Microbial Motility and Chemotaxis

for most bacteria (not spirochetes), bacterial flagellar motility movement (2)

1. "runs" are when flagella rotate CCW and the organism "runs" in a straight line 2. "tumbles" are when flagella rotate CW and organism can reorient in a new direction

what occurs in presence of no/low attractant (steps) (5)

1. MCP undergoes a conformational change 2. conformational change and help from CheW (coupling protein) leads to the autophosphorylation of CheA (histidine kinase) 3. CheA-P kinase activity active, phosphorylates CheY (response regulator) 4. CheY controls flagellar rotation to "tumble" (CW) and get to new area 5. to stop tumbling, CheZ (phosphotase) removes the phosphate group off of CheY to promote running again

two cell surface proteins necessary for Synechococcus motility:

1. SwmA: S-layer protein 2. SwmB: huge protein (10K AAs)

what are the homologous portions of the archaellum (in comparison to bacteria) (2)

1. archaeal flagellins (structural proteins) homologs to bacterial pilin 2. overall components are homologous to bacterial type IV pili

chemoeffectors and specificity (3)

1. attractants can be organics (AAs, sugars, etc.) or inorganics (nitrate, phosphate, etc.) 2. repellents tend to be toxic compounds (acids, metals) 3. different organisms have different subsets of receptors to sense chemicals relevant to their lifestyle

the four types of sensory systems to find optimal environments:

1. chemotaxis (sensing of chemicals. ie. finding food or host; avoiding toxins) 2. phototaxis (sensing specific wavelengths of light) 3. aerotaxis (sensing oxygen and energy, redox, etc) 4. magnetotaxis

spirochetes morphology of flagella (3)

1. flagella are located in the periplasm (called endoflagella) 2. equal numbers of flagella at each pole (1-50 depending on species) 3. flagella are wrapped around the body of the cell, overlapping at the center

advantages of spirochete motility (3)

1. flagella are protected from damage or shearing in the periplasm (not external) 2. movement possible in viscous liquids where standard flagella would stall 3. flagella are not external and cannot elicit an antigenic response; may be important for pathogenic spirochetes

eukaryotic flagella (and cilia) (qualities) (4)

1. flagella tend to be long and there is only a few of them; cilia are short and there are many of them 2. beat in a whip-like pattern (back and forth) in the same plane 3. powered by ATP 4. unrelated to bacterial and archaeal flagella

three behaviors of motility + turn directions (3)

1. forward: CW -- CCW 2. reverse: CCW -- CW 3. flex (tumble equivalent): CCW -- CCW or CW -- CW

common features of the magnetotactic bacteria (6)

1. gram negative 2. motile by flagella 3. respiratory (incapable of fermentation) 4. negative taxis to atmospheric concentration of O2 (most tend to be microaerophilic) 5. contain magnetosomes 6. wide distribution in freshwater and marine sediments in oxic/anoxic border

magnetotactic bacteria diversity (2)

1. heterogenous polyphyletic group with various morphologies 2. members of alpha, delta, and gamma proteobacteria and the nitrospira group

spirochetes (general qualities of organism) (4)

1. long, slender helical bacteria that belong in a singular phylum 2. metabolically diverse, can be strict anaerobes to obligate aerobes; most are heterotrophs 3. gram negative 4. both free living and host-associated, some pathogens

bacterial flagellum (qualities) (4)

1. made of one protein, flagellin 2. helical rotary structure, similar to a propeller (instead of whipping in same plane) 3. except for spirochetes, flagella is external to cell and anchored to cell envelope via basal body 4. powered by PMF (or Na+MF in marine bacteria)

mechanism of spirochetes motility (3)

1. mechanism of thrust differs from standard bacterial flagellar motility 2. as flagella turn, they push against the cell body and force it to turn like a corkscrew 3. flagella at each end must be rotating in OPPOSITE directions to propel the cell

two major types of membrane bound receptors:

1. methyl-accepting chemotaxis protein (MCP), different MCPs determine specificity to what organism responds to 2. Aer: specifically E. coli, sensor system for FAD/FADH levels to monitor ETC

normal vs. chemotaxis movement (1,1)

1. motile bacteria normally move by "random walk" with random variation of tumbles and runs 2. in a presence of an attractant, bacteria swim with bias towards attractant (biased random walk) with fewer tumbles and longer runs

what occurs in the presence of high attractant (steps) (4)

1. no conformational change occurs of MCP and CheW (coupling protein) is inactive 2. autophosphorylation of CheA is inhibited, so CheA-P cannot form 3. CheY also remains unphosphorylated due to the inactive kinase CheA-P 4. CCW rotation occurs, meaning organism "runs" to the area of attractant

structure/building of bacterial flagellum (4)

1. overall structure and protein components conserved in all bacteria w/ small variations 2. flagellum built from the cell surface outward (monomers exported and added to tip) 3. flagellum is hollow 4. the basal body embedded in the membrane is homologous to type III secretion system

uniting feature of magnetotatic bacteria

contain crystals of magnetic mineral in membrane-enclosed structures (invagination of the cell membrane) called magnetosomes, aligned along the long axis of the cell

moving on surfaces with type IV pili (qualities of pili, mechanism) (3,2)

1. pili made of proteins named pilins 2. synthesized from the base 3. pilin proteins are made as "prepilins" which are processed as exported (prepilin peptidase) (archaea similarity) 1. mechanism of motility: extension, attachment, retraction (grappling hook mechanism) -> propel itself to attachment 2. powered by ATP hydrolysis

adaptation (in context of chemotaxis) (definition, proteins involved, relationship) (1,2,2)

1. process of an organism to stop responding to a stimulus to wait for further instruction by "reseting" sensory system 1. CheB: methyl esterase (demethylation) 2. CheR: methyl transferase (adds methyl) 1. CheA is dependent on the methylation of the MCP 2. shift from high to low attractant = increasing methylation by CheR to activate CheA (decreases sensitivity) = P-CheA kinase activity active = P-CheA phosphorylates CheB = P-CheB removes methyl groups to decrease CheA activity (increase sensitivity)

four types of bacteria and their types of gliding motility on surfaces:

1. pseudomonas aeruginosa: pilus based twitching motility 2. myxobacteria: adventurous and social motility 3. filamentous cyanobacteria: mechanism involves slime extrusion and pili, but mechanism not understood 4. flavobacteria: mechanism unknown, but involves movement of cell surface proteins

two types of myxobacterial motility (2)

1. social: extension and retraction of pili to pull the cells (group movement) 2. adventurous: involves slime (possibly to push the cell), cell surface proteins, and helical cytoskeleton

important "FYI" about spirochetes (2)

1. spirilla are NOT related to spirochetes 2. spirilla have EXTERNAL flagella at both poles, while spirochetes have INTERNAL flagella

archaellum and chemotaxis general qualities (5)

1. synthesized from base (proteins made as prepilin like proteins that are processed as exported by prepilin peptidase like enzyme) 2. rotate as bundles to allow swimming in liquid; do not extend/retract like pili 3. powered by ATP hydrolysis 4. no central channel in the flagella 5. chemotaxis system proteins are conserved in Bacteria and Archaea

purpose of motility and often required for what? (1,1)

1. to identify optimal environments for growth and replication 1. often required for colonization of hosts by symbionts and pathogens

what organism does not do swimming the same way as most bacteria? why? (1,1)

1. unicellular marine cyanobacteria Synechococcus 2. does not contain a flagella or any apparent external motility apparatus, mechanism of swimming in liquid not understood

magnetotactic bacteria (phylogenetic relationship, magnetite crystals, function) (1,1,3)

1. unknown whether or not ability to produce magnetosomes evolved more than once or passed through HGT (genes are on large island) 1. size and shape of the magnetite crystals is species specific 1. cells passively orient themselves along the earth's geomagnetic field using internal magnet as a compass 2. by moving north along field (in north hemi, north is at an angle) they move deeper towards a lower [O2] 3. may increase efficiency of aerotaxis by reducing the 3D search for best oxygen concentration to one dimension

peritrichous flagella vs. monotrichous flagella (qualities, movement) (1,3 + 1,2)

P: bundle of flagella around whole body 1. CCW rotation of condensed bundle allows movement in a single direction (run) 2. bundle flies apart when all flagella go in different direction (CW) to do tumbling 3. from tumbling can reorient itself in new direction M: one single flagella on the polar end 1. CCW movement generates run in a certain direction 2. CW allows for random orientation