Microbiology Unit 3 Study Guide – Key Concepts and Step-by-Step Guidance

Explain the following terms:

Background

Topic: Microbial Metabolism, Pathogens, and Taxonomy

These terms are foundational in microbiology and relate to how microorganisms obtain energy, their classification, and unique infectious agents.

Key Terms:

• Chemoheterotroph: An organism that obtains both energy and carbon from organic molecules.

• Photoautotroph: An organism that uses light as an energy source and carbon dioxide as a carbon source.

• Prion: An infectious protein that lacks nucleic acids and causes neurodegenerative diseases.

• Mycoses: Diseases caused by fungi.

• Viroid: A small, circular RNA molecule that infects plants.

• Taxonomy: The science of classifying organisms.

• Systematics: The study of the diversity of organisms and their evolutionary relationships.

Step-by-Step Guidance

1. For each term, identify its root words (e.g., 'chemo', 'hetero', 'troph') to help deduce its meaning.

2. Recall examples of organisms or diseases associated with each term (e.g., prions cause mad cow disease).

3. Think about how each term fits into the broader context of microbial classification or disease.

4. Write a concise definition for each term, focusing on what makes it unique.

Try defining each term before checking your answers!

Q1. Briefly describe the three domain system of classification, including the domains and the groups of organisms they contain. Describe the characteristics of the organisms which determine the domain into which they fit.

Background

Topic: Microbial Taxonomy and Classification

This question tests your understanding of the highest level of biological classification and the criteria used to distinguish between the three domains of life.

Key Terms and Concepts:

• Three Domains: Bacteria, Archaea, Eukarya

• Criteria: Cell type, membrane lipids, ribosomal RNA sequences, presence/absence of peptidoglycan, etc.

Step-by-Step Guidance

1. List the three domains and give an example of an organism in each.

2. Describe the main characteristics that distinguish each domain (e.g., cell wall composition, membrane lipids, genetic sequences).

3. Explain how these characteristics are used to assign organisms to a domain.

4. Consider how molecular data (like rRNA sequences) revolutionized classification.

Try outlining your answer before checking the full explanation!

Q2. Describe the way organisms are named using the binomial nomenclature system.

Background

Topic: Scientific Naming and Taxonomy

This question focuses on the standardized system for naming organisms, which is essential for clear scientific communication.

Key Terms:

• Binomial Nomenclature: Two-part scientific naming system (Genus species)

• Italicization: Convention for writing scientific names

Step-by-Step Guidance

1. Recall the two components of a scientific name and their formatting (Genus capitalized, species lowercase, both italicized or underlined).

2. Think of an example (e.g., Escherichia coli).

3. Explain why this system is used and how it avoids confusion.

Try writing an example scientific name before checking the answer!

Q3. List and briefly describe the various methods used to classify and identify microorganisms (bacteria, specifically).

Background

Topic: Microbial Identification and Classification

This question addresses the laboratory and molecular techniques used to distinguish and categorize bacteria.

Key Methods:

• Morphological characteristics

• Staining techniques (e.g., Gram stain)

• Biochemical tests

• Serological methods

• Molecular techniques (e.g., PCR, DNA sequencing)

Step-by-Step Guidance

1. List each method and briefly describe what it tests or reveals about the bacteria.

2. Consider which methods are used for initial identification versus detailed classification.

3. Think about the advantages and limitations of each method.

Try listing at least three methods before checking the full list!

Q4. What characteristics are used to group viruses into taxonomic families? What is a viral species? What are the suffixes that are used to represent genus, family and order names for viruses?

Background

Topic: Viral Taxonomy

This question tests your knowledge of how viruses are classified and named.

Key Concepts:

• Genome type (DNA or RNA, single or double stranded)

• Capsid symmetry

• Presence of envelope

• Host range

• Suffixes: -virus (genus), -viridae (family), -virales (order)

Step-by-Step Guidance

1. List the main characteristics used to classify viruses into families.

2. Define what is meant by a 'viral species.'

3. Recall the standard suffixes for genus, family, and order in viral taxonomy.

Try matching the suffixes to their taxonomic rank before checking the answer!

Q5. Describe the different types of viral genomes that are possible.

Background

Topic: Viral Genetics

This question focuses on the diversity of viral genetic material.

Key Concepts:

• DNA or RNA

• Single-stranded (ss) or double-stranded (ds)

• Positive-sense or negative-sense (for RNA viruses)

• Segmented or non-segmented genomes

Step-by-Step Guidance

1. List the possible nucleic acid types found in viruses.

2. Describe what is meant by positive-sense and negative-sense RNA.

3. Explain the significance of segmented genomes.

Try to recall at least three types before checking the answer!

Q6. Briefly describe four ways in which fungi can cause disease in humans.

Background

Topic: Medical Mycology

This question explores the mechanisms by which fungi can be pathogenic to humans.

Key Concepts:

• Direct tissue invasion

• Allergic reactions

• Toxin production (mycotoxicosis)

• Opportunistic infections

Step-by-Step Guidance

1. List four mechanisms by which fungi can cause disease.

2. Provide a brief example or explanation for each mechanism.

Try to think of examples for each mechanism before checking the answer!

Q7. What structures form the basis for the classification of fungi? What are the four groups into which fungi are currently classified?

Background

Topic: Fungal Taxonomy

This question addresses the morphological and reproductive features used to classify fungi.

Key Concepts:

• Sexual reproductive structures (spores)

• Major groups: Zygomycota, Ascomycota, Basidiomycota, Deuteromycota (or "Fungi Imperfecti")

Step-by-Step Guidance

1. Identify the main reproductive structures used in fungal classification.

2. List the four major groups and a key characteristic of each.

Try to match each group to its reproductive structure before checking the answer!

Q8. Compare and contrast the fungi, protozoa, algae and helminthes in terms of their cell composition, means of obtaining food, nutritional type and cellular arrangement.

Background

Topic: Microbial Diversity

This question requires you to analyze similarities and differences among major groups of eukaryotic microbes and parasites.

Key Concepts:

• Cell wall presence and composition

• Autotrophic vs. heterotrophic nutrition

• Unicellular vs. multicellular organization

Step-by-Step Guidance

1. Create a table or chart comparing each group across the requested features.

2. List whether each group is unicellular, multicellular, or both.

3. Describe how each group obtains nutrients (e.g., absorption, ingestion, photosynthesis).

4. Note the presence or absence of a cell wall and its composition.

Try filling out a comparison table before checking the answer!

Q9. Compare and contrast superficial, systemic and subcutaneous mycoses.

Background

Topic: Fungal Diseases

This question focuses on the classification of fungal infections based on the depth and location of infection.

Key Concepts:

• Superficial: Affecting skin, hair, nails

• Subcutaneous: Affecting deeper skin layers, often after trauma

• Systemic: Affecting internal organs, often via inhalation

Step-by-Step Guidance

1. Define each type of mycosis and where it occurs in the body.

2. List examples or typical causative fungi for each type.

3. Compare the severity and typical route of infection for each.

Try to think of an example for each type before checking the answer!

Q10. Distinguish between a prion and a viroid.

Background

Topic: Unusual Infectious Agents

This question tests your understanding of two unique types of infectious agents that differ from viruses and bacteria.

Key Concepts:

• Prion: Infectious protein, no nucleic acid

• Viroid: Infectious RNA, no protein coat, infects plants

Step-by-Step Guidance

1. Define each agent and its composition.

2. Describe the types of organisms each infects.

3. List diseases associated with each.

Try to write one key difference before checking the answer!

Q11. Using the information in chapter 4 (4.2, 4.3, 4.4) of your textbook and the list of organisms found on the “yellow sheet” construct a table that places each of the organisms on the sheet in 1) one of the classes of Proteobacteria, 2) the high G+C Gram positives or 3) low G+C Gram positives; Then, in an additional column in table briefly describe the unique characteristics of the organisms in the group where the organism has been placed.

Background

Topic: Bacterial Classification

This question requires you to apply your knowledge of bacterial taxonomy and characteristics to classify specific organisms.

Key Concepts:

• Proteobacteria classes (Alpha, Beta, Gamma, Delta, Epsilon)

• High G+C Gram positives (Actinobacteria)

• Low G+C Gram positives (Firmicutes)

Step-by-Step Guidance

1. Review the list of organisms provided on the “yellow sheet.”

2. For each organism, determine its taxonomic group based on textbook information.

3. Place each organism in the appropriate column (Proteobacteria class, high G+C, or low G+C).

4. In a new column, write a brief note about a unique characteristic of each organism.

Try classifying a few organisms before completing the full table!