Microbiology Exam 3 Notes

Genetics and Microbiology

  • Genetics: Studies biological information. Deals with genes, heredity, and information flow.
  • Genes: Units of information made of DNA that carry information about particular traits.
  • Genetic Processes: Fundamentally similar in all organisms.
  • Evolution: All organisms share the same genetic code.

DNA Structure

  • DNA: Polymer of nucleotides (A, G, C, T).
  • Double Helix: Two anti-parallel strands joined by hydrogen bonds (A-T, G-C).

Central Dogma of Molecular Biology

  • Information Flow: DNA → RNA (mRNA) → Protein.
  • Replication: DNA copies itself.
  • Transcription: DNA makes an RNA (mRNA) copy.
  • Translation: mRNA directs protein synthesis.
  • Gene Definition: Holds information to build a protein.

Genetic Recombination

  • Bacteria: Do not have sexual reproduction.
  • Binary Fission: Bacteria replicate by dividing into two identical cells (clones).
  • Horizontal Gene Transfer: Creates recombinants without reproduction.

Eukaryotes vs. Bacteria

  • Eukaryotes: Undergo sexual reproduction, cells are diploid (2N), meiosis produces haploid (N) cells (sperm or eggs), fertilization restores diploid state.
  • Bacteria: Monoploid (x=1), divide by binary fission (similar to mitosis), do not undergo meiosis or fertilization.

Horizontal Gene Transfer in Bacteria

  • Transformation: Uptake of naked DNA by a cell.
    Transformation=uptakeofnakedDNATransformation = uptake of naked DNA
  • Conjugation: Transfer of genetic material via direct contact (pilus).
  • Transduction: Transfer of bacterial genes mediated by a bacteriophage (virus).

Transformation

  • Definition: Uptake of naked DNA.
  • Process: Donor cell dies, releases DNA fragments, recipient cell takes up fragment, DNA swaps spots, creating a recombinant cell.

Conjugation

  • Definition: Transfer of genetic material via direct contact.
  • F+ Cells: Contain a plasmid called the F factor which has genes that allow it to make a pilus that will connect it to other cells.
  • Process: F+ cell makes a copy of the F factor and transfers it to an F- cell via a pilus, converting the F- cell to F+.

Transduction

  • Definition: Transfer of bacterial genes via a bacteriophage.
  • Process: Bacteriophage infects a cell, replicates, bacterial DNA is mistakenly incorporated into new phage particles, new phage infects another bacterium, transferring new genes.

Microorganisms, Humans, and Disease

  • Bacteria: Categorized as pathogens, mutualists, or opportunists.
  • Pathogen Example: Bacillus anthracis, Mycobacterium tuberculosis
  • Mutualist Example: E. coli, Staph epidermidis
  • Opportunist Example: Pseudomonas
  • E. coli: Usually good, but can be bad (strain 0157H7, UTIs).

General Terms and Principles

  • Pathogen: Microorganism capable of causing disease.
  • Infection: Successful invasion and growth of pathogens in the body.
  • Disease: Abnormal state where the body cannot perform its functions properly.
  • Host: Organism that shelters and supports pathogen growth.
  • Infectious Disease: Disease caused by infective pathogens.
  • Degenerative Disease: Disease not caused by a specific pathogen.

Pathology

  • Definition: Study of disease in an individual.
  • Includes: Etiology (cause), pathogenesis (development), effects/treatments.

Normal Microbiota

  • Definition: Microbes that are supposed to be there.
  • Location: Inside or on the body surface without causing disease.
  • Composition: Bacteria, fungi, and protozoa.
  • Symbiotic Relationship: Usually mutualistic (e.g., E. coli makes vitamin K).
  • Microbial Antagonism: Good bacteria prevent pathogens from growing

Types of Symbiosis

  • Commensalism: One benefits, the other is unaffected.
  • Parasitism: Pathogen is involved.
  • Opportunistic Pathogens: Cause disease under certain circumstances.

Classification and Terminology of Infectious Diseases

  • Symptoms: Subjective reports.
  • Signs: Objectively measurable changes.
  • Diagnosis: Based on signs and symptoms.
  • Syndrome: Specific group of signs and symptoms that always accompany a certain disease.

Severity and Duration of Disease

  • Acute: Rapid, severe symptoms, short duration.
  • Chronic: Slow, less severe symptoms, longer duration.
  • Latent: Causative agent dormant, causes disease later.

Extent of Host Involvement

  • Local: Confined to a small part of the body.
  • Systemic: Spread throughout the body.
  • Primary Infection: Initial cause of disease.
  • Secondary Infection: Occurs after host is weakened.
  • Subclinical: No signs or symptoms (asymptomatic).

Nosocomial Infections

  • Definition: Acquired in a hospital.
  • Culprits: Opportunistic, drug-resistant bacteria.

Pathogenesis and Graph

  • Pathogenesis: Development of a disease.
  • Stages: Incubation, prodromal, illness, decline, convalescence periods.
  • Graph:
    • X-axis: Disease progression
    • Y-axis: Number of microorganisms

Disease Progression Graph

  • Key Stages:
    • Incubation: No signs/symptoms.
    • Illness: Symptoms building up.
    • Decline: Pathogens decreasing.
    • Convalescence: Recovery.

Microbial mechanisms of Pathogenicity

  • Traditional View: Microbes enter the body from the outside.
  • Portal of Entry: How a pathogen gets into the body.
  • Two examples: Integumentary system, Mucous membranes
  • Preferred Portal and Adherence: Some pathogens prefer specific entry sites. Pathogens need to attach to host tissue (adherence).

Overcoming Host Cell Defenses/Penetration:

  • Capsules: Protect against phagocytosis.
  • Enzymes: Help bacteria persist (leukocidins, hemolysins, coagulases).

How Bacteria Damage the Body:

  • Direct Damage: Harm/destroy cells.
  • Indirect Damage: Immune system causes damage.
  • Making toxins

Direct Damage by Toxins

  • Exotoxins: By products of bacterial metabolism and are released into the host
  • Endotoxins: Part of the cell wall and released only when the cells die.

Exotoxins vs. Endotoxins

  • Exotoxins: Proteins that are mainly in gram-positive cells and are external.
  • Endotoxins: Are actually part of the cell wall in gram-negative.

Affect the Host In Specific Ways With Exotoxins:

  • Cytotoxins: Kill/render inactive.
    Diphtheria toxin inhibits protein synthesis in host cellsDiphtheria \ toxin \ inhibits \ protein \ synthesis \ in \ host \ cells
  • Neurotoxins: Interfere with the transmission of nerve impulses.
  • Enterotoxins: Adversely affect cells lining the gastrointestinal tract.
  • Antibodies Against These Toxins are called - Antitoxins

Endotoxins

  • Part of the cell wall. This death of the bacterial cell releases the toxin (LPS).
  • Cause chills/fever due to the stimulation of IL-1 (messenger molecules).
  • Can cause shock 1:1 with blood pressure

Septic Terms:

  • Sepsis: Response of your body that is inappropriate, triggers immune system.
  • Septa Scma: Growth of bacteria in the bloodstream.
  • Toxic Shock: Exotoxin
  • Septic Shock: Endotoxin

Interleukin Steps that Occur Due to Endotoxins:

  1. Macrophage ingests gram-negative bacterium.
  2. Bacterium is degraded which releasing endotoxins.
  3. IL 1 is released and induced.
  4. Il1 then induces hypothalamus to produce prostaglandins. End goal being RESET the body's “thermostat” which producing fever
  • Viruses cause cytopathic effects (CPE), which may cause cell death or damage.
  • Interferons Are proteins created by produced by host cells after a viral infection to protect their neighbors from the virus.

Epidemiology and Transmission of Disease

  • Definition: Study of disease in populations, including transmission, incidence, frequency, and distribution.
    (CDC) Centers for disease control/ (WHO)World health organization
  • Incidence: % that gets the disease during a given time period
  • Prevalence: % of population which has the disease during a given time period
    Virulence: Degree of pathogenicity for a given pathogen;

Virulence Measurement

  • Lethal dose for 50% inoculated hosts (LD50) or
  • ID50( infectious dose for 50 % of inoculated hosts
  • Lower the # more Virulent or Deadly; It can range from 1 cell to 1Billion

Disease Transmission

  • Transmitted - 1 to another is A Communication
  • How easily it can be communicated is - The Contagiousness
  • Non-Communicable = not transferred 1 – 1 = acquired from the environment.

General Terms:

  • Sporadic: Occurs occasionally in a pop.
  • Endemic: Always/ Constantly present in a population
  • Epidemic: Acquired rapidly by people in a Given area
  • Pandemic: Epidemic Worldwide

Spread of Infections

  • Reservoir = Continual source if infective pathogens
  • Human infected other humans - Most human diseases
  • Animal - Zoonoses
  • Diseases + Vector Like mosquitos (animal reservoirs…they bit another human)
  • Rabies -Main One!!!!!!!! (animals)
  • Soil, water-Pathogen - Can Live stably outside for a Host

Types of Transmission:

Contact- Transmission (Living Reservoid)

  • Direct: Physical contact with a resevior and Host; This is actual literal Touching.
  • Indirect :Living resovoir to a host that goes through an objects called a Fomite.(None Living)
  • Droplet Less 1 meter thru mucous, sneezing/coughing
  • Aairbone: Cough/sneezes ,leaves room
    NOTE: IF it not Contagious .. it is vehicle.. non Living Reservior

Arthropods +Mosquitos +Ticks

*Biological 1: 1 Touch that arthropod harbos pathogen / passes to HOST
Called Biological transmission for direct contact
if the thing goes and gets it = indirect living is mosiquito
not- living= FOMITE / and indirect

Viruses - General Principles

  • Nonliving obligate intracellular parsites
  • OR the simplest living things there are (depends upon your definition of "life")
    ALWAYS contain
  • Nucleic acid
    *Information - (DNA.Or, RNA)
  • protein coat (the “capsid”)
    sometiems contains - enveloped

Host Range + virions of Virus:

  • Host range = very specific on the cells it can infect
  • Virion = Mature effective particle that exists
    Arrangements Nucleic is genome , Nucleic acid = Single or DNA . Linear to Circuler
  • The coat is calles the Capsid - Proteins in subunits “= Capsomers
    Virus spikes (CarboHydrates + Lipids= Bonds to Host cells; The infected machinery

General Morphology:

  • Helical =Spring or slinky.
  • All Virus 20 sided faces / Each piece of the Triangles Capsomers with / DNA (Internal)
  • Enveloped = If lack an E , = “NAked” viruses / USALLY= ANIMAL VIRUSES.
  • Complex = Head with complex attacted / BAcertiophages (Complex V)1 to1 C

Virus Taxonomy:

NOT ALL ARE realated (from evolves) Cannot TREE the Virus
Based on: Nucleic acid ,Lcycle strat ,or morph..
notassigned NORMAL class - Groups IN Genera or species but varies depending YOU ASK!
Viralspecies. = SAME genetic into Eco log (range from Hosts..regular names)

Viral Taxonomy and Examples

*Species HIV is (fam Retrovire- is Genus Levtinivirus)
Polio (fam Pinornavir - is Enteroviridae)
Rabies (Rhabdovir is Lysavirus)
DNA

  • HPV FAM=Papovaviridae + Genus is papillomavirus