- A research team
from the University of Maryland has found the mechanism that allows P.aeruginosa to survive under
sudden excess of water.
- These organisms
have special channels on their cell surface that are activated during
water build up inside the organism.
- They allow water
out of the cell to maintain water level and to prevent bloating and
certain bacteria are exposed to excess water, it can lead to osmolysis
, where the cell bursts due to
large amount of water or osmotic imbalance. A research team from the University
of Maryland has now found that the pathogenic Pseudomonas aeruginosa
utilizes membrane channels that are tension
activated to prevent swelling and bursting. This bacterium is the prime cause for hospital acquired infections
understanding of how it persists could be used to develop methods to eliminate
it. The study was published in the journal General
is a highly adaptable bacterium that can survive even in harsh environment. In a
hospital, it is present on the surface of medical equipment and can infect
patients who are immunocompromised and lead to life threatening conditions.
P. aeruginosa's Adaptability
can survive in very harsh environments and one of the main reasons behind their
adaptability is that they can survive sudden increase in water. During
rainfall, there would be an increase in water level surrounding bacteria and
this leads to osmotic entry of water into the cell. As the water continues to
enter, the cells burst after swelling and die. However, in certain bacteria,
including the gut bacteria Escherichia
, once the level of water inside the cell increase beyond a certain
level, mechano-sensitive channels in the walls of the bacterium open. This allows
small osmolytes to leave the cell, thereby preventing the cell from swelling
‘Mechano-sensitive channels are special channels present on the cell surface which allow water out of the cell during sudden water excess.’
are two mechano-sensitive channels that are present in such bacterium to
monitor the amount of osmolytes that leave the cell. When the osmotic pressure
is small across the cellular membrane, then MscS
is activated and small osmolytes are removed from the cell.
When the osmotic pressure across the cellular membrane is high, then MscL
is is activated and large
osmolytes are removed from the cell.
research team from the University of Maryland led by Dr. Sergei Sukharev
discovered through their experimental studies that P. aeruginosa
can tolerate larger amounts of osmotic shocks when
compared to E. coli
. The higher
adaptability of P. aeruginosa
be due to lowered permeability to water and its ability to release osmolytes
Mechano-sensitive Channels of P.aeruginosa
permeability to water
- Increased time
available for the cell to respond to osmotic shocks due to lower water
- Nearly 20% of the
organism's dry weight is reduced within a period of 28 milliseconds.
mechano-sensitive channels that are expressed by P.aeruginosa
The organism has one type of MscL channel. This type of channel predominates
and is present at a far greater density in P.aeruginosa
than in E.coli
. This leads to the
release of more number of large osmolytes from the organism.
The organism has two types of MscS channel. These channels, though present in
lower numbers than MscL, also contribute significantly to improve adaptability
of the organism. These channels are activated sooner when the cells begin to
swell. These channels release only small amounts of osmolytes from the cell to
lower the membrane tension, if they are successful then the MscL channels may
not be activated, preventing the MscL channels from releasing more osmolytes
than is necessary.
Sukharev said that the current study would help in gaining a better
understanding of how the physiological response to osmotic pressure occurs in
bacteria and the adaptations that they carry to survive it. The study also
showed that P. aeruginosa
better osmotic stability when compared to E.
is a well-known nosocomial pathogen, affecting people during hospitalization.
The incidence of P. aeruginosa in the U.S hospitals is
- 0.4 percent (4
per 1000 discharges)
- It is the fourth
most common nosocomial pathogen
- It accounts for
10.1% of all infections acquired at hospitals.
India, the prevalence of P. aeruginosa
found to be between 10.5 to 30%,
largely due to better survival ability of the organism.
current study conducted by Dr. Sukharev and colleagues show that the ability of
the organism to survive in an environment in sudden water rich environment
which is evidenced by the presence of this organism in numerous reservoirs in
the hospital like
alarming factor about P. aeruginosa
that is found to be associated with multidrug
. Patients who acquire this pathogen are often faced with longer
period of hospitalization with increased risk for mortality. 50% of patients
acquire a fatal infection due to this condition. An insight into the mechanisms
that improve their adaptability can be utilized to develop novel drug therapy
that limit the spread of this infection
- Incidence of
Multidrug Resistant Pseudomonas Aeruginosa Isolated from Burn Patients and
Environment of Teaching Institution - (https:www.ncbi.nlm.nih.gov/pmc/articles/PMC4080000/)
- Resistance Pattern of Pseudomonas aeruginosa in a Tertiary
Care Hospital of Kanchipuram, Tamilnadu, India - (https:www.ncbi.nlm.nih.gov/pmc/articles/PMC4080001/)
- (New study explains extraordinary
resilience of deadly bacterium)
aeruginosa in Healthcare Settings - (https:www.cdc.gov/hai/organisms/pseudomonas.html)