Quorum Sensing - Kin Selection - Virulence
Melih Kaplan - 2359537
Quorum sensing is an adaptive trait of the sociality of the bacteria, and it is closely
related to cooperative ability. The efficiency of the quorum sensing is dependent on a
ratio of “cooperative phenotype advantage” to “competition and cheating” of the
bacterial populations and their density behavior combined with it. (Schluter, et al.,
2016)
QS is mainly measured with the release of the extracellular factors released by the
individuals and the response by the other individuals of the population. Accordingly
to the response, the structure of the population is determined.
In the article named “Kin selection, quorum sensing and virulence in pathogenic
bacteria” the researchers took benefit from an in vivo experiment using mice to
investigate the relationship between quorum sensing and the relatedness of the
strains of the pathogenic bacteria.
In the experiment, two strains, the wild-type able to respond to the quorum sensing
factors, and lasR not able to respond to those factors, are used. The reason why
these two strains are used was due to the ease of examination of only one variable.
Therefore, they aimed to have a causative explanation for the quorum sensing and
pathogen evolution relationship. They found that high relatedness favors the QS
wild-type, which can build a cooperating system, while low relatedness favors lasR
mutants that can make use of extracellular factors of the wild-type, in a way, the lasR
strain is the cheater corrupting the cooperation. In low-relatedness samples where
two strains are present simultaneously, the quorum sensing was not strong due to
the cheating behavior of lasR, and thus, no such behavior as kin selection is
observed, in contrast to high-relatedness samples where cooperation is the main
driver of pathogenicity and virulence
Another finding was that higher relatedness brings about an increase in growth and,
thus, a higher virulence due to the fact that cooperation is only advantageous when
all the individuals are committed to it. As a comment, the relatedness and the
virulence should be considered as a crucial dynamic duo for the quorum sensing
evolution. (Rumbaugh, et al., 2012)
