Name: sulfur cycling through microbial reactions
Uploaded: 2026-03-12T13:57:43.000Z
Duration: 1 min 29 s
Channel: JoVE

Le soufre inorganique circule dans l’environnement sous forme de sulfate, soufre élémentaire et sulfure.Les volcans et les sources hydrothermales émettent des gaz soufrés comme le sulfure d’hydrogène, contribuant de manière vitale au cycle du soufre.Par exemple, dans des environnements anoxiques riches en organique près des sources hydrothermales, les bactéries réductrices de sulfate convertissent principalement le sulfate en sulfure d’hydrogène.Ce gaz, toxique pour la plupart des formes de vie, est transformé par divers micro-organismes en sulfate ou soufre élémentaire moins nocif.Dans des conditions riches en oxygène, des bactéries oxydantes de soufre comme Thiobacillus convertissent le sulfure d’hydrogène en soufre ou sulfate, formant parfois de l’acide sulfurique et abaissant le pH local.En revanche, les bactéries soufrées vertes et violettes transforment le sulfure en granules de soufre, que Thiomargarita et des microbes similaires oxydent davantage en sulfate.Le soufre élémentaire peut être réduit en sulfure par des bactéries anaérobies spécialisées et des archées.En plus des transformations inorganiques, les algues marines forment du diméthylsulfure, un composé sulfureux organique volatil, qui est transformé dans l’atmosphère en aérosols favorisant la formation des nuages et aidant à réguler le climat terrestre.

microbes et cycle du soufre

Microbes and the Sulfur Cycle

Le soufre est un élément vital dans les systèmes biogéochimiques de la Terre. Il transite par divers états inorganiques, notamment le sulfate (SO₄²⁻), le soufre élémentaire (S⁰) et le sulfure (S²⁻). Les mécanismes abiotiques et biologiques à travers les environnements oxique et anoxiques médiatisent de manière complexe ces transformations. Le sulfate, la forme de soufre la plus oxydée, est principalement stocké dans les roches, les sédiments marins et les eaux océaniques, agissant comme un réservoir à long terme dans le cycle mondial du soufre.Dans les milieux oxyques, des bactéries chimio-autotrophes telles que Thiobacillus spp. catalysent l’oxydation des composés soufrés réduits. Le sulfure (H₂S), dérivé de la dégazation volcanique ou des émissions hydrothermales, est oxydé biologiquement en soufre élémentaire et en sulfate. Inversement, dans des conditions anoxiques, les bactéries réductrices de sulfate (SRB) comme Desulfovibrio spp. réalisent une réduction dissimilatrice du sulfate. Ce processus anaérobie réduit le sulfate en sulfure via le sulfite (SO₃²⁻) comme intermédiaire clé, souvent couplé à l’oxydation du carbone organique.Les phototrophes anoxygénés, y compris les bactéries soufrées vertes et violettes, oxydent le sulfure en granules de soufre intracellulaires. Ces granules sont ensuite oxydés en sulfate par de grandes bactéries chimiotrophes telles que Thiomargarita spp., qui contribuent à l’acidification en libérant des protons lors de l’oxydation. Dans les écosystèmes de sources hydrothermales, les chimioautotrophes oxydant le soufre exploitent l’énergie du sulfure pour fixer le dioxyde de carbone, soutenant ainsi des communautés microbiennes et fauniques complexes dans les habitats marins profonds.Le phytoplancton marin libère du diméthylsulfoniopropionate (DMSP) pour réguler la pression osmotique. Le clivage bactérien du DMSP produit le diméthylsulfure (DMS), un composé volatil qui pénètre dans l’atmosphère. La photooxydation du DMS produit des aérosols sulfates, qui influencent la condensation des nuages et le dépôt de soufre atmosphérique sur les écosystèmes terrestres. En fin de compte, les plantes et les microbes assimilent et réduisent ce sulfate tout en synthétisant des acides aminés contenant du soufre tels que la cystéine et la méthionine, complétant ainsi le cycle.

Microbes et cycle du soufre

Sulfur is a vital element in Earth's biogeochemical systems. It transitions through various inorganic states, including sulfate (SO&#8324;&#178;&#8315;), ...

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Education

Enseignement

JoVE Core

Microbiology

Microbiologie

Unit

Unité

Microbial Ecology

Écologie microbienne

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

sulfur cycling through microbial reactions

Sulfur cycling depends on microbial reactions that move sulfur through rocks, water, soil, and the air. In Earth systems, sulfur shifts among inorganic forms such as sulfate, elemental sulfur, and sulfide. These changes happen through both abiotic processes and biological activity in oxic and anoxic environments.

Sulfate is the most oxidized form of sulfur. It is stored mainly in rocks, marine sediments, and ocean water, where it acts as a long-term reservoir in the global sulfur cycle. In oxygen-rich settings, chemolithoautotrophic bacteria such as Thiobacillus spp. oxidize reduced sulfur compounds.

Sulfide, often present as H2S, can come from volcanic outgassing or hydrothermal emissions. Microbes can oxidize this sulfide into elemental sulfur and then into sulfate. In oxygen-free environments, sulfate-reducing bacteria such as Desulfovibrio spp. carry out dissimilatory sulfate reduction, which converts sulfate to sulfide through sulfite as an intermediate and is often linked to organic carbon oxidation.

Some microbes use sulfur in light-filled but low-oxygen habitats. Green and purple sulfur bacteria, which are anoxygenic phototrophs, oxidize sulfide and store the sulfur as intracellular granules. Large chemolithotrophic bacteria such as Thiomargarita spp. can then oxidize these granules further to sulfate. This process releases protons and can make the surrounding environment more acidic.

Sulfur cycling also powers life at hydrothermal vents. There, sulfur-oxidizing chemoautotrophs use energy from sulfide to fix carbon dioxide. Their activity supports complex microbial and animal communities in deep-sea ecosystems.

Sulfur also moves through the atmosphere. Marine phytoplankton release dimethylsulfoniopropionate, or DMSP, to help control osmotic pressure. Bacteria break DMSP down into dimethylsulfide, or DMS, a volatile gas that enters the atmosphere. Sunlight then photooxidizes DMS into sulfate aerosols, which affect cloud formation and sulfur deposition on land. Plants and microbes take up this sulfate and reduce it while making sulfur-containing amino acids such as cysteine and methionine, completing the cycle.

Sulfur Cycling Through Microbial Reactions

sulfur-cycling-through-microbial-reactions

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key terms and concepts

Explore how microbes move sulfur through sulfate, sulfide, and sulfur granules in oxic, anoxic, and marine environments across the sulfur cycle.

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microbiology

Sulfur Cycling Through Microbial Reactions

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