Quorum Sensing: What Is It?

To begin with, I’d like to mention that it has been a while since I last wrote a blog post, around 10 months ago. And now, I believe that it’s time to begin writing about science once more. I’d like to try to write about what I’m into, or my current work or study once a week. This week, it’s Quorum Sensing!

A lot of people ask what exactly quorum sensing is, well the definition written in a paper by Melissa Miller and Bonnie Bassler (2001) describes quorum sensing being the process and regulation of gene expression in response to fluctuations in cell-population density.

Bacterial quorum sensing
Bacterial Quorum Sensing. Left shows individual bacterial cell releasing autoinducers when no threshold has been reached. Right shows a community of cells with large amount of autoinducers thus causing quorum sensing based gene expression and eventually the activation of this community of cells.

The paper by Miller and Bassler (2001) describes in detail the way in which chemical signals, called autoinducers, can induce the process of quorum sensing. For example, bacterial cells are able to release these autoinducers signals which build up in concentration. Once the minimum threshold limit for these autoinducers have been reached, gene expression can occur in the affected population of bacteria causing a response from them.

This could be anything from a potential toxin to a simple chemical reaction between the population of bacterial cells. It’s known that gram-positive and gram-negative bacteria use quorum sensing as a way of communicating with one another, usually to cause physiological activities.

The discovery and understanding of quorum sensing opens up multiple ways in which cells, in general, could possibly communicate within a small to large population. It’s been known that quorum sensing largely looks into the cell density of a particular population, if the autoinducer threshold has been met, for example, pathogenic bacteria could potentially express and release toxins into the host.

From the paper presented by Miller and Bassler (2001) there has been a large number of different discoveries and potential explanation to why certain bacteria’s behaving in a particular way.

One particular way in which quorum sensing could potentially be useful in a study would possibly be within the world of cancer. It’s know that cancers cells, which usually mutate due to a number of potential factors, could possibly have certain links to quorum sensing.

By monitoring and evaluating how certain types of cancers function, we could potentially see how they communicate. Using the logic within quorum sensing, and how that occurs within a number of different types of cells, it could allow for a number of different types of detection tools and ways in which quorum sensing can be used in order to potentially prevent cancer.

To end this blog post, I’d like to post an awesome TED-Ed video by Bonnie Bassler herself as she explains quorum sensing.

Paper: “Quorum sensing in bacteria” by Miller and Bassler (2001)


Hugs help protect against Colds by boosting social support

Lets get psychological for a second here, the folks at Cornegie Mellon University tested whether hugs act as a form of social support, aids protecting stressed people from getting sick such as a cold. The findings were published in the Association for Psychological Science journal.

Sheldon Cohen and his team chose hugging as a social support example because they’re a marker of having a more intimate and close relationship with another person. They already knew that those who have some social support are partly protected from the effects of stress on the psychological state of the individual, such as depression and anxiety.

On the 404 healthy adults tested, a telephoned questionnaire was done whereby these adults are asked during a 14 day period their state is. This included the frequency of conflicts and receiving hugs. These participants were intentionally exposed to a common cold virus and monitored in quarantine to assess the progress of infection, and if they develop any signs and symptoms.

The results showed that those who had social support had a reduced risk of infection associated compared to those who were associated with conflicts. It also showed those that were infected, those with greater social support and more frequent hugs results in a less severe illness symptom.

Cohen mentions “that being hugged by a trusted person may act as an effective means of conveying support and that increasing the frequency of hugs might be an effective means of reducing the deleterious effects of stress”. He goes on to also state, “The apparent protective effect of hugs may be attributable to the physical contact itself or to hugging being a behavioral indicator of support and intimacy.”

So to conclude, those who receive more hugs are generally more protected from infections, even if it allows for skin to skin contact, it psychologically aids in improving the well being of that individual. Give a hug, get a hug.

Free Hugs

Source: Hugs Help Protect Against Colds by Boosting Social Support

Image: Free Hugs

Binge drinking disrupts immune system activity in young adults

Recently read a study based on young adults (aged 18 – 34) who drank enough to exceed 0.08 Blood Alcohol Content (BAC) showed signs of increased immune function. But at 2 and 5 hours later, their immune system showed reduced activity compared to those who are sober.

It’s clear that alcohol affects the immune system in many ways, from hours to days after exposure. This study focus’ on the early effects of alcohol of the immune system while blood alcohol content is still elevated.

Volunteers were given a high-dose alcohol content. Blood was collected pre-ingestion of alcohol, 20 mins, 2 hours and 5 hours post alcohol ingestion. Flow cytometry and enzyme-linked immunosorbent assay (ELISA) techniques were used.

Results showed an increase in total circulating leukocytes, monocytes and natural killer cells only after 20 mins after ingestion, where BAC was at around 130 mg/dL. There was also an increase in tumor necrosis factor (TNF)-Alpha levels. AT 2 to 5 hours, immune function and activity reduced. It concluded that binge alcohol increased immune activity and function in it’s early pro-inflammatory state, which was followed by an anti-inflammatory state thereafter.

Afshar, M., Richards, S., Mann, D., Cross, A., Smith, G., Netzer, G., Kovacs, E. and Hasday, J. (2014). Acute Immunomodulatory Effects of Binge Alcohol Ingestion. Alcohol. [online] Available at: http://www.alcoholjournal.org/article/S0741-8329(14)20186-8/abstract [Accessed 30 Dec. 2014].