Microbiology Unit 1

Microbiology Study Notes

Protozoa and Helminths

• Giardia: causes giardiasis, a diarrheal disease
  • Moves using flagella
• Trichomonas: causes trichomoniasis, a sexually transmitted infection
  • Moves using flagella
• Entamoeba: causes amoebiasis, an intestinal infection
  • Moves using pseudopodia
• Plasmodium: causes malaria, a blood-borne disease
  • Moves using sporozoites
• Flagyl: an antiprotozoal medication that works by inhibiting DNA replication

Fungi

• Characteristics of fungi:
  • Eukaryotic
  • Heterotrophic
  • Decomposers
• Types of fungi:
  • Yeast: single-celled, spherical
  • Mold: multicellular, filamentous
• Dimorphic fungi: can exist in two forms, such as yeast and hyphae
  • Example: Histoplasma capsulatum
• Mycosis: a fungal infection
• Antifungal medications:
  • Work by inhibiting fungal cell wall synthesis
  • Work by inhibiting fungal DNA replication

Helminths

• Types of helminths:
  • Cestodes: tapeworms
  • Trematodes: flukes
  • Nematodes: roundworms
• Examples of helminths:
  • Taenia: tapeworm
  • Clonorchis: liver fluke
  • Dirofilaria: heartworm
  • Enterobius: pinworm
• Vermox: an antihelminthic medication that works by inhibiting worm muscle contraction
• Helminthic therapy: using helminths to treat diseases, such as inflammatory bowel disease

DNA and Genes

• Structure of DNA:
  • Double helix
  • Composed of nucleotides
• Gene:
  • Segment of DNA that codes for a protein
  • Expression: process of creating a protein from a gene
• Genotype:
  • Genetic makeup of an individual
• Phenotype:
  • Physical characteristics of an individual
• Who determined the structure of DNA:
  • James Watson and Francis Crick
• Nucleotides:
  • Building blocks of DNA and RNA
  • Composed of sugar, phosphate, and nitrogenous base
• Complementary base-pairing:
  • Adenine pairs with thymine
  • Guanine pairs with cytosine
• Anti-parallel:
  • Strands of DNA run in opposite directions
• Chromosome:
  • Single molecule of DNA and associated proteins
• DNA replication:
  • Process of creating a new DNA molecule
  • Involves helicase, polymerase, and ligase
• Gyrase:
  • Enzyme that relieves DNA tension during replication
• Helicase:
  • Enzyme that unwinds DNA during replication
• Polymerase:
  • Enzyme that synthesizes new DNA strand
• Ligase:
  • Enzyme that seals gaps in new DNA strand

Gene Expression and Translation

• Gene expression:
  • Process of creating a protein from a gene
• Transcription:
  • Process of creating mRNA from DNA
  • Involves RNA polymerase
• Translation:
  • Process of creating a protein from mRNA
  • Involves ribosomes, tRNA, and mRNA
• Codon:
  • Sequence of three nucleotides that codes for an amino acid
• Anticodon:
  • Sequence of three nucleotides that complements a codon
• Start codon:
  • AUG, codes for methionine
• Stop codons:
  • UAG, UAA, and UGA, terminate protein synthesis
• Ribosomes:
  • Site of protein synthesis
• mRNA:
  • Template for protein synthesis
• tRNA:
  • Brings amino acids to ribosomes during protein synthesis

Genetic Engineering and PCR

• Goal of traditional recombinant DNA technology:
  • To introduce a gene into an organism
• Steps of traditional recombinant DNA technology:
  • Isolate DNA
  • Cut DNA using restriction enzymes
  • Insert gene into plasmid
  • Introduce plasmid into host cell
  • Select for transformed cells
• Goal of PCR:
  • To amplify a specific DNA sequence
• Steps of PCR:
  • Denature DNA
  • Anneal primers
  • Extend primers using Taq polymerase
  • Repeat steps
• CRISPR:
  • A gene editing tool that uses a Cas-9 enzyme and guide RNA
  • Discovered by Jennifer Doudna and Emmanuelle Charpentier

Viruses

• Size range of viruses:
  • 20-400 nanometers
• Types of viruses:
  • Helical: rod-shaped
  • Polyhedral: many-sided
  • Complex: combination of helical and polyhedral
• Bacteriophage:
  • A virus that infects bacteria
  • Discovered by Felix d'Herelle
• Plaques:
  • Clear areas on a bacterial lawn where viruses have infected and killed bacteria
• Phage therapy:
  • Using bacteriophages to treat bacterial infections
• Steps in the lytic cycle:
  • Attachment
  • Penetration
  • Uncoating
  • Replication
  • Assembly
  • Lysis
• Steps in the lysogenic cycle:
  • Attachment
  • Penetration
  • Uncoating
  • Integration
  • Replication
  • Induction
  • Lysogenic conversion
• How viruses enter human/animal cells:
  • Attach to receptors on host cells
  • Enter host cells through endocytosis or membrane fusion
• Acute infections:
  • Cause symptoms that resolve quickly
• Latent infections:
  • Remain dormant in host cells for a long time
• Persistent infections:
  • Cause chronic symptoms

Immunology

• Types of immunity:
  • Natural
  • Artificial
• Helper T cells:
  • Activate B cells and other immune cells
  • Recognize antigens presented by MHC-II
• Cytotoxic T cells:
  • Kill infected cells
  • Recognize antigens presented by MHC-I
• Antigen-presenting cells (APCs):
  • Dendritic cells
  • Macrophages
  • B cells
• Interleukins:
  • Cytokines that activate immune cells
• Natural killer cells:
  • Kill infected cells and tumor cells
  • Don't require antigen presentation
• Monoclonal antibodies:
  • Laboratory-produced antibodies that target specific antigens
  • Used for diagnosis and treatment of diseases

Vaccines and Antimicrobial Medications

• Types of vaccines:
  • Live, attenuated
  • Inactivated
  • Subunit
  • Conjugate
• mRNA COVID vaccines:
  • Use mRNA to instruct cells to produce a protein
• Penicillin:
  • Discovered by Alexander Fleming
  • Inhibits bacterial cell wall synthesis
• Narrow-spectrum antibiotics:
  • Effective against a specific type of bacteria
• Broad-spectrum antibiotics:
  • Effective against a wide range of bacteria
• How antimicrobial medications function:
  • Inhibit cell wall synthesis
  • Inhibit DNA replication
  • Inhibit protein synthesis
  • Disrupt cell membranes

Microbiology and Disease

• Pathology:
  • Study of the causes and effects of diseases
• Etiology:
  • Study of the causes of diseases
• Pathogenesis:
  • Study of the development of diseases
• Infection:
  • Presence of pathogens in the body
• Disease:
  • Pathological state that results from an infection
• Normal flora:
  • Microorganisms that live on and inside the body
  • Provide benefits such as fermentation and immune system development
• Microbial antagonism:
  • Competition between microorganisms for resources
• Opportunism:
  • Ability of microorganisms to cause disease in compromised hosts
• Koch's postulates:
  • Criteria for determining the cause of a disease
• Communicable:
  • Able to be transmitted from one person to another
• Contagious:
  • Able to be transmitted through direct contact
• Noncommunicable:
  • Not able to be transmitted from one person to another
• Incidence:
  • Number of new cases of a disease in a population over time
• Prevalence:
  • Total number of cases of a disease in a population at a given time
• Sporadic:
  • Occurs occasionally and randomly
• Endemic:
  • Continuously present in a population
• Epidemic:
  • Widespread outbreak of a disease
• Pandemic:
  • Global outbreak of a disease