Presentation Information
[P02-240]Widespread Distribution and Diversity of Chemolithoautotrophic Phosphite-Oxidizing Microorganisms across Aquatic Environments
○Takafumi Yamanaka1, Thi Thuy Linh Cao1, Akio Kuroda1, Ryuichi Hirota1 (1. Hiroshima University, Graduate School of Integrated Sciences for Life (Japan))
Keywords:
dissimilatory phosphite oxidation,aquatic environments,metagenome-assembled genomes,phosphorus redox cycle,chemolithoautotrophy
[Purpose] Phosphite (HPO32−) is a reduced phosphorus compound that can serve as a potential electron donor in the phosphorus redox cycle. Although phosphite occurs at only nanomolar concentrations in natural environments and its formation is thermodynamically unfavorable, it is utilized by dissimilatory phosphite-oxidizing microorganisms (DPOM). These microorganisms oxidize phosphite via the ptx-ptd gene cluster and fix CO2 as their sole carbon source, supporting chemolithoautotrophic growth. However, despite being identified in diverse environments, the distribution and ecological roles of DPOM remain poorly understood. In this study, we investigated the distribution, diversity, and metabolic potential of DPOM across aquatic environments in Japan.
[Method] We collected 116 environmental samples from 28 locations, including marine, brackish, and freshwater environments, and established anaerobic enrichment cultures using phosphite as the sole electron donor to selectively enrich phosphite-oxidizing microorganisms. Phosphite oxidation activity was monitored to identify positive enrichments. Shotgun metagenomic sequencing was performed on active cultures, followed by genome reconstruction to assess phylogenetic diversity and metabolic potential of DPOM.
[Results and Discussion] DPOM were detected in 35 samples from 16 sites across marine, brackish, and freshwater environments without clear geographic or environmental constraints, indicating widespread distribution. Metagenomic analysis recovered 13 high-quality metagenome-assembled genomes (MAGs) with >95% completeness and <4% contamination, including four completely circularized genomes. All recovered DPOM were affiliated with bacterial lineages. Phylogenomic analysis showed that these MAGs represent novel species within Desulfotignum and novel species—and potentially novel genera—within UBA1062 (class Desulfomonilia). Marine DPOM were affiliated with Desulfotignum, whereas euryhaline DPOM within UBA1062 were distributed across a broad salinity range, indicating ecological differentiation. The ptx-ptd gene cluster was highly conserved (>95% identity) across lineages. Distinct carbon fixation pathways were identified, with the Wood-Ljungdahl pathway in marine DPOM and the reductive glycine pathway in euryhaline DPOM, suggesting metabolic differentiation. The widespread occurrence of DPOM despite low phosphite concentrations suggests cryptic phosphorus redox cycling or localized niches of phosphite turnover. The high conservation of the ptx-ptd gene cluster suggests strong functional constraints and/or horizontal gene transfer. These results indicate that phosphite oxidation is a widespread metabolic strategy.
[Conclusion] DPOM are widely distributed in aquatic environments and represent an underappreciated component of the global phosphorus cycle. These findings suggest that phosphite oxidation contributes to microbial energy metabolism and may shape microbial biogeography across aquatic environments.
[Method] We collected 116 environmental samples from 28 locations, including marine, brackish, and freshwater environments, and established anaerobic enrichment cultures using phosphite as the sole electron donor to selectively enrich phosphite-oxidizing microorganisms. Phosphite oxidation activity was monitored to identify positive enrichments. Shotgun metagenomic sequencing was performed on active cultures, followed by genome reconstruction to assess phylogenetic diversity and metabolic potential of DPOM.
[Results and Discussion] DPOM were detected in 35 samples from 16 sites across marine, brackish, and freshwater environments without clear geographic or environmental constraints, indicating widespread distribution. Metagenomic analysis recovered 13 high-quality metagenome-assembled genomes (MAGs) with >95% completeness and <4% contamination, including four completely circularized genomes. All recovered DPOM were affiliated with bacterial lineages. Phylogenomic analysis showed that these MAGs represent novel species within Desulfotignum and novel species—and potentially novel genera—within UBA1062 (class Desulfomonilia). Marine DPOM were affiliated with Desulfotignum, whereas euryhaline DPOM within UBA1062 were distributed across a broad salinity range, indicating ecological differentiation. The ptx-ptd gene cluster was highly conserved (>95% identity) across lineages. Distinct carbon fixation pathways were identified, with the Wood-Ljungdahl pathway in marine DPOM and the reductive glycine pathway in euryhaline DPOM, suggesting metabolic differentiation. The widespread occurrence of DPOM despite low phosphite concentrations suggests cryptic phosphorus redox cycling or localized niches of phosphite turnover. The high conservation of the ptx-ptd gene cluster suggests strong functional constraints and/or horizontal gene transfer. These results indicate that phosphite oxidation is a widespread metabolic strategy.
[Conclusion] DPOM are widely distributed in aquatic environments and represent an underappreciated component of the global phosphorus cycle. These findings suggest that phosphite oxidation contributes to microbial energy metabolism and may shape microbial biogeography across aquatic environments.
Comment
To browse or post comments, you must log in.Log in