Microscopy And Biofilms

Front 1

Magnification

Def

Back 1

The degree by which an object appears larger than its actual size.
Ex; a bacterium 25 μm long when viewed under 1000x magnification will appear to be 25,000 μm.

Front 2

Resolution

Def

Back 2

efers to the size of the smallest detail visible, a by-product of a microscope’s resolving power.

Front 3

Resolving power

Def

Back 3

A function of the λ of the illuminating source and the numerical aperture.

As λ (measured in nm) decreases, RP increases

RP= ___ λ_______
2 x NA

Front 4

Illumination Source

Back 4

Source of light
λ (measured in nm) = distance between 2 peaks of a light wave

Front 5

Biofilm

Def

Back 5

Complex microbial communities

Characteristics?

Hint 5

-Take place in a liquid and solid surface interface

-Differential gene expression

Front 6

Differential Gene Expression?

Back 6

Not all the cells are producing the same microbial cells, but might create something different.

Cells at the surface may be creating different microbials cells then those in the center of the biofilm

Front 7

BioFilm Formation

Generic

Back 7

1. Trace organic molecules adhere to wall of surface.

2. Surface charge is neutralized, attracts free-floating ”pioneer” colonizers.

3. Initial colonizers attach using slime layers (a type of glycohalyx) or mechanical attachment proteins called fimbriae. Sheer force increases strength of fimbriae attachment.

4. Bacteria secrete polysaccharides and other exopolymers that creates a web trapping further metals and nutrients.

5. Secondary colonizers arrive, often using waste metabolites from pioneer bacteria as an energy source.

6. Using chemotaxis additional colonizers are attracted to the growing biofilm.

7. As the biofilm grows to a certain thickness it creates enough fluid turbulence which knocks off some of the bacteria. These microbes float downstream to attach to new surfaces.

Front 8

BioFilm Formation

P. aeruginosa

Back 8

1. Attachment via Type IV pili

2. Monolayer

3. Twitching ->micrcolonies

4. Polysaccharide secretion

5. Mature biofilm

6. Physical break-up or triggered release

Front 9

BioFilm Formation

Intracellular (e.coli)

Back 9

1. FimH adhesion at the tip of type I pili –attachment and invasion of bladder epithelial cells

2. Irregular rods -> matrix encased cocci – Would start to excrete exopolysaccharide and turn into one shape and take on an organized shape

Front 10

Mature Biofilms

Back 10

Contain many species of microbes and may develop an oxygen gradient supporting anaerobic as well as aerobic growth.

Front 11

PCD- Programmed Cell Death

Back 11

Death when the population of the biofilm reaches a certain density. The die-off creates available surface for a new round of growth.

Front 12

Quorum Sensing

Def?

Back 12

Density dependent communication

How does it work?

Hint 12

Involves Signal molecule (autoinducers) + receptor protein.
Receptor binding at high enough level signifies presence of other bacteria.

Front 13

Quorum Sensing

Autoinducers

Gram Positive and Gram Negative

Back 13

Gram Negative = Acyl Homoserine Lactones (AHL)

Gram Positive = eptides or modified peptide molecules

Front 14

Quorum Sensing

Autoinducers

Types of AHI?

Back 14

Ai-1 – is intra specific communicating (same type)

Ai-2 – Is an inter specific communicatory (different types)

Front 15

Activities regulated by

Back 15

1. Nutrient Cycling – Helps to avoid competition from other cells, cells making a decision to share the energy
2. Attachment
3. Detachment
4. Swarming Motility
5. Programmed Cell death
6. Sporulation
7. Release of virulence factors/toxins
8. Release of antibiotics
9. Increased genetic competence
10. Changes in cell wall structure
11. Activation of polysaccharide secretion pathways

Front 16

Why antibiotics are less effective against biofilms?

Back 16

1. Fluid dynamics
2. Physical protection (polysaccharide layer or cellular layer)
3. Metabolic diversity
4. Acquisition of gene for antibiotic resistance
5. Programmed Cell death