0:00 Introduction
0:13 LPS
0:26 Objectives
0:42 About LPS
1:03 Founder of LPS
1:08 Toxins
1:52 Role in Bacteria
2:32 Structure
2:42 Sugar
3:52 Lipid
4:24 in Immune system
4:45 Usage
5:17 Conclusion

Lipopolysaccharides | LPS | Endotoxin | Bacterial toxin | Inflammation | Basic Science Series

Lipopolysaccharides (LPS), also known as lipoglycans and endotoxins. They are called lipoglycans because they are consist of a lipid and a polysaccharide component. They are called endotoxin because they are present in the bacterial cell wall (endo) and are extremely very toxic to the human body.

• The toxic activity of bacterial LPS was first discovered and termed "endotoxin" by Richard Friedrich Johannes Pfeiffer. Who distinguished between exotoxins and endotoxin. The exotoxin is the toxin that is released by bacteria into the surrounding environment, and endotoxins, which he considered to be a toxin kept "within" the bacterial cell and released only after the destruction of the bacterial cell wall. Subsequent work showed that the release of LPS from gram-negative microbes does not necessarily require the destruction of the bacterial cell wall, but rather, LPS is secreted as part of the normal physiological activity of membrane vesicle trafficking in the form of bacterial outer membrane vesicles (OMVs).

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• LPS is the major component of the outer membrane of Gram-negative bacteria, contributing greatly to the structural integrity of the bacteria.

• LPS protects the membrane from certain kinds of chemical attacks. LPS also increases the negative charge of the cell membrane and helps stabilize the overall membrane structure.

• LPS induces a strong response from normal animal immune systems. It has also been implicated in non-pathogenic aspects of bacterial ecology, including surface adhesion, bacteriophage sensitivity, and interactions with predators such as amoebae.

• Now let us discuss the structure of LPS. LPS is composed of two major parts, one is sugar and another is a lipid.

• Sugar part is a repetitive glycan polymer contained within an LPS is referred to as the O antigen, O polysaccharide, or O side-chain of the bacteria. The composition of the O chain varies from strain to strain. For example, there are over 160 different O antigen structures produced by different E. coli strains.

• The presence or absence of O chains determines whether the LPS is considered rough or smooth. Full-length O-chains would render the LPS smooth, whereas the absence or reduction of O-chains would make the LPS rough.

• Bacteria with rough LPS usually have more penetrable cell membranes to hydrophobic antibiotics, since a rough LPS is more hydrophobic. In smooth LPS, O antigen is exposed on the very outer surface of the bacterial cell, and, as a consequence, is a target for recognition by host antibodies.

• The Core domain always contains an oligosaccharide component that attaches directly to lipid A and commonly contains sugars such as heptose and 3-Deoxy-D-manno-oct-2-ulosonic acid (also known as KDO, keto-deoxyoctulosonate).

• LPS acts as the prototypical endotoxin because it binds the CD14/TLR4/MD2 receptor complex in many cell types, but especially in monocytes, dendritic cells, macrophages, and B cells, which promotes the secretion of pro-inflammatory cytokines.

• Being of crucial importance to Gram-negative bacteria, these molecules make candidate targets for new antimicrobial agents.


• The molecular mimicry of some LPS molecules is thought to cause autoimmune-based host responses. Molecular mimicry is defined as the theoretical possibility that sequence similarities between foreign and self-peptides are sufficient to result in the cross-activation of autoreactive immune cells by pathogen-derived molecules.

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