Micro 4.1 Bacteriology

What are prokaryotes?

Simplest of cells

What do prokaryotes lack?

Lack major membrane-bound organelles.

What happens because prokaryotes have no organelles to protect proteins being produced?

Transcription and translation happen at the same time.

What is the site for the majority of a prokaryotic cell's functions?

Cell membrane

What are some functions that occur at the cell membrane in prokaryotes?

Metabolism, synthesis, etc.

Are all prokaryotes single-celled organisms?

All are single celled organisms but some do form colonial structures and live in groups.

What are the two groups of prokaryotes?

Archae and Bacteria

What is unique about Archae?

Unique cell wall and cell membrane structure, live in extreme env.

What is the other group of prokaryotes besides Archae?

Bacteria

What are cell envelopes?

Outer layers of a cell separating it from the environment.

What layer will always be present in a cell envelope?

Cell Membrane

What percent of bacteria have at least one additional layer to the envelope?

99%

What is the additional layer most bacteria have?

Cell Wall

What bacteria have no cell wall?

Mycoplasma spp.

What is high in the cell membrane of Mycoplasma spp.?

Cortisol

What do cell walls provide?

Protection against osmotic pressure and give the cell a defined shape.

What is peptidoglycan?

Protein/sugar compound that makes up the cell wall structure of bacteria

Where is peptidoglycan found?

Only present in bacteria, not found in any other cell type including Archae

What are the protein-sugar based subunits of peptidoglycan?

NAG and NAM

How are NAG and NAM linked?

Linked together forming a 'chain-link' structure.

What do gaps between subunits of peptidoglycan allow?

Free passage of molecules across the cell wall.

What is the Gram stain?

Laboratory procedure that allows for the identification of bacteria under a microscope AND also divides them into two groups.

What do the dyes in Gram stain adhere to?

Peptidoglycan in the cell wall.

What is the first dye used in Gram stain?

Crystal Violet

What does Crystal Violet do?

Adheres to the outside of the cell

What is Gram's Iodine?

Mordant that fills in the gaps left unstained.

What is used to break down membranes and decolorize in Gram stain?

Acid (Ethanol or Acetone)

What is the final dye used in Gram stain?

Safranin

What does Safranin stain?

Any remaining unstained parts on the outside of the cell.

What color does Gram Positive stain?

Purple

How many layers does a Gram Positive envelope have?

2 layers

What are the two layers in Gram Positive?

Cell membrane and Thick Peptidoglycan Cell Wall

What sugar is found in the Gram Positive cell wall?

Teichoic acid

What color does Gram Negative stain?

Red

How many layers does a Gram Negative envelope have?

3 layers

What are the three layers in Gram Negative?

Cell membrane, Thin Peptidoglycan cell wall, and Outer membrane

What happens during decolorizing in Gram Negative?

Outer membrane is removed allowing Safranin to stain the cell wall.

What is the periplasmic space?

Area between wall and outer membrane.

Where is the outer membrane found?

Only in Gram negative bacteria

What does the outer membrane contain?

Porins that only allow small molecules to pass through

What does the outer membrane restrict?

Access of many antibiotics into the cell

What is LPS?

Lipopolysaccharide

When is LPS released?

When the cell is damaged

Why is LPS toxic?

It is toxic to other cells (Endotoxin)

What happens when more LPS is released?

Stronger symptoms (inflammation & fever)

What gives cells a defined shape?

Cell wall

What type of reproduction do bacteria use?

Asexual

What is binary fission?

Cell division without a nucleus

What is a daughter cell in binary fission?

An exact genetic copy of mother cell

What is generation time?

Time it takes to complete one full division cycle

What happens to population size during binary fission?

Population doubles, exponential

What does faster growth result in?

Faster disease onset with pathogens

What does anucleated mean?

Lacking a nucleus

Where is DNA found in bacteria?

In the 'nucleoid' region

When does the nucleoid form?

During cell division

How many chromosomes do bacteria have?

1 circular chromosome

Do bacterial chromosomes have introns?

No, all genes are used and vital to survival

How is the chromosome organized?

Supercoiled by proteins called gyrase

Is gyrase found in eukaryotes?

No

Can bacteria share genetic information with unrelated species?

Yes

Why is horizontal gene transfer possible?

Because of simple and universal chromosome structure

What are the three basic types of horizontal gene transfer?

Conjugation, Transduction, Transformation

What is conjugation?

'Bacterial sex'

How do cells connect during conjugation?

Through a pili

What do bacteria share in conjugation?

Non-chromosomal DNA (Plasmids)

What transfers genes during transduction?

Bacteriophages

What does transformation involve?

Bacteria scavenge 'free' DNA from dead cells

What did transformation lead to?

The discovery of DNA

Why do bacteria have limited movement options?

Because of cell wall

What does the cell wall prevent?

Prevents cell from flexing and changing shape

What structure helps bacteria 'walk' on surfaces?

Pili

What is the most common bacterial motility structure?

Flagella

What is phototaxis?

'Light' & 'move'

What is chemotaxis?

'Chemical' & 'move'

What are endospores?

Most resistant life form in existence

Which genera produce endospores?

Bacillus, Lactobacillus, Clostridium spp.

When do endospores form?

During extreme stress

Are endospores metabolically active?

No, metabolically inactive

What is glycocalyx?

Secretions that surround a single cell

What is the most common glycocalyx?

Capsule

What does glycocalyx prevent?

Phagocytosis

What are biofilms?

Secretions that surround a community of cells

What species composition do biofilms usually have?

A diversity of different species

What do biofilms protect against?

Water loss, chemical disinfectants, and antibiotics

Where are medically relevant biofilms found?

Plaque, catheters, surgical equipment, CF patients

How must biofilms be removed?

Mechanically removed

Why do bacteria produce toxins?

To defend their resources or fight pathogens

What is an example of an endotoxin?

LPS

What is an example of an exotoxin?

Botulinum toxin

What else can be used as a bacterial defense?

Antibiotics

What is CRISPR-Cas9?

Clustered Regulatory Interspaced Short Palindromic Repeats

Where was CRISPR discovered?

In E. coli

What can CRISPR genes include?

Genes found in viruses

What is Cas9?

A nuclease (breaks down DNA/RNA)

Who discovered CRISPR-Cas9 function?

Dr. Charpentier and Dr. Doudna

What happens during viral infection in CRISPR?

Cas9 protein seeks out the same genes found in CRISPR and destroys them

What human immune component is CRISPR similar to?

Adaptive immune response and antibodies

What has CRISPR revolutionized?

Genetic engineering

What can CRISPR target?

Specific genes for removal and replacement

What do you need to live?

Food and water and a safe place.