Med Micro 10 - Biofilm

Question 1

Definition of biofilm

Answer 1

A microbial (bacterial, fungal, algal) community, enveloped by the extracellular biopolymer which these microbial cells produce, that adheres to the interface of a liquid and a surface. Typically on something solid, but also on surface of lakes,

Question 2

Tower

Answer 2

work more like a city. different bacteria expressing different genes at different times. towers can form in biofilms hundreds of micrometers high

Question 3

Main points of biofilm production

Answer 3

Change form from planktonic to biofilm - essentially enter, bind initially based on nutrient availability via cationic interaction (epitopes, pili), then bind irreversibly via polysaccharide, more bind (cell division and recruitment)… fragments or planktonic bacteria are released from biofilm to bind elsewhere.

Question 4

Acute vs chronic

Answer 4

acute caused by planktonic (and some biofilm), Chronic caused by biofilm

Question 5

Advantages that biofilm provides to the bacteria

Answer 5

Difficult to eradicate, extracellular material produced which acts as defense, change form - collaborate, antibiotics kill rapidly dividing cells but biofilm grow slow, antibiotic resistance; some that bind to biofilm cannot normally bind. Neutrophils release lots of chemicals, can cause damage which releases more nutrients,

Question 6

Mechanical debridement

Answer 6

Removal of biofilm and dead tissue. Remove from open wounds or ulcers by scrapping.

Question 7

Biofilm formation (compare above)

Answer 7

Initial binding reversibly, then polysaccharides bind irreversibly, allow. Mature biofilm often have pores to allow liquid and nutrients to flow in.

Question 8

Examples of gene regulation

Answer 8

Polysaccharide regulation and pores; regulated by quorum sensing

Question 9

Phagocytes and biofilms

Answer 9

release of pro-inflammatory enzymes and cytokines leading to inflammation and subsequent tissue destruction resulting in increase in nutrients. Our immune system selects for pathogens that can hide…

Question 10

Microbial communication

Answer 10

constantly secreting molecules

Question 11

What type of molecules do types of bacteria release in quorum sensing?

Answer 11

Gram +: typically oligopeptides, bound by extracellular receptors. Gram -: small lipid soluble molecules or AHL, enters via transporter

Question 12

Vibrio fisheri and symbiosis

Answer 12

Concentrated in light organ of hawaiian squid. Lots of nutrients in there for the bacteria. At high concentration they release autoinducers which cause them to make them create light. Squid can control the amount of light so it forms no shadow at night when moon shines on it. Release extra bacteria during the day, grow during the day,

Question 13

Quorum sensing

Answer 13

The regulation of gene expression in response to fluctuations in cell population density. Produce and release signal molecules into the environment called autoinducers

Question 14

Another word for autoinducer

Answer 14

Self-stimulation

Question 15

Possible Ecological Roles for Quorum Sensing

Answer 15

Chemotaxis; Coordination of gene expression (up or down) in initial population; Coordination of gene expression and bacterial behaviour among multiple populations; Avoidance of host defence responses; Direct communication between the bacterium and the host

Question 16

Why does initial population need to regulate its genes?

Answer 16

It’s vulnerable, doesn’t want to express some virulence factors initially. It will want to bind first (pili)

Question 17

Direct communication between the bacterium and the host

Answer 17

Example: nodules of bacteria (essentially biofilm surrounded by plant) which provide nitrogen fixation

Question 18

Interspecies, intraspecies, inter kingdom

Answer 18

Interspecies: 2 species of bacteria. intraspecies: self. inter kingdom: bacteria and plant

Question 19

Process of quorum sensing

Answer 19

1. Bacteria leak a chemical into their surroundings. 2. As bacteria increase, chemical increases until there’s enough to generate a response. 3. Independent, solitary bacterial cells can become part of a much larger, multicellular organism known as a biofilm, when the amount of a certain chemical reaches a particular level

Question 20

Why is quorum sensing “all or nothing”?

Answer 20

Don’t want to waste energy if it won’t be effective, and don’t want to generate infectious disease until there are enough bacteria.

Question 21

Process when hiding with coagulase

Answer 21

Hide from immune system by forming clots, then once it reaches quorum, it wants to escape

Question 22

Why is a biofilm called a multicellular organism?

Answer 22

Like city. Different cells have different roles with different genes expressed.

Question 23

Population changes

Answer 23

The bacteria appear relatively innocuous as they quietly grow in number. When their population reaches a certain level, instant changes occur in their behaviour, appearance and metabolism. Changes can overwhelm immune system, include binding, reproduction, releasing toxins and/or invasion, causing disease (virulence)

Question 24

AHL

Answer 24

Acyl homoserine lactone. An autoinducer family

Question 25

Autoinducers,,,

Answer 25

Signalling molecules must be small, and move across membranes passively or actively, They must be recognized and alter the behaviour patterns and gene expression of the recipient. There are similar to pheromones

Question 26

Quorum sensing and evolution

Answer 26

S. mutans. Regulate genes which are involved with attacking other bacteria and have ability to uptake and integrate DNA - evolution! Naturally competent. . . . . numerous bacteriocins and genetic competence, resulting in killing of other species, DNA release, and gene exchange

Question 27

Bacteriocin

Answer 27

chemicals that attack other bacteria

Question 28

Biofilm treatment?

Answer 28

New treatments - prevent binding; anti quorum sensing chemicals?

Question 29

What might be a good way to take advantage of what we know about quorum sensing and biofilm formation in the development of new antimicrobials?

Answer 29

Inhibit the AHL and autoinducers to block their function; convince bacteria that it has quorum early so it can be taken care of by immune system. Both of these can block biofilm.

Question 30

Other than AHL in quorum sensing, how might the environment regulate gene expression, especially during infectious disease?

Answer 30

Temperature, pH, nutrient availability esp. iron, bile (lysteria)

Question 31

Using diagram compare the genetics of quorum sensing and another form of gene regulation

Answer 31

Quorum: secrete molecule, affects self and neighbours, result.