Exam I Review Guide - Microbiology

Exam I – Review Guide

Know all the scientists discussed in Chapter 1 and be able to match them with their contributions to the field of Microbiology.

• Key Scientists: Review the scientists covered in Chapter 1 and understand their specific contributions to microbiology.

Be able to identify correct binomial nomenclature – know which is the genus and which is the species name, and correct formatting.

• Binomial Nomenclature:

  • Genus is capitalized, species is lowercase.

  • Both are italicized or underlined. Example: Escherichia coli or Escherichia coli.

Know the general characteristics of microorganisms (ex: what types of organisms are included, where they’re found, cell types (uni-, multi-, and acellular), size ranges, etc).

• General Characteristics of Microorganisms:

  • Types: Bacteria, Archaea, Fungi, Protozoa, Algae, Viruses.

  • Habitats: Ubiquitous; found in diverse environments.

  • Cell Types: Unicellular, multicellular, acellular.

  • Size Range: Varies greatly (e.g., bacteria ~1-5 μm, viruses ~20-300 nm).

Most microorganisms are not pathogenic, most are beneficial.

• Most microorganisms are beneficial rather than pathogenic.

The three currently accepted domains in the phylogenetic tree of life

• Three Domains of Life:

  • Bacteria

  • Archaea

  • Eukarya

Be able to identify and match bacterial shapes and arrangements with the appropriate description.

• Bacterial Shapes and Arrangements:

  • Shapes: Coccus (spherical), Bacillus (rod-shaped), Spirillum (spiral).

  • Arrangements: Strepto- (chains), Staphylo- (clusters).

Define complex vs defined media and understand the differences.

• Complex vs. Defined Media:

  • Defined Media: Exact chemical composition is known.

  • Complex Media: Contains ingredients of unknown composition (e.g., nutrient broth).

Know the different types of microscopy and which use light to illuminate a specimen vs those that use electrons.

• Types of Microscopy:

  • Light Microscopy: Uses light to illuminate (e.g., brightfield, darkfield, phase contrast).

  • Electron Microscopy: Uses electrons to illuminate (e.g., TEM, SEM).

Be able to calculate the total magnification of a slide using the ocular and objective lenses magnifying power.

• Total Magnification:

  • Total
    ewline Magnification = Ocular
    ewline Lens
    ewline Magnification
    ewline × Objective
    ewline Lens
    ewline Magnification

Define enrichment media and know what it’s used for/what types of organisms would you use it to culture.

• Enrichment Media:

  • Used to favor the growth of specific microorganisms.

Understand the concept of resolution and what it means if something has a resolution of “X” power.

• Resolution: The ability to distinguish between two points. Lower resolution number means better resolution.

Compare scanning electron microscopy (SEM) to transmission electron microscopy (TEM) and when you would want to use each.

• SEM vs. TEM:

  • SEM: Provides detailed surface views.

  • TEM: Provides detailed internal views.

Why we use oil with the oil immersion lens.

• Oil is used with the oil immersion lens to reduce light refraction and increase resolution.

Know the correct order of the Gram stain and what happens at each step.

• Gram Stain Order:

  • Crystal Violet (primary stain): Both Gram-positive and Gram-negative cells are stained purple.

  • Gram’s Iodine (mordant): Forms a complex with the crystal violet and traps it in the cell.

  • Alcohol (decolorizer): Gram-positive cells remain purple; Gram-negative cells become colorless.

  • Safranin (counterstain): Gram-positive cells remain purple; Gram-negative cells become pink/red.

How we prepare a smear and why it’s important to heat fix.

• Smear Preparation:

  • A thin film of specimen is spread on the slide.

  • Heat fixing kills the bacteria and adheres them to the slide.

Know the different types of stains we talked about, how bacteria will appear when each type is used (ex: Gram + appears purple, etc), how stains can be classified (simple stain, differential, special, etc), and characteristics of special stains like capsule and flagellar stains.

• Types of Stains:

  • Simple Stain: Uses one dye to visualize cells.

  • Differential Stain: Distinguishes between bacteria (e.g., Gram stain).

  • Special Stain: Used to identify specific structures (e.g., capsule, flagella).

  • Gram + appears purple. Gram - appears pink/red.

Capsules contribute to pathogenicity! Understand the characteristics of bacterial capsules.

• Bacterial Capsules:

  • Enhance pathogenicity by preventing phagocytosis.

How humans have utilized microbes, both historically and in the present day.

• Humans have utilized microbes for food production, medicine, and bioremediation.

Bergey’s Manual is the source for bacterial and archaeal classification.

• Bergey’s Manual:

  • The primary resource for bacterial and archaeal classification.

Know the differences between prokaryotes and eukaryotes (general structures, etc) and be able to compare and contrast them (ex: what is found in ONLY prokaryotes vs what is found in ONLY eukaryotes).

• Prokaryotes vs. Eukaryotes:

  • Prokaryotes: No nucleus, no membrane-bound organelles.

  • Eukaryotes: Nucleus and membrane-bound organelles.

  • Only Prokaryotes: nucleoid.

  • Only Eukaryotes: lysosomes, mitchondria, chloroplasts, cytoskeleton, endoplasmic reticulum (smooth and rough), nucleolus, and golgi apparatus.

Know the characteristics of plasmids, inclusions, endospores, flagella, pili, axial filaments, fimbriae, ribosomes, nucleoids, lysosomes, mitochondria, chloroplasts, cytoskeleton, endoplasmic reticulum (smooth and rough), nucleolus, and golgi apparatus.

• Cellular Structures:

  • Plasmids: Extrachromosomal DNA.

  • Inclusions: Storage granules.

  • Endospores: Dormant, resistant structures.

  • Flagella: Motility.

  • Pili: Attachment or genetic transfer.

  • Axial Filaments: Internal flagella in spirochetes.

  • Fimbriae: Attachment.

  • Ribosomes: Protein synthesis.

  • Nucleoids: Region containing DNA in prokaryotes.

  • Lysosomes: Digestion.

  • Mitochondria: ATP production.

  • Chloroplasts: Photosynthesis.

  • Cytoskeleton: Structure and support.

  • Endoplasmic Reticulum: Protein and lipid synthesis.

  • Nucleolus: Ribosome synthesis.

  • Golgi Apparatus: Processing and packaging of proteins.

When bacteria may use endospores and why.

• Bacteria form endospores under harsh conditions for survival.

Understand the different bacterial appendages and what they’re used for.

• Bacterial Appendages:

  • Flagella: Movement.

  • Fimbriae and Pili: Attachment.

  • Capsules: Protection and attachment.

Characteristics of biofilms (where they form, how they’re organized, microbial composition, etc)

• Biofilms:

  • Form on surfaces in moist environments.

  • Organized communities of microorganisms.

Define chemotaxis and understand the difference between positive and negative chemotaxis.

• Chemotaxis:

  • Movement in response to a chemical stimulus.

  • Positive Chemotaxis: Movement towards a favorable stimulus.

  • Negative Chemotaxis: Movement away from a repellent stimulus.

Characteristics of the Gram (-) outer membrane and why these can contribute to pathogenicity.

• Gram-Negative Outer Membrane:

  • Contains lipopolysaccharide (LPS), which can act as an endotoxin, contributing to pathogenicity.

Characteristics of atypical cell walls and which organisms contain peptidoglycan.

• Atypical Cell Walls:

  • Some bacteria lack cell walls or have atypical walls (e.g., Mycoplasma).

  • Peptidoglycan is found in bacterial cell walls.

Be able to match flagellar arrangement terms with descriptions of how the flagella are arranged on a cell.

• Flagellar Arrangements:

  • Monotrichous: Single flagellum.

  • Amphitrichous: Flagella at both ends.

  • Lophotrichous: Tuft of flagella at one end.

  • Peritrichous: Flagella all over the cell surface.

Define the terms: halophile, hyperthermophile, psychrophile, methanogen, and mesophile. Know what type of environment is described by each.

• Environmental Terms:

  • Halophile: High salt concentration.

  • Hyperthermophile: Very high temperature.

  • Psychrophile: Low temperature.

  • Methanogen: Produces methane.

  • Mesophile: Moderate temperature.

Know the differences between Gram (+) and Gram (-) cell walls and be able to identify each from a diagram.

• Gram-Positive vs. Gram-Negative Cell Walls:

  • Gram-Positive: Thick peptidoglycan layer; no outer membrane.

  • Gram-Negative: Thin peptidoglycan layer; outer membrane containing LPS.

Which organisms have 70S ribosomes and which have 80S.

• Ribosomes:

  • 70S: Bacteria and Archaea.

  • 80S: Eukaryotes.

Characteristics of bacterial and archaeal cell walls and how they compare.

• Bacterial and Archaeal Cell Walls:

  • Bacterial: Peptidoglycan.

  • Archaeal: Pseudopeptidoglycan or other polysaccharides.

Match the following eukaryotic organelles with their function: golgi apparatus, lysosome, cytoskeleton, smooth ER, and nucleolus.

• Eukaryotic Organelles:

  • Golgi Apparatus: Modifies and packages proteins.

  • Lysosome: Digests cellular waste.

  • Cytoskeleton: Provides structure and support.

  • Smooth ER: Lipid synthesis and detoxification.

  • Nucleolus: Ribosome synthesis.

Understand the endosymbiotic theory and how it relates to eukaryotic organelles (mitochondria and chloroplasts).

• The endosymbiotic theory suggests that mitochondria and chloroplasts originated as symbiotic bacteria living inside eukaryotic cells.

Which classes of eukaryotic microbes contain pathogens.

• Eukaryotic Microbes with Pathogens:

  • Protozoa, Fungi, Helminths, and Algae.

Know the general characteristics of protozoans (feeding, reproduction, types of locomotion, habitats, etc).

• Protozoans:

  • Feeding: Heterotrophic.

  • Reproduction: Sexual and asexual.

  • Locomotion: Flagella, cilia, pseudopods.

  • Habitats: Moist environments.

Know the general characteristics of Helminths.

• Helminths:

  • Parasitic worms.

Fungal spores and bacterial spores are not the same.

• Fungal Spores = reproductive / Bacterial Spores = Survival

Describe the different types of fungal hyphae (nonseptate vs septate).

• Fungal Hyphae:

  • Septate Hyphae: Divided by cross-walls (septa).

  • Nonseptate Hyphae: Not divided by septa.

Know reproductive strategies of fungi (ex: outward growth of hyphae, fragmentation, spore formation).

• Fungal Reproduction:

  • Hyphal Growth: Extension of hyphae.

  • Fragmentation: Hyphae break off and grow.

  • Spore Formation: Production of spores.

General characteristics of algae.

• Algae:

  • Photosynthetic eukaryotes.

Describe the general cycle of pinworm and what leads to it spreading.

• Pinworm Cycle:

  • Infection via ingestion of eggs.

Different methods for cultivating and identifying fungi from medical specimens.

• Cultivating Fungi:

  • Use of selective media like Sabouraud dextrose agar.

  • Microscopic examination for identification.

While these topics are outlined here for Exam 1, you should be studying all the material we’ve covered on the slides and in lecture as part of the final will be comprehensive.