Biofilms in Ecology and Medicine

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Questions and Answers

What is the primary reason antibiotics often fail when treating biofilm-related infections on medical devices?

Biofilms enhance the immune response.

Biofilms prevent molecular signaling among cells.

Antibiotics do not reach the biofilm effectively. (correct)

Microbial cells are dormant in biofilms.

What is quorum sensing in the context of microbial communication?

A method for bacteria to physically connect.

The automatic division of bacterial cells at high density.

Density-dependent communication using molecular signals. (correct)

A process that requires bacterial cells to be in close proximity.

Which of the following processes is triggered when the concentration of a peptide becomes sufficiently high in Streptococcus pneumoniae?

Production of antibiotics.

Bacterial cell division.

Release of virulence factors.

Transformation to a competent state. (correct)

What effect do competent cells have on noncompetent cells in a biofilm of Streptococcus pneumoniae?

They kill noncompetent cells and release their DNA. Signup and view all the answers

How does Vibrio fischeri manage its luminescence?

By producing a diffusible molecule called autoinducer. Signup and view all the answers

What is a primary concern regarding biofilms on medical devices?

Biofilms can lead to serious illness and device failure. Signup and view all the answers

What main component makes up the slimy matrix of a mature biofilm?

Extracellular polymeric substances Signup and view all the answers

How do microbes within a biofilm interact with one another?

Waste from one microbe may serve as energy for another. Signup and view all the answers

What is one protective feature that biofilms provide to microbes?

Protection against harmful agents like UV light Signup and view all the answers

What happens to the metabolic activity of microbes in different locations within a biofilm?

There is considerable heterogeneity in metabolic activity. Signup and view all the answers

What are extracellular polymeric substances (EPS) primarily composed of?

Polymers including polysaccharides and proteins Signup and view all the answers

How do biofilms contribute to the genetic exchange among microorganisms?

By allowing uptake of DNA present in the extracellular polymeric substances Signup and view all the answers

Where can biofilms commonly be found in natural settings?

On rocks and other surfaces in aquatic environments Signup and view all the answers

Study Notes

Biofilms

Ecologists first noticed the prevalence of microbes in biofilms in aquatic environments in the 1940s.
Biofilms are slimy, encased communities of microbes found ubiquitously in nature.
They cause corrosion on boat hulls.
They pose a significant risk on medical devices like implants and catheters, often causing infections.
Biofilms can also impede wound healing.
Biofilm formation begins with microbes attaching to surfaces conditioned by proteins and molecules present in the environment.
Microbes create a slimy matrix of polymers, called extracellular polymeric substances (EPS) or extracellular matrix (ECM), which includes polysaccharides, proteins, glycoproteins, glycolipids, and DNA.
EPS allows the microbes to adhere stably to the surface, and additional polymers are secreted as the biofilm matures and thickens.
Mature biofilms are dynamic communities of microorganisms with varying metabolic activity and the presence of persister cells.
Biofilm microbes interact in several ways, including utilizing waste products as energy sources and communicating through molecules.
DNA in the EPS can be taken up by members of the community, enabling gene transfer between cells and species.

Biofilm Protection

Biofilms protect microbes from harmful agents like UV light and antibiotics.
This protection is attributed to both the EPS and physiological changes within the biofilm.
Biofilms on medical devices can resist antibiotic treatment, leading to systemic infections.

Quorum Sensing

Quorum sensing is a density-dependent cell-to-cell communication mechanism in microbes.
It was first observed in the Gram-positive bacterium Streptococcus pneumoniae.
S. pneumoniae cells release a small protein, which accumulates as the population grows.
High concentrations of the protein trigger some cells to become "competent"—able to take up DNA, a process called transformation.
Competent cells then release a chemical called bacteriocin, which destroys non-competent cells in the population.
The lysis of non-competent cells releases DNA that can be taken up by competent cells.
Lysed cells also release virulence factors that enable competent cells to infect tissues, causing diseases like pneumonia and meningitis.

Vibrio fischeri

The marine luminescent bacterium Vibrio fischeri lives within the light organs of certain fish and squid.
V. fischeri regulates its luminescence through the production of a diffusible molecule called autoinducer, which is an N-acylhomoserine lactone (AHL).
Many Gram-negative bacteria produce AHL-derived signal molecules.
These signal molecules activate the expression of specific genes, regulating diverse functions.
AHLs are known to regulate diverse functions in bacteria, including bioluminescence, biofilm formation, and virulence.

Inter-species Quorum Sensing

Quorum sensing can also occur between different species of bacteria, enabling them to coordinate their activities within a microbial community.
The ability of different species of microbes to communicate through quorum sensing helps create a complex, interwoven network of interactions within biofilms.
It is also linked to the ability of some bacteria to disrupt the normal functioning of the host, causing disease.
This complex interplay between bacteria, driven by quorum sensing, highlights the need for new therapeutic strategies that target the communication systems of biofilms.

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Description

Explore the fascinating world of biofilms, their formation, and their implications in both natural ecosystems and medical settings. Understand how these microbial communities pose risks in various environments, including their role in corrosion and infection on medical devices. Join us to delve deeper into the structural and functional aspects of biofilms and their impact on health and ecology.