Name: lipopolysaccharides and gram-negative defense
Uploaded: 2025-06-12T09:39:09.000Z
Duration: 1 min 19 s
Channel: JoVE

脂多糖（LPS）对革兰氏阴性菌至关重要，可提供结构支持并帮助其逃避免疫系统。 LPS 由脂质A、核心寡糖和O抗原组成。脂质A的生物合成始于细胞质中的尿苷二磷酸N-乙酰葡萄糖胺，其随后发生酶促酰化反应。它形成一个四酰基化中间产物，随着更多脂肪酸的加入，该中间产物会经历一系列修饰反应。进一步的酰化反应生成六酰化的脂质A；随后，糖基转移酶依次将核心寡糖连接到脂质A上。然后，该脂质A-核心复合物通过MsbA转运蛋白被转运穿过内膜。与此同时，O抗原在细胞质中于载体脂质上组装，然后翻转至周质空间。在周质空间中，O抗原单位被聚合并连接到脂质A-核心上，形成完整的脂多糖（LPS）。最后，脂多糖转运系统将脂多糖（LPS）转运通过周质空间并将其整合到外膜中，从而增强细菌的防御能力。

脂多糖的形成

Formation of Lipopolysaccharides

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&#33026;&#36136;A&#20316;&#20026;LPS&#30340;&#27602;&#24615;&#32452;&#20998;&#65292;&#22312;&#32454;&#32990;&#36136;&#20869;&#21512;&#25104;&#65292;&#36215;&#22987;&#24213;&#29289;&#20026;&#23615;&#33527;&#20108;&#30967;&#37240;N-&#20057;&#37232;&#27688;&#22522;&#33889;&#33796;&#31958;&#65288;UDP-GlcNAc&#65289;&#12290;&#37238;&#20419;&#30340;&#37232;&#22522;&#21270;&#21453;&#24212;&#20381;&#27425;&#21521;UDP-GlcNAc&#28155;&#21152;&#33026;&#32938;&#37240;&#65292;&#24418;&#25104;&#22235;&#37232;&#22522;&#33026;&#36136;A&#21069;&#20307;&#12290;&#35813;&#20013;&#38388;&#20307;&#32463;&#21382;&#36827;&#19968;&#27493;&#20462;&#39280;&#65292;&#21253;&#25324;&#39069;&#22806;&#30340;&#37232;&#22522;&#21270;&#65292;&#26368;&#32456;&#29983;&#25104;&#20845;&#37232;&#22522;&#33026;&#36136;A&#12290;&#19968;&#20123;&#32454;&#33740;&#22914;&#27801;&#38376;&#27663;&#33740;&#21644;&#40736;&#30123;&#26438;&#33740;&#65292;&#36890;&#36807;&#28155;&#21152;&#30967;&#37240;&#20057;&#37255;&#33018;&#25110;&#27688;&#22522;&#38463;&#25289;&#20271;&#31958;&#65288;aminoarabinose&#65289;&#36827;&#19968;&#27493;&#20462;&#39280;&#33026;&#36136;A&#65292;&#20174;&#32780;&#22686;&#24378;&#23545;&#25239;&#33740;&#32957;&#30340;&#25269;&#25239;&#21147;&#12290;&#23436;&#20840;&#32452;&#35013;&#30340;&#33026;&#36136;A&#20173;&#38170;&#23450;&#20110;&#20869;&#33180;&#65292;&#31561;&#24453;&#21518;&#32493;&#20462;&#39280;&#12290;
&#26680;&#24515;&#23521;&#31958;&#19982;O&#25239;&#21407;&#30340;&#32452;&#35013;
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LPS&#30340;&#32452;&#35013;&#19982;&#36716;&#36816;
&#33026;&#36136;A&#19982;&#26680;&#24515;&#23521;&#31958;&#36830;&#25509;&#21518;&#65292;MsbA&#32763;&#36716;&#37238;&#23558;&#20004;&#32773;&#20174;&#20869;&#33180;&#36716;&#36816;&#33267;&#33180;&#38388;&#38553;&#12290;&#19982;&#27492;&#21516;&#26102;&#65292;&#32858;&#21512;&#30340;O&#25239;&#21407;&#34987;&#32763;&#36716;&#36827;&#20837;&#21608;&#36136;&#31354;&#38388;&#12290;&#36830;&#25509;&#37238;&#23558;O&#25239;&#21407;&#19982;&#33026;&#36136;A-&#26680;&#24515;&#23521;&#31958;&#22797;&#21512;&#29289;&#36890;&#36807;&#20849;&#20215;&#38190;&#36830;&#25509;&#65292;&#23436;&#25104;LPS&#32467;&#26500;&#12290;
&#25104;&#29087;&#30340;LPS&#38543;&#21518;&#36890;&#36807;Lpt&#65288;&#33026;&#22810;&#31958;&#36716;&#36816;&#65289;&#31995;&#32479;&#36816;&#36755;&#33267;&#22806;&#33180;&#65292;&#35813;&#22810;&#34507;&#30333;&#22797;&#21512;&#20307;&#30830;&#20445;LPS&#30340;&#27491;&#30830;&#23450;&#20301;&#12290;&#27492;&#36716;&#36816;&#36807;&#31243;&#20381;&#36182;ATP&#65292;&#30001;&#20869;&#33180;&#20013;&#30340;LptBFG&#22797;&#21512;&#20307;&#25552;&#20379;&#33021;&#37327;&#12290;LPS&#30340;&#27491;&#30830;&#23450;&#20301;&#22686;&#24378;&#20102;&#22806;&#33180;&#30340;&#31283;&#22266;&#24615;&#65292;&#25552;&#39640;&#32454;&#33740;&#23545;&#25239;&#29983;&#32032;&#12289;&#23487;&#20027;&#20813;&#30123;&#22240;&#23376;&#21450;&#29615;&#22659;&#32961;&#36843;&#30340;&#25269;&#25239;&#21147;&#12290;

Education

教育

JoVE Core

Microbiology

微生物学

Unit

单元

Microbial Metabolism

微生物代谢

KEY TERMS AND CONCEPTS

关键术语与概念

lipopolysaccharides and gram-negative defense

Lipopolysaccharides (LPS) are important parts of the outer membrane of Gram-negative bacteria. They help stabilize the membrane and help protect bacteria from host immune responses. LPS has three main parts: lipid A, a core oligosaccharide, and an O antigen.

LPS biosynthesis and assembly depend on a coordinated set of enzymes and transport steps. The molecule is also known as an endotoxin. It can activate Toll-like receptor 4 (TLR4) in the host and trigger strong immune responses. In severe cases, this response can lead to inflammation and septic shock.

Lipid A is the toxic part of LPS. It is made in the cytoplasm, beginning with uridine diphosphate N-acetylglucosamine, or UDP-GlcNAc. Enzymes add fatty acids in a stepwise acylation process to form a tetra-acylated precursor. Further acylations produce mature hexa-acylated lipid A. Some bacteria, including Salmonella and Yersinia, add phosphoethanolamine or aminoarabinose to lipid A. These changes can increase resistance to antimicrobial peptides. The finished lipid A stays anchored in the inner membrane.

The core oligosaccharide is added next by glycosyltransferases. This core region helps maintain membrane integrity and acts as a scaffold for the O antigen. The O antigen is a repeating sugar chain made separately on the lipid carrier undecaprenyl phosphate. Its length and sugar makeup vary among bacterial species. These differences can affect immune recognition and virulence.

After lipid A is linked to the core oligosaccharide, the MsbA flippase moves both parts across the inner membrane. At the same time, the polymerized O antigen is flipped into the periplasm. A ligase then joins the O antigen to the lipid A-core complex to finish LPS assembly. The mature LPS is carried to the outer membrane by the Lpt transport system, which is a multiprotein complex. The inner-membrane LptBFG complex uses ATP for energy. Proper LPS placement strengthens the outer membrane and increases resistance to antibiotics, host immune factors, and environmental stressors.

Lipopolysaccharides and Gram-Negative Defense

lipopolysaccharides-and-gram-negative-defense

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formation of lipopolysaccharides

Lipopolysaccharides (LPS) are important parts of the outer membrane of Gram-negative bacteria. They help stabilize the membrane and help protect bacteria from host immune responses. LPS has three main parts: lipid A, a core oligosaccharide, and an O antigen. LPS biosynthesis and assembly depend on a coordinated set of enzymes and transport steps. The molecule is also known as an endotoxin. It can activate Toll-like receptor 4 (TLR4) in the host and trigger strong immune responses. In severe...

key terms and concepts

Learn how lipopolysaccharides are built, moved, and attached in Gram-negative bacteria, and how LPS helps protect cells and trigger immune responses.

Lipopolysaccharides and Gram-Negative Defense | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Lipopolysaccharides and Gram-Negative Defense

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