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

يدور الكبريت غير العضوي في البيئة على شكل كبريتات، كبريت عنصري، وكبريتيد.تطلق البراكين والفتحات الحرارية المائية غازات الكبريت مثل كبريتيد الهيدروجين، مما يساهم بشكل حيوي في دورة الكبريت.على سبيل المثال، في البيئات الخالية من الأكسجين والغنية بالمواد العضوية بالقرب من الفتحات الحرارية المائية، تقوم البكتيريا المخفضة للكبريتات بتحويل الكبريتات بشكل رئيسي إلى كبريتيد الهيدروجين.هذا الغاز، السام لمعظم الكائنات الحية، يتحول بواسطة كائنات دقيقة مختلفة إلى كبريتات أقل ضررا أو كبريت عنصري.في الظروف الغنية بالأكسجين، تقوم البكتيريا المؤكسدة للكبريت مثل ثيوباسيلوس بتحويل كبريتيد الهيدروجين إلى كبريت أو كبريتات، وأحيانا مكونة حمض الكبريتيك وخفض الرقم الهيدروجيني المحلي.من ناحية أخرى، تقوم بكتيريا الكبريت الخضراء والبنفسجية بتحويل الكبريتيد إلى حبيبات كبريتية، والتي تقوم ثيومارجريتا والميكروبات المشابهة بأكسدتها إلى كبريتات.يمكن تحويل الكبريت العنصري إلى الكبريتيد مرة أخرى بواسطة البكتيريا اللاهوائية المتخصصة والعتائق.بالإضافة إلى التحولات غير العضوية، تشكل الطحالب البحرية ثنائي ميثيل كبريتيد، وهو مركب عضوي متطاير من الكبريت، يتحول في الغلاف الجوي إلى رذاذ يعزز تكوين السحب ويساعد في تنظيم مناخ الأرض.

الميكروبات ودورة الكبريت

Microbes and the Sulfur Cycle

الكبريت عنصر حيوي في الأنظمة البيوجيوكيميائية للأرض. ينتقل عبر حالات غير عضوية مختلفة، بما في ذلك الكبريتات (SO₄²⁻)، والكبريت العنصري (S⁰)، والكبريتيد (S²⁻). الآليات اللاحيوية والبيولوجية عبر البيئات المؤكسدة والخالية من الأكسجين تتوسط هذه التحولات بشكل معقد. الكبريتات، وهو أكثر أشكال الكبريت أكسدة، يخزن بشكل رئيسي في الصخور والرواسب البحرية والمياه المحيطية، ويعمل كخزان طويل الأمد في دورة الكبريت العالمية.في البيئات المؤكسدة، تقوم البكتيريا الكيميائية الذاتية التغذية مثل ثيوباسيلوس spp. بتحفيز أكسدة مركبات الكبريت المختزلة. الكبريتيد (H₂S)، الناتج من انبعاثات الغازات البركانية أو الانبعاثات الحرارية المائية، يتأكسد بيولوجيا إلى الكبريت والكبريتات العنصريين. وعلى العكس، في حالات نقص الأكسجين، تقوم بكتيريا تقليل الكبريتات (SRB) مثل أنواع Desulfovibrio بتقليل الكبريتات بشكل متشابك. تقوم هذه العملية اللاهوائية بتحويل الكبريتات إلى كبريتيد عبر الكبريتيت (SO₃²⁻) كوسيط رئيسي، وغالبا ما يقترن بأكسدة الكربون العضوي.تؤكسد الكبريتات الضوئية عديمة الأكسجين، بما في ذلك بكتيريا الكبريت الأخضر والبنفسجي، إلى حبيبات كبريت داخل الخلية. يتم تأكسد هذه الحبيبات إلى كبريتات بواسطة بكتيريا كيميائية ضخمة مثل ثيومارغاريتا إسب.، والتي تساهم في الحموضة عن طريق إطلاق البروتونات أثناء الأكسدة. في الأنظمة البيئية للفتحات الحرارية المائية، تستفيد الكائنات الكيميائية المؤكسدة للكبريت من الطاقة من الكبريتيد لتثبيت ثاني أكسيد الكربون، داعمة المجتمعات الدقيقة الميكروبية والحيوانات في المواطن البحارية العميقة.تفرز العوالق النباتية البحرية ثنائي ميثيل سلفونيوبروبيونات (DMSP) لتنظيم الضغط الأسموزي. ينتج الانقسام البكتيري ل DMSP ثنائي ميثيل كبريتيد (DMS)، وهو مركب متطاير يدخل الغلاف الجوي. ينتج الأكسدة الضوئية لDMS رذاذات كبريتية، تؤثر على تكثف السحب وترسيب الكبريت الجوي على النظم البيئية الأرضية. في النهاية، تقوم النباتات والميكروبات باستيعاب وتقليل هذا الكبريتات أثناء تصنيع الأحماض الأمينية التي تحتوي على الكبريت مثل السيستين والميثيونين، مما يكمل الدورة.

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

JoVE Core

Microbiology

علم الأحياء الدقيقة

Unit

وحدة

Microbial Ecology

علم البيئة الميكروبية

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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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