Microbiology Course Quiz

Medical Microbiology MICR433/533 Spring 2025

• Classroom: SDS 100
• Class Time: 10:00 AM - 10:50 AM
• Instructor: Radhey Kaushik
• Office Hours: Tuesdays, 1:00 PM - 2:00 PM
• Office: McFadden Biostress Building-SNP 252B
• Phone: 605-688-5501
• Email: [email protected]
• Course URL: https://d2l.sdbor.edu/
• Textbook: Nester's Microbiology: A Human Perspective by Anderson, Salm, and Beins, 10th edition, 2022

Grading Scheme (Undergraduates)

• 3 Term Tests (40 points each): 120 points
• 1 Final Exam: 80 points
• Quizzes, take-home assignments, and in-class activities: 50 points
• Total Points Possible: 250 points (converted to a 100% scale)

Grading Scheme (Graduates)

• 3 Term Tests (40 points each): 120 points
• 1 Final Exam: 80 points
• 50 points additional essay assignment: 50 points
• Total Points Possible: 300 points (converted to a 100% scale)

Tests and Exams

• Format: Written tests can be a combination of essay, case study, short answer, multiple choice, fill-in-the-blank, matching, true/false, etc.
• Timing: All quizzes, term tests, and the final exam are conducted in class, during designated class time/final exam time.

Basis for Letter Grade

• A: 89.6% - 100%
• B: 79.6% - 89.5%
• C: 69.6% - 79.5%
• D: 55% - 69.5%
• F: Below 55%

Term Tests Dates

• Monday, February 3rd, 2025
• Friday, February 28th, 2025
• Wednesday, April 2nd, 2025
• Each test is worth 40 points

Final Exam Details

• Monday, May 5th, 2025, 9:15 AM - 11:15 AM
• Covers material since the 3rd exam (~55-65 points)
• Includes comprehensive questions on previously covered material (~15-25 points)

Course Format

• 3 Sections:
  • Review of basic microbiology concepts
  • Review of host responses to infection
  • System-by-system study of infectious diseases

Microbiology and Microorganisms

• Definition: Microbiology is the study of the microbial world.
• Existence: Microorganisms have existed for billions of years.
• Evolution: Higher life forms evolved from microscopic forms; therefore, microbes are fundamental to all life.
• Importance: All organisms, including humans, require the activities of microorganisms to survive.

Microbiology and Microorganisms (Microbes)

• Living (cellular): Microorganisms
• Non-living (acellular): Other infectious agents
• Combined: Collectively called 'microbes'
• Properties: Can change their properties, are capable of rapid adaptation/evolution due to rapid generation times and simple genomes, are very diverse, and are both beneficial and harmful.

The Human Microbiome

• Location: Skin and mucosa are populated by characteristic communities of microorganisms.
• Microbiota/Flora: Collectively called 'normal microbiota' or 'normal flora'.
• Ratio (cells): Many sources claim a 10:1 ratio of microbial to human cells, but recent estimates are closer to 3:1 or 1:1.

The Human Microbiome Project

• Started in: 2007
• Technologies: Used DNA sequencing to characterize microbial communities in the human body.
• Definition: The term 'microbiome' has two meanings: • The total genetic content of a microbial community • The microbial community itself
• Culture Limitations: Less than 1% of microorganisms can be cultured in a lab; therefore, DNA technologies are frequently used for characterization.

Human Microbiome Roles

• Disease Prevention: Normal microbiota prevent disease by competing with pathogens.
• Food Degradation: Assist in the breakdown of foods.
• Immune System Development: Promote the development of the immune system.
• Reduced Allergies: Early exposure to certain microbes may lessen the likelihood of allergies, asthma, and other diseases.
• Brain and Behavior, Weight: Affect brain chemistry, behavior, and weight gain.
• Imbalance/Health Harm: Disturbances in normal microbial populations can harm a person's health by creating imbalances.
• Active Research: The effect of the human microbiome on health and disease is an active area of research.

Microorganisms in the Environment

• Recycling: Microorganisms are masters of recycling materials that other organisms cannot break down.

• External/Internal Roles:

  • External: • Degrading cellulose in plants (leaves/trees) • Sewage and waste-water treatment
  • Internal: • Cellulose degradation in the digestive tracts of animals (e.g., cattle, sheep, deer)

• Nitrogen Fixation: Microorganisms recycle and use atmospheric nitrogen, converting it into forms other organisms can use

Commercial Benefits of Microbes

• Food Production: Used in bread, beer, fermented drinks, yogurt, buttermilk, cheese, and probiotics (live organisms with health benefits).
• Bioremediation: Microbes can degrade toxic materials (sewage, waste, water, petroleum, PCBs, DDT, trichloroethylene), oil spills, and radioisotopes to clean up environmental pollutants.
• Commercial Products: Microbes synthesize commercial products like cellulose, amino acids, hydroxybutyric acid, hydrogen gas, ethanol, oils, insect toxins, and antibiotics.
• Biotechnology: Microbes are critical in biotechnology, such as medically important products (insulin), recombinant proteins, vaccines, and genetic engineering of plants.

Microbes as Research Tools

• Model Organisms: Microorganisms are effective model organisms to study metabolism and genetics since they share similar fundamental properties with higher life forms.
• Similarities: Similar mechanisms are used by cells in all living organisms, making bacteria easy to study and helping to understand basic scientific concepts.
• Growth Rate: Fast growth rate allows for the rapid generation of research data.
• Cost Effectiveness: Cultivation in simple and inexpensive mediums allows for more cost-effective study.
• Advances: Bacteria and yeast are critical for many major advances in understanding life.

Microbes and Disease

• Beneficial Microbes: Most microorganisms are beneficial (~87%).
• Disease Causation: A very small minority (~3%) of microbes are pathogens, causing diseases.
• Opportunistic Microbes: 10% of microbes are opportunistic.
• Medical Microbiology: Medical microbiology focuses on the study of disease-causing microbes (pathogens).
• Historical Examples:
  • Smallpox: Killed millions
  • Plague (1347-51): Killed 25 million
  • Flu Pandemic (1918-19): Killed more Americans than World Wars I, II, Korean, Vietnam, and Iraq wars combined.
• Modern Advancements: Modern sanitation, vaccination, quarantine, and effective antibiotics have dramatically reduced the rate of infectious diseases.
• Continuing Challenges: Infectious diseases remain a significant problem globally, especially with new emerging and reemerging infectious diseases

Remaining Major Challenges (Emerging Infectious Diseases)

• Emerging Infectious Disease (EID): An infectious disease whose incidence has increased or is newly recognized.
• Examples of EIDs: COVID-19, Ebola, Congenital Zika syndrome, Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS), Hepatitis C, Certain types of influenza (Swine flu), Lyme disease, Acquired Immunodeficiency Syndrome (AIDS), Hantavirus pulmonary syndrome, Mad-cow disease.
• Long-established diseases: Long-established diseases (malaria, tuberculosis) are becoming more common recently.

Reasons for Emerging or Re-emerging Infectious Diseases

• Pathogen Evolution: Changes in pathogen ability to infect new hosts or increased virulence
• Changes in Host Characteristics: Change in virulence of infectious agents
• Life Style Changes: Changing life styles that provide opportunities for infectious agents to spread
• Antibiotic Resistance: Resistance to antibiotics is increasing.
• Vaccination Gaps: Ignorance of childhood vaccinations
• Elderly Exposure: Increase of elderly people becoming susceptible to a variety of infections
• Global Travel/Mobile Population: Increased global travel and mobile population allowing for more rapid spread of infectious disease
• Immunocompromised Hosts: Immunocompromised individuals are more susceptible to serious infections.

Chronic Diseases Caused by Bacteria/Viruses

• Peptic Ulcers: Helicobacter pylori
• Cervical Cancer: Human papillomavirus (HPV)

Microbial World

• Domains: Bacteria, Archaea, Eucarya (Eukarya)
• Prokaryotes: Bacteria and Archaea are collectively referred to as prokaryotes (lacking a true nucleus)
• Distinction: Though they exhibit some similarities structurally, Bacteria and Archaea have significant differences in their chemical composition and are unrelated.

The Bacteria

• Cell Type: Single-celled prokaryotes
• Nucleus: Lacks a true nucleus and internal lipid-bound organelles.
• Genetic Material: Genetic information stored in DNA in a region called the nucleoid.
• Shapes: Commonly spherical, cylindrical, or spiral.
• Cell Walls: Have rigid cell walls containing peptidoglycan, which is not found in other domains.
• Reproduction: Multiply by binary fission.
• Appendages: May have appendages (flagella) for motion, which can also indicate pathogenicity.

The Archaea

• Similarities to Bacteria: Single-celled prokaryotes, similar shapes, have flagella and cell walls, multiply by binary fission.
• Peptidoglycan Absence: Lack of peptidoglycan in the cell wall.
• Extremophiles: Tend to live in extreme environments like high salt, high temperatures, and extreme cold.

The Eucarya

• Descriptions: Members of the 'Eucarya' domain are called eukaryotes, which have a true or membrane-bound nucleus and other organelles inside the cell.
• Characteristics: • May be single-celled or multicellular • Always have a true nucleus • Contain internal organelles (e.g., mitochondria, chloroplasts) that are more complex compared to prokaryotes. • Have an internal scaffolding called the cytoskeleton to define cell shape.
• Example Eukaryotes: Algae, fungi, protozoa, and multicellular parasites (e.g., helminths).

Scientific Names of Microbes

• Binomial system: Used to name microorganisms.
• Genus: The first name is capitalized and italicized.
• Species: The second name is not capitalized, and both are italicized.
• Example: Escherichia coli
• Abbreviation: First word is abbreviated with the first letter capitalized (e.g., E. coli)
• Strains: Members of a species can vary slightly and are given different strain designations (e.g., E. coli strain B or E. coli strain K12).
• Informal Grouping: Groups of similar microbes might be informally grouped by names resembling their genus name, but are not italicized (e.g., species of Staphylococcus are called staphylococci).

Morphology of Bacteria

• Shape Classification: Bacteria exhibit different shapes, and this characteristic is used to describe, classify and identify them.
• Basic Shapes:
  • Coccus (spherical)
  • Rod (bacillus; cylindrical)
  • Further variations: vibrio (curved rod), spirillum (curved rod forming spirals), spirochete (long spiral-shaped cell with a flexible cell wall and unique motility mechanism) and pleomorphic (bacteria vary in shape).
• Coccobacillus: A rod-shaped bacteria which is short enough to be mistaken for a coccus

Grouping of Bacteria

• Colony Structure: Colony structure is related to the way bacteria divide.
• Binary Fission: Prokaryotes primarily reproduce via binary fission
• Division Plane: They form chains, packets, or clusters depending on the plane in which they divide.
• Identification: Cell groupings (chains, clusters) help in bacterial identification.

Acellular Infectious Agents

• Overview: Viruses, viroids, and prions are acellular infectious agents—meaning they lack cellular structure.
• Lack of Reproduction: Viruses, viroids, and prions cannot reproduce independently. Therefore, they are not considered living microorganisms and require a host to reproduce.
• Viral Structure: A protein coat that surrounds the nucleic material (DNA or RNA), giving them variety of shapes.
• Viral Lifestyle: Unable to proliferate outside of a host cell, and depend on the host cell's machinery to reproduce.
• Viral Classification: Viruses are considered obligate intracellular parasites/agents.

Viroids and Prions

• Viroids: Simpler than viruses, consisting of a single piece of RNA (often lacking a protein coat). They are smaller than viruses and can only replicate inside cells. They are a cause of several plant diseases.
• Prions: Composed entirely of protein without any nucleic acid. They are linked with neurodegenerative diseases called Transmissible Spongiform Encephalopathies (TSEs).

Acellular Infectious Agents - Table

• Viruses: Consist of either DNA or RNA surrounded by a protein coat. Obligate intracellular agents that utilize host cellular machinery/resources for replication.
• Viroids: Consists solely of RNA; lack a protein coat. They are obligate intracellular agents that use host cell machinery for replication.
• Prions: Protein-based agents; lack DNA or RNA. Misfolded versions of normal cellular proteins cause normal proteins to misfold.

Next Lecture

• Cells and observational methods. (Chapter 3, selected topics).

Test your knowledge of microbiology with this quiz that covers various topics, including classification, reproduction, and grading schemes. Perfect for students studying the principles of prokaryotic organisms and their characteristics. Challenge yourself and see how well you understand the fundamental concepts in microbiology.