chapter 10.1 case study, inhibition of Streptococcus mutans biofilms with bacterial- derived outer membrane vesicles

Aim:

determine if OMVs made by Burkholderia thailandensis can inhibit planktonic growth and biofilm, formation of Streptococcus mutans

Hypothesis:

B. thailandensis OMVs possess antimicrobial and antibiofilm activity against S. mutans. 

background

Biofilms: complex environments of bacteria and other microbes that require cooperation and communication.

Outer membrane vesicles: small lipid- enclosed packages that bud off from bacterial membranes. They can contain DNA/ RNA, proteins, antimicrobial compounds, and more. They bind to and fuse with the surfaces of other cells, delivering their contents into the other cell. They are used as a defense strategy to compete with other bacteria. They help interbacterial communication. OMVs can protect the extracellular matrix, it can also disrupt other bacterial biofilms. Gram -ve bacteria can shed OMVs in response to environmental stressors. The vesicles contain small molecules, proteins, lipids, polysaccharides, RNA/DNA. B. thailandenis OMWs possess antimicrobial compounds (peptidoglycan hydrolases HMNQ) and long chain rhamnolipids

step 1:

a. Left

• S. mutans grown

• Treated with PBS: phosphate buffer saline: salt water with phosphate in it

A. right

• S. mutans grown

• Treated with OMV: outer membrane vesicles with antimicrobial cmp from B. thai

• In circle, there is a zone of inhibition, where treatment was put onto the plate

B. 

• Treatment is NOT added to a plate, it is added into a liquid culture where S. mutans were inoculated. This medium does not have any nutrients

Why did they present this as their first piece of data?

• Show that OMV antimicrobial activity can be held on solid and liquid media

• Confirms that OMVs do kill

What does this data mean? Are the data in the two panels redundant?

• A. growth on solid media, killing cells after they are grown

• B. inhibition of growth, preventing them from growing

• These graphs are NOT talking ab biofilm formation, colonies are not the same as biofilm

step 1: Wanted to look at anti-biofilm activity (Cultures were already grown before the experiment)

Against which of the following lifestyles are Burkholderia OMVs effective antimicrobials

• recall/ asterisks: indicate statistical significance in data comparisons. (*, p<0.05, statistically significant) (**, p<0.01, highly significant) (***, p<0.001, very highly significant)

• Both biofilm and planktonic growth. OMVs inhibit both

In which lifestyle are OMVs more effective than gentamicin in reducing bacterial growth?

• Both 

• Look @ brackets

step 2:

conclusions

• B. thailandenis OMVs are effective antimicrobials against planktonic and biofilm S. mutans

• The OMVs reduce biofilm cell density, potentially by increasing cell death and reducing biofilm thickness

Recall. Hypothesis: B. thailandensis OMVs possess antimicrobial and antibiofilm activity against S. mutans.  Accept or reject???