Bacterial Cells: Structure/Function

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Describe Eukaryotic Cells

- Cells from Mammalian organisms
- Includes algae, fungi, protozoa
- Composed of a plasma membrane, cytoplasm, centrioles, and the membrane bound organelles: mitochondria, ER, golgi, and the nucleus

Describe Prokaryotic Cells

- Includes the 300 different types of bacteria
- Composed of a cell wall, membrane, cytoplasm, ribosomes, and a nucleoid
- All are unicellular
- Have cytochromes in place of mitochondria

What is a capsule and its function?

- The capsule is a polysaccharide outer cover that some bacteria have
- It is used for attachment to the host cell
- Represents a determinant of pathogenicity
- It makes it hard for neutrophils to engulf it

What is the function of pilli?

- Most gram negative bacteria use pilli to transfer DNA from one bacteria to another (a sex organ)
- Also for attachment

What are the 3 types of bacteria and what color do they stain?

1. Gram + has a thick peptidoglycan layer that stains bluish/purple in crystal violet
2. Gram - has a thin peptidoglycan layer that stains red/pink in safranin
3. Acid fast (Mycobacterium) has a cell wall with mycolic acid

What is the periplasmic space?

In Gram - bacteria, the space between the cytoplasmic membrane and the outer membrane and the between the outer membrane and the cell wall. It is filled with toxins.

Bacterial Nomenclature

Binomial: genus + species

Define Species

Strains with a high degree of overall similarities that differ fromother strains

Define genus

A collection of similar species

What 3 things can the nomenclature indicate?

1. Morphology
2. Discoverer
3. Disease association

Why is bacterial classification important?

Because it
A. Facilitates proper lab identification of clinical isolates
B. Necessary for determining etiology of infectious diseases
C. Essential to nomenclature

How is phylogenetic relatedness determined?

By comparison of the 16S rRNA sequences

What is the average diameter and length of bacteria?

0.2 - 2.0 um in diameter and 2 - 8 um in length

Wht are the 3 shapes of bacteria?

1. Cocci - spherical
2. Bacilli - elongated
3. Spirochetes - spiral

What shapes can bacteria take duing reproduction?

1. Diplococci (pairs)
2. Streptococci (chains)
3. Staphylococci (clusters)

What type of bacteria are the Neisseria genus? (N. gonorrhea, N. sicca, N. meningitis)

Gram Negative Diplococci

What type of bacteria are Streptococcus pneumoniae?

Gram Positive Diplocci

Are all streptococci gram negative or positive?

Gram positive

What are 2 examples of a single bacillus associated with disease?

1. E. Coli - diarrhea, septicemia, UTI
2. Pseudonomas auruginosa - cystic fibrosis, burn trauma

What are 2 exampls of coccobacilli that are associated with disease?

1. Bordetella pertussis - whooping cough
2. Hemophilus influenza - childhood meningitis

What is an example of a Vibrio bacteria?

Vibrio cholera - profuse diarrhea

What are 2 examples of a disease associated Spirochete?

1. Borellia burgdorferi - Lyme Disease
2. Treponema pallidum - Syphillis

What agar is good to use to grow bacteria that has demanding requirements?

Blood agar

What agar is good to use for acidic bacteria like Neisseria?

Chocolate agar

What is chocolate agar?

heated blood agar (heat denatures the Hb)

What agar is used to isolate gram negative bacteria?

EMB agar

What is EMB agar?

Eosin Methylene Blue on agar that does not allow growth of gram positive bacteria

What is useful about growth agar?

isolate colonies so we can study metabolic activities, other associated function, and color changes

What is Klebsiella?

- a genus of gram negative, oxidase negative, rod shaped bacteria that lives in the GI tract and causes UTI and pneumonia.
- when grown on nutrient agar, forms mucoid cultures

What are proteus species?

- Live in the GI tract and cause kidney infection (pyelonephritis)
- form mucoid cultures

Why do mucoid cultures present?

Due to overproduction of capsule

What colors do E. coli, staph, and strep appear in colony isolation?

1. E. coli - green
2. Staph - gold
3. Strep - white

What do oxidase positive bacteria possess?

cytochrome c oxidase (so they can use oxygen for energy production)

What are nucleoids

areas of DNA concentration

What kind of ribosomes do bacteria have?


What do cytoplasmic granules contain?


How do bacteria compartmentalize their long DNA

the gyrase enzyme supercoils DNA

What are the 3 components of the bacterial envelope?

1. Capsule
2. Cell Wall
3. Outer Membrane

What is the Cell Wall of Gram + bacteria composed of?

1. Peptidoglycan
2. Teichoic acid
3. Lipoteichoic acid

What is the Cell Wall of Gram - bacteria composed of?

1. Peptidoglycan
2. Periplasmic space
3. Outer membrane
4. Proteins
5. LPS

What is peptidoglycan made up of?

glycan chains of GlcNAc and MurNAc crosslinked by a peptide bridge

What is teichoic acid?

polyribitol phosphate or glycerol phosphate crosslinked to peptidoglycan. It is the major surface antigens used for serological typing. Also is a source of adherence and transport. Only in Gram +

What is lipoteichoic acid?

lipid linked teichoic acid. Only in Gram +

What is in the periplasmic space?

enzymes for transport, degradation, and synthesis. For example, phosphatases, proteases, endonucleases, binding proteins, AAs, inorganic ions, chemoreceptors, and drug resistance enzymes. It detects environmental factors and transports needed nutrients into the cell. Only in Gram -

What is the outer membrane?

phospholipids and saturated fatty acids. Gram - only. Serves as a permeability barrier and antibiotic resistance.

What are the 3 components of LPS?

1. Lipid A - an important endotoxin
2. Core - polysaccharides like KDO
3. O Antigen

What is the purpose of the cell wall?

protect the cell membrane from osmotic lysis and determine the shape and rigidity of the cell

What are the components of peptidoglycan?

Alternating residues of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) linked by B-1-4 glycosidic bonds

What are 2 factors that affect the integrity of the cell wall?

1. Beta lactam antibiotics (penicillin, cephalosporins) inhibit cell wall formation
2. Lysozyme degrades the structural integrity of the cell wall's peptidoglycan

How does penicillin inhibit cell wall formation?

By binding to transpeptidase preventing cross linkage

What distinguishes the bacterial cytoplasmic membrane with Eukaryotic membranes?

The lack of sterols

What are the 5 functions of the cytoplasmic membrane?

1. Osmotic barrier
2. Electron and Photon transport (site of ATP production)
3. Cell wall biosynthesis
4. Chemotaxis and flagella activity
5. Transport of molecules

What causes bacterial septic shock?

Lipid A (from the LPS in Gram Negative bacteria) activates macrophages that will produce abnormal amounts of cytokines (IL-1 and TNF alpha). IL-1 goes to hypothalamus and upregulates the thermostat (fever). TNF alpha goes to endothelial lining of blood vessels and increases permeability which decreases pressure (hypotension). Can also stimulate T-Cells to increase IFNy production. Depresses iron release in circulation (bacteria won't grow as fast). Regulates release of sugar (hypoglycemia).

What are 3 functions of LPS?

1. Confers a negative charge to bacteria (G- only)
2. Repels hydrophobic molecules like antibiotics, bile salts, and detergents
3. Induces fever in a bacterial infection

What is the LPS equivalent in G+ bacteria?

LTA (lipoteichoic acid)

What 2 bacterial genera characteristically create spores?

1. Bacillus (aerobes)
2. Clostridium (anaerobes)

When does sporulation occur?

When bacteria is under environmental stress (i.e. lack of nutrients, extreme temperatures) because spores resist physical and chemical conditions that are detrimental

What components of spores help them resist detrimental chemical and physical conditions?

1. Keratin is in the spore's coat making it resist chemicals
2. Calcium and dipicolinic acid contribute to heat resistance

What is the medical significance of spores?

disease dissemination

How do you destroy a spore?

Autoclaving at 121 degrees celsius for 20 min

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