lecture 2b: internals, motility and viruses

Protoplast

Plasma membrane plus everything inside it

Nucleoid

Region of the cell containing the genome (usually one circular dsDNA chromosome)

Plasmid

Small, circular, self-replicating DNA with non-essential genes (e.g. antibiotic resistance)

The 70S ribosome = ______ (small) + ______ (large)

30S and 50S

30S contains ______ rRNA, 50S contains ______ and ______ rRNA

16S, 23S, and 5S

Capsule/slime layer functions

Attachment, protection from phagocytosis, resist desiccation

Fimbriae

Short protein filaments for sticking to surfaces and forming pellicles

Pili are used for attachment and ______, and type IV pili cause ______ motility

Conjugation (genetic exchange), twitching

Carbon storage inclusions: ______ (lipid) and ______ (glucose polymer)

PHB, glycogen

Volutin

Polyphosphate granules storing phosphate and energy

Magnetosomes contain ______ or ______ and allow ______

Fe₃O₄, Fe₃S₄, magnetotaxis

Gas vesicles are ______ and ______, give planktonic cells ______, and cyanobacteria form ______

Protein, gas-filled, buoyancy, blooms

Endospore-forming genera: ______ (aerobic) and ______ (anaerobic)

Bacillus, Clostridium

Why spores are resistant

Coat and cortex, two membranes, dehydrated core, Ca-dipicolinic acid, SASPs

______ and ______ protect the spore's DNA

SASPs and Ca-dipicolinic acid

Sporulation stages: asymmetric division → ______ → engulfment → ______ → coat synthesis → maturation → ______

Septation, cortex formation, mother cell lysis

In stage VI the core is dehydrated to ______% of a vegetative cell's water

10–30%

Monotrichous / amphitrichous / lophotrichous / peritrichous

One flagellum / both ends / tuft / all around the cell

Flagellar parts: ______ (made of flagellin), ______ (flexible coupling), ______ (motor)

Filament, hook, basal body

Basal body rings: L = ______, P = ______, MS = ______, C = ______

LPS, peptidoglycan, membrane, cytoplasm

Flagella are powered by the ______, with ______ proteins forming an H⁺ channel

Proton motive force, Mot

In peritrichous cells, ______ rotation bundles flagella (run) and ______ rotation causes a tumble

CCW, CW

Gliding motility

Flagella-independent, slower and smoother than swimming, needs a surface (slime, type IV pili, glide proteins)

Taxis

Directed movement in response to a chemical or physical gradient

Bacteria sense ______ (not spatial) concentration changes, producing a ______ random walk

Temporal, biased

Eukaryotes have a ______ SA/V ratio than prokaryotes (0.3 vs. ______)

Lower, 3

Eukaryotic ribosomes are ______S, and their chromosomes are linear with ______ proteins

80, histone

Endosymbiotic hypothesis

Mitochondria and chloroplasts evolved from bacteria

Evidence for the endosymbiotic hypothesis

Semi-autonomous, circular DNA without histones, 70S ribosomes, two membranes, porins in the outer membrane

Mitochondria are most related to ______, chloroplasts to ______

Rickettsia, cyanobacteria

Obligate intracellular pathogen

Reproduces only inside living cells, no independent metabolism

Nucleocapsid

Genome + capsid

Capsids are built from ______, which aggregate into ______ in icosahedral capsids

Protomers, capsomeres

Helical / icosahedral / binal capsid examples

TMV / HPV (20 faces) / T4 phage

Viral envelope

Host-derived lipid bilayer with viral spike proteins

HIV attaches to ______ and infects only ______

CD4, humans

Replication cycle: adsorption → ______ → ______ → assembly → ______

Penetration/uncoating, synthesis, release

Phage "ghost"

Empty capsid left outside after the phage injects its nucleic acid

Animal viruses enter by ______ or ______

Membrane fusion, endocytosis

Naked viruses are released by ______ , enveloped viruses by ______

Lysis, budding

In influenza, ______ lets virions exit the cell and ______ lets them adsorb to the next host

Neuraminidase (N), hemagglutinin (H