The structure of biofilms are dependent on the environment in which they exist and nutrient availability. The collection of microorganisms within a biofilm are all embedded in an extracellular matrix with water channels. 

Structure of Biofilms

Quorum sensing is how different cell species in biofilms can communicate with one another, specifically about cell density. This is an essential response to environmental stimuli facilitated by autoinducers. 

Quorum Sensing

Biofilms are prevalent inside of human bodies and on many of the devices we use. While few biofilms are helpful for example in our intestinal and respiratory tracts, many can be harmful to our health.

Applications of Biofilms to Human Health

Biofilms form complex three-dimensional shapes, such as cones and mushrooms, which contain channels for fluid movement. Researchers can observe and track the water currents flowing through these biofilm structures by recording video of the movement of fluorescently coated beads.

Tracking Water Currents in Biofilms

The formation of a biofilm progresses through five key stages: first, the initial attachment of planktonic cells to a surface; second, irreversible attachment and colonization; third, maturation through microbial growth and the enlargement of cell clumps; fourth, continued maturation with the production of extrapolymeric substances (EPS) and fusion of clumps; and finally, the dispersal of cells from the mature biofilm to colonize new areas.

Biofilm Formation

Biofilms are complex, surface-attached colonies of microbes that form in layered communities. Living within a biofilm provides microbes with significant survival advantages in nature, as the structure retains water to prevent desiccation and offers protection against predation. Furthermore, biofilms hinder the effectiveness of antibiotics and disinfectants, making these microbial communities particularly challenging to eradicate in clinical settings.

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Microbial growth is indicated by the increase in number of cells by division of parent cells into daughter cells. 

Microbial Growth

A glycocalyx is a carbohydrate-rich sugar coat that forms an additional envelope structure exterior to the cell wall in some prokaryotic cells. This layer allows cells to adhere to surfaces, which is a critical step in the formation of layered microbial colonies known as biofilms. There are two primary types of glycocalyces: highly organized capsules and loosely attached slime layers.

Glycocalyx

https://openstax.org/details/books/microbiology/

Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

OpenStax Microbiology Textbook

Asexual reproduction is a method of reproduction in which a single parent cell gives rise to daughter cells, without the use of new genetic material. It is the only way prokaryotes can reproduce/divide. 

Asexual Reproduction

Also known as doubling time, generation time for bacteria is measured as the time it takes for the population to double in number. 

Generation Time

When microbes are introduced to a new environment, they follow a typical growth pattern, which consists of four phases:
1) Lag Phase
2) Log Phase
3) Stationary Phase
4) Death Phase

Growth Curve 

There are many different methods for measuring microbial growth. Each method falls into one of two categories:
- Direct 
- Indirect

Methods for Measuring Microbial Growth

Biofilms

The maximum growth of a microbial population is dependent upon its specific ideal physical and chemical conditions.

Growth Conditions

In order to maintain a healthy environment, we needed to develop ways to control microbial growth and reduce the microbial count to safe levels for public health. "Safe levels" depends on the type of environment you are in. A medical setting will require much lower microbial counts than inside our homes, and therefore require higher levels of decontamination

Controlling Microbial Growth

The glycocalyx and slime layer help bacteria to adhere to external surfaces or other bacteria to produce colonies. These structures prevent phagocytosis and desiccation (the capsule retains water). 

Functions of Glycocalyx & the Slime Layer

A capsule is a specific type of glycocalyx characterized as an organized layer located immediately outside of the bacterial cell wall. It is typically composed of polysaccharides or proteins. By forming a distinct, clear boundary around the cell, capsules help protect the microbe and facilitate its adherence to surfaces.

Capsule

A slime layer is a type of glycocalyx characterized as a loosely organized layer that is weakly attached to the exterior of the cell wall, making it relatively easy to wash off. Structurally, slime layers can be composed of polysaccharides, glycoproteins, or glycolipids, and they assist in cellular adherence.

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