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Exploration of Quorum Sensing Disruption in Bacterial Pathogens

Posted by Karn Piana 
Exploration of Quorum Sensing Disruption in Bacterial Pathogens
September 23, 2018 04:00AM
For those interested in plant pathogens and microbiology with a faint speculative aromatic ambiance, I offer an exploratory plunge into black pools of strange water.

Erwinia Amylovora, after oozing from a past season's canker and hitching a ride from an insect into a bloom, next undergoes an epiphytic phase of life. "An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water or from debris accumulating around it" -Wikipedia. From a few initiatory as yet non-virulent cells, the bacteria rapidly reproduces itself into a population numbering in the tens of millions on the surface of the flower. Pollinators continue to spread the contagion to other flowers and the epiphytic phase continues in new hosts. With moisture and sufficient numbers, the bacteria become virulent and infect the nectary. Thus begins a pathogenic cascade of destruction.

Biofilm forming bacteria coordinate action and behavior through a process called quorum sensing. Each cell emits a molecular signal called an autoinducer into the environment. As populations increase, this signal emission becomes denser. One might imagine single snowflakes giving way to white out conditions in a blizzard or a soccer stadium full people blowing on vuvuzela horns. At the appropriate frequency, a morphologic shift occurs. In biofilm forming bacteria this would coincide with switching from a flagella (locomotive sperm tail) to an adhering Fimbria ( "velcro" pilus strands) interlinked architecture. In other words, the singular organism reacts to a certain population density by binding itself together with proteins into an amalgamated organism comprised of other cells interlinked within a sugary protective matrix.

It is known that E. Amylovora produces a biofilm once inside of the xylem. Biofilms are produced in gram negative bacteria such as this one through AHL ( N-acyl homoserine lactones ) autoinducer quorum signaling. My question is, does quorum sensing play a role in the epiphytic phase of population increase within the bloom prior to virulence? If so, does this present a potential point of counter attack through a strategy of disrupting or interfering with quorum sensing in the pathogen populations by using some kind of autoinducer analog?

These questions led me to this paper, "Plant Food Extracts and Phytochemicals: Their role as Quorum Sensing Inhibitors." This article compiles a huge amount tantalizing research on the effect of a wide range of common plant extracts (vegetable, fresh herbs and spices, as well as fruit extracts). The researchers include extensive referable tables showing the plant used, the concentration, the target bacteria, the biological action (supress biofilm, motility reduction, arcane molecular protein chaos), the mechanism of action (AHL mimicking, AHL inhibition), and reference to research for further investigation should that be desired.

For example, mention of thyme as a powerful antibiotic has come up in discussion of E. Amylovora here on this forum in the past. A quick reference to the tables in the article shows that thyme inhibits both biofilm formation and swarming motility. "Swarming motility is a rapid and coordinated translocation of a bacterial population across solid or semi-solid surfaces, and is an example of bacterial multicellularity and swarm behaviour." -Wikipedia.

Karn Piana
Zone 7 Semi-Arid Steppe
Northern New Mexico

Edited 5 time(s). Last edit at 09/23/2018 04:41AM by Karn Piana.
Re: Exploration of Quorum Sensing Disruption in Bacterial Pathogens
March 15, 2019 06:11AM
This is fascinating. As I attempt to comprehend this, is the notion here that some sort of sound impedance may potentially disrupt pathogenic behavior. E.g. playing Mozart at the right frequency in the orchard may reduce disease?
Re: Exploration of Quorum Sensing Disruption in Bacterial Pathogens
March 15, 2019 02:39PM
The translation that matters here, Jason, goes like this:

Microbial diversity well-stocked with food resources (fatty acids) creates a competitive reception by which fire blight bacteria will falter.

The term quorum sensing emphasizes that a minimum amount of "something" is necessary to achieve an effective biofilm. Fire blight bacteria achieving quorum sensing through a numbers onslaught is one side of the coin. Luckily for fruit growers, a competitive surface environment is the other. Different microbes have different skill sets, which when combined as a counter to a pathogen, allow Nature's magic to proceed in thwarting disease.

Utilizing effective microbes (along with karanja oil and seaweed as essential food resources) in what's been dubbed a Competitive Colonization Boost during bloom is one approach to creating biofilm protection (sometimes called a bacteriophage) by means of a functioning microbe community on the blossom surface.

Please play Mozart if you wish but the point is our orchestra needs to be underscored with diversity!

Lost Nation Orchard
Zone 4b in New Hampshire

Edited 3 time(s). Last edit at 03/15/2019 03:04PM by Michael Phillips.
Re: Exploration of Quorum Sensing Disruption in Bacterial Pathogens
March 15, 2019 07:51PM
Hi Jason,

Quorum sensing does not involve sound; it is contingent on chemical / molecular compounds which are secreted in regular intervals by individual bacteria. The presence and concentration of this molecule is used as a means to determine population. Once the concentration of the secreted molecules reaches a certain environmental potency, the bacteria change their physical form from an individual entity to one where the entire population links together like chainmail and produce a kind of impervious slime. I was attempting to use words like frequency and signal emission to describe this, but I can see how they confused things...

I was curious if it were possible to disrupt this molecular signaling to inhibit biofilm formation, evidently the term for this is "Quorum Quenching". This conversation was intended as an exploration of potential not as a description of established protocol.

Karn Piana
Zone 7 Semi-Arid Steppe
Northern New Mexico
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