Microbe motility/biofilm

Question 1

Lacking flagella

Answer 1

Atrichous (Streptococci)

Question 1

1 polar flagella

Answer 1

Monotrichous (Vibrio cholera)

Question 2

2+ flagella at one polar end

Answer 2

Lophotrichous

Question 3

Flagella at both ends

Answer 3

Amphitrichous

Question 4

Flagella surrounding the cell

Answer 4

Peritrichous (E. coli)

Question 5

Flagella structure

Answer 5

The flagella has a motor and stator. The motor has multiple rings of proteins. The FliF ring maintains the scaffold. The FliG ring switches the direction of the motor, while FliN and FliM regulate the switching of direction. The stator has protons flow through it to generate rotation.
The flagella has a basal body with the ring proteins. There is a T3SS for the secretion of flagella proteins. There is a holow rod structure that connects the structures by the inner and outer membranes. This connects to a hook that allows for flexible movement. Which is connected to the flagellar filament by junction proteins. The filament is built from proto-filaments.

Question 6

Flagella movement (run and tumble)

Answer 6

When the motor moves anti-clockwise, the flagella move clockwise. During a run, all flagella rotate in the same direction, allowing for straight movement. Then a signal or just randomly phosphorylates motor proteins, causing a change in rotation (anti-clockwise). Since some flagella start moving in opposite directions, it causes the bacteria to tumble and change direction. When in environment that is preffered, it may tumble more. When moving towards an attractant, some will not tumble.

Question 7

Chemotaxis

Answer 7

The MPC receptor is bound by a ligand, forming a dimer. This dimer binds CheW and CheA. CheA gets phosphorylated and phosphorylates CheY. CheY-P then goes to interact with the motor, causing a change in direction, causing tumbling.

Question 8

Twitching motility

Answer 8

Twitching motility is used on solid surfaces such as glass, plastic or high % agar. It is done using the Type 4 pilus.

Question 9

Type 4 Pilus

Answer 9

The pilus is composed of PilA/pilin subunits. Synthesized prepilin is cleaved by PilD, which methylates mature pilin. PilB binds to the basal body. PilB activates PilC which rotates, adding new PilA subunits to the pilus, extending it. This keeps extending until it attaches to a surface. When attached, the tension signals conformational change in the basal body. This releases PilB and allows PilT to bind. PilT causes PilC rotation in the opposite direction, removing PilA. This causes a retraction, pulling the bacteria forward.

Question 10

Gliding motility

Answer 10

This is used by bacteria that lack flagella or pilus. These bacteria form bowling pin shapes rather than rod shapes. They use adhesins that bind to the surface to move forward.
One was found where there is a long narrow protruding adhesin that attaches and extends, pushing the bacteria forward.

Question 11

Swarming

Answer 11

Swarming is a social behavior that helps bacteria take over a surface quickly. The bacteria start off in a circular clump but then extend, forming branches of swarms. The bacteria elongated and use flagella to move. Quorum signalling coordinates it and biosurfactant allows for faster movement by lower surface tension.

Question 12

Surfactin

Answer 12

This molecule acts as a detergent, lowering surface tension, allowing for faster movement. They have hydrophobic tails that clump them together and hydrophilic heads that interact with water on the outside of the clump.

Question 13

Quorum Sensing (SWARMING)

Answer 13

This involves communication between bacteria using secreted molecules. These include autoinducers. They often bind transcription factors and alter expression. In Pseudomonas they can promote surfactin production. If there are enough QS molecules, The bacteria swarm

Question 14

Swarming regulation

Answer 14

Signals from the environment can alter their ability to swarm. When grown in nutrient rich LB agar, they do not swarm much until later once they start starving. While in lower nutrient agar they swarm much faster due to starving.
Microbes can release ethanol when food is present. Ethanol signals for swarming. If yeast is near food it releases ethanol. The pseudomonas detect this and swarm towards it, killing the yeast for its nutrients.

Question 15

Biofilm

Answer 15

Structured community of microbial cells encased in an extracellular matrix and adherent to each other or surfaces. Exhibited by a majority of bacteria and fungi.

Question 16

Biofilm matrix

Answer 16

Biofilm cells are embedded in a matrix of extracellullar polymeric substances (EPS). The matrix surround and immobilises the cells. The matrix is comprised of water-soluble polysaccharides, proteins, extracellular DNA and insoluble compounds such as cellulose and lipids.

Question 17

Biofilm Matrixome

Answer 17

Proteins, adhesins, lipids, and enzymes that break down nutrients.

Question 18

Biofilm properties

Answer 18

It can provide a structural role that leads to stratification. It can provide affect antibiotic tolerance and resistance. It allows external digestion of molecules. It can allow them to compete with other microbes for space. It can stop molecules from entering

Question 19

Biofilm controls

Answer 19

c-di-GMP, QS signalling and small-RNAs are involved in controlling biofilm formation. Environmental conditions also affect biofilm formation.

Question 20

Route to infection via water

Answer 20

Vibrio cholera can form biofilms on plankton. Using pilus and flagellum, they attach to detritus and zooplankton. Once attached they get the signal to form a biofilm. If water is not properly filtered, they can reach humans.

Question 21

Nitrification

Answer 21

Nitrite oxidisers produce ammonia. Ammonia oxidisers produce nitrite. When living together, they can share waste together.

Question 22

Physical and chemical properties of biofilm

Answer 22

They can absorb chemicals/molecules like a sponge. They can release enzymes to biodegrade solid waste.
The matrix provides protection against phage invasion.

Question 23

Biofilms are a hotspot of biomineralisation.

Answer 23

Biofilms allow for the remediation of toxic compounds into non-toxic forms. Calcium precipitation forms calcium minerals.

Question 24

Interactions between matrix molecules

Answer 24

Hydrogen bonds, ionic interactions and hydrophobic interactions give the matrix structure.
CdrA is a protein that promotes aggregation.

Question 25

Stratified communities

Answer 25

Oxygen is consumed (by aerobes) at a faster rate than it can diffuse through the biofilm, forming an oxygen gradient, causing the middle to become anaerobic.
Nutrient gradients can form.
PH gradients form from the bacteria producing acidic products.
Gradients can form from signalling molecules.

Question 26

Dental plaque

Answer 26

The positioning of bacteria can alter the outcome. Some bacteria are cooperative, some are competitive. So when the bacteria colonise the gum by the teeth, different areas can have different bacteria depending on their interactions. When the gum gets damaged, the bacteria can seep along the tooth root. Biogeography affects virulence and treatment outcome.

Question 27

Oxygen gradients

Answer 27

O2 gradients can cause metabolic differentiation. The outer layer being aerobic and the middle layer being anaerobic.

Question 28

Redox balencing

Answer 28

In pseudomonas aerigunosa biofilms. The top layer uses respiration (oxic env) while the middle uses fermentation (Anoxic env). Phenazines are extracellular molecules that act as snorcles, allowing bottom bacteria to survive without oxygen. Oxidised phenazines are sent from the oxic top to the anoxic bottom to accept electrons and the reduced version is sent to the top. The oxic bacteria express genes under RhoS control. The anoxic bacteria express genes under Anr control.

Question 29

Oxygen gradient influence on matrix proteins

Answer 29

The Bacillus subtilus biofilm is coated in BslA. In an environment with oxygen it forms disulfide bonds, forming a water proof layer. While in the bottom layer without oxygen, no such disulfide bonds form, allowing uptake of nutrients from agar.

Question 30

Biofilm infection

Answer 30

The existence of a biofilm can cause reoccurring infections. With the bacteria sitting in the biofilm surviving. Implants are prone to infection as they provide a surface to bacteria that lacks our defences, it can cause chronic infection. When on tissues, it causes tissue damage

Question 31

Biofilm, antibiotic tolerance

Answer 31

The matrix can deactivate and block entry. The chemical and pH environment can also affect antibiotics. Metabolically active subpopulations can produce beta-lactamases and eflux pumps. Metabolically inactive subpopulations express less of the antibiotics targets. The negatively charged matrix components can bind and slow positive antibiotics.

Question 32

Antibiotic resistance mutagenesis

Answer 32

In planktonic populations. Mutations can arise spontaniously or induced by antibiotics. Further selection and competition leads to the resistant bacteria proliferation.
In biofilms. There can be antibiotic induced mutagenesis in the outer layers, and stress induced mutagenesis in the inner layers. There is low competition in the biofilm, so low and high resistance bacteria are retained, increasing diversity.

Question 33

Combatting Biofilms.

Answer 33

Surface modification can be made to implants to repel/kill bacteria. These can be using a smart surface that is stimuli responsive, utilising topography (patterning, texture) or chemical mods.
Nanoparticles or small molecular agents can be used to get drugs into the biofilm.
Enzymes can degrade the matrix to get into the centre.
Biofilms can be removed using shear stress an non-thermal plasma.