1) Bacteria have evolved to form biofilm communities that allow them to better survive threats like the human immune system. Biofilms are structured groups of bacterial cells encased in a self-produced protective matrix. 2) Within biofilms, bacteria can communicate with each other through quorum sensing, coordinating their behavior for survival. 3) Studies have shown that bacterial pathogens like Salmonella can survive longer in dry environments like milk powder by forming biofilms, making them more resilient and better able to cause illness if consumed. Biofilms allow pathogens to withstand harsh storage conditions and stomach acids.

1. Bacteria Biofilm
Dr. Yousef Elshrek

2. • As humans, our environment consistently
exposes us to a variety of dangers.
Tornadoes, lightning, flooding and
hurricanes can all hamper our survival.
• Not to mention the fact that most of us can
encounter swerving cars or ill-intentioned
people at any given moment.

3. • Thousands of years ago, humans realized that
they could better survive a dangerous world if
they formed into communities, particularly
communities consisting of people with
different talents.
• They realized that a community is far more
likely to survive through division of labor– one
person makes food, another gathers resources,
still another protects the community against
invaders.
• Working together in this manner requires
communication and cooperation.

4. • Inhabitants of a community live in close
proximity and create various forms of shelter
in order to protect themselves from external
threats.
• We build houses that protect our families
and larger buildings that protect the entire
community.
• Grouping together inside places of shelter is a
logical way to enhance survival.

5. • With the above in mind, it should come as no
surprise that the pathogens we harbor are
seldom found as single entities.
• Although the pathogens that cause acute
infection are generally free-floating bacteria –
also referred to as planktonic bacteria – those
chronic bacterial forms that stick around for
decades long ago evolved ways to join together
into communities.
• Why? Because by doing so, they are better able
to combat the cells of our immune system bent
upon destroying them.

6. • It turns out that a vast number of the pathogens
we harbor are grouped into communities called
biofilms “a structured community of bacterial cells
enclosed in a self-produced polymeric matrix and
adherent to an inert or living surface.”
• That means bacteria can join together on
essentially any surface and start to form a
protective matrix around their group.
• The matrix is made of polymers – substances
composed of molecules with repeating structural
units that are connected by chemical bonds.

7. • Biofilms form when bacteria adhere to surfaces in
aqueous or dry ( e.g. in milk powder) environments
and begin to excrete a slimy, glue-like substance
that can anchor them to all kinds of material – such
as metals, plastics, soil particles, medical implant
materials and, most significantly, low moiture food,
human or animal tissue.
• The first bacterial colonists to adhere to a surface
initially do so by inducing weak, reversible bonds
called van der Waals forces.
• If the colonists are not immediately separated from
the surface, they can anchor themselves more
permanently using cell adhesion molecules,
proteins on their surfaces that bind other cells in a
process called cell adhesion.

8. • These bacterial pioneers facilitate the
arrival of other pathogens by providing
more diverse adhesion sites.
• They also begin to build the matrix that
holds the biofilm together.
• If there are species that are unable to
attach to a surface on their own, they
are often able to anchor themselves to
the matrix or directly to earlier
colonists.

9. • During colonization, things start to get interesting.
• Multiple studies have shown that during the time a
biofilm is being created, the pathogens inside it can
communicate with each other thanks to a
phenomenon called quorum sensing (fig. 1).
• Although the mechanisms behind quorum sensing
are not fully understood, the phenomenon allows a
single-celled bacterium to perceive how many other
bacteria are in close proximity.
• If a bacterium can sense that it is surrounded by a
dense population of other pathogens, it is more
inclined to join them and contribute to the
formation of a biofilm.

11. • Bacteria that engage in quorum sensing
communicate their presence by emitting
chemical messages that their fellow infectious
agents are able to recognize.
• When the messages grow strong enough, the
bacteria respond en masse, behaving as a group.
• Quorum sensing can occur within a single
bacterial species as well as between diverse
species, and can regulate a host of different
processes, essentially serving as a simple
communication network.
• A variety of different molecules can be used as
signals.

14. • Biofilms cause sanitary and industrial nuisances.
• Besides the positive ecological roles assumed by
sessile microbial communities, biofilms that
form in industrial and medical settings, in
particular on indwelling medical devices, are
difficult to eradicate and are therefore
associated with both health and economic
issues.
• During the last decade, their negative impact on
human activities has stimulated research aimed
at providing clues to fight detrimental biofilms

15. • A study just published in the International Journal of
Food Microbiology examined the survival rates of free-
floating cells of salmonella enterica Tennessee versus
those in biofilm form when stored in dry milk powder
for up to 30 days.
• In such a dry environment, pathogens cease to
reproduce, but adhere to surfaces and produce a biofilm
that protects them from a harsh environment when
placed in such a dry environment. Experts disagree over
whether pathogens prompted to produce biofilms in this
way are more or less likely to survive passage into the
human intestine and thus more likely to cause illness.

16. • "Biofilms are becoming an increasing
problem within the food industry due to their
ability to adhere to surfaces and withstand
current sanitation practices," the paper states.
• Low moisture foods
• At various points during the study, the
Salmonella was tested in a simulated
gastrointestinal system. It survived this long-term
storage in large numbers but the biofilm
Salmonella proved more resilient than the free-
floating cells.

17. • The researchers from US institute Virginia Tech also
said the bacteria's stress response to the dry
conditions made it more likely to cause disease. And
they added that biofilms allowed the Salmonella to
survive the harsh, acidic environment of the gut,
increasing its chances of reaching the intestines.
• Outbreaks of Salmonella associated with dried foods
such as nuts, cereals, spices, spices, powdered milk
and pet foods have been associated with more than
900 illnesses in the past five years, the scientists
claimed. These foods were previously thought to be
safe, because their dry nature would protect them
from microbial growth.