Lecture 2: General Features of Bacteria

Bacteria are prokaryotes that are small and simple, they have no _________ or _______-_____ nucleus

Organelles, membrane-bound

What are the 2 main ways that bacteria transfer genes?

• Vertical gene transfer

  • Binary Fission (aka asexual reproduction)

• Horizontal gene transfer

  • Via extrachromosomal and mobile genetic elements

What are some advantages of replication via binary fission?

• Only one parent cell is needed to reproduce

• Daughter cells are clones of the parent

• Rapid Division

  • Produce great #s quickly

Define Generation Time

The average time it takes for one bacterium to divide and give rise to 2 daughter cells

A bacteria with a quick replication time that caused disease would likely be associated with ____ onset of symptoms, and vice versa

Acute

Why do we study bacterial structure and function?:

1. It aids in identifying the disease for diagnosis

2. Aids in our understanding of pathogenic mechanisms and pathogenesis of diseases caused by bacteria

3. Helps us to develop therapeutics and vaccines

What are the 3 broad categories that make up the structure of bacteria cells?

1. Cell envelope

2. Cytoplasmic structures

   1. Nuclear body

   2. ribosomes

   3. inclusions

   4. spores

3. Surface receptors

   1. Capsule

   2. Flagella

   3. Fimbriae/pili

Which is larger prokaryotes or eukaryotes?

Eukaryotes

What are the 3 main shapes of bacteria?

1. Coccus

   1. Spherical

2. Rod

   1. Bacilli

3. Spirochete

   1. Spiral

Define staphylococcus

A clump of spherical shaped cells

T/F: Both gram ± bacteria have peptidoglycans

True, Gram + has more peptidoglycans than Gram -

Which of these structures is only present in gram + bacteria?

1. Thin cell wall

2. Lipopolysaccharide (LPS) Layer

3. Thin single-layer of peptidoglycan

4. Teichoic Acids

5. Two periplasmic spaces

4

Which type of bacteria has a thick peptidoglycan layer?

Gram + Bacteria

What are teichoic acids? Where are they found?

Anionic polymers that form a significant part of the cell wall in most Gram-positive bacteria, serving structural and functional roles

LPS are only found in gram _ bacteria

-

The LPS makes up the ________ layer of Gram - bacteria, an example of an LPS in this layer is Lipid A, what does it do?

It is an endotoxin that induces fever

The cell envelope (cell wall+ associated structures) is made up of 4 components/categories, what are they? What is their function?

1. Structural support and protection

   1. Maintains shape of the wall

2. Selective Barrier/Transport

   1. Porins

      1. In gram - only

      2. Allow passage of small molecules

   2. Teichoic Acids

      1. In gram + only

      2. Help regulate movement of cations

3. Enzymes in the cell wall

   1. The enzymes help to..

      1. Break down complex nutrients

      2. Make nutrients easier to transport across the cell membrane

4. Virulence and Immune Evasion

   1. Surface proteins in the wall

      1. They adhere to host tissue

      2. They resist phagocytosis or antibody attack

Which color does Gram + bacteria stain?

Purple

Which color does Gram - bacteria stain?

Pink

Why does Gram + bacteria stain purple? What causes them to retain that stain?

The highly cross-linked and thick layer of peptidoglycan

Why does Gram - bacteria stain pink? What causes them to retain that stain?

• Since it lacks the thick peptidoglycan layer it can’t retain the stain when the decolorizer is added

• So, when the pink (safarin) stain is added after then it takes it up

T/F: You cannot get false +s when using gram staining

• False, you can due to human error

  • Examples

    • Over/under colorization

    • Thick smears

    • Excessive heat used to fix

    • Excessive washing

What is gram variable staining? Is it natural or human error?

• Gram variable staining is when you get both gram ± cells

• Natural, some species have ± versions of their bacteria

T/F: Gram + bacteria will always stain gram + IF there is no human error

• False, some bacteria can be Gram + and just be resistant to stain

  • This would be things like thick lipid layers, etc.

Define Atrichous vs Peritrichous

• Atrichous is bacteria that don’t have flagella

• Peritrichous are bacteria that do have flagella

What are flagella?

They are filamentous appendages that allow bacteria to move in liquid environments

What are Pili?

• Thread like appendages, smaller than flagella

• Mainly found in Gram -

• They are used for adhesion and conjugation

  • Short attachment pili (aka fimbriae)

  • Long conjugation Pili (Sex pili)

What is the difference between Pili and Flagella

Flagella are used for movement in liquids, Pili are used to adhesion and conjugation (and for gliding/twitching motility)

Type _ Pili provide bacteria with motility on solid surfaces

• Type IV Pili

  • They provide twitching and gliding motility

  • Act like a grappling hook

Define these 3 similar terms

1. Capsule

2. Slime Layer

3. Biofilm

1. A well organized thick, gelatinous outer covering that is outside of the bacterial cell wall

2. Loose, unorganized, easily removable gel-coating outside of the bacterial cell wall

3. Structured community of bacteria enclosed in a self-produced slime matrix attached to the surface

Encapsulated bacteria produce ______ colonies

Mucoid

Describe the difference between Microbiota and Microbiome

• Microbiota

  • The community of living microorganisms in a specific environment

• Microbiome

  • The entire ecosystem of the microorganisms, the genetic material and the surrounding environment

T/F: Microbiomes are important to all animals health

True

What is the term that goes with this definition?

Highly resistant, dormant structures formed inside certain bacteria that allow the bacteria to survive extreme conditions

Endospores

T/F: The structure of the bacterial cell envelope determines whether the organism is gram-positive or gram-negative

True

T/F: Gram + bacteria have a thin layer of peptidoglycan in their cell wall and an extra outer membrane

False, This is Gram -

T/F: The outermost layer of the gram + cell envelope is LPS

False, this is Gram -

T/F: Bacteria use flagella and pili for movement in different environments

True

T/F: Microbiome is a monomicrobial community

False

T/F: Endospores can germinate into vegetative cells when conditions become favorable

True

T/F: Bacterial capsule facilitate host immune recognition and phagocytic killing

False