BIO 120.11 | Module 1: Cell Locomotion

Most common type of pilus

Conjugation pilus

Type of pili for twitching motility in Bacteria & Archaea

Type IV pilus

• Protein structure shorter but higher in number than pili

• Surface attachment

Fimbriae

• Resembles tiny grappling hook

• found in SM1 group (unculturable Archaea)

• Attachment (networked biofilm)

Hamus / hami

• Thin (2-10 nm), long protein filamentous structure

• All Gram-negative

• Many Gram-positive and Archaea

Pilus / pili

Functions of pili

cantd

• Conjugation (genetic exchange)

• Adhesion

• Nanowires (Conducting electrons for metabolism)

• Twitching motility (Type IV) - Bacteria & Archaea

• DNA-binding (Type IV)

Type of pili for DNA-binding

Type IV

T/F: Pili is shorter but higher in number than fimbriae

FALSE

Fimbriae is shorter but higher in number than pili

Function of fimbriae

Surface attachment

Function of hamus

Attachment (networked biofilm)

Basis of packaging prokaryotic chromosome

Supercoiling

5 internal prokaryotic cell structures

ccrip

• Cytoplasm

• Chromosome

• Ribosome

• Inclusion bodies

• Plasmid

• Aqueous mixture of

  • Macromolecules (lipids, nucleic acids)

  • Small organic molecules (macromolecule precursors)

  • Various inorganic ions

  • Ribosome

Cytoplasm

• Large complexes of protein and RNA

• Site of protein synthesis

• Quantity is growth-dependent

  • Thousands/cell depending on growth phase/rate

Ribosomes

Describe number of ribosomes per growth phase

• Lag phase = relatively low

• Log phase = thousands

• Stationary = start to decline

• Decline/death = decline (lowest)

Size of ribosome in bacteria

• 70S

  • 50S

    • 5S rRNA, 23S rRNA, 31 proteins

  • 30S

    • 16S rRNA, 21 proteins

  • Not additive bc it’s a sedimentation rate (Svedberg)

Main genetic element that aggregates in prokaryotic cytoplasm to form nucleoid

Chromosome

Typical configuration of prokaryotic chromosome

• One copy

• Haploid (1 set)

• Closed circular dsDNA

• Small & compact genome

  • 500 - 10,000 genes

  • 0.5 - 10M bp

• Basis of packaging: supercoiling

• Genes are sometimes clustered (operons)

T/F: Prokaryotic chromosomes are haploid

TRUE

Positively charged proteins that tightly pack DNA to form nucleosomes in Archaea

Histones

T/F: Plasmid replicates separately from chromosome

TRUE

T/F: Archaea have histones, bacteria have histone-like proteins

TRUE

Highly differentiated, dormant, light refractive, non-reproductive survival structure

Endospore

• One or more linear or circular dsDNA

• Smaller than chromosome

• Copies: 1, few, or >100

• Replicates separately from chromosome

Plasmid

• Endospore structure

• Layer of spore-specific proteins

Spore coat

Describe genome of bacteria

• 500 - 10,000 genes

• 0.5 - 10 M base pairs

T/F: 70S ribosome and 16S rRNA are found in both Bacteria and Archaea and is the basis of tree of life.

TRUE

16S rRNA gene sequence of bacteria is the reason why it is considered a separate domain and no longer under Kingdom Monera

Example of special properties conferred by plasmid

• Unique metabolism

• Antibiotic resistance

• Toxin resistance

• Virulence factors

• Bacteriocin

• Conjugation

• Endospore structure

• Made of peptidoglycan

Cortex

Reason why Cyanobacteria was reclassified from being a blue-green algae to a bacteria

It has 16S rRNA sequence

• Endospore structure

• Develops from vegetative cell CM

Core wall

Where can u find sulfur granules

Periplasm, but it appears to reside in cytoplasm

Harsh conditions tolerated by endospores

drenc

• Drying

• Radiation

• Extreme heat

• Nutrient depletion

• Chemicals

Typically contains genes that are not essential but often confer special properties on a cell

Plasmid

When does sulfur granules form

When elemental sulfur accumulates from sulfide oxidation (H₂S → S⁰)

Endospore-forming genera

Gram (+) Bacillus (aerobic), Clostridium (anaerobic)

Describe endospore structure

• Exosporium: outer proteinaceous layer

• Spore coat: layer of spore-specific proteins

• Core wall: derived from vegetative CM

• Cortex: made of peptidoglycan

• DNA: contained in the core

• Endospore structure

• Outer proteinaceous layer

Exosporium

What happens to sulfur granules when sulfide becomes limiting

Oxidized

Vegetative cells vs. Endospores

	Vegetative cell	Endospore
Microscopic appearance	Nonrefractile	Refractile
Calcium	Low	High
Dipicolinic acid	Absent	Present
Enzyme activity	High	Low
Respiration rate	High	Low/absent
Macromolecular synthesis	Present	Absent
Heat resistance	Low	High
Radiation resistance	Low	High
Chemical resistance	Low	High
Lysozyme	Sensitive	Resistant
Water content	High (80-90%)	Low (10-25%)
Small acid-soluble spore proteins	Absent	Present

T/F: The number of plasmids a bacterial cell has would have implications on the amount of energy it spends, i.e., more plasmids = more energy exhausted

TRUE

Increased no. of plasmids = increased energy expenditure

In archaea, histones are positively charged proteins that tightly pack DNA to form _

nucleosomes

• Forms from accumulation of elemental sulfur due to sulfide oxidation

• Oxidized when sulfide becomes limiting

• Periplasm (appears to reside in cytoplasm)

Sulfur granules

• Forms when there’s excess of carbon

• Polymer- and storage-form of glucose

• Carbon and energy reservoir

Glycogen

4 functions of inclusion bodies

• Highly specialized functions

• Energy reserves

• Reduction of osmotic stress

• Space-saving storage units

• Endospore structure

• Contained in the core

DNA

• Forms when there’s excess of lipids, carbon

• Carbon / energy source

Poly-B-hydroxybutyric acid (PHB), Poly-B-hydroxyalkanoate (PHA)

3 types of endospores

• Terminal: at the very end or pole of cell

• Subterminal: near the end but not the end; in between the center and end of cell

• Central: in center

• Poly-B-hydroxybutyric acid (PHB), Poly-B-hydroxyalkanoate

• Glycogen

Carbon storage polymers

Describe life cycle of endospore-forming bacteria

1. Vegetative cell

2. Harsh conditions (ercdn) can trigger cell to enter sporulation and become a

   1. Sporulating cell with developing endospore inside,

   2. such that eventually mature endospore will be released

   3. Once conditions have become favorable enough for growth again,

      1. Mature endospore can revert back to its vegetative cell state and enter germination

TLDR: Germination (vegetative), Sporulation (endospore)

Inclusion bodies for inorganic materials

• Polyphosphate granules

• Sulfur granules

• Carbonate minerals

Enclosed in single layer membrane (instead of unit), composed of proteins

Inclusion bodies

• Forms when phosphate is in excess

• Phosphate source for nucleic acid, phospholipid, ATP synthesis

Polyphosphate granules

• Confers buoyancy

• Allows cells to position themselves in region of water column best suited to their metabolism

• Conical-shaped, made of 2 diff proteins

Gas vesicle

• e.g., Benstonite of Gloeomargarita

  • Contains barium, strontium, magnesium

  • Ballast

  • Way to sequester carbonate (source of CO2) to support autotrophic growth

Carbonate minerals inclusion bodies

4 types of inclusion bodies

• Carbon storage polymers

• Polyphosphate, sulfur, carbonate minerals

• Gas vesicles

• Magnetosomes

• Biomineralized particles of magnetites, greigites

• Allow cells to efficiently locate the microaerophilic zones they thrive in

• Allow cells to orient themselves in magnetic field

Magnetosome

Conical-shaped structure composed of 2 different proteins

Gas vesicle

• Contains barium, strontium, magnesium

• Ballast

• Way to sequester carbonate (CO2) source to support autotrophic growth

Benstonite of Gloeomargarita

Movement of cells by some kind of self-propulsion

Motility

Importance of motility

• Allows bacteria to find/exploit new resources/habitat

• Allows bacteria to escape unfavorable conditions (e.g., toxic chemicals, predators)

2 types of motility

• Swimming

• Surface motility

Individual movement in liquid powered by rotating flagella / archaella

Swimming

T/F: Flagella rotate at constant speed

FALSE

Flagella does not rotate at constant speed; depends on strength of PMF

Which is faster: bacteria or cheetah

• Bacteria = 60 cell lengths/sec; 1000 rev/sec

• Cheetah = 25 body lengths/sec

• Discontinuous movement

• CCW: runs, CW: tumbles, randomly reorients, CCW: runs again

• name also species

Peritrichously flagellated cells, e.g., E. coli

• Continuous movement

• Faster than peritrichous

• Reversible / unidirectional

Polarly flagellated cells

• CCW: runs

• CW: runs in reverse direction

• name also species

Reversible polarly flagellated, e.g., Pseudomonas

• CW: runs

• Stops, randomly reorients

• CW: runs again

• name also species

Unidirectional, e.g., Rhodobacter

Typical colony morphology of gliding bacteria

Rod-shaped or filamentous

• Involves crawling over surfaces

• Requires attachment to surface

• Results in distinctive colony morphology

  • Cells can move out and away from center of colony

• Slower than swimming (<10mm/sec)

Surface motility

4 types of surface motility

• Swarming

• Twitching

• Gliding

• Sliding

• Surface movement powered by extension and retraction of type IV pili

• Found in Bacteria and Archaea

• name also species

Twitching; Pseudomonas aeruginosa

• Smooth continuous motion along long axis of cell

• Without aid of external propulsive structures (e.g., pili, attachment organelles)

• Not found in Archaea; mostly in rod-shaped or filamentous Bacteria

• name also species

Gliding; Oscillatoria

• Multicellular surface movement over semisolid medium

• Mediated by flagella, archaella, type IV pili

• name also species

Swarming; Proteus mirabilis, P. aeruginosa

T/F: Cells tumble frequently in the dark

TRUE (if they’re scotophobotactic)

• Passive surface translocation powered by growth / cell division

• Facilitated by surfactants (rhamnolipids) and other compounds (exopolysaccharides)

• name also species

Bacillus subtilis

• Ability to sense and respond to stimuli in their environment

• Stimuli: physical or chemical

• Response: move towards (attractant), move away (repellent)

Taxis

Ecological significance of taxis

• Directed movement enhances cell’s access to resources

• Allow cells to avoid harmful substances that could damage or kill them

7 types of taxis

pocsham

• Phototaxis

• Osmotaxis

• Chemotaxis

• Scotophobotaxis

• Hydrotaxis

• Aerotaxis

• Magnetotaxis

• Response to chemical stimuli

• Sense environmental stimuli and transmit signals to flagella/archaella, causing it to alter its rotation

• name also species

Chemotaxis; Gliding bacteria

• Movement in response to gradient of light intensity

• Allows phototrophic organisms to position themselves most efficiently to receive light for photosynthesis

• name also species

Phototaxis; Filamentous Cyanobacteria

Identify movement

• No attractant =

• Attractant present =

• No attractant = random movement

• Attractant present = directed movement (to it)

• Response to absence of light (fear of the dark)

• Cells tumble frequently in the dark

• Mechanism that prevents phototrophic organisms from swimming away from lighted zone into darkness

• name also species

Scotophobotaxis; Chlorochromatium aggregatum

Directed movement with respect to gradients of O₂

Aerotaxis

Directed movement with respect to gradients of available water

Hydrotaxis

Directed movement with respect to ionic strength gradient

Osmotaxis

• Causes bacterial cells to point up or down so that they can swim either towards or away from O₂ at surface

• Allows bacteria to align themselves with earth’s magnetic field lines

• Exhibits aerotaxis

Magnetotaxis

T/F: Magnetotactic bacteria do not actually exhibit directed motility towards magnetic fields but exhibit aerotaxis

TRUE

Towards oxic-anoxic transition zone (OATZ)

Movement towards attractant

Biased random walk (random walk = more tumbles)

2 types of bacteria coming together

Consortium