3rd Lecture Notes

Describe coccus shape

Just circular

Describe coccobacillus shape

Longer than coccus but shorter than bacillus

Describe bacillus shape

Very long rod

Describe vibrio shape

Crescent-shaped rod

Describe spirillum shape

Stiff and rigid spiral/corkscrew

• also moves with flagella on the outside

Describe spirochete shape

Flexible spiral

• moves with axial filaments, corkscrew motion

Describe pleomorphic shape

No fixed shape

• can depend on conditions

What shape is staphylcoccus?

Coccus

What shape is chlamydia?

Coccobacillus

What shape is escherichia?

Bacillus

What shape is crescentus?

Vibrio

What shape is campylobacter?

Spirillum

What shape is borrelia?

spirochete

What shape is corynebacterium?

pleomorphic

The shape of bacteria comes from the ____ inside

proteins

What are more complex bacterial shapes?

1. filamentous bacteria

2. fruiting body formers

Explain filamentous bacteria

• they grow filaments

  • long, thread-like chains

• they form mycelium

  • a network made of filaments

• they seem very similar to fungi but they are bacteria

  • bec/ they have branching filaments (mycelium and fungal hyphae)

• ex.

  • streptomyces - produces antibiotics

  • cyanobacteria

Explain complex bacteria

• they can aggregate together and form fruiting bodies

• fruiting bodies are multicellular structures that produce spores

• hard to culture because very picky about environment

• ex.

  • myxococcus

Explain diplococci

Pairs of cocci

Explain streptococci

chains of cocci

• beads on a string

Explain staphylocci

Irregular clusters of cocci

• grape-like shape

Explain sarcina

cubical packets of 8 cocci

• four in the front

• four in the back

What is average sized bacteria?

• 1.1-1.5 um wide x 2-6 um long

• like escherichia coli (rod bacillus shape)

Smallest bacteria size?

• around 0.3 um

  • around size of large virus

• like mycoplasma

  • has no cell wall but has cell membrane

  • so they’re naturally resistant to antibiotics (penicillin) bec/ they target cell wall

Largest bacteria size?

• up to 600 um long x 80 um wide

• like epulopiscium fishelsoni

• large enough to be seen w/o microscope

Explain shape and size relationship in bacteria

• bacteria must take in nutrients and get rid of waste quickly

• rate of this is determined by surface area-to-volume ratio (SA/V)

• there is a limit on sizing

Explain bacteria surface area

The greater the surface area, the more collision surface area there is for nutrient uptake

• faster rate (which is good)

What happens when cell gets bigger?

The volume of the cell increases more then surface area

Explain SA/V ratio of small cells

It has high SA/V ratio

• higher ratio means efficient nutrient uptake (better)

Explain SA/V ratio of large cells

Has low SA/V ratio

• so there’s less efficient exchange

What is SA/V formula (for cocci)?

SA/V ratio = 3/r

• r = radius of cell

What does smaller radius mean?

Higher SA/V ratio

• more efficient

What does larger radius mean?

Lower SA/V ratio

• less efficient

Explain cell membrane (plasma membrane)

• all bacteria must have cell membrane

  • bec/ all living things have membrane

• functions

  • controls what goes in and out

  • energy production (bec/ no mitochondria)

Explain peptidoglycan (cell wall)

• only bacteria domain has this

  • but not every bacteria has it (ex. mycoplasma)

• cell wall provides

  • structure

  • shape

  • protection from cell lysing in hypotonic environment

What does gram positive cell have?

• thick peptidoglycan later

• only has one membrane (plasma membrane)

Streptococcus and staphylococcus are gram…

positive

What does gram negative cell have?

• thin peptidoglycan layer

• has two membranes

  • plasma membrane

  • outer membrane (LPS)

E. coli and salmonella are gram…

negative

Explain S/layer

Protein or glycoprotein surface layer outside the cell wall

• provides protection and support

Explain capsule/slime layer

It’s a sticky coating made of polysaccharides

• functions

  • helps bacteria stick to surfaces

  • protects against phagocytosis (so immune cells don’t engulf and destroy bacteria)

Explain DNA in bacteria

• bacteria do not have true nucleus (nucleoid region)

• chromosome is circular, double-stranded DNA)

Explain plasmids

They are small pieces of DNA separate from chromosome

• they carry extra gene and genetic information

  • for antibiotic resistance

  • also virulence factors

• they can be transferred between bacteria (conjugation)

Explain storage inclusions

Different from inclusions

• they are structures inside bacteria where they store nutrients, building blocks, and special material for surviving in changing environments (hypotonic)

  • like pantry

List nutrient/energy storages that bacteria have

1. glycogen

2. carbon

3. phosphate

4. sulfur

5. amino acids

Explain glycogen storage

Glucose is stored in the form of

• glycogen (polysaccharide)

Explain carbon storage

Carbon is stored inside poly-B-hydroxybutyrate (PHB)

• PHB is a lipid-like polymer

  • it’s made from repeating hydroxybutyrate units

• function as long-term carbon and energy storage

Explain phosphate storage

Phosphate is stored as polyphosphate granules

• function

  • important source for ATP production

  • backbone for nucleic acid (RNA and DNA synthesis)

Explain sulfur storage

Sulfur is stored as sulfur gobules

• function

  • used for energy metabolism

  • building sulfur-containing amino acids (cysteine and methione)methionine

Explain amino acid storage

Amino acids are stored as cyanophycin granules

• made of arginine and aspartic acid

• function

  • nitrogen storage

  • backup for protein building

Explain inclusions

This is how bacteria move, not storage

• there is

  • gas vacuoles

  • magnetosomes

Explain gas vacuoles inclusion

They are hollow, gas-filled protein structures inside bacteria

• in bacteria growing in water

  • like cyanobacteria

• when filled up with gas, cell becomes lighter and floats

• when there’s less gas, cell then sinks

• controls buoyancy movement

Explain magnetosomes inclusion

Controlled by cytoskeleton protein MamK

• it helps line cells up

• acts like compass, letting bacteria orient along Earth’s magnetic field

• ex. magnetospirillum gryphiswaldense (model)

What are the structures that are contained in the bacterial cytoplasm?

1. cytoskeleton

2. ribosomes

3. intracytoplasmic membranes

4. nucleoid and plasmids

5. inclusions

What are the types of cytoskeleton molecules found in bacteria?

1. FtsZ

2. MreB

3. CreS

Explain FtsZ

• found in many, not all, bacteria

• helps with asexual replication (binary fission)

  • forms ring in center of cell during division

  • directs wall synthesis when wall splits

• similar to tubulin in eukaryotes

Explain MreB

• found in many rod-shaped bacteria

• forms helical (coil-like) structures inside cell

• guides proteins that synthesize cell wall

  • determines rod shape

• very similar to actin in eukaryotes

Explain CreS (Crescentin)

• found in some curved, crescent-shaped bacteria

• slows down making of peptidoglycan

  • which makes cell wall look uneven, hence crescent shape

• similar to intermediate filaments in eukaryotes

Explain ribosomes in bacteria

This is the site of protein synthesis

• the size is 70S

• which is smaller than eukaryotic ribosomes (80S)

• many antibiotics target bacterial ribosomes and not eukaryotic ribosomes

Explain intracytoplasmic membranes (ICMs) inside bacteria

ICMs are specialized membrane systems found inside the cytoplasm of some bacteria

• they are basically folds/extensions of plasma membrane that have specialized functions

• not all bacteria have them

Function of ICMs in photosynthetic bacteria?

ICMs house pigments (like chloropyll) and proteins to capture light

• for photosynthesis

Function of ICMs in nitrifying bacteria?

ICMs contains enzymes for energy metabolism

• function is to help bacteria oxidize nitrogen compounds

Explain episomes

They are a special kind of plasmid

• they can integrate into bacterial chromosome and replicate with it

• ex.

  • F (fertility) factor plasmid can exist independently OR integrate into chromosome

Explain plasmids and horizontal gene transfer (HGT)

• plasmids plays big role in HGT through conguation

• cell has conjugative plasmid with genes for sex pilus

  • sex pilus is long, thin tube that connects two bacterial cells

• sex pilus forms a bridge

• then a strand of plasmid DNA is transferred

• both cells have the plasmid and can replicate

What are the different types of plasmids?

1. conjugate plasmids

2. R plasmids

3. virulence plasmids

4. col plasmids

Explain R plasmids

They carry genes that provide resistance to antibiotics

• can spread between bacteria through conjugation

Explain virulence plasmids

They carry genes that make bacteria more pathogenic (harmful)

• can encode toxins, adhesion proteins, or other factors that can damage host cells

• ex. E coli. plasmids that produce enterotoxins

Explain col plasmids

They carry genes that makes bacteriocins

• bacteriocins are proteins that kill other bacteria

• this helps bacteria compete with neighbors for resources

• ex. E. coli producing colicins to kill competing strains

Functions of plasma membrane in bacteria

1. barrier

   • separate cytoplasm from outside

2. selective permeability

   • controls what goes in and out

3. metabolic site

   • in bacteria, many vital processes happen in membrane

Explain metabolic processes in membrane

• in bacteria/archaea, processes happen in membrane like

1. electron transport chain (ETC)

   • ATP generation

2. photosynthesis

   • pigments are inside membrane

3. transport systems

   • proteins pump nutrients and ions in/out

In eukaryotes, metabolic processes like respiration and photosynthesis occur in ______

organelles, not membrane

• like mitochondria and chloroplasts

Describe the fluid mosaic model

This describes the structure of the plasma membrane

• it’s made of

  • amphipathic lipids

  • membrane proteins

• membrane is flexible and proteins float like mosaic

Define amphiphatic lipids

They are phospholipids with:

• hydrophilic heads (water loving)

• hydrophobic tails (water hating)

What are the membrane proteins?

• integral proteins

  • embedded in the membrane

• transmembrane proteins

  • span the entire bilayer

What are the lipids that bacteria have?

Hopanoids

• function is to stabilize and strengthen membrane

What are the lipids that eukaryotes have?

Sterols

• found in membrane

• like cholesterol in animals

• make membrane sturdy and less fluid

• pretty absent in prokaryotes