9/9 Chapter 3: Bacteria and Archaea (Nanotubes to ribsomes)

What are nanotubes? What are they used for?

• Very thin, long, tubular extensions of the cytoplasmic membrane

• Used as channels to transfer amino acids or to harvest energy by shuttling electrons to iron-rich substances

What is the S layer? And are they always produced?

• Single layers of thousands of copies of a single protein linked together like tiny chain link fences

• Only produced when bacteria are in a hostile environment (provides extra protection)

What is the glycocaylx? What are the two types it could be?

• Coating of repeating polysaccharide or glycoprotein units

• More common than S layers and it’s mainly polysaccharides

• Can be an Slime layer or capsule

What are the differences between slime layer and capsule (glycocaylx)?

• Slime layer: loose, protects against loss of water and nutrients (can easily dissociate)

• Capsule: more tightly bound, denser, and thicker; produce a sticky (mucoid) character to colonies on agar (very organized and harder to dissociate)

Why are capsules important when it comes to pathogens and bacteria?

• Formed by many pathogenic bacteria

• Have greater disease-causing abilities (increased virulence)

• Protect against host white blood cells called phagocytes (capsule makes them slippery so they can escape phagocytes)

What is high vs low virulence?

Virulence: a bacteria cells ability to cause a disease/infection

• ex: high virulence = 90% infection rate vs low virulence = 50% infection rate

What can capsules and slime layers (glycocaylx) form? What is plaque? What is biofilm responsible for?

Biofilm

• Plaque on teeth protects diverse bacteria/microbes from becoming dislodged

• Responsible for persistent colonization of plastic catheters, IUDs, metal pacemakers, and other implanted medical devices (can cause issues)

What do biofilms prevent from happening?

They prevent antibiotics from reaching microbes inside the biofilm near/towards the surface they are attached to

• Fungi, viruses, etc. can attach to bacteria too

What are the 3 functions of the cell wall?

1. Helps determine the shape of a bacterium (keeps rigidity)

2. Provides strong structural support to keep the bacterium from bursting or collapsing because of changes in osmotic pressure:

• Certain drugs target the cell wall, disrupting its integrity and causing cell lysis (disintegration or rupture) of the cell

3. Gains its relative rigidity from peptidoglycan

What is osmotic pressure? And what is lysis?

Environmental pressure caused by uneven solute concentrations

• Good cell walls can resist this

• Lysis: cell breaking/rupturing

What is peptidoglycan? And is it in human cells? And is it a specific target for drugs?

It’s the main component of cell walls and is not in human cells

• Is a unique target for drugs because it’s only in bacteria

What is the structure of peptidoglycan?

• Compound of a repeating framework of long alternating G and M glycan (sugar) chains cross-linked by short peptide (protein) fragments (only linked on the M sugars)

• Provides a strong but flexible support framework

What happens when the peptidoglycan structure is broken? Where do antibiotics target and what are some examples of antibiotics?

If broken then the rows will separate meaning the cell wall is weak

• Antibiotics target the cross-bridge to break the cell wall and the enzyme that makes the cross-bridge

• Antibiotics include penicillin, amoxicillin, ampicillin, etc.

The cell wall can be gram-______ or _____? And it is important for what two things?

The cell wall can be gram-negative/positive

• It’s important for gram staining and what antibiotics can be used on the cell wall

What is a gram-positive cell wall? And what are the two things unique to gram-positive cell walls and what’s their functions?

Thick, homogenous sheet of peptidoglycan: 20 to 80 nm in thickness (contains more layers of peptidoglycan)

• Contains teichoic acid (on top of wall) and lipoteichoic acid (goes through wall):

• Function in cell wall maintenance and enlargement

• Contribute to the acidic charge on the cell surface

What is a gram-negative cell wall? What is unique to the negative cell walls?

• Single, thin sheet of peptidoglycan: 1 to 3 nm in thickness

• Thinness gives gram-negative cells more susceptibility to lysis

• Contains Outer membrane over peptidoglycan (Helps protect against some antibiotics)

Is penicillin more likely to hit the gram negative or positive cell wall? And which type of bacteria is more difficult to kill?

Positive because it is on the outside not protected by an outer membrane

• Whereas it can’t diffuse through the outer membrane

• GRAM-NEGATIVE IS MORE DIFFICULT TO KILL AND INHIBIT THAN GRAM POSITIVE

Describe the composition of the outer membrane. What two molecules are present within the outer membrane and what are their functions?

• Similar in composition to most membranes, except it contains specialized polysaccharides and proteins

1. Lipopolysaccharide:

• Signaling molecules and receptors

• Endotoxin

2. Porin proteins:

• Special membrane channels in outer membrane allow certain chemicals to penetrate: affects entry of antibiotics and other chemicals

What is the endotoxin part of Lipopolysaccharides?

Part of the membrane that can cause septic shock or inflammation if there are too many

• It is specifically the lipid portion of the LPS

1. Does the outer membrane increase resistance

2. What do alcohol based compounds do to the outer membrane?

3. And how does the outer membrane effect what drugs can be used to treat infections?

1. Yes, it’s Resistant to certain antimicrobial chemicals

2. Alcohol-based compounds dissolve lipids in the outer membrane and therefore damage the cell:

• Alcohol swabs used to cleanse the skin before certain medical procedures

3. Treatment of infections caused by gram-negative bacteria requires drugs that can cross the outer membrane

What are the steps of gram staining?

1. Crystal violet. Is added to the cells in the smear. It stains them all the same purple color.

2. Gram’s Iodine. Is added as a stabilizer that causes dye to crystallize in cell wall. Thicker gram positive cell walls more firmly trap crystals compared to gram negative.

3. Alcohol. Dissolves lipids in outer membrane and removes dye from peptidoglycan in gram negative cells which becomes colorless

4. Safranin (red dye). Red dye is demonstrated by applying safranin in final step in gram negative cells which but red dye masked by peptidoglycan in gram positive

What cells have non typical cell walls? Explain what Mycobacterium and Norcardia are (Acid-fast bacteria)?

Acid-fast bacteria which are harder to kill than gram-negative and Archaea

• Mycobacterium and Norcardia: Are acid-fast bacteria that contain peptidoglycan and stain gram-positive, but bulk of cell wall is composed of unique lipids called Mycolic acid

What is Mycolic acid? Why is it important for pathogenicity?

It is thick and rigid

• Very-long-chain fatty acid (impenetrable)

• Found in the cell walls of acid-fast bacteria

• Contributes to the pathogenicity of the bacteria

• Makes bacteria highly resistant to certain chemicals and

dyes (can’t gram stain)

Why are Archaea cell walls unusual? What do they lack?

• Exhibit unusual and chemically distinct cell walls

• Some have cell walls composed entirely of polysaccharides

• Others have cell walls made of pure protein

• All lack true peptidoglycan structure and some lack a cell wall entirely

What are Mycoplasmas and what do they lack? What is unique about its cell membrane? What is a common infection it causes? Will penicillin work on this bacterium?

• Type of bacterium that naturally lack a cell wall (must use other antibiotics than penicillin because there is no cell wall which it targets)

• Sterols in the cell membrane stabilize the cell against lysis

• Mycoplasma pneumoniae: “walking pneumonia”

What are L forms?

• Some bacteria that naturally have a cell wall to start off but lose it during part of their life cycle

• Role in persistent infections

• Resistant to antibiotics

What is the cytoplasmic membrane? What is its five functions?

• A phospholipid bilayer with proteins embedded (channels, enzymes, etc.)

Functions:

1. Energy reactions (ATP production)

2. Nutrient processing

3. Synthesis

4. Regulates transport of nutrients and wastes

5. Selectively permeable: special carrier mechanisms for passage of most molecules

Top hat question: the outer membrane contributes an extra barrier in gram-positive bacteria that makes them impervious to some antimicrobial chemicals, so they are generally more difficult to inhibit or kill than gram-negative bacteria. True or false?

False. Switch the gram negative/positive terms

Top Hat question: Which of the following bacterial appendages is typically not used for attachment? Slime layer, flagellum, pilus, or frimbriae?

Flagella

• slim layer is not a appendage

• Pilus, fimbriae, and flagella are the three appendages

• Flagella= motility

Where in a bacterial cell would you find the genetic material? (Select all that apply) Nucleus, Nucleolus, Nucleocaspid, Nucleoid, and Plasmid?

Nucleoid and plasmid

• ITS A BACTERIAL CELL

What is the cytoplasm of a cell?

Inner most structure

• 70 to 80% water plus complex mixture of sugars, amino acids, and salts

What are bacterial chromosomes and plasmids? What is the structure of the chromosomes? And where are plasmids located?

1. The hereditary material of most bacteria exists in the bacterial

chromosome. The chromosome is circular and double stranded DNA

• DNA is aggregated in the nucleoid

• There’s usually only one chromosome

2. Plasmids: NOT IN NUCLEUS it’s freely suspended in cell and is only in some cells

• Nonessential pieces of DNA: Confer protective traits such as

drug resistance and toxin and enzyme production