Microbial ‘phosphorus gatekeeping’ found at center of study exploring 700,000 years of iconic coastline

(Press-News.org) A new study has dug deep into the past of the coastal dunes of an iconic Queensland location in a bid to better understand how microscopic processes in the soil support some of the most biodiverse landscapes on Earth.

Published in Nature Geoscience, the team of researchers from Griffith University, University of Sydney and Stockholm University investigated a sequence of coastal dunes of different ages (from 0-700,000 years old) in Cooloola National Park near Rainbow Beach to understand how soil microorganisms coped with severely declining levels of nutrients such as phosphorus in soil as the dunes got older.

Phosphorus is an element that is essential for all living things. It plays a crucial role in various physiological processes, including energy metabolism, cell membrane formation, and photosynthesis.

“We know a lot about the traits plants use to cope with phosphorus deficiency but have little knowledge about how soil microbes cope with it,” said Professor Charles Warren, senior author from the University of Sydney.

“This knowledge gap has constrained our ability to understand how phosphorus-limited ecosystems work.”

Fellow co-lead author Dr Orpheus Butler from Griffith’s Australian Rivers Institute said the team found that microbes – such as fungi and bacteria – had really strong physiological strategies to deal with low phosphorus levels.

These strategies include the swapping out of membrane phospholipids with non-phosphorous lipids, and accumulation of various types of microbial fats.

“Our study highlights that soil microbes use sophisticated strategies to deal with phosphorus scarcity, and that these strategies significantly shape how ecosystems function and evolve over long timescales,” he said.

“Microbes almost act as ‘phosphorus gatekeepers’ in the soil.

"The plants and the microbes are kind of competing for the phosphorus but there is reciprocity involved.

"Microbes do need the plants to grow, because if there are no plants there is no carbon for the microbes to eat. So, it's competition and facilitation at the same time.”

Professor Warren said the results of this study were important because it revealed the general strategies enabling microbes to survive and thrive in extremely phosphorus-poor soils.

“We used a naturally phosphorus-poor native ecosystem to uncover the traits that allow microbes to thrive on P poor soils, but the findings are equally relevant to managed agricultural systems that often P limited,” he said.

“The important next steps are to apply our knowledge of microbes to improving productivity of phosphorus-limited ecosystems.”

Dr Butler said low-fertility soils supported some of the most biodiverse landscapes on Earth, such as tropical rainforests and mediterranean-climate shrublands, so these results offered some important conservation and biodiversity insights into this microscopic process.

“A lot of ecosystems worldwide are what we call phosphorus limited, which means that phosphorus is the nutrient that's constraining the growth of the system more than any other nutrient,” he said.

"This is often the case in old landscapes such as our study site in Cooloola National Park, because soil phosphorus declines over time due to weathering of minerals.

“Australia is a really strong example of that; many Australian soils are really depleted of phosphorus. So, we think of phosphorus as being the master nutrient that controls many things. But in these old ecosystems, a lot of the phosphorus in the soil ends up being soaked up by the microorganisms.

“But by finding ways to use their phosphorus more efficiently, the microbes free up a huge amount of phosphorus for the plants to take up.

“So, these findings have widened our understanding of terrestrial ecosystems by highlighting a strong but overlooked interplay going on beneath the surface between microorganisms and the long-term trajectory of ecosystem development.”

The study ‘Microbial physiology conserves phosphorus across long-term ecosystem development’ has been published in Nature Geoscience.

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