BIMM 120 Midterm 2

What happens when bacterial flagella become mutated?

Flagella can be nonfunctional (impaired motility [swim, swarm & chemotactic signals] + disrupts assembly & rotation)

What are the phenotypes that you can see from flagella mutations?

Loss of motility, reduced swim/swarm, irregular movement, colony morphology changes

What is the ion selector in bacterial flagella and why is it important for movement?

Mot AB complex (chooses protons/sodium for movement)

What is the difference between bacterial flagella and F-type ATPase in the movement of protons across the membrane

flagella use proton/sodium flow into cell for rotation energy, while F-type ATPase uses proton flow into cell to generate ATP

What component allows for the change in rotation based upon chemotactic/ aerotactic/ thermotactic signals?

C-ring switch complex

How are their flagella assembled? Base to tip or tip to base?

• for bacterial flagella, new material added to the end

• for bacterial fimbriae & archael flagella, new material added to base

What are the similarities and differences between archeal and bacterial flagella?

• similar: rotating structures w/ filament, direction of rotation controlled by chemotaxis

• dif: filaments thinner than bacteria + no homologues, diff types of pili, MotAB vs. ATP-drive, p/smf vs ATP hydrolysis, base-to-tip vs tip-to-base

How does bacterial flagella assembly differ with bacterial fimbriae?

Fimbriae used for attachment, conjugation, or twitching (homolog to type IV pilus = T4P, no constituents similar to bacterial flagella, driven by ATP hydrolysis but homolog pieces to F-type ATPase)

Polar Flagella

used for swimming and grow out of the bacterial cell wall and at “one” pole of the bacteria - CCW and CW rotation, sodium motive force

Lateral Flagella

grow throughout the bacterial cell wall and associate with surface contact and viscous media, proton motive force

Periplasmic Flagella

grow in the periplasm and associated with spirochete movement

Type IV Pili

extends + attaches to surface & retracts to jerk cell forward (twitch motility), gliding motility = thru smooth surface + same mechs (PliT binding to ATP causes domain movements responsible for pilus retraction

What happens when bacterial cells goes from swimming to swarming

flagella + SMF/sodium motive force -> flagella + PMF, high density

What rotation corresponds to running?

Counterclockwise (CCW)

What rotation corresponds to tumbling/changing directions?

Clockwise (CW)

How do bacteria move across their concentration gradients during high deterrent/low attractant concentrations?

CheW -> CheA -> CheY -> binds to FliGMN -> CW -> tumbling

How do bacteria move across their concentration gradients during high attractant concentrations?

CheW -> CheA -> CheB -> demethylation -> CCW -> smooth swimming

Are attractants/ deterrents hydrophobic/ hydrophilic?

Attractants & deterrents are hydrophilic

What proteins are important in chemotactic/ thermotactic/ aerotactic movement?

• chemotactic = CheA + CheY + CheW + CheB

• aerotactic = Aer

• thermotactic = Tsr

Tsr

heat seeking + serine, senses proton motive force to increase energy of system

Trg

ribose + galactose + heat seeking

Tap

dipeptides + cold seeking

Aer

oxygen seeking/senses respiration

Tar

aspartate + maltose + pH, heat and cold seeking, moves to opposite of environ; warm environ = tar moves to cold

How does antimicrobial resistance occur?

• genetic mutations

• horizontal gene transfer

• efflux pumps

• enzymatic degradation/beta-lactamases

• biofilm formation

How does ppGpp concentration alter bacterial growth in E. coli?

alarmone of stringent response under nutrient starvation → inhibits translation + DNA metabolism + membrane potential, changes to oxygen + pH + osmotic shock + temperature

What is the specific beta-lactamase mechanism in reference to AMR?

hydrolyzing B-lactam ring of antibiotics to prevent binding to PBPs for peptidoglycan synthesis (lactam rings not used for cell wall synthesis & can cause cells to lyse) ; serine = serine, metallo = zinc ions

How is capsule formation important in evading the immune system and how does it aid in AMR?

adds protective layer to make it harder for antibiotics to enter, evade immune detection, enhance biofilm formation + adhesion

Why is biofilm production important in AMR and for bacteria in general?

Communities that assist w/ impeding antibiotic diffusion, growth of slow-growing persister cells (persistent state due to environmental stress) + horizontal gene transfer

Where do microbes like to live?

• Obligate anaerobes = bottom of the flask away from the water-air interface

• Facultative anaerobes = throughout but prefers surface

• Obligate aerobes = top of broth

• Microaerophiles = just below the surface

Why are Western diets so detrimental for our gut microbiome/ health?

High fat intake = intestinal permeability increases for toxic bacteria to enter circulation, low-grade inflammation leads to insulin resistance + oxidative stress + metabolic disorders + decreases SCFA production

What are the mutualistic relationships in the gut microbiome?

• Fermentation processes

• Regulation of inflammation

• Energy for host cells

• Outcompete pathogens

What is the mechanism at which Pseudomonas aeruginosa begins the process of translation of its virulence factors?

• Blocked rotation of their flagella -> increase intracellular cAMP -> leading to translation of Vfr genes

• Type IV pili binds to a surface -> resistance in retraction -> increases intracellular cAMP -> translation of Vfr genes

How do virulence factors move out of the cell?

Hydrophilic to pass thru hydrophobic cell wall → change confirmation + recruit hydrophobic components to move out of the cell → reconfigure to be water soluble for host to be infected

How does Enterohemorrhagic E. coli (EHEC) alter the expression of LEE?

expression controlled by chemical + physical factors that act on mechanosensors (E. coli binds to intestinal tract to alter cytoskeleton to create pedestals that it can adhere to; attaching/effacing)

How is LEE going to help EHEC to colonize the gut?

Destroy microvilli + tightly adhere to host cells

How do the genes of LEE become translated?

Regulated by environmental signals, Ler is activated (positive regulator of LEE)

How does bacterial persistence come about?

subpop of bacteria exhibits characteristics that are distinct from common bacteria → dormant state where they are resistant to antibiotics & can exit state to grow under favorable conditions → constant bacterial infections + combo of factors + makes persister-targeted treatments difficult w/ inhibitions

How are pilin-based nanowires important?

Use of E-pilin that conduits long range electron transport to extracellular terminal electron acceptors like iron oxides/methane-producing microorganisms (abundance of aromatic AAs in pilin-based wires allows transport of electrons along pilin)

Bacteria having intracellular compartmentalization

• cytoskeleton that organizes cellular processes, tubulins, actins, intermediate filaments

• segregation of plasmids (SopA P-loop ATPase)

• energy transduction apparatuses for light-driven proton pumping + ion gradient-driven ATP synthesis (bacterial rhodopsin, F-type ATPases + bacterial flagella)

What are the three types of horizontal gene transfer?

conjugation, transduction, and transformation

Conjugation

Bacteria creates pilus that attaches to another bacteria and is used to exchange DNA from one to another

Transduction

Bacteriophages inject DNA from a different bacteria into the bacteria that they want to infect

Transformation

Bacteria takes up DNA/plamids from environment into themselves

What is the GroES/EL protein and which corresponds to the cap?

• protein that is important in helping misfolded proteins properly folded (GroEL captures unfolded/partially folded proteins to try & fold them correctly, while GroES binds to GroEL when ATP is bound; sequentially active + ATP dependent w/ hydrolysis)

• cap = GroES and barrel = GroEL