Biofilms

Question 1

What is the definition of a biofilm?

Answer 1

A fixed microbial community encased in EPS

Question 2

What does EPS stand for?

Answer 2

Extracellular polymeric substances

Question 3

What are the requirements for a biofilm to form?

Answer 3

A liquid environment with minimal nutrients

Question 4

Are biofilms limited to one species?

Answer 4

No they can be one or multiple species

Question 5

Do biofilms form on organic or inorganic surfaces?

Answer 5

Both

Question 6

What does hardy mean in a biofilm sense?

Answer 6

Difficult to dislodge

Question 7

What is the main role of a biofilm?

Answer 7

It protects the bacteria

Question 8

What is the reversible step of the biofilm lifecycle?

Answer 8

The adherence of cells to a substrate

Question 9

What is the irreversible attachment step of a biofilm lifecycle?

Answer 9

Bacterial adhesion and secretion of EPS

Question 10

What is the first part of the maturation of the biofilm?

Answer 10

The formation of microcolonies

Question 11

What is the term that describes the escape of bacteria from the biofilm and subsequent formation of biofilms?

Answer 11

Dispersion

Question 12

How are bacteria classified according to their attachment to surfaces?

Answer 12

Planktonic cells - free
sessile cells - attached to surface

Question 13

What structures of bacteria help to firmly attach to substrate?

Answer 13

fimbriae, pili, and adhesions

Question 14

What happens to bacteria right after they attach to a substrate?

Answer 14

They begin to produce EPS

Question 15

When do bacteria start to grow/multiply in the biofilm lifecycle?

Answer 15

After they begin to secrete EPS

Question 16

How does the EPS matrix generate?

Answer 16

The EPS allows for quorum sensing to take place splooge splooge splooge

Question 17

What structures in a biofilm delivers nutrients to the bacteria while rejecting extraneous products?

Answer 17

Water Channels

Question 18

How do periphery cells of biofilms revert?

Answer 18

They go back to a planktonic lifestyle, sloughing off mature biofilm to colonize new sites

Question 19

What are the roles of EPS? (4)

Answer 19

1. Resist stress
2. Trap nutrients
3. Hold the biofilm together
4. Protect the bacteria within

Question 20

What is the composition of a biofilm?

Answer 20

80-90% water, the rest is EPS, bacterial cells, and other organic/inorganic material

Question 21

What part of the biofilm is most of the dry mass? (50-90%)

Answer 21

The extracellular matrix

Question 22

What is the composition of the ECM?

Answer 22

The EPS

Question 23

What is the composition of EPS?

Answer 23

It is a hydrated gel consisting of polysaccharides, and some other macromolecules like proteins, nucleic acids, and lipids

Question 24

Are EPS properties standardized throughout populations?

Answer 24

No, they change based on the organisms and environment

Question 25

Why would a biofilm structure vary according to the environment? (staphylococci)

Answer 25

It is usually made of polysaccharides, but is made of proteins/eDNA in lower nutrient concentrations, and made of fibrin when in blood (lots of fibrogen)

Question 26

What can cue different biofilm formations?

Answer 26

Different environmental signals

Question 27

What is the process that allows chemical signals to communicate with each other, respond to population densities, and regulate gene expression?

Answer 27

Quorum Sensing

Question 28

What happens in the quorum sensing pathway when bacteria accumulate?

Answer 28

The bacteria produce, release, and detect signaling molecules

Question 29

What are the quorum sensing pathway signaling molecules called?

Answer 29

Autoinducers

Question 30

What happen when a threshold concentration of autoinducers is reached in a bacterial population?

Answer 30

Coordinated behaviours are triggered like biofilm maturation, virulence factor production, and EPS synthesis

Question 31

What is a homogenous biofilm?

Answer 31

A biofilm with one species of bacteria in it

Question 32

What is cell differentiation within a biofilm?

Answer 32

Certain cells with express different genes and perform different functions

Question 33

What kind of process is involved with the switching of cells between sessile and planktonic states?

Answer 33

Changes in genetic expression

Question 34

List some environmental factors that may induce biofilms to grow differently?

Answer 34

Temperature, pH, shear stress, nutrient availability, surface properties

Question 35

How do biofilms affect human health?

Answer 35

Some are helpful and some are harmful

Question 36

What type of biofilms line the intestinal and respiratory mucosa and play a role in fighting off infections?

Answer 36

Normal microbiota

Question 37

Where are three areas that biofilms can be harmful to human health?

Answer 37

1. Plaque on the teeth -> periodontal/dental disease 2. Biofilms in wounds -> infection 3. Biofilms on medical devices -> infections in catheters, artificial joints, or contact lenses

Question 38

What is the danger of pseudomonas aeruginosa?

Answer 38

It colonizes biofilms in the airways of cystic fibrosis patients that can infect the lungs

Question 39

What kind of infections are associated with biofilms?

Answer 39

Chronic infections that are difficult to treat

Question 40

How do biofilms stop biocides from accessing bacteria? (4)

Answer 40

1. Electrostatic interactions 2. Hydrophobic interactions 3. Size exclusion 4. Degradation of Biocides

Question 41

What are the 4 types of cells involved with biofilm resistance?

Answer 41

1. Biofilm Phenotype 2. Persister cells 3. Slow growth 4. Adapted Cells

Question 42

How do biofilm phenotype cells contribute to biofilm resistance?

Answer 42

They change in gene and protein expression to be a part of the biofilm

Question 43

How do persister cells contribute to biofilm resistance?

Answer 43

They exhibit multidrug tolerance

Question 44

How do slow growth cells contribute to biofilm resistance?

Answer 44

They limit the cell's uptake of biocides

Question 45

How do adapted cells contribute to biofilm resistance?

Answer 45

They develop a greater tolerance to biocides

Question 46

What are the 4 ways that cells can resist antibiotics within metabolically active surface cells?

Answer 46

1. Efflux of antibiotics 2. Inactivation of antibiotics by enzyme 3. Alteration of the target molecule 4. Cell surface modification to prevent antibiotic entry

Question 47

What structure within surface cells is responsible for the efflux of antibiotics?

Answer 47

The efflux pump

Question 48

How does the physical biofilm act as an antibiotic resistor? (3)

Answer 48

1. Mechanical barrier 2. Limited penetration 3. Antibiotic neutralization by enzymes

Question 49

How are persister cells distributed throughout a biofilm?

Answer 49

They are spread evenly throughout the entire depth

Question 50

What are the bacterial biofilm immune escape mechanisms?

Answer 50

1. Mechanical protection 2. Reduced immune recognition 3.Immune modulation 4. Resisting phagocytosis

Question 51

Explain bacterial mechanical protection from immune cells

Answer 51

the EPS prevents the immune cells from easily accessing and engulfing the bacteria

Question 52

Explain bacterial reduced immune recognition

Answer 52

biofilm bacteria alter surface antigens, so the immune system has a harder time recognizing them

Question 53

Explain bacterial immune modulation

Answer 53

quorum sensing can regulate genes and produce immune modulating molecules

Question 54

Explain how biofilms will resist phagocytosis?

Answer 54

The structural resistance can make it difficult for macrophages and neutrophils to engulf the bacteria

Question 55

What is the name of the big idea of how biofilms can contribute to our natural environments

Answer 55

Phytoremediation

Question 56

What is bioremediation?

Answer 56

The use of microbes to remove pollutants or xenobiotics

Question 57

What is the difference between bioaugmentation and biostimulation?

Answer 57

Bioaugmentation is the adding of specific organisms to enhance the existing populations and promote biodegradation Biostimulation is the adding of electron donors or acceptors to stimulate naturally occurring microbial populations

Question 58

What are the limitation of bioaugmentation and biostimulation?

Answer 58

Bioaugmentation - the microbe cannot usually be established in the environment Biostimulation - there may not be enough existing microbial population

Question 59

How does bioremediation contribute to the cleanup of oil spills?

Answer 59

"fertilizer" containing nitrogen and phosphorus biostimulates microbes to break down the oil

Question 60

How do biofilms contribute to wastewater treatment?

Answer 60

They act as a biofilter for medium grain nutrients and organic carbon

Question 61

What are the three types of detrimental biofilms in nature?

Answer 61

Biofouling in aquatic systems - biofilms on ships, pipes, and underwater structures increase drag and lead to costly maintenance Corrosive biofilms - accelerate corrosion on bridges, water distribution systems, and oil rigs Biofilms in drinking water systems - They harbor pathogens, reducing water quality and leading to potential health risks

Question 62

How do autoinducers affect change?

Answer 62

They enter cells and change transcription

Question 63

What are electrostatic interactions in biofilms?

Answer 63

positively charged molecules will bond to the matrix before they reach bacteria

Question 64

In persister cells, is the tolerance of biofilm bacteria linked to genetic or phenotypic differences?

Answer 64

Phenotypic

Question 65

Why are slow growth bacteria usually found in the deeper layers of biofilms?

Answer 65

There is oxygen and nutrient limitation at deeper layers