Name: spirochete shape, motion, and disease
Uploaded: 2025-06-12T09:21:19.000Z
Duration: 1 min 30 s
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Les spirochètes sont des bactéries à Gram négatif enroulées classées dans l’embranchement des spirochètes. Les endoflagelles des spirochètes produisent un mouvement semblable à celui d’un tire-bouchon, permettant de se déplacer à travers des matériaux ou des tissus visqueux. Le genre Spirochaeta comprend des spirochètes anaérobies et aérobies facultatives qui vivent librement dans l’eau douce, les sédiments et les océans. Les espèces notables incluent Spirochaeta plicatilis des environnements sulfidiques d’eau douce et marins. Cristispira est un genre de spirochètes que l’on trouve dans le style cristallin de nombreux mollusques bivalves comme les palourdes, les moules et les huîtres. Le genre Treponema comprend les spirochètes anaérobies ou microaérophiles qui sont des commensaux ou des agents pathogènes des humains et des animaux, tels que Treponema denticola, commun dans la cavité buccale humaine. De nombreuses espèces du genre Borrelia sont pathogènes. Borrelia burgdorferi, par exemple, provoque la maladie de Lyme, qui est transmise par les tiques. Les genres Leptospira et Leptonema sont des spirochètes strictement aérobies qui oxydent les acides gras à longue chaîne, comme l’acide oléique, des tissus de leur hôte ou de l’environnement pour favoriser leur croissance. Leptospira interrogans est un parasite chez l’homme et provoque la leptospirose.

phylum bactérien spirochètes

Bacterial Phylum Spirochaetes

Les spiroch&#232;tes, appartenant au phylum des Spirochaetes, sont des bact&#233;ries uniques &#224; Gram n&#233;gatif, mobiles, finement spiral&#233;es, allong&#233;es et flexibles. Elles vivent dans les s&#233;diments aquatiques et chez les animaux, certaines &#233;tant responsables de maladies comme la syphilis. Les spiroch&#232;tes sont r&#233;partis en huit genres selon leur habitat, leur pathog&#233;nicit&#233;, leur phylog&#233;nie et leurs caract&#233;ristiques morphologiques.
Leur motilit&#233; caract&#233;ristique provient de flagelles internes appel&#233;s endoflagelles, situ&#233;s dans l&#8217;espace p&#233;riplasmique. Ces endoflagelles sont ancr&#233;s aux p&#244;les cellulaires et s&#8217;&#233;tendent le long de la cellule, entour&#233;s par une gaine externe flexible. Lorsqu&#8217;ils tournent, ils g&#233;n&#232;rent une torsion qui provoque un mouvement ondulatoire de la cellule, facilitant sa progression en forme de tire-bouchon &#224; travers des substances visqueuses ou les tissus.
Les spiroch&#232;tes sont souvent confondus avec les spirilles, cellules h&#233;lico&#239;dales munies de flagelles polaires. Contrairement aux spiroch&#232;tes, les spirilles ne poss&#232;dent ni gaine externe, ni endoflagelle, ni mouvement en tire-bouchon. Les spirilles sont plus rigides et plus larges, tandis que les spiroch&#232;tes sont plus fins (environ 0,5 &#956;m) et hautement flexibles.
Le genre Spirochaeta comprend des spiroch&#232;tes libres, ana&#233;robies ou a&#233;robies facultatifs, pr&#233;sents dans les eaux douces, les s&#233;diments et les milieux marins. Spirochaeta plicatilis vit dans les habitats dul&#231;aquicoles et marins sulfid&#233;s, avec des faisceaux d&#8217;endoflagelles entourant son cylindre protoplasmique spiral&#233;. Spirochaeta stenostrepta, ana&#233;robie strict vivant dans les boues riches en H_2S, fermente les sucres en &#233;thanol, ac&#233;tate, lactate, CO_2 et H_2.
Le genre Cristispira, unique au style cristallin des mollusques comme les palourdes et les hu&#238;tres, contribuerait &#224; la digestion dans leur tractus digestif. Trouv&#233;es chez des mollusques marins et d&#8217;eau douce, les Cristispira n&#8217;ont pas encore &#233;t&#233; cultiv&#233;es, et leur adaptation sp&#233;cifique &#224; cet habitat reste mal comprise.
Les spiroch&#232;tes ana&#233;robies ou microa&#233;rophiles du genre Treponema sont des commensaux ou des pathog&#232;nes des humains et des animaux. Treponema pallidum, agent de la syphilis, est particuli&#232;rement mince (0,2 &#956;m) avec une morphologie ondul&#233;e. Il est g&#233;n&#233;ralement d&#233;tect&#233; par microscopie en champ sombre dans les l&#233;sions syphilitiques.
D&#8217;autres esp&#232;ces comprennent T. denticola, pr&#233;sent dans la cavit&#233; buccale humaine et associ&#233; aux maladies parodontales. Il fermente les acides amin&#233;s en ac&#233;tate, CO_2, NH_3 et H_2S. T. saccharophilum vit dans le rumen des ruminants, o&#249; il fermente les polysaccharides v&#233;g&#233;taux, tandis que T. primitia et T. azotonutricium colonisent les intestins de termites, participant &#224; la fermentation de la cellulose, &#224; l&#8217;ac&#233;togen&#232;se et &#224; la fixation de l&#8217;azote.
Le genre Borrelia regroupe des pathog&#232;nes comme Borrelia burgdorferi, agent de la maladie de Lyme, transmis par les tiques. B. burgdorferi est unique par son chromosome lin&#233;aire. D&#8217;autres esp&#232;ces de Borrelia infectent les animaux d&#8217;&#233;levage et les oiseaux, &#233;galement transmises par les tiques.
Les genres Leptospira et Leptonema comprennent des spiroch&#232;tes strictement a&#233;robies qui oxydent des acides gras &#224; longue cha&#238;ne, tels que l&#8217;acide ol&#233;ique, pour leur croissance. Les esp&#232;ces de Leptospira sont fines, finement spiral&#233;es et souvent recourb&#233;es &#224; chaque extr&#233;mit&#233;. Ce groupe comprend des esp&#232;ces libres (L. biflexa) et parasitaires (L. interrogans).
Les souches de L. interrogans infectent humains et animaux, les rongeurs &#233;tant les principaux h&#244;tes, bien que les chiens et les porcs puissent &#233;galement &#234;tre porteurs. Chez l&#8217;humain, la leptospirose est l&#8217;affection la plus courante caus&#233;e par Leptospira, pouvant entra&#238;ner des l&#233;sions r&#233;nales et h&#233;patiques, une n&#233;phrite, une jaunisse, voire une insuffisance r&#233;nale ou la mort. La bact&#233;rie p&#233;n&#232;tre dans l&#8217;organisme par les muqueuses ou des plaies cutan&#233;es lors de contacts avec des animaux infect&#233;s. Les animaux domestiques, notamment les chiens, sont vaccin&#233;s contre la leptospirose dans le cadre du vaccin combin&#233; contre la maladie de Carr&#233;, la leptospirose et l&#8217;h&#233;patite.

Phylum bactérien Spirochètes

Les spiroch&#232;tes, appartenant au phylum des Spirochaetes, sont des bact&#233;ries uniques &#224; Gram n&#233;gatif, mobiles, finement spiral&#233;es, ...

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spirochete shape, motion, and disease

Spirochetes are a group of gram-negative bacteria with a thin, flexible, tightly coiled shape. They live in aquatic sediments and in animals. Some species are harmless, while others cause diseases such as syphilis and Lyme disease.

A key feature of spirochetes is their movement. They use endoflagella, which are flagella located inside the periplasm, the space under the outer layer of the cell. These endoflagella attach at the cell poles and run along the length of the bacterium inside a flexible outer sheath. When they rotate, they twist the cell into a corkscrew-like motion that helps it move through thick liquids and tissues.

Spirochetes are often confused with spirilla. Spirilla are helical or rod-shaped cells with polar flagella, but they lack an outer sheath and endoflagella. They are also more rigid and larger. Spirochetes are much thinner, about 0.5 micrometers wide, and they bend easily.

Scientists divide spirochetes into eight genera based on habitat, pathogenicity, phylogeny, and other traits. The genus Spirochaeta includes free-living species that can live without oxygen or with little oxygen. These bacteria are found in freshwater, sediments, and oceans. Spirochaeta plicatilis lives in sulfidic freshwater and marine habitats, and its endoflagella form bundles around the coiled cell. Spirochaeta stenostrepta is an obligate anaerobe in H2S-rich muds. It ferments sugars and produces ethanol, acetate, lactate, CO2, and H2.

Cristispira is another genus. It lives in the crystalline style of mollusks such as clams and oysters and helps with food processing in their digestive tracts. It is found in both freshwater and marine mollusks, but it has not been cultured, so its special adaptation to this habitat is still unclear.

Treponema species are anaerobic or microaerophilic spirochetes that live as commensals or pathogens in humans and animals. Treponema pallidum causes syphilis and is extremely thin, about 0.2 micrometers wide, with a flat, wavy shape. Dark-field microscopy is often used to detect it in syphilitic lesions. Other species include T. denticola in the human mouth, where it is linked to gum disease, T. saccharophilum in the rumen of ruminants, and T. primitia and T. azotonutricium in termite guts, where they help with cellulose fermentation, acetogenesis, and nitrogen fixation.

The genus Borrelia includes important pathogens such as B. burgdorferi, which causes Lyme disease and spreads through tick bites. This species is unusual because it has a linear chromosome. Other Borrelia species cause disease in livestock and birds and are also transmitted by ticks.

Leptospira and Leptonema are strictly aerobic spirochetes that grow by oxidizing long-chain fatty acids such as oleic acid. Leptospira species are thin, finely coiled, and often hooked at both ends. The group includes free-living L. biflexa and parasitic L. interrogans. Rodents are the main hosts for L. interrogans, although dogs and pigs can also carry it. In humans, leptospirosis can damage the kidneys and liver and may cause nephritis, jaundice, renal failure, or death. The bacteria enter through mucous membranes or skin breaks after contact with infected animals. Dogs are vaccinated against leptospirosis with a combined distemper–leptospira–hepatitis vaccine.

Spirochete Shape, Motion, and Disease

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key terms and concepts

Explore spirochete structure, corkscrew motility, and major genera like Treponema, Borrelia, and Leptospira, plus diseases such as syphilis and Lyme disease.

Spirochete Shape, Motion, and Disease | 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

Spirochete Shape, Motion, and Disease

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