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Temperature and Geographic Location Impact the Distribution and Diversity of Photoautotrophic Gene Variants in Alkaline Yellowstone Hot Springs

Summary

Scientists studied bacteria that use sunlight to survive in extremely hot alkaline springs in Yellowstone National Park. They found that the location of the spring matters more than temperature in determining which types of bacteria live there, especially for the heat-loving bacteria called Chloroflexi. The study revealed these bacteria have various genes for capturing energy from light and fixing nitrogen and carbon, making them important players in these extreme environments.

Background

Alkaline hot springs in Yellowstone National Park harbor diverse photoautotrophic bacteria including cyanobacteria and anoxygenic phototrophs like Chloroflexi. Previous research has focused on oxygenic photosynthesis in cyanobacteria, but understanding of anoxygenic phototroph ecophysiology and distribution remains limited due to their taxonomic and metabolic diversity.

Objective

This study examined the distribution of genes involved in phototrophy, carbon fixation, and nitrogen fixation across eight alkaline hot spring sites in Yellowstone National Park near the upper temperature limit of photosynthesis to determine whether temperature or geographic isolation is the primary driver of phototrophic community composition.

Results

Geographic isolation played a larger role than temperature in selecting for distinct phototrophic Chloroflexi based on pufLM gene analysis, while cyanobacterial photosystem genes showed higher richness at 62°C sites. Calvin cycle genes showed site-specific distributions suggesting adaptation to local conditions, while 3-hydroxypropionate bicycle genes were widespread and abundant. Multiple nifH gene sequences were recovered associated with both cyanobacteria and Chloroflexi, including Roseiflexus species lacking complete nitrogenase genes.

Conclusion

Temperature and geographic location both influence photoautotrophic gene distribution in Yellowstone hot springs, with temperature selecting for distinct cyanobacterial groups at >68°C while geographic location selects for phototrophic Chloroflexi. The findings suggest that photoautotrophic bacteria distributions are shaped by a combination of abiotic and biotic factors, and recovered gene sequences contribute to understanding the evolutionary history of photosynthesis and nitrogen fixation.
  • Published in:Microbiology Spectrum,
  • Study Type:Metagenomic Survey,
  • Source: 10.1128/spectrum.01465-21, PMID: 35575591
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