2.3: Microbial Structure - Bacterial Cytosol

Ribosomes

composed of RNA and proteins, made up of large and small subunits, key player in translation to make proteins

differences between prokaryotic and eukaryotic ribosomes

functionally the same but structurally slightly different

granules

storage bodies, specialized granules for sugar/fat/phosphates, can also just store waste

Endospores

produced under threatening environmental conditions (sporulation), purpose is to protect and survive, they cannot reproduce but they can exist in the endospore state for years

*Bacillus spp.* and *Clostridium spp.*

can produce endospores

layers to an endospore

core, cell wall, cortex, spore coats, exosporium

core

DNA, ribosomes, granules

Cell wall

normal gram-positive peptidoglycan

cortex

thick layer of loosely cross-linked peptidoglycan (modified cell wall)

spore coats

highly cross-linked keratin proteins as well as other structural proteins

exosporium

not always present, varies in composition but mostly proteins and carbohydrates

endospore formation

cell begins to be depleted of nutrients, chromosome is duplicated and separated, cell is separated into sporangium and forespore, sporangium engulfs forespore, sporangium actively synthesizes spore layers around forespore, cortex and outer coat layers are deposited, mature endospore, free spore is released with loss of sporangium, germination occurs when conditions are favorable again

nucleoid

bacteria don’t have a nucleus, region of dense genomic DNA, prokaryotic genomes considered smaller than eukaryotic genomes

enzymes used in chromosome condensation

DNA gyrase, topoisomerase

scaffolding proteins

assist in condensing the chromosome provide a way to save space

CRISPR

clustered regularly interspaced short palindromic repeats, family of DNA sequences within prokaryotic genomes, flanked by viral DNA from previous infections

Cas

CRISPR associated genes/proteins, DNA endonuclease, uses crRNA to target specific complementary DNA sequences

CRISPR/Cas

bacterial “immune system”, has a memory that will destroy viral genomic material the bacterium has previous encountered

plasmids

small circular pieces of DNA, considered more fluid than chromosome, contains non essential genes that are only kept if advantageous, can combine with other DNA to form new plasmids

engineered plasmids

synthetically made or modified by scientists

colicin (Col) plasmids

code for bacteriocins

degradative plasmids

code for digestive enzymes

fertility (F) plasmids

code for conjugation genes

Virulence plasmids

code for genes important for pathogenicity

PAI

pathogenicity island, series of virulence genes

resistance (R) plasmids

code for resistance to antibiotics or other toxic chemicals