Name: sulfur-using bacteria that harvest light
Uploaded: 2025-06-12T09:22:25.000Z
Duration: 1 min 28 s
Channel: JoVE

I batteri fototrofi anossigenici che non generano ossigeno come prodotto della fotosintesi includono lo zolfo viola, il non zolfo viola, lo zolfo verde e i batteri verdi non solforati.I batteri dello zolfo viola appartengono a diversi generi della classe Gammaproteobacteria, tra cui Chromatium. Si trovano prevalentemente nei laghi meromitici ricchi di zolfo e in genere hanno granuli di zolfo nelle cellule.Al contrario, i batteri viola non solforati, classificati in alfa e betaproteobatteri, prosperano in ambienti a basso contenuto di zolfo. Un genere chiave è Rhodomicrobium.Entrambi i gruppi di batteri viola hanno sistemi di membrana fotosintetica intracellulare lamellare e contengono batterioclorofilla a o b.I batteri solforati verdi appartengono al phylum Chlorobi. Contengono batterioclorofilla c, d o e, alloggiata nei clorosomi, come si vede nella specie rappresentativa Chlorobaculum tepidum. Prosperano in ambienti ricchi di zolfo e di acque profonde.I batteri verdi non solforati sono classificati nel phylum Chloroflexi. La maggior parte delle specie, tra cui Chloroflexus aurantiacus, sono filamentose e contengono batterioclorofille a o c per la fotosintesi.

batteri fototrofi

Anoxygenic Phototrophic Bacteria

I batteri fototrofi anossigenici costituiscono un gruppo eterogeneo di microrganismi che eseguono la fotosintesi senza produrre ossigeno. Comprendono principalmente i batteri purpurei sulfurei, i batteri purpurei non sulfurei, i batteri verdi sulfurei e i batteri verdi non sulfurei. Questi batteri sono classificati all&#8217;interno delle linee filogenetiche dei Gammaproteobacteria, Alphaproteobacteria, Betaproteobacteria, Chlorobi e Chloroflexi, ognuna con adattamenti fisiologici ed ecologici distinti.
I batteri purpurei sulfurei appartengono ai Gammaproteobacteria e prosperano in ambienti anossici ricchi di zolfo, come laghi meromittici, sedimenti marini e paludi salmastre. Utilizzano l&#8217;acido solfidrico (H_2S) come donatore di elettroni per la fotosintesi, producendo inizialmente zolfo elementare (S_0), che viene accumulato all&#8217;interno delle cellule, e successivamente ossidato a solfato (SO_4^2-). I generi rappresentativi includono Chromatium e Thiocapsa. Questi batteri contengono batterioclorofilla a o b, e utilizzano un fotosistema di tipo Q per la cattura della luce.
I batteri purpurei non sulfurei, appartenenti agli Alphaproteobacteria e Betaproteobacteria, sono metabolicamente versatili e si sviluppano in ambienti con basse concentrazioni di H_2S. Agiscono generalmente come fotoeterotrofi, utilizzando la luce come fonte di energia e i composti organici come fonte di carbonio, ma alcune specie possono crescere come fotoautotrofi utilizzando H_2, bassi livelli di H_2S o Fe^2+. Possiedono anch&#8217;essi fotosistemi di tipo Q e contengono batterioclorofilla a o b. I generi degni di nota includono i Rhodobacter e i Rhodospirillum.
I batteri verdi sulfurei, classificati nei Chlorobi, sono fototrofi rigorosamente anaerobi e non mobili che utilizzano H_2S come donatore di elettroni. A differenza dei purpurei sulfurei, accumulano S_0 all&#8217;esterno delle cellule e si affidano al ciclo dell&#8217;acido citrico inverso per la fissazione della CO_2. Contengono batterioclorofilla c, d o e, racchiusa nei clorosomi&#8212;strutture uniche per la raccolta della luce. Il Chlorobaculum tepidum &#232; una specie ben studiata che prospera in ambienti solfidrici con scarsa luminosit&#224;.
I batteri verdi non sulfurei, o fototrofi anossigenici filamentosi, appartengono ai Chloroflexi. Crescono principalmente come fotoeterotrofi, ma possono anche eseguire la fotosintesi autotrofa utilizzando H_2 o H_2S. Il loro sistema fotosintetico &#232; un ibrido tra quelli dei batteri purpurei e quelli verdi sulfurei, contenente sia un fotosistema di tipo Q sia clorosomi. Il Chloroflexus aurantiacus &#232; una specie rappresentativa, comunemente trovata nelle sorgenti termali. Il genere affine Thermomicrobium, non fototrofo, &#232; un termofilo con insoliti lipidi di membrana.
Gli eliobatteri sono batteri fototrofi anossigenici Gram-positivi appartenenti al phylum Firmicutes. Possiedono un fotosistema di tipo FeS e producono in modo unico batterioclorofilla g. Crescono come fotoeterotrofi, utilizzando composti organici come piruvato, lattato, acetato o butirrato. Il gruppo comprende cinque generi: Heliobacterium, Heliophilum, Heliorestis, Heliomonas e Heliobacillus. Le cellule sono a forma di bastoncello o filamentose, con Heliophilum che forma fasci mobili.
Un altro gruppo distinto di fototrofi anossigenici &#232; rappresentato dal Chloracidobacterium thermophilum, appartenente al phylum Acidobacteria. Questo batterio termofilo &#232; stato scoperto in tappeti microbici delle sorgenti termali. Condivide alcune caratteristiche con i batteri verdi sulfurei, come la produzione di batterioclorofilla a e c nei clorosomi e l&#8217;uso di un fotosistema di tipo FeS. Tuttavia, a differenza dei batteri verdi sulfurei, C. thermophilum &#232; tollerante all&#8217;ossigeno e pu&#242; crescere in condizioni aerobiche. &#200; un fotoeterotrofo che utilizza acidi grassi a catena corta come fonte di carbonio, ma &#232; privo di capacit&#224; autotrofe.
Questi batteri svolgono ruoli essenziali nei cicli globali dello zolfo e del carbonio, prosperando in nicchie ecologiche caratterizzate da basse concentrazioni di ossigeno e alta disponibilit&#224; di zolfo.

Batteri Fototrofi

I batteri fototrofi anossigenici costituiscono un gruppo eterogeneo di microrganismi che eseguono la fotosintesi senza produrre ossigeno. Comprendono ...

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sulfur-using bacteria that harvest light

Anoxygenic phototrophic bacteria are light-harvesting bacteria that do not release oxygen during photosynthesis. They include purple sulfur bacteria, purple nonsulfur bacteria, green sulfur bacteria, green nonsulfur bacteria, heliobacteria, and Chloracidobacterium thermophilum. These groups belong to the Gammaproteobacteria, Alphaproteobacteria, Betaproteobacteria, Chlorobi, Chloroflexi, Firmicutes, and Acidobacteria lineages, and each group has its own habitat and way of using light.

Purple sulfur bacteria live in sulfur-rich, oxygen-free settings such as meromictic lakes, marine sediments, and salt marshes. They use hydrogen sulfide as an electron donor for photosynthesis. They first make elemental sulfur, store it inside the cell, and later oxidize it to sulfate. Common examples include Chromatium and Thiocapsa, and these bacteria contain bacteriochlorophyll a or b and use a Q-type photosystem.

Purple nonsulfur bacteria belong to the Alphaproteobacteria and Betaproteobacteria and are more flexible in how they live. They usually act as photoheterotrophs, which means they use light for energy and organic compounds for carbon. Some species can also grow photoautotrophically with hydrogen, low levels of hydrogen sulfide, or iron(II). Rhodobacter and Rhodospirillum are well-known genera, and these bacteria also contain bacteriochlorophyll a or b and Q-type photosystems.

Green sulfur bacteria are strict anaerobes, which means they grow only without oxygen, and they do not move. They use hydrogen sulfide as an electron donor, but unlike purple sulfur bacteria, they store elemental sulfur outside the cell. They fix carbon dioxide through the reverse citric acid cycle. Their light-harvesting structures are chlorosomes, and they contain bacteriochlorophyll c, d, or e. Chlorobaculum tepidum is a well-studied species that can live in sulfidic places with very little light.

Green nonsulfur bacteria, also called filamentous anoxygenic phototrophs, belong to Chloroflexi. They are mainly photoheterotrophs, but they can also do photoautotrophy with hydrogen or hydrogen sulfide. Their photosynthetic system combines features seen in purple and green sulfur bacteria. They have a Q-type photosystem and chlorosomes, and Chloroflexus aurantiacus is a common example from hot springs. Thermomicrobium is a related nonphototrophic genus with unusual membrane lipids.

Heliobacteria are gram-positive anoxygenic phototrophs in the phylum Firmicutes. They use an FeS-type photosystem and make bacteriochlorophyll g, which makes them different from the purple and green groups. They grow photoheterotrophically and use organic compounds such as pyruvate, lactate, acetate, or butyrate. The group includes Heliobacterium, Heliophilum, Heliorestis, Heliomonas, and Heliobacillus. These cells may be rod-shaped or filamentous, and Heliophilum can form motile bundles.

Chloracidobacterium thermophilum is another anoxygenic phototroph from the phylum Acidobacteria. It was discovered in microbial mats of thermal springs. It shares features with green sulfur bacteria because it makes bacteriochlorophyll a and c in chlorosomes and uses an FeS-type photosystem. However, it can tolerate oxygen and can grow aerobically. It is a photoheterotroph that uses short-chain fatty acids as a carbon source, but it does not have autotrophic growth. Together, these bacteria help drive sulfur and carbon cycling in low-oxygen, sulfur-rich environments.

Sulfur-Using Bacteria That Harvest Light

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anoxygenic phototrophic bacteria

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diversity of archaea iv

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diversity of protists i

Excavata Protists and Their Adaptations

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diversity of protists ii

Alveolates: Ciliates, Dinoflagellates, Apicomplexans

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diversity of protists iii

Rhizaria: Pseudopods, Tests, and Skeletons

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diversity of protists iv

Amoebozoa: Movement and Life Cycles

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key terms and concepts

Explore how anoxygenic phototrophic bacteria use light without making oxygen, from purple and green sulfur bacteria to heliobacteria and thermal spring species.

Sulfur-Using Bacteria That Harvest Light | 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

Sulfur-Using Bacteria That Harvest Light

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