Microbiology Basics Quiz

Introduction to Clinical Microbiology and Immunology

• This field studies microorganisms and their impact on human health.

What is Microbiology?

• Microbiology is the study of microorganisms.
• Microorganisms exist as single cells or clusters.
• Viruses are considered microorganisms, even though they are acellular.

Why Study Microbiology?

• Microorganisms significantly impact human life.
• Microbes are ubiquitous (present everywhere).
• Microbes are extremely adaptable.

Positive and Negative Impacts on Human Life

• Microbes are responsible for the cycling of many elements such as carbon, nitrogen, phosphorus, hydrogen, sulfur, and oxygen.
• More photosynthesis is carried out by microbes than by green plants.
• Bacteria, fungi and viruses lead to many diseases found in humans, animals and plants.
• Microorganisms are important for agriculture – nitrogen fixation, and cellulose-digesting bacteria in herbivores.
• Microbes are vital for food production (cheeses, yogurts, pickles, alcoholic beverages, breads).
• Food spoilage and foodborne illnesses are also linked to microbes.

Energy & the Environment

• Methane is a product of methanogenic bacteria.
• Microbes can be used to clean up the environment (bioremediation).
• Microbes can break down spilled oil, solvents, and pesticides.

Organisms & the Future

• Biotechnology, particularly using genetically modified microbes, is used for large-scale production.
• Examples include antibiotics and insulin.

Two Empires and Three Domains

• Prokaryotes: Lack a nucleus.
• Eukaryotes: Have a true nucleus.
• Domains: Archaea, Bacteria, Eukaryota

History of Microbiology

• Microbiology's development started in the 19th century.
• The field has expanded rapidly since then, leading to subdisciplines.
• Key milestones include:
  • 1684: Leeuwenhoek's crude microscope led to the visualization of microorganisms.
  • 1798: Jenner's development of cowpox vaccination for smallpox.
  • 1847-1850: Semmelweis' introduction of hand hygiene.
  • 1861: Pasteur disproved spontaneous generation.
  • 1884: Koch's postulates were published and Gram's stain developed.
  • 1929: Fleming discovered penicillin.
  • 1933: Ruska developed the electron microscope.
  • 1953: Watson and Crick proposed the DNA double helix.
  • 1983-1984: Isolation and identification of HIV, and PCR techniques developed.
  • 1995: Chicken pox vaccine approved in the U.S.
  • 2005: "Super-resistant" HIV strain isolated in NYC.

Future Trends

• Microbiology is crucial for responding to emerging infectious diseases.
• There's a need to develop more efficient and environmentally friendly industrial technologies.
• New drugs and vaccines are needed to combat antibiotic resistance.
• Further development in molecular techniques is vital for studying microbes in their natural environments.
• Proteomics and genomics – sequencing and analysis of microbes, and related proteome studies, are of major importance.

Biological Characteristics of Microorganisms

• Microorganisms are categorized based on their structural characteristics, their chemical compositions, and their biosynthetic (metabolic pathways), and genetic organization/classification systems.
• The protists include Algae, Protozoa, Fungi, and Slime Molds.

Major Groups

• Major Groups:
  • Eukaryotes (Algae, Protozoa, Fungi, Slime Molds)
  • Prokaryotes (Bacteria, Archaebacteria)
  • Viruses
  • Prions

Prokaryotes vs Eukaryotes

• Prokaryotes have 70S ribosomes, lack membrane-bound organelles and defined nucleus, and are typically smaller than eukaryotic cells. Cell walls contain peptidoglycan.
• Eukaryotes have 80S ribosomes, possess membrane-bound organelles and a defined nucleus, and are generally larger than prokaryotic cells. Their cell walls can vary depending on the organism involved, but they do not contain peptidoglycan.

Algae, Protozoa, Fungi, and Slime Molds

• Note specific types of algae, protozoa, fungi (including yeasts and molds), and slime molds.

Viruses

• Acellular, obligate intracellular parasites and infect all cells (microbial and non-microbial).
• Consist of either DNA or RNA enclosed in a capsid (some enveloped).
• Proteins associated with capsids are vital to determine viral tropism and how viruses attach to the host cells.
• Viruses replicate inside host cells before exiting.

Viral Replication

• Provide a general description of the steps in viral replication.

Prions

• Proteinaceous infectious particles causing neurodegenerative diseases (e.g., scrapie, BSE).

Prokaryotes (Bacteria & Archaebacteria)

• Relatively small, lack a nuclear membrane, have circular DNA in nucleoids, able to exchange genetic info via plasmids, divided into aerobes and anaerobes (how they obtain energy).
• Note other characteristics of prokaryotes, including quorum sensing.

Bacteria: Size, Shape, Arrangement

• Bacteria can be categorized according to their shape (cocci, bacilli, spirilla, vibrio, etc...).
• Bacterial cells have cell walls composed of peptidoglycan.

Main Groups of Bacteria

• List and describe major groups of bacteria, with examples.

Bacterial Cell Walls

• Gram-positive bacteria have thick peptidoglycan layers and teichoic acids, resulting in differing staining properties from gram-negative bacteria which have thin walls and outer membrane.

Gram Staining

• Gram staining is a differential staining technique used to differentiate between gram-positive and gram-negative bacteria.
• Steps in gram staining:
  • Staining with crystal violet and iodine to stain both gram-positive and gram-negative bacteria alike.
  • Treatment with alcohol or acetone to decolorize gram-negative cells.
  • Counterstaining with safranin, staining decolorized gram-negative cells.
• Gram-positive bacteria stain purple, gram-negative bacteria stain pink.
• Differences in cell wall structure lead to different staining patterns due to varying cell wall compositions.

The Gram Negative Envelope

• Outer membrane (LPS), cell wall (peptidoglycan), cytoplasmic membrane.

The Gram Positive Envelope

• Cell wall (thick peptidoglycan layer), cytoplasmic membrane.

Bacterial Cell Structure

• Cell Envelope
• Pili (aka fimbriae), flagella (structure and functions).
• Capsule and other appendages outside of envelope
• Endospores and spore formation.

Staining

• Types of stains: simple and differential stains (Gram stain, acid-fast, etc.)
• Fixing is an important pre-staining step.
• Methods of fixing specimens include heat and chemical methods.

Negative Staining

• Negative staining techniques help visualize capsules and other cell structures in microorganisms.

References

• List of microbiology textbooks and resources used as references.

Test your knowledge of key concepts in microbiology, including the differences between eukaryotic and prokaryotic cells, the role of microorganisms in various environments, and features of bacterial cell walls. This quiz covers crucial topics that underpin the study of microorganisms and their impact on our world.