CH 5: Nucleoid & Ribosome + Specialized structures

Bacterial DNA is organized in a region called ____

Nucleoid

Chromosome

Essential genes

• Often circular and 1/cell

Plasmids

Non-essential genes

• circular

• much smaller

• Varying copies per cell

Replicate independently from chromosome

Often transferred to other cells in Horizontal Gene Transfer

Cells use _____ to synthesize proteins

Ribosomes

Protein synthesis =

Translation

• mRNA → Protein

Ribosome location? made up of?

• Located in the Cytoplasm and nucleoid edge

• Made of many Protein and RNA molecules

• 2 subunits

Prokaryotic and Eukaryotic ribosome size:

Prokaryotic: 70S

Eukaryotic: 80S

_____ and ______ provide evidence for endosymbiosis

Mitochondria and Chloroplasts

How does the mitochondria and chloroplasts provide evidence?

1) Resemble bacteria in shape and size

2) Can divide independent of the cell

3) Have a double membrane

4) Have bacterial-like genomes (circular and sequence)

5) Have 70s ribosomes like prokaryotic cells

Glycocalyx

Means “sugar shell”

• Made mostly of layres of polysaccharide (some polypeptides)

Bacterial structures made of glycocalyx

1) Capsule

2) Slime layer

Capsule

Neatly organized and firmly attached

Slime layer

Unorganized, soft, and loose

Functions of the Glycocalyx

1) Attachment and protection

• Can help initial formation of biofilms

• Capsules help escape phagocytosis

2) Help prevent dehydration

3) Source of nutrients or could help prevent nutrient loss

S layer

External protein lattice outside the peptidoglycan layer

• Has pores or is permeable to nutrients from other molecules

• Cells might lose a capsule or S-layer in certain growth conditions

What does the S-Layer help?

Strengthen cell wall or avoid host immune cells

Pilin (Pili)

Protein polymers from external structures

1) Fimbriae

2) Pili

Fimbriae

Attach cells to surfaces (e.g., host tissue or biofilms)

• Thinner and shorter; many per cell

Pili

Larger, tubular, one or few per cell

• Conjugation (sex) Pili- DNA transer

• Tethering, twitching, and gliding, no rotation

Fimbriare and Piki may trigger an _____ _____ in host or trigger host cell _________

Immune response

Endocytosis

Flagellin (flagella and cell motility)

Protein polymers that make up the long filament of the bacterial Flagella

Flagella use? (prokaryotic)

1) Used in most prokaryotic motility

2) Spin like a propeller (both directions)

3) Powered by a Proton Motive Force

4) Mobility helps with Photo- and chemotaxis

5) Might trigger immune response

Eukaryotic Flagella and Cilia (Convergent Evolution)

1) Helps with chemotaxis

2) Made up of Microtubules (extension of cytoskeleton)

3) This is still underneath the cell membrane

4) Microtubules slide by each other with help of motor proteins

5) Whip-like motion

6) ATP is hydrolyzed as an energy source

Spirochetes (a group of bacteria)

have bundles of Endoflagella located under the outer membrane/sheath

• in the periplasm

Axial Filament

Structure of endoflagella

• rotation creates corkscrew motility

Chemotaxis

a cell moving in response to a stimuli

• Toward an attractant or away from a repellent

• Involved rotation of the flagella that propels the cell

Stalks

Large fibers made up of membranous extensions

• Found on a few species

• Secrete adhesion factors and help with surface attachment

Thylakoids

Specialized membrane infoldings that contain photosystems and pigments for harvesting light energy (Phototrophs)

Cytoplasmic inclusions

Concentrated deposits or micro compartments found inside the cell

• Useful for storage and unique environments

• Not the same as eukaryotic membrane-bound organelles

Storage granulues (Cytoplasmic inclusion)

Storage of nutrients such as glycogen, sulfar, and phosphate

• ex/ metachromatic granules

Gas vesicles

aquatic bacteria inflate/deflate for buoyancy

Magnetosomes

Store crystals and magnetite (Iron oxides) for magnetotaxis or movement based on Earth’s geomagnetic field

• like a compass

Carboxysomes

compartments for CO₂ fixation in cyanobacteria (photosynthesis)