Gram positive gram negative bacteria1/7/2024 Furthermore, LPS can enter the human system through pharmaceutical preparations such as parenteral drug products, which can activate the complement system by the alternative pathway and can result in the death of a patient.Ī weak immune system is another breach in the barrier that leads to the endotoxic effects of LPS during an infection process. Though these products are subject to digestion upon oral intake, it represents a health risk for patients with gastrointestinal disease. Many food products, supplements, and probiotics can pose a health risk as they contain gram-negative bacteria or LPS. LPS is a potent pyrogen for which the immune system mounts an immediate response. However, gut lesions or a diet rich in lipids facilitate transport across the membrane into the systemic circulation. The body has developed compartmentalization to prevent high amounts of LPS from entering the bloodstream. However, it can induce toxicity if it reaches the basal side, which has exposure to the deeper tissues. The LPS does not damage the gut epithelium of the luminal side. LPS can enter the bloodstream through intestinal absorption of the LPS produced by gut bacteria. LPS is a serologically reactive bacterial toxin, and as little as 1 to 2 mg entered intravenously can be lethal. Hence, more pathogenic bacteria have evolved their lipid A moiety to evade host immune attacks. gingivalis, may activate a different signal (such as TLR4 instead of TLR2 and the strictly cylindrical lipid A, as Rhodobacter sphaeroides, tend to be antagonistic to TLRs. Interestingly, canonical Lipid A, such as from non-invading E.coli, are speculated to be agonistic, while less conical lipid A, such as P. It mainly imparts the potential to induce attachment, colonization of the host, and the ability to circumvent host defense mechanisms. Modifications in the O-antigen plausibly play an essential role in the infection process. The size or the composition of the O-antigen can reliably indicate the virulence potential of a bacterial strain. In contrast to lipid A, O-antigens are the most variable part of the LPS molecule that imparts antigenic specificity to the molecule. On the other hand, most gram-negative bacteria show innate resistance to many antimicrobial therapies due to the presence of LPS because it develops a permeability barrier at the cell surface. LPS recognition by the host is crucial for clearing the infections of invading bacterial pathogens. Hence, the overall immune activation and response depend upon the structure of lipid A moiety of LPS. Though lipid A moiety is a very conserved part of the LPS, the structure differs among different strains, species, and subspecies of bacteria. Even when the immune system causes lysis of the bacterial cells, lipid A containing fragments of the membrane released in the circulation cause fever, diarrhea, and in adverse circumstances, lead to septic (endotoxic) shock. Thus, LPS can be used for the early detection of infection since it induces an innate immune response, specifically through Toll-like receptors (TLRs). Of the three components, lipid A is the most bioactive component of LPS and a potent part of the endotoxin response generated by a molecule. In non-capsulated bacterial strains, such as E.coli, Pseudomonas, etc., LPS is exposed to the cell surface, while in the capsulated strains such as Klebsiella pneumonia, Haemophilus influenza, etc., LPS is present below the capsular layer. Contrary to the usual biological membrane, the gram-negative bacterial membrane does not have a phospholipid bilayer but an asymmetric bilayer with LPS on the outside and phospholipid on the inside. The outer membrane is exposed to the outside environment, while the inner membrane envelops the cytoplasm. The gram-negative bacterial cell membrane is composed of an outer membrane and an inner membrane. Besides, LPS is also a recognized biomarker due to its central role in host-pathogen interaction that facilitates the infection process. Due to its unique properties, LPS has gained considerable research focus to understand its complex structure, biogenesis, transport, and assembly. Also, the size and composition of LPS are highly dynamic among bacterial species. More specifically, the O-antigen imparts serological distinction to the bacterial species. Since different types of LPS are present in different genera of gram-negative bacteria, LPS is used for serotyping gram-negative bacteria. Most bacterial LPS molecules are thermostable and generate a robust pro-inflammatory stimulus for the immune system in mammals. Inherent to gram-negative bacteria, LPS provides integrity to the bacterial cell and a mechanism of interaction of the bacteria to other surfaces. The lipid A component varies from one organism to another and is essential in imparting specific pathogenic attributes to the bacteria.
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