Microbiology Study Guide: Unit 2 Exam Preparation

Microbiology Study Guide: Unit 2 Exam

Important Vocabulary

This section covers essential terms and concepts that are foundational for understanding microbiology. Mastery of these terms is crucial for success in the course and on the exam.

• Domain, Kingdom, Phylum, Class, Order, Genus, Species: Hierarchical levels of biological classification, from broadest (domain) to most specific (species).

• Specific epithet: The second part of a species name in binomial nomenclature, identifying the species within a genus.

• Homologous recombination: Exchange of genetic information between similar or identical DNA molecules.

• Transposon: A DNA sequence that can change its position within the genome, sometimes creating or reversing mutations.

• Transformation, Transduction, Conjugation: Three main mechanisms of horizontal gene transfer in bacteria.

• Transfection: Introduction of foreign nucleic acids into cells.

• Plasmid: Small, circular DNA molecule found in bacteria, separate from chromosomal DNA.

• Insertion, Inversion, Frame shift mutation, Nonsense mutation, Silent mutation: Types of genetic mutations affecting DNA sequence and protein synthesis.

• Codon: A sequence of three nucleotides that codes for a specific amino acid.

• Mutagenic: Capable of causing mutations.

• Polymerase Chain Reaction (PCR): Laboratory technique used to amplify DNA sequences.

• Biochemical test: Laboratory methods to identify microorganisms based on their biochemical activities.

• Morphology: Study of the form and structure of organisms.

• Serology: Study of blood serum and immune responses.

• Gram Stain: Differential staining technique to classify bacteria as Gram-positive or Gram-negative.

• Vector: An organism that transmits pathogens between hosts.

• Hyphae: Filamentous structures of fungi.

• Capsid: Protein shell of a virus.

• Matrix protein, Envelope, Glycoproteins: Structural components of viruses.

• Bacteriophage (phage): Virus that infects bacteria.

• Prophage: Phage DNA integrated into a bacterial genome.

• Biochemical test, Asexual cycle, Sexual cycle: Methods and cycles in microbial reproduction and identification.

• Viral transformation, Lytic phase, Lysogenic phase: Stages and outcomes of viral infection in host cells.

Phylum/Genera You Should Know

Familiarity with these bacterial genera and their characteristics is important for identification and understanding of microbial diversity.

• Yersinia

• Vibrio

• Neisseria

• Borrelia

• Bacillus

• Pseudomonas

• Rhizobium

• Cyanobacteria

• E. coli

• S. pyogenes

Example: Yersinia pestis is the causative agent of plague.

Viruses You Should Know

Recognize the following viruses, their structure, and diseases they cause.

• Papilloma virus

• Epstein-Barr virus (EBV)

• Hepatitis B

• Varicella virus (VZV/Chicken pox)

• Human Immunodeficiency virus (HIV)

Example: Hepatitis B virus causes liver infection and can lead to chronic liver disease.

Sample Questions and Key Concepts

Classification of Microorganisms

Microorganisms are classified into several major groups based on their cellular structure, metabolism, and genetic characteristics.

• Bacteria: Prokaryotic, unicellular organisms with peptidoglycan cell walls.

• Fungi: Eukaryotic organisms, can be unicellular (yeasts) or multicellular (molds), with chitin cell walls.

• Protozoa: Unicellular, eukaryotic organisms, often motile and lacking cell walls.

• Viruses: Acellular infectious agents composed of nucleic acid (DNA or RNA) and a protein coat (capsid); may have an envelope.

Horizontal Gene Transfer

Horizontal gene transfer (HGT) is the movement of genetic material between organisms other than by vertical transmission (from parent to offspring). It is a major mechanism for genetic diversity in bacteria.

• Transformation: Uptake of free DNA from the environment by a bacterial cell.

• Transduction: Transfer of DNA from one bacterium to another via bacteriophages (viruses that infect bacteria).

• Conjugation: Direct transfer of DNA between two bacterial cells through a pilus.

Gene Expression: In each HGT method, the acquired DNA may be integrated into the host genome and expressed, leading to new traits.

Cell Biology and Disease

• HeLa cells: Immortal human cell line used in scientific research; contributed to advances in cell biology, cancer research, and virology.

• Malaria: Caused by Plasmodium species; complex life cycle and antigenic variation make it difficult to study and treat.

Viruses: Structure and Classification

• Are viruses alive? Viruses are not considered alive because they cannot reproduce or carry out metabolism independently; they require a host cell.

• Viral Structure: Composed of nucleic acid (DNA or RNA), protein coat (capsid), sometimes an envelope derived from host cell membrane.

• Classification: Based on nucleic acid type, presence of envelope, shape, and replication strategy.

Taxonomy and Nomenclature

• Genus name: Always capitalized and italicized or underlined; not an adjective; used in binomial nomenclature.

• Carl Woese's Taxonomic Scheme: Based on ribosomal RNA (rRNA) sequences; divides life into three domains: Bacteria, Archaea, Eukarya.

Bacterial Morphology

• Spirilla: Spiral-shaped bacteria.

• Other shapes: Cocci (spherical), bacilli (rod-shaped), vibrios (comma-shaped), spirochetes (flexible spirals).

Pathogenic Bacteria and Disease

• Streptococcus pyogenes: Leading cause of strep throat and other infections.

• Pseudomonas species: Can cause food poisoning and infections, especially in immunocompromised individuals.

Vector-Borne Diseases

• Mosquitoes: Transmit malaria, yellow fever, dengue, and other diseases.

• Ticks, lice, mosquitoes: Act as vectors by carrying and transmitting pathogens between hosts.

Virus Structure and Function

• Viruses vs. Other Pathogens: Viruses lack cellular structure, organelles, and ribosomes; composed mainly of protein and nucleic acid.

• Viral Classification: Based on nucleic acid type (DNA or RNA), presence of envelope, and replication cycle.

• Unique Features: Viruses cannot reproduce outside a host cell and are not affected by antibiotics.

Table: Comparison of Microbial Groups

Feature	Bacteria	Fungi	Protozoa	Viruses
Cell Type	Prokaryotic	Eukaryotic	Eukaryotic	Acellular
Cell Wall	Peptidoglycan	Chitin	None	None
Reproduction	Binary fission	Spores, budding	Binary fission, sexual	Host-dependent
Genetic Material	DNA	DNA	DNA	DNA or RNA
Metabolism	Yes	Yes	Yes	No

Key Equations and Laboratory Techniques

• Polymerase Chain Reaction (PCR): Amplifies DNA using cycles of denaturation, annealing, and extension.

• Gram Stain: Differentiates bacteria based on cell wall structure.

Equation for PCR amplification:

$N = N_0 \times 2^n$

Where $N$ is the final number of DNA molecules, $N_0$ is the initial number, and $n$ is the number of cycles.

Summary Tips for Exam Preparation

• Review all vocabulary and be able to define and apply each term.

• Understand the differences between major microbial groups.

• Be familiar with the structure, classification, and replication of viruses.

• Know examples of important bacteria and viruses and the diseases they cause.

• Practice sample questions to test your understanding of key concepts.