Microbio 4000 Chapter 5 Key Concepts

Bacilli

rods

Spirochetes

long corkscrew

Cocci

spheres

vibrio

commas

spirilla

short spirals or helical

coccobacilli

oval

pleomorphic

many shapes

strepto-

chains

diplo-

pairs

tetrads

2×2 shape, 2D

Sarcinae

3D cuboidal packets

staphhylo-

clusters

Peptidoglycan

Glycan chains, made up of polymers and disaccharides (NAG and NAM) with short peptides that cross-link glycan chain

Role of cell wall

Pass nutrients, structure, osmotic pressure.

Differences in Gram+ and Gram- bacteria

Gram+: cell wall, purple stain, techoic and lipotechoic acids present,

Gram-: outer membrane, pink stain, periplasm, LPS (lipid A), porins, s-layer

How is the cell wall medically relevant

Cell walls are the target of common antimicrobials and antibiotics. This means microbes containing a cell wall can be targeted and have antimicrobials made for medical use.

Who is Rebecca Lancefield

Microbiologist that discovered how Gram+ cell walls are diverse and can be used for identification and become recognized by our immune system. This is called lancefield grouping (serological, or antibody based) testing).

Which bacteria do not Gram-stain well

Mycobacteria: cell wall contain waxy mycolic acid which makes them resistant to gram-staining

Mycoplasma: lakc a cell wall, no PG or OM, membrane contains sterols

Archea: Pseudomurein (not PG but similar), and S-layers

Algae: Polysaccharides (cellulose or pectins)

Fungi : Polysaccarides (chitin) and glycoproteins

Passive transport

Moves with the concentration gradient
Simple diffusion: direct transport through membrane
Facilitated diffusion: uses a protein channel or carrier

Osmosis

passive movement of water molecules
isotonic: no change
hypertonic: volume shrinks (plasmolysis)
hypotonic: volume expands (lysis)

Active transport

moves against concentration gradient
requires input of energy: ATP (siderophores), coupled transport (symport and antiport), light-driven pumps, high energy metabolite (group translocation, not ATP)

What is bacterial secretion and what is it used for. Compare to Eukaryotes

Bacteria secrete proteins, DNA, and large molecules to interact with the environment. Eukaryotes move extracellular proteins via vesicles, golgi, and exocytosis

nucleoid

region where bacterial DNA is organized containing a singular chromosome which is often circular, some bacteria may contain plasmids as well, transferred via horizontal gene transfer.

Ribosomes

For protein synthesis, located in cytoplasm and nucleoid edge, 2 subunits. Prok have 70S ribosome and Euk have 80S ribosome

Glydcocalyx

“sugar shell” made up of mostly layers of polysaccharides.

function: attachment and protection, prevent dehydration, source of nutrients or could help prevent nutrient loss, help form biofilms, help escape phagocytosis

Capsule: neatly organized, firmly attached
slime layer: unorganized, soft, and loose

S-layer

external protein lattice outside PG layer that helps strengthen cell wall, has pores.

Pili

Fimbriae: attach cells to surfaces, thinner, shorter, many per cell, made up of Pilin protein polymers
Conjugation Pilus: facilitates transfr of DNA between cells
May provide slight motility, may trigger immune response in host.
Stalks: membranous extensions of cytoplasm that secrete adhesion factors.

Flagella

Long filament strutures, used for motility, spin like a propeller
powered by PMF, helps with photo- and chemotaxis, may trigger immune response. Made up of flagellin protein

Cilia

made up of microtubules (extensions of cytoskeleton), underneath cell membrane, whip like motion, ATP is hydrolyzed as energy source.

Axial filament

bundles of endo flagella located under OM / sheath, in periplasm, rotation creates corkscrew motility.

Gas vesicles

aquatic bacteria inflate/deflate for buoyancy

storage granules

storage of nutrients like sulfur and phosphate

magnetosomes

store magnetite (iron oxides) for magnetotaxis

inclusions

aggregates in cytoplasm, often misfolded proteins

Specialized membranes

thylakoids, chlorosomes

Endosymbiosis

Larger cell engulfed smaller bacterial cells and provided protection, smaller cells also benefited.

Mitochondria and Chloroplasts are evidence

• resemble bacteria in shape and size

• have bacterial-like genomes (circular and sequence)

• have 70S ribosomes

• can divide independent of cell

• have a double membrane