Aerobic Anoxygenic Phototrophy in Microbial Ecosystems

Aerobic anoxygenic phototrophy describes a mode of light‐driven energy conservation in which bacteria harvest photons via bacteriochlorophyll‐containing reaction centres without splitting water or evolving oxygen. Operating under fully oxic conditions, these photoheterotrophs supplement heterotrophic metabolism with photonic energy, enhancing survival and growth in nutrient‐limited environments. They are polyphyletic, spanning several proteobacterial clades and more recently recognised phyla such as Gemmatimonadota and Myxococcota. In marine and freshwater euphotic zones, aerobic anoxygenic phototrophs (AAPs) can account for a substantial fraction of total bacterioplankton biomass, accelerating carbon turnover and influencing trophic interactions. Recent advances in genomics, metatranscriptomics and neural‐network‐driven community analyses have unveiled fine‐scale taxonomic diversity, diel regulatory rhythms and the ecological drivers shaping their distribution. By linking phototrophic capability to nutrient cycling, stress resilience and global biogeochemical fluxes, research on AAPs illuminates a key functional niche at the interface of light‐driven and organic‐matter‐driven metabolism, with implications for ecosystem modelling and novel biotechnological applications.

Research from Nature Portfolio

One study uncovered unexpected photosynthesis gene clusters encoding type II reaction centres in uncultivated Myxococcota lineages, revealing that predatory bacteria may possess a chimeric lifestyle combining heterotrophy and light‐driven energy conservation. Metatranscriptomic data confirmed active expression of these clusters across diverse environments, and heterologous expression experiments demonstrated functional pigment biosynthesis capable of driving photochemical reactions. This work broadens the recognised phylogenetic scope of aerobic anoxygenic phototrophy and suggests an evolutionary legacy of vertical inheritance with multiple losses in related lineages.

An untargeted cultivation approach yielded novel members of the Gemmatimonadota phylum, providing axenic cultures for detailed genomic and cell‐biological analyses. Although the focus was on cell‐division mechanisms, genomic surveys of these isolates confirmed the presence of complete photosynthesis gene clusters, consistent with aerobic anoxygenic phototrophic potential previously inferred in this phylum. By establishing robust cultivation protocols, this work paves the way for functional characterisation of light‐driven metabolism in understudied bacterial groups.

Aerobic Anoxygenic Phototrophy in Microbial Ecosystems publication trend

The graph below shows the total number of articles in aerobic anoxygenic phototrophy in microbial ecosystems across all publications each year (not limited to Nature Index journals).

Technical terms

Aerobic anoxygenic phototrophy (AAP): Light‐driven energy conservation in bacteria under aerobic conditions without oxygen evolution.

Reaction centre type II: Membrane‐embedded protein complex using bacteriochlorophyll to convert light into electron flow in anoxygenic phototrophs.

Photoheterotrophy: Metabolic strategy combining phototrophic energy capture with organic carbon assimilation.

Bacteriochlorophyll a: Photosynthetic pigment enabling absorption of near‐infrared light in many AAPs.

Photosynthesis gene cluster (PGC): Genomic region encoding the enzymes and complexes required for bacteriochlorophyll synthesis and assembly of reaction centres.

Metatranscriptomics: Study of community‐wide gene expression to assess active metabolic processes in environmental samples.

References

1. Globally distributed Myxococcota with photosynthesis gene clusters illuminate the origin and evolution of a potentially chimeric lifestyle. Nature Communications (2023).
2. Diurnal cycles drive rhythmic physiology and promote survival in facultative phototrophic bacteria. ISME Communications (2023).
3. Ecology of aerobic anoxygenic phototrophs on a fine-scale taxonomic resolution in Adriatic Sea unravelled by unsupervised neural network. Environmental Microbiome (2024).
4. An untargeted cultivation approach revealed Pseudogemmatithrix spongiicola gen. nov., sp. nov., and sheds light on the gemmatimonadotal mode of cell division: binary fission. Scientific Reports (2024).
5. Gemmatimonas groenlandica sp. nov. Is an Aerobic Anoxygenic Phototroph in the Phylum Gemmatimonadetes. Frontiers in Microbiology (2021).