Bacterial Structure & Function & Virulence | Alison Weiss | 01/21/25 Notes Part 1

What is a disease?

A change from general good health, involving disruption of normal structure or functioning of the body caused by not good nutrition, genetic abnormalities, structural or functional disorders, and trauma.

What are some examples of infectious diseases?

Prions, viruses, bacteria, fungi, protozoa.

What are prions?

Single protein that is very small.

What are viruses?

Average about 100 nanometers, have few proteins, and must commandeer the machinery of the cells they invade to reproduce.

How do bacteria sizes compare to one another, and what is bacteria?

Bacteria vary in size, but are at least 10 times bigger than viruses; they are single-celled organisms that can reproduce independently.

How do single-cell parasites compare to bacteria?

Single-cell parasites are at least 10 times larger than bacteria.

How big are multicellular parasites?

They can be so large that they can often be seen with the naked eye; for example, tapeworms can be 20 feet long.

What are the 3 types of life?

Archaebacteria, Eukaryotes, and usually Eubacteria.

Eukaryotes divide into which two groups?

Eubacteria and Archaebacteria.

What is Eubacteria?

Bacteria of medical importance.

What is Archaebacteria?

A collection of evolutionary distinct organisms primarily found in extreme terrestrial and aquatic environments.

Where do antibiotics work in therapeutics?

In the cell wall and cytoplasm (internal).

Where do antibodies/vaccines work?

On the cell-surface (external).

What does PAMPS stand for?

Pathogen-Associated Molecular Patterns.

What is PAMPS and what does it do?

It is a conserved structure on microorganisms that includes cell wall structures of bacteria; it is recognized by the innate immune system and jump-starts the immune response, induces inflammation, cytokine release, and can cause symptoms of disease in the absence of living bacteria.

What are the differences between Prokaryotes and Eukaryotes?

They differ in their nucleoid or nucleus structure, in chromosome shape, the presence of membrane-bound organelles, peptidoglycan in the cell wall, sterols or cholesterol presence, and ribosome size (70S in prokaryotes, 80S in eukaryotes).

What does the bacterial cytosol contain?

Enzymes that generate ATP, cell wall, RNA, and DNA.

Where are Prokaryotic (70S) ribosomes found?

Throughout the cytoplasm and on the membrane.

Where is the DNA found in bacteria?

In the cytoplasm, supercoiled to manage its size.

What does the cell wall determine?

The shape and species properties of the bacterium.

What are the 3 main shapes of bacteria?

Sphere (coccus), rod (bacillus), and spiral or curved (spirochete or vibrio).

What does the peptidoglycan cell wall do?

Protects from environmental stress, provides strength, maintains shape, and limits the penetration of molecules.

What is the medical importance of cell walls?

Cell walls protect from some host defenses and play a role in adherence to host cells.

What is selective toxicity unique to?

Bacteria; it is a target for many antibiotics.

What is the gram stain procedure used for?

It is used to classify bacteria and consists of fixation, crystal violet, iodine treatment, decolorization, and counter stain (safranin).

What is the primary difference between gram-positive and gram-negative bacteria?

Gram-positive bacteria retain crystal violet and appear purple, while gram-negative bacteria only stain with safranin and appear red.

What are characteristics of gram-positive bacteria?

They have 1 membrane, 40 layers of peptidoglycan, and contain lipoteichoic acid.

What are characteristics of gram-negative bacteria?

They have 2 membranes, 1 layer of peptidoglycan, and contain lipopolysaccharide.

What is peptidoglycan made of?

A highly cross-linked mesh of peptides and polysaccharides.

What do antibiotics attack regarding bacterial structure?

They attack cross-linking, with examples including penicillin, cephalosporin, and vancomycin.

What is the structure of gram-positive bacteria composed of?

Multiple peptidoglycan layers and lipoteichoic acid near the inside and teichoic acid near the outside.

What is the structure of gram-negative bacteria composed of?

Porin, lipopolysaccharide, outer membrane, periplasmic space, 1 peptidoglycan layer, and plasma membrane.

What are bacterial capsules?

They are outside the bacterial cell wall, usually carbohydrate-based, and prevent penetration of dye.

What are the functions of a capsule?

Protection from harsh environments, permeability barrier, surface attachment, and anti-phagocytic properties.

Capsules are often associated with what?

Pathogenicity; encapsulated bacteria are virulent, while those without a capsule are avirulent.

What does it mean that capsules are antigenic?

They can induce protective antibodies that promote engulfment by phagocytes.

What does the capsule protect the bacterium from?

Phagocytosis; antibodies to the capsule promote uptake, leading to elimination by phagocytosis.

What is the term for surface appendages on bacteria?

Flagella, which are rope-like filaments of coiled protein subunits called flagellin.

What are flagella involved in?

Bacterial movement (motility).

What is chemotaxis composed of?

Nutrients and sugars, including those from humans.

What is the role of motility in pathogenesis?

It mediates tissue invasion by traversing cellular/extracellular barriers and accessing intestinal cells.

What are Pili-Surface Appendages and what are they involved in?

Present over the entire surface, made of protein (pilin), and are involved in transformation, bacterial movement, serving as phage receptors, and anti-phagocytic functions.

What is Pap Pili associated with?

E-coli that causes urinary tract infections.

What is the model of Pilus Assembly composed of?

About 200 pili per cell, containing 100 proteins per pilus, 6 structural genes, and 5 genes for assembly and secretion.

What is Sporulation?

A mechanism to ensure survival during adverse conditions, triggered by nutrient deprivation; it involves one bacterium making one spore.

What does the free endospore revert back to?

A vegetative cell (germination) when it encounters favorable growth conditions.

What are spores resistant to?

Killing by heat over 2 hours of boiling, drying, freezing, pH extremes, deleterious chemicals, antibiotics, and radiation.

What are sterilization procedures examples?

Bleach and autoclaving (exposure to high temperature and pressure).

What influences disease severity and what is its formula?

(virulence * pathogen dose) / (health status * immune response).

How would seasonal flu, COVID-19, and Ebola rate in terms of death rate from lowest to highest?

Flu, COVID-19, then Ebola.

What are some underlying conditions that could impact health status?

Diabetes, chronic lung disease, cardiac disease, and age (65 years or older).

Does the Immune Response reduce or enhance disease?

It can both reduce and enhance disease.

What does a high pathogen dose mean?

Healthcare workers are constantly exposed and get very close to highly infectious individuals.

What are the 5 steps in the pathogenic process?

Infect the host, grow and spread, evade defenses, damage host, and transmission.

What are steps 1-3 of the pathogenic process called?

Normal microbiome.

What are steps 1-4 of the pathogenic process called?

Pathogens (virulence factors).