The applicaions of nano biofilms

1. Nano biofilms: An emerging
biotechnology application
Authors: Kimia Kazemi, Yasmin Ghahramani,
Masoomeh Yari Kalashgrani

2. Abstract
• Biofilm, a cooperating community of microorganisms, consists of microbial cells
attached to the surface. This kind of lifestyle protects microorganisms from
environmental threats, prepares higher nutrients for them, and facilitates genetic
exchange. However, more sterilant and antibiotics are needed for killing
microorganisms in biofilm compared to floating ones.
• There are various standard methods for detecting biofilms' structure, including
Confocal Scanning Laser Microscopy and Atomic Force Microscopy. Some
conditions, including hydrodynamics, nutrient availability, surface and interface
properties, and content of microbes, will build the biofilm’s structure.
• Biofilm formation phases include initiation, maturation, maintenance, and
dissolution. Biofilms contain extracellular polymeric substances, which cause more
mechanical stability, water retention, and nutrient sorption. They may have benefits
in the industry, medicine, etc. Some biofilms consist of cellulose bacteria producing
bacterial nanocellulose, making the biofilm retain moisture and trap carbon dioxide.
These cellulose bacteria can be generated through two methods; static method vs.
agitated method.
• This review gathered data about biofilm formation, its advantages and
disadvantages for microorganisms and environments, and their applications in
various areas. In the end, we explain the applications we think they may have.

3. Introduction
• The word biofilm defined by Bill Costerton is the
prevailing microbial lifestyle and can exist in any system
with microorganisms. More than 99% of microorganisms
on the earth can live together by forming a biofilm. There
was a slow progression in medical microbiology made by
biofilm theory, while the direct observation of causative
bacteria in recalcitrant chronic infections showed they
grow in biofilms.
• Protection of bacteria in lakes and stream from amoeba is
through the mechanisms which protect them from
phagocytosis in animal systems. Biofilm is a complicated
structure that consists of various microorganisms and a
mostly extracellular polymeric substances (EPS) matrix all
around it, letting biofilm attach to inert or organic surfaces.
• Several surface factors are associated with the initial
bacterial passion, such as charge, hydrophobicity, and
roughness resulting from organic molecules such as
proteins adsorption on the surface.

4. Benefits of biofilm formation for
microorganisms
• Biofilm formation has some benefits for microorganisms that are explained in
detail in this section. These benefits include access to a flowing system that bring
a higher concentration of diffusible nutrients close to a surface, producing micro
niches through metabolic activities, better genetic exchange and protection from
the host’s immune system and toxicants by the presence of glycocalyx matrix,
restrict transferring to a hostile environment.
• Also, the microorganisms become more resistant to disinfectants in the biofilm’s
structure. The concentrations of sterilant and antibiotics used to kill
biofilm bacteria are 1000-1500 times more than concentrations needed for killing
floating cells of the same species.
• Also, biofilm formation causes 65-80% of all infections. Table 1 shows the list of
ecological benefits of the growth way of biofilms.

5. Table 1. Ecological benefits of the biofilm
Function Relevance
Adhesion to surfaces Primary biofilms and microcolonies
Prerequisite for further biofilm development
Aggregation of cells, formation
of flocs and biofilms
Immobilization of cells
High cell density is possible
EPS as a structural element of
biofilms
Mechanical stability
Development of micro consortia
Matrix for exchange of signalling molecules
Light transmission into biofilm depth
Protective barrier Tolerance against biocides, metals, toxins
Protection of exoenzymes by complexation
Protection against some predator species
Sorption properties Accumulation of nutrients
Water retention, protection against desiccation
Accumulation of pollutants in sludge

6. Disadvantages of biofilm formation for
microorganisms
• The compositions of biofilms will compete for nutrients and terminal electron acceptors.
Also, if many biomass microscopic predators exist in the biofilm area, it will be easy to
break down biofilm.
How can biofilms affect the environment and humans negatively?
• If biofilms form on the food processing equipment, the quality of the equipment will be
decreased. Also, fouling of ship hulls, heat exchangers, and pipelines caused by biofilms
reduces heat transfers and increases fluid frictional and corrosion.
• Some pathogens make biofilm on the surface that causes harm to humans and
environments, such as Yersinia enterocolitica, Listeria monocytogenes, Escherichia coli
O157:H7, and Campylobacter jejuni.

7. • This biofilm formation is harmful in medical and dentistry, which leads
to health problems.
• In industrial systems, when biofouling occurs, the problem begins. Fish
farming will be harmed by biofouling because it will be removed costly,
and even when removed from the cages and nets, it can cause
equipment failure and be harmful to fish health
How does the biofilm form?
The figure shows the development model of biofilms includes initiation,
maturation, maintenance, and dissolution that requires intercellular
signalling and has a profile of gene transcription that varies from floating
bacteria.
• First, the bacteria get close to the surface then make a
transient association with a surface which allows looking for a place
to settle down. Then the bacteria will choose a neighbourhood to
live in. At last, the three-dimensional biofilm will appear.
• Nowadays, confocal scanning laser microscopes (CSLM) are used for
studying biofilm structure and function [29]. This method visualizes
complete-hydrated samples and reveals the three dimensional structure
of biofilms in detail.
• The biofilm's essential structural component is a microcolony, a
separated community of bacterial cells surrounded by a matrix that
may consist of one or more species.

8. Architecture
of a typical
biofilm

9. • Biofilms consist of Bacterial nanocellulose that can survive against other organisms when the
resources are limited. This nanocellulose has advantages for biofilm. For example, they can retain
moisture, trap carbon dioxide produced during the tricarboxylic acid cycle, provide floating bacterial
cells, protect against UV radiation, severe chemical environment, and anaerobic environment.
• Although bacterial nanocellulose has a variety of applications in different industries, it has high-cost
production and a lack of durability, specifically in a humid environment that limits the use of this
multifunctional material.

10. Extracellular polymeric substances (EPS)
• EPS are a combination of biological polymers, producing mechanical stability and scaffolds that
benefit biofilm cells, including synergistic micro consortia establishment, water retention, and
enhancement of nutrient absorption, protection against antimicrobials, viruses, and disinfectants.
• A variety of biopolymers such as proteins, polysaccharides, and nucleic acids can affect these
functions. The origination of these biopolymers is different community members and
specific organisms that can produce them in particular times or conditions.
• Biofilm formation, persistence, and physiochemical behaviour in clinical, industrial,
and environmental conditions depend on EPS.

11. Nanocellulosic
structures in
biofilms
• One of the extracellular polymeric substances is
bacterial cellulose (BC) which has high water
retention and superior mechanical strength to other
natural hydrogels.
• BC can be used as an implant with no fibrotic tissue
formation due to its biocompatibility. This kind of
biocompatibility lets these nano cellulosic structures
used for artificial skin products, wound dressing,
surface patterned implants, and blood vessels.
• These nano cellulosic structures also can be used
as bio nanocomposites as they are the most
renewable polymers in the world.

12. Biofilm
applications
that benefit
the
environment
and humans
• The technology of cleaning the environmental
pollutants up using microorganisms is called
bioremediation. It is better to manipulate
biological processes to treat toxic effluents
because they benefit economically. Using biofilm
for bioremediation is safer and more proficient
than planktonic microorganisms because of their
better chance of survival and adaptation via their
matrix.
• Among all of the organisms existing in the
environment, the one which secrets polymers
and forms biofilms on the surface of hydrocarbons
is suitable for treating recalcitrant or slow-
degrading compounds since they have high
microbial biomass and also they can immobilize
compounds via bioaccumulation, biosorption, and
biomineralization.

13. Medical
applications
of biofilms
• Preparation of cellulosic biofilm using
Acetobacter xylinum can be used as a temporary skin
substitute, for example, skin grafts, in human second-
and third-degree skin burns, infectious thermolysis, face
peeling, tattoo abrasions, trophic venous and chronic
ulcers, and Hansenian legs.
• The tubular BNC hydrogels can be substituted as blood
vessels in regenerative medicine instead of vessels that
have been removed from the legs or the chest for the
bypass.
• These tubular BNCs can also replace bile ducts, ureter,
and oesophagus in conditions like cancer and complex
surgical interventions on these organs because they can
act as free cells. Still, in vivo, they can act as cell
colonies temporary implants.

14. Conclusion
• Biofilm is a manner of life in microorganisms, protects them from environmental
threats such as amoeba that exists in lakes and streams and phagocytosis in animal
systems. Extracellular substances are parts of biofilm and play a vital role in the
biofilm attached to the surfaces.
• Biofilm forming lets the microorganisms access high sources of nutrients, promote
their genetic exchange, and have high-level protection against the host’s immune
system. Because of this reason, there is a need for more concentration of sterilants
and antibiotics to eradicate the biofilm. The development of biofilms consists of
four steps, including initiation, maturation, maintenance, and dissolution using
intercellular signalling.
• Several factors affect the biofilm structure, for example, surface and interface
properties, nutrient enrichment, the composition of the microbial community, and
hydrodynamics. Some biofilms consist of bacterial nanocellulose that can retain
moisture, trap the produced carbon dioxide, provide floating bacteria, protect
against UV and severe chemical environments.
• Also, the extracellular polymeric substances may consist of celluloses that have
high water retention and high mechanical strength. These celluloses
are biocompatible and let used for artificial skin products, wound dressing, surface
patterned implants and blood vessels.