Microbiology exam 1

Differentiate among bacteria, archaea, and eukaryotic microorganisms.

• Bacteria: Prokaryotic, cell walls with peptidoglycan, found in various environments.

• Archaea: Prokaryotic, no peptidoglycan, often live in extreme environments.

• Eukaryotic Microorganisms: Have a nucleus and membrane-bound organelles (e.g., fungi, protozoa, algae).

Identify two acellular infectious agents studied in microbiology.

1. Viruses – Consist of DNA or RNA within a protein coat; require a host to replicate.

2. Prions – Infectious proteins that cause neurodegenerative diseases.

Compare and contrast the relative sizes of different microbes.

• Prions (10nm)

• Viruses( 100nm)

• Bacteria/archea ( 1 micrometer)

• Eukaryotes ( 10 micrometers)

Who first used aseptic technique in surgery?

Joseph Lister – Introduced antiseptic surgery

Recall the differences between eukaryotic and prokaryotic cells.

• Eukaryotes: Have membrane-bound organelles and an organized nucleus.

• Prokaryotes: Lack a nucleus and membrane-bound organelles.

List the three major domains of life.

1. Bacteria

2. Archaea

3. Eukarya

How do you correctly write a binomial name for a microorganism?

• Format: Genus species (italicized or underlined).

• Example: Escherichia coli (or E. coli after first use).

What are the Five I’s of microbiology, and what does each step entail?

Inoculation – Introducing a sample into a medium for growth.

Incubation – Allowing the sample to grow under controlled conditions.

Isolation – Separating a single species from a mixed sample.

Inspection – Examining colonies for characteristics.

Identification – Determining the microbe’s identity.

What are the three physical states of media, and when is each used?

1. Liquid (broth) – Used for growing large numbers of bacteria.

2. Semisolid – Used to assess motility and biochemical reactions.

3. Solid (agar plates/slants) – Used for isolation and colony morphology studies.

Compare and contrast selective and differential media.

Selective media: Inhibits the growth of some microbes while allowing others to grow (e.g., MacConkey agar selects for Gram-negative bacteria).

Differential media: Distinguishes between species based on metabolic properties (e.g., Blood agar differentiates hemolytic activity).

Differentiate between brightfield, fluorescence, phase contrast, and darkfield microscopy.

• Brightfield: Standard light microscope; best for stained specimens.

• Fluorescence: Uses fluorescent dyes and UV light for visualization.

• Phase contrast: Enhances contrast of live, unstained cells.

• Darkfield: Uses a special condenser to make specimens appear bright on a dark background.

Which organisms are small enough that electron microscopy is needed to see them?

Viruses

Explain and give examples of simple, differential, and special stains.

• Simple stain: Uses a single dye to visualize cell shape and structure (e.g., methylene blue).

• Differential stain: Differentiates between cell types (e.g., Gram stain, Acid-fast stain).

• Special stain: Highlights specific structures (e.g., Capsule stain, Endospore stain, Flagella stain).

Why is a differential stain important in medical microbiology?

• Helps identify bacterial types for diagnosis.

• Differentiates Gram-positive and Gram-negative bacteria, guiding antibiotic treatment.

• Identifies acid-fast bacteria (e.g., Mycobacterium tuberculosis).

List the structures all bacteria possess

• Cell membrane – Regulates transport in and out of the cell.

• Cytoplasm – Contains enzymes, nutrients, and ribosomes.

• Ribosomes – 70S ribosomes for protein synthesis.

• Chromosomal DNA – A single circular chromosome containing genetic material.

Identify three structures some but not all bacteria possess.

1. Flagella – For motility.

2. Capsule – A protective outer layer.

3. Plasmids – Extra-chromosomal DNA carrying non-essential genes.

Describe three major shapes of bacteria.

1. Coccus (spherical) – Example: Staphylococcus aureus.

2. Bacillus (rod-shaped) – Example: Escherichia coli.

3. Spirillum (spiral-shaped) – Example: Helicobacter pylori.

Provide at least four terms to describe bacterial arrangements.

1. Diplo- (pairs) – Diplococcus

2. Strepto- (chains) – Streptobacillus

3. Staphylo- (clusters) – Staphylococcus

4. Tetrad (groups of four) – Micrococcus

Describe the structure and function of six different bacterial exterior structures.

1. Flagella – Motility.

2. Fimbriae – Attachment to surfaces.

3. Pilus – Conjugation (DNA transfer).

4. Capsule – Protection from phagocytosis.

5. Slime Layer – Biofilm formation.

6. Cell Wall – Provides structural support.

Explain how a flagellum works.

The flagellum rotates like a propeller using a basal body, hook, and filament, powered by a proton motive force (H+ gradient).

Recognize and define pilus, fimbriae, and flagella.

• Pilus – A tubular structure for conjugation.

• Fimbriae – Hair-like structures for attachment.

• Flagella – Long, whip-like structures for movement.

Define and recognize amphitrichous, peritrichous, monotrichous, and lophotrichous flagella.

Monotrichous – Single flagellum at one end.

Lophotrichous – A cluster of flagella at one end.

Amphitrichous – Flagella at both ends.

Peritrichous – Flagella all over the cell.

Define and understand the function of a capsule and a slime layer.

Capsule – A thick, structured layer preventing phagocytosis.

Slime Layer – A loose, sticky layer aiding in biofilm formation.

Differentiate between the two main types of bacterial envelope structure.

Gram-positive – Thick peptidoglycan, teichoic acids, no outer membrane.

Gram-negative – Thin peptidoglycan, outer membrane with lipopolysaccharides.

Discuss the differences in lipids and peptidoglycan between Gram-positive and Gram-negative cell walls.

Gram-positive: Thick peptidoglycan, teichoic acids.

Gram-negative: Thin peptidoglycan, outer membrane with lipopolysaccharides (LPS

Name a substance in the envelope structure of some bacteria that can cause severe symptoms in humans

Lipopolysaccharide (LPS) endotoxin in Gram-negative bacteria causes fever and septic shock.

Detail the causes and mechanisms of sporulation and germination

Sporulation: Occurs in harsh conditions; Bacillus and Clostridium form endospores.

Germination: Spores return to a vegetative state when conditions improve.

Name four divisions ending in –cutes and describe their characteristics

Firmicutes – Gram-positive, spore-forming (e.g., Bacillus).

Actinobacteria – High G+C Gram-positive bacteria (e.g., Mycobacterium).

Proteobacteria – Gram-negative, diverse metabolism (e.g., Escherichia).

Tenericutes – Lack a cell wall (e.g., Mycoplasma).

Define a species in terms of bacteria

A bacterial species is a group of organisms with similar genetic and phenotypic characteristics that reproduce through binary fission rather than sexual reproduction

Differentiate between macronutrients and micronutrients.

Macronutrients – Required in large amounts (C, H, O, N, P, S).

Micronutrients (Trace Elements) – Required in small amounts (Fe, Zn, Mg).

Define saprobe and parasite, and explain why these terms can be an oversimplification.

Answer:

• Saprobe – Decomposes dead organic matter for nutrients.

• Parasite – Lives on or inside a host, causing harm.

• Oversimplification? Many organisms exhibit facultative behavior, meaning they can switch between saprobic and parasitic lifestyles depending on conditions.

Compare and contrast the processes of diffusion and osmosis.

• Diffusion – Movement of solutes from high to low concentration.

• Osmosis – Movement of water across a membrane from low solute to high solute concentration.

Identify the effects of isotonic, hypotonic, and hypertonic conditions on a cell.

• Isotonic – No net water movement; cell remains stable.

• Hypotonic – Water enters the cell; may cause lysis (bursting).

• Hypertonic – Water exits the cell; may cause plasmolysis (shrinking).

Name two types of passive transport and one type of active transport.

Passive Transport:

1. Simple diffusion – Direct movement of molecules across a membrane.

2. Facilitated diffusion – Uses carrier proteins but requires no energy.

Active Transport:

• Endocytosis (or ATP-powered pumps) – Requires energy to move substances against a gradient.