Introduction to the Microbial World

• Microbiology is the study of microbes.

Major Groups of Microbes

• Microbes include fungi, bacteria, protozoa, worms, viruses, and algae.

Impact of Microbes

• Microbes were ancient organisms that have a massive impact and are ubiquitous.
• Microbes are essential for energy/nutrient flow.
• Microbes are used in biotechnology and recombinant DNA.
• They are used in the production of food, drugs, hormones, vaccines, and pesticides.
• Microbes are utilized in bioremediation, a process that uses organisms to remove pollutants.
• Many global deaths are due to emerging and re-emerging infectious diseases.

Epidemics and Improving Health

• Epidemics are widespread occurrences of infectious diseases.
• Advances in medicine, sanitation, and awareness have greatly improved health outcomes and reduced the impact of infectious diseases.
• Heart Disease, Lung Cancer, and Stroke are the 3 main causes of death in the U.S.
• Ischemic heart disease is the leading cause of death in high-income countries.
• Neonatal conditions are the leading cause of death in low-income countries.

Scientific Method

• The steps in the scientific method include:
  • Observation
  • Asking a question
  • Developing a hypothesis
  • Making a prediction and performing experiments
  • Analyzing the data
  • Developing a conclusion
  • Communicating/publishing results
• The scientific method involves testing a hypothesis through experimentation, analyzing data, and determining if the hypothesis is supported or falsified.

History of Microbiology

• Aristotle introduced the belief that life arose from nonliving matter through spontaneous generation.
• In the 1660s, Hooke studied dead cells.
• In the 1670's, Leeuwenhoek studied live cells including microbes..
• Francesco Redi questioned spontaneous generation and proposed biogenesis of maggots in the late 1660s.
• Redi's experiment questioned if spontaneous generation applied to microbes.

Spontaneous Generation Debate

• Anthony van Leeuwenhoek discovered animalcules and described bacteria and protozoa in the late 1670s to early 1720s.
• Scientists like Needham and Spallanzani continued debating spontaneous generation in the mid-1700s.
• In the 1860s, Pasteur disproved spontaneous generation and invented pasteurization.
• Pasteur also saved the wine and silk industries and studied microbes and disease.
• Tyndall discovered endospores and sterilization techniques.
• Tyndall found that some bacteria existed in heat-stable (endospore) and heat-sensitive forms.
• Semmelweis noticed higher death rates in maternity wards staffed by medical students compared to midwives in the 1800s.
• Joseph was the father of modern antisepsis in the 1800s.
• Joseph sprayed instruments, skin, wounds, and dressings with an antiseptic (carbolic acid) before surgery.
• Aseptic technique helped to reduce the incidence of gangrene.
• Robert developed culture techniques in the 1800s.
• Robert experimented with bacterial growth media and agar and discovered Koch's postulates.
• Koch's Postulates are used to prove the cause of an infectious disease and relate a specific microbe to a specific disease.

Golden Age of Microbiology

• The Golden Age of Microbiology occurred from 1857-1914.
• Discoveries during this period included the relationship between microbes and disease, immunity, and antimicrobial drugs.
• Both Pasteur and Robert were bitter rivals.
• In 1796, Edward Jenner inoculated a person with cowpox virus and noted gave immunity for smallpox.
• Vaccination is derived from "vacca," the Latin word for cow.

Chemotherapy and Modern Advancements

• Paul Ehrlich in 1910 developed salvarsan, a synthetic arsenic drug, to treat syphilis.
• Alexander Fleming discovered lysozyme in 1922 in tears, saliva, and sweat, which exhibited chemotherapeutic properties.
• In the 1930s, sulfonamides were synthesized and continue to be used.
• Alexander Fleming discovered penicillin in 1928; it was tested clinically and mass-produced in the 1940s.
• The emergence of special fields of microbiology continues to this day and includes immunology, virology, chemotherapy, microbial genetics, biotechnology, pharmaceuticals, gene therapy, nanotechnology, and bioremediation.

Origins and Types

• The probable origin of the universe was 14 billion years ago.
• The origin of earth was 4 billion years ago.
• The earliest prokaryotic cells appeared around 4 billion years ago.
• The earliest eukaryotic cells appeared around 2 billion years ago.
• Two cell lines emerged: Prokaryotes Eukaryotes.
  • Prokaryotes are microscopic, unicellular organisms that lack nuclei and membrane-bound organelles.
  • Eukaryotes are unicellular or multicellular organisms with a nucleus and membrane-bound organelles.
• Viruses are acellular, parasitic particles composed of nucleic acid and protein.

Classification of Microbes

• Taxonomy is the classification of life according to evolutionary relationships.
• Taxonomy provides universal names for organisms and is a reference for identifying organisms.
• There are 5 Kingdoms and 3 Domains for the Traditional Whitaker System.
• Arranged from broadest to most specific, they are listed as: Domain, Kingdom, Division/Phylum, Subphylum, Class, Order, Family, Genus, Species.
• There are three domains: Bacteria, Archaea, Eukarya.
• Bacteria (or Eubacteria) are abundant with no membrane-bound organelles and recycle carbon.
  • They are also nitrogen fixers.
  • Examples include Cyanobacteria (blue-green algae), Escherichia coli, Staphylococcus aureus, and Bacillus anthracis.
• Archaea are descendants of primitive prokaryotes adapted to extreme environments.
• Methanogens generate methane gas as a waste product.
• Halophiles live in excessively salty environments.
• Hyperthermophiles (thermoacidophiles) live in hot environments.

Viruses

• Classification of bacteria can be done phenotypically based on morphology and growth characteristics.
• Classification of bacteria can be done molecularly based on genes, RNA and antigens Immunology).
• Bergey's Manual of Determinative Bacteriology is a taxonomic scheme.
• Dichotomous keys are used to identify organisms according to their characteristics.
• Viruses are diverse and have a genetic molecule.
• Most Microbes Are Beneficial or Harmless and 95% of microbes are our friends.