Welcome! This blog is being created by students in the courses Population Ecology and Biological Diversity at the University of Oregon. It is one component of their work, and for each course will unfold throughout the term. +Jessica Green & Ann Womack
Monday, June 10, 2013
does your Microbiome say to Mosquitoes?
sometimes seems that after a weekend of camping with a friend one of you is
covered by mosquito bites while the other has not been touched. It doesn’t seem
to matter the amount of bug spray you both bathe in, someone just seems to
attract mosquitoes more than the other. Recent scientific finding indicate that
this may be the case. The study done by Verhulst, et.al in 2011 shows that the
variation in the microbial community on individual’s skin produces a body odor
specific that that person. This effects how attracted mosquitoes are to that
individual. Absent of bacteria human sweat does not smell like anything at all
(4). They extrapolated that the more diverse your skin microbiota is the less attractive
you are to mosquitoes. They believe that diversity is an important factor in
the ability of the skin to host a special group of bacteria that produces compounds
that repel mosquitoes (4). This and other studies on this topic have important
implications for the creation of new methods for malaria prevention.
experiments performed by researchers in Wageningen University in the
Netherlands studied specifically on the Anopheles
gambiae sensu stricto mosquito (1). This particular mosquito plays a key
role in malaria transmission. When females decide where to land they pay
attention to a number of physical and chemical clues. (3). In order test how
the microbial community of the skin effects how mosquitoes are attracted to
individuals they looked at 48 men of various ethnicities. They tried to
neutralize variables to make the experiment focus only on skin microbiome. The asked that, “Volunteers were requested to
refrain from drinking alcohol, eating garlic, onions or spicy food, taking a
shower, using perfumed cosmetics and were asked to wear nylon socks provided by
the research team for the twenty-four hours before the sampling event.
Volunteers were free from chronic illnesses and not using any medication on a
regular basis. The socks provided by the research team (100% polyamide, 40
denier, Hans Textiel, The Netherlands) were washed twice with 70% ethanol and
dried in a ventilated oven at 80°C before use. Volunteers were instructed not
to use soap the last time they showered before the experiment”(3). They then
took microbial samples from the underside of the left foot using glass beads.
The researchers tested those beads to see how attracted mosquitoes were to
them. The beads were sterilized between each trail (3).
analyzed their collected data using 16S rRNA sequencing on 116 samples from the
glass beads. The graph below should the results of the different individuals.
PA means “Poorly Attractive” and HA stands for “Highly Attractive”.
The graph above shows that there was a large
variation in the attractiveness of the participants microbes to mosquitoes.
What the above graph
shows is that there is a positive correlation between the average number of
bacteria in the sample from the foot and the attractiveness of the sample to
mosquitoes (3). This is significant, as it shows that the number of microbes
you have on our skin really does affect the degree of attractiveness has to
interesting result they found was in relation to phylogenetic diversity. They
found that PA individuals had significantly higher phylogenetic diversity than
what the HA individuals had (3). This implies that the more diversity an
individual has, the less likely they are going to be attractive to mosquitoes. They
also found that the abundance of a certain microbe, Staphylococcus spp., was present 2.62 times higher in HA groups
than PA groups. They also saw that Pseudomonas
spp. was 3.11 times more abundant in the PA groups than the HA groups (3).
There is another study
that evaluated the effect of several volatile compounds commonly found on the
human skin on the attractiveness to mosquitoes. The four microbes they chose
were Bacillus subtilis, Brevibacterium epidermidis, Corynebacterium
minutissimum, Pseudomonas aeruginosa and Staphylococcus epidermidis
because of their role in producing human body odor (5).
They used a dual-choice olfactometer to look at how the mosquito
Anopheles gambiae would react to the four microbial species listed above (5).
Below is a representation of the apparatus they used to run the tests. They
judged attractiveness by comparing the mosquitoes reaction to that of ammonia,
which is a know attractant for that species of mosquitoes.
They found definite
discrepancies in the mean relative attractiveness between the four different
species. This is meant to give us a better idea of what parts exactly of our
body odor and microbial community cause mosquitoes to be attracted to us.
It is obvious that Corynebacterium minutissimum has the
highest mean relative attractiveness. This is very interesting in respect to
the last study discussed in the beginning of this paper, which seemed to imply
that Staphylococcus spp. was most
closely associated with a high level of attractiveness to mosquitoes. In this
study, it is shown that this microbe has the lowest level of attractiveness compared
to the others they choose to study.
What all this suggests
is that there are definitely some microbes that affect the attractiveness of an
individual to a mosquito more than others. This is a great discovery with huge
implications for the prevention of malaria in the future. However it seems as
though maybe before we begin to develop treatments or medications from this
data, further research is needed. We need to isolate exactly what microbe or
combination of factors cause mosquitoes to be attracted to an individual and
why a greater diversity of microbes yields less attraction. After we make these
discoveries it will also be important to look at what reducing or eliminating
those microbes from our skin might do to our biological processes. The human
microbiome is inexplicitly linked to how malaria is transmitted. However if we
find a safe and responsible way to do so, the implication would be enormous for
the prevention of malaria. If we could stop mosquitoes from transmitting
malaria through biting people a huge world issue would be solved.
-(1) "Microbial Communities
On Skin Affect Humans' Attractiveness to Mosquitoes." ScienceDaily.
ScienceDaily, 10 Jan. 2012. Web. 29 May 2013. <http://www.sciencedaily.com/releases/2011/12/111229091845.htm>.
-(2) "Microbial Communities
on Skin Affect Humans' Attractiveness to Mosquitoes." Microbial
Communities on Skin Affect Humans' Attractiveness to Mosquitoes. N.p., n.d.
Web. 29 May 2013. <http://www.eurekalert.org/pub_releases/2011-12/plos-mco122711.php>.
-(3) "Composition of Human
Skin Microbiota Affects Attractiveness to Malaria Mosquitoes." PLOS
ONE:. N.p., n.d. Web. 29 May 2013. <http://www.plosone.org/article/info:doi/10.1371/journal.pone.0028991>.