Endotoxin Causes Damage to the Host - Online Tutor, Practice Problems & Exam Prep

Endotoxin, specifically lipopolysaccharide (LPS), is a crucial component of the outer membrane of gram-negative bacteria, with lipid A being its toxic part. When gram-negative bacteria are lysed, lipid A can enter the bloodstream, potentially causing septic shock, characterized by fever, low red blood cell count, and life-threatening cytokine storms. These storms lead to rapid blood vessel dilation, significantly lowering blood pressure and affecting vital organs like the heart and kidneys, which can result in death if not managed promptly.

Endotoxin

In this video, we're going to begin our lesson on endotoxin and how endotoxin causes damage to the host. And so endotoxin is actually the specific molecule lipopolysaccharide or LPS for short. And so endotoxin or lipopolysaccharide refer to the same exact specific molecule. And recall that this endotoxin or lipopolysaccharide, LPS, is actually found in the outer membrane of gram-negative cells.

Now, also recall that the lipopolysaccharide or LPS contains the molecule lipid A. And so lipid A is actually going to be the toxic component of the LPS that can actually trigger an inflammatory response and trigger other responses as well. And so lipid A can actually be released by these gram-negative bacterial cells during bacterial cell or bacterial cell lysis.

And so if we take a look at our image down below, what you'll notice is over here on the left-hand side, we're peptidoglycan, but surrounding their thin layer of peptidoglycan, but surrounding their thin layer of peptidoglycan, surrounding their thin cell wall, they have this outer membrane. And in the outer membrane of gram-negative cells is the endotoxin molecule, the lipopolysaccharide or the LPS.

And so if we zoom in to this endotoxin or lipopolysaccharide, what you'll notice is that it has this O-antigen region, which is going to be a polysaccharide. Then it has a core polysaccharide region, which remains relatively consistent. The O-antigen region tends to change across different strains of gram-negative, different species of gram-negative.

And then, at the very bottom, what you'll see is this molecule here which is going to be the lipid A region of the endotoxin or of the lipopolysaccharide and this region right here is specifically the toxic component that can cause the damaging effects to the host.

And so we'll get to talk a little bit more about endotoxin and its damaging effects as we move forward in our course, but for now this is our brief introduction to endotoxin and how it causes damage and we'll be able to learn more as we move forward. So I'll see you all in our next video.

Lipid A Causes Septic Shock

In this video, we're going to talk about how lipid A can cause septic shock. Recall from some of our previous lesson videos that lipid A is the toxic portion of endotoxin or lipopolysaccharide. Recall that the endotoxin or lipopolysaccharide is found in the outer membrane of gram-negative bacteria. Now if these gram-negative bacteria are lysed or ruptured, then that could cause the release of the lipid A molecule. If lipid A is released and infects the bloodstream, it could initiate a culmination of systematic responses referred to as septic shock. Septic shock can include symptoms such as fever, anemia, or low red blood cell count, weakness, diarrhea, and inflammation. Lipid A can also cause life-threatening cytokine storms, which, recall, is just a massive release of cytokines or chemicals used for communication signals during immune responses. By causing this cytokine storm, it could result in the rapid dilation of the blood vessels or rapid enlargement of the blood vessels, and that can significantly decrease blood pressure. Septic shock can have physiological effects on the heart, the vascular system, and other body organs as well. Ultimately, since septic shock is life-threatening, it could potentially lead to death.

If we take a look at our image down below, notice on the left-hand side we're showing a person with lungs infected with some kind of gram-negative bacteria. Notice that if the gram-negative bacteria enter the bloodstream, then, when these gram-negative bacteria are lysed or rupture, they could release lipid A into the bloodstream. If the infection enters into the bloodstream, it could potentially move to other organs as well. Organs such as the brain, kidneys, liver, and heart are all examples of organs that could be infected. This could lead to, once again, septic shock. Severe physiological effects on these different organs mean that in many cases, patients are not able to recover and could lead to death.

This concludes our brief lesson on how lipid A causes septic shock and how that can be life-threatening. We will be able to get some practice applying these concepts as we move forward and learn more. I'll see you all in our next video.

What part of lipopolysaccharide (LPS) is the dangerous portion of the endotoxin during bacterial infections?

• A. O-antigen.
• B. Lipid-A.
• C. Core Polysaccharide.
• D. The entire lipopolysaccharide molecule.

What type of bacteria create endotoxins?

• A. Gram-negative.
• B. Gram-positive.
• C. Both gram-negative & positive.
• D. Endotoxins are only produced by protozoa.

Lipid A is the toxic component of LPS. When pathogenic bacteria release Lipid A into the bloodstream the infected individual may experience septic shock. Lipid A represents _______.  

• A. A focal infection.
• B. An exotoxin.
• C. A systemic infection.
• D. An endotoxin.
• E. A and B.
• F. C and D.

An endotoxin:

• A. Is an AB toxin.
• B. Is created by gram-positive bacteria.
• C. Is heat stable and will not denature.
• D. Triggers T cells to release cytokines.

Here’s what students ask on this topic:

What is endotoxin and where is it found?

Endotoxin, specifically known as lipopolysaccharide (LPS), is a molecule found in the outer membrane of gram-negative bacteria. The LPS molecule consists of three main parts: the O antigen, the core polysaccharide, and lipid A. Lipid A is the toxic component responsible for triggering inflammatory responses in the host. When gram-negative bacteria undergo lysis, lipid A can be released into the bloodstream, leading to various harmful effects, including septic shock.

How does lipid A cause septic shock?

Lipid A, the toxic portion of lipopolysaccharide (LPS), can cause septic shock when released into the bloodstream. This release typically occurs when gram-negative bacteria are lysed. Once in the bloodstream, lipid A triggers a series of systemic responses, including fever, anemia, weakness, diarrhea, and inflammation. It can also cause life-threatening cytokine storms, which involve a massive release of cytokines, leading to rapid blood vessel dilation and a significant drop in blood pressure. These effects can impact vital organs such as the heart, kidneys, liver, and brain, potentially leading to death if not managed promptly.

What are the components of lipopolysaccharide (LPS)?

Lipopolysaccharide (LPS) is composed of three main regions: the O antigen, the core polysaccharide, and lipid A. The O antigen is a polysaccharide that varies among different strains of gram-negative bacteria. The core polysaccharide is relatively consistent across different species. Lipid A is the toxic component of LPS and is responsible for triggering inflammatory responses and other damaging effects in the host.

What are the physiological effects of septic shock caused by lipid A?

Septic shock caused by lipid A can have several physiological effects on the body. These include fever, anemia (low red blood cell count), weakness, diarrhea, and inflammation. A significant concern is the occurrence of cytokine storms, which involve a massive release of cytokines, leading to rapid dilation of blood vessels and a significant drop in blood pressure. This can affect vital organs such as the heart, kidneys, liver, and brain, potentially leading to organ failure and death if not treated promptly.

How does the structure of lipopolysaccharide (LPS) contribute to its function?

The structure of lipopolysaccharide (LPS) is crucial to its function. LPS consists of the O antigen, core polysaccharide, and lipid A. The O antigen varies among different bacterial strains, helping the bacteria evade the host's immune system. The core polysaccharide provides structural stability. Lipid A, the toxic component, is embedded in the outer membrane of gram-negative bacteria and is released upon bacterial lysis. This release triggers inflammatory responses and can lead to septic shock, demonstrating the importance of LPS's structure in its pathogenic role.