed fever-postpartum infections in 1847.
• Louis Pasteur discovered fermentation by yeast in 1857.
• Joseph Lister pioneered the first use of an antiseptic in 1867.
• Robert Koch showed bacteria cause infections with medical microbiology, pure culture technology in 1876-81.
• Dmitri Ivanovsky first described a virus in 1892.
• Alexander Flemming created the first antibiotic, penicillin, in 1928.

Scientific Method

• The scientific method includes observation, question, hypothesis, experiment, conclusion, and result.

Scientific Method Approaches

• Qualitative methods look at the overall problem but not numerical evidence.
• Qualitative methods look for categories like events, descriptions, and comments.
• Qualitative methods implement an inductive process-developing theories from the data gathered.
• Quantitative methods focus on data that can be measured numerically and generalizes data across subjects.
• Quantitative methods involve data collected in numbers and analyzed in statistics. Quantitative methods include a deductive process-experimental, descriptive, or other type of comparison.

Microbiology, a Human Perspective

• Learning outcomes for this section include:
• Explaining the importance of microorganisms in human health and the surrounding environment.
• Listing three commercial benefits of microorganisms.
• Describing why microorganisms are useful research tools.
• Describing the role of microbes in disease, including examples of past triumphs and remaining challenges.

The Human Microbiome

• The human body carries an enormous population of microorganisms called the normal microbiota.
• These organisms play an essential role in human health.
• They prevent disease by competing with disease-causing microbes, aiding digestion, and promoting development of the immune system.
• The microbiota may decrease allergies and asthma, and affect brain chemistry/body weight.
• The Human Microbiome Project started in 2007.

Microorganisms in the Environment

• They play roles in recycling of nutrients.
• They oxygen production through photosynthesis.
• They assist with nitrogen fixation.
• They decompose material.
• They degrade cellulose in and in the digestive tracts of ruminants.
• The National Microbiome Initiative (NMI) started in 2016 and expands the scope of microbiome research.

Commercial Benefits of Microorganisms

• They are used in food production and fermentation such as beer, yogurt, cheeses, buttermilk, and baking bread using yeast.
• They assist with biodegradation.
• They also degrade environmental pollutants, and lessen damage from oil spills.
• They can be applied to Bioremediation; the use of microorganisms to hasten decay of pollutants.
• Bacteria synthesize commercially valuable products such as antibiotics, ethanol, hydrogen gas, amino acids, insect toxins, and cellulose.
• Biotechnology includes use of microbiological and biochemical techniques to solve practical problems.
• Genetic engineering supports the production of medications by certain microorganisms, including insulin for treatment of diabetes.
• Genetic engineering also assists the Production of plants with desirable qualities.

Microbes as Research Tools

• Model organisms have same fundamental metabolic and genetic properties as higher life forms.
• All cells composed of same chemical elements.
• Synthesis of the cell structure happens by similar mechanisms.
• Duplicate DNA
• Degradation of foods happens via the same metabolic pathways.
• "What is true of elephants is also true of bacteria, and bacteria are much easier to study" (Jacques Monod).
• Grow very quickly on inexpensive growth media.

Microbes and Disease

• Most microorganisms are beneficial or not harmful.
• Some are pathogens that can cause disease.
• Damage to body tissues can be the result of pathogen's growth and products.
• Damage can also be the result of the body's defense mechanisms.
• The influenza of 1918 to 1919 killed more Americans than died in WWI, WWII, Korean, Vietnam, and Iraq wars combined.
• The COVID-19 pandemic has resulted in the death of more than 1,000,000 people worldwide, including over 200,000 Americans.

Nonhuman Epidemics

• Epidemics are not limited to human populations.
• The great Irish famine in the 1800s was due to a microbial disease of potatoes.
• In 2013, a bacterial disease was found in Southern Italy that kills olive trees.
• The 2013 epidemic spread to Spain and France, contributing to a worldwide drop in olive oil production.
• A fungal disease called “wheat blast" devastated wheat crops in South America. The wheat blast also spread to Bangladesh in 2016, resulting in loss of more than 35,000 acres of crops.
• Frog populations around the world have been decimated by a fungal disease called chytridiomycosis.

Past Triumphs

• Smallpox has been eradicated.
• Smallpox once killed one-third of victims and left others blind or scarred.
• The disease devastated unexposed populations, such as native inhabitants of the Americas.
• No reported cases since 1977, but laboratory stocks of virus remain.
• The Black death- Plague deaths less than 100 per year.
• The Black death killed one-third of population of Europe between 1347 to 1351 which is approximately 25 million people.
• Control of rodent populations and human respiratory secretions help prevent the spread of Black Death.
• Antibiotics are also valuable for treatment of Black Death/Plague
• Polio has been nearly eliminated by vaccination.

Emerging Infectious Diseases

• An Emerging Infectious Disease (EID) is one that has become more common in recent decades.
• These newly recognized diseases include COVID-19, Ebola, Congenital Zika syndrome, Middle East respiratory syndrome (MERS), Influenza, Lyme disease, AIDS, Hantavirus pulmonary syndrome, and Mad cow disease.
• Some diseases that have become more common are Malaria and Tuberculosis.
• Disease agents evolve and infect new hosts.
• Disease agents evolve and cause different types of damage to host.
• Disease agents evolve and become resistant to antibiotics.
• Mobile populations can carry pathogens around the globe.
• Diseases such as malaria and cholera have largely been eliminated from developed countries, but still exist in many parts of the world.
• Expansion off cities into rural areas allows closer contact with organisms that people have not encountered previously.
• Decades of vaccination have controlled many common diseases in developed countries.
• Lack of first-hand knowledge of the dangers of diseases can lead people to fear vaccines more than the diseases they prevent. Diseases such as measles, mumps, and whooping cough are nearly eliminated from developed countries but could become more common again with declining vaccination rates.

Chronic Diseases

• Chronic diseases may be caused by microorganisms.
• Stomach ulcers, once thought to be caused by stress, are often caused by the bacteria Helicobacter pylori.
• Cervical cancer is caused by human papilloma virus (HPV).

Members of the Microbial World

• Domains include; Bacteria, Archaea, and Eukarya.
• Compare and contrast characteristics of members of these domains.
• Explain the organism's scientific name and features.
• Be able to compare and contrast the algae, fungi, and protozoa.
• Be able to compare and contrast viruses, viroids, and prions.

Microbial World Domains

• Bacteria: prokaryotes that are unicellular.
• Archaea: prokaryotes that are unicellular.
• Eukarya: have eukaryotes that can be unicellular or multicellular; Algae, Protozoa, Fungi, and Helminths are within this domain.
• Acellular Infectious Include: viruses, viroids, and prions.

Scientific Names

• Binomial System of Nomenclature: two words.
• Genus (capitalized).
• Species name (not capitalized).
• Genus and species are italicized or underlined.
• Genus abbreviated.
• Name often reflects the characteristic of organisms or it honors a scientists such as Escherichia (honors Theodor Escherich)
• coli means they live in the colon.
• Members of a species with important minor differences may be indicated with a strain designation (E. coli K12).
• Informal names that resemble genus names are not italicized.
• Members called staphylococci are from the genus Staphylococcus are.

Bacteria

• Single-celled prokaryotes that are cylindrical, spherical, or spiral.
• Rigid cell wall contains peptidoglycan (unique to bacteria).
• Flagella.
• Multiply via binary fission.
• Obtain energy from a variety of sources (some are photosynthetic).

Archaea

• Single-celled prokaryotes similar in size, shape, and properties to bacteria.
• Differ chemically from bacteria.
• Cell walls lack peptidoglycan.
• Ribosomal RNA sequences are different in relation to bacterial RNA
• Many are extremophiles, living in high salt concentrations.