The phycosphere is a microscale mucus region that is rich in organic matter surrounding a phytoplankton cell.
This high nutrient environment creates a microbiome and a diverse food web for microbes such as bacteria and protists.
[2] In terms of comparison, the phycosphere in phytoplankton has been suggested analogous to the rhizosphere in plants, which is the root zone important for nutrient recycling.
In the phycosphere, the phytoplankton release of specific chemical exudates elicits a response from bacterial symbionts who exhibit chemotaxis signaling, thereby enabling the recruitment of microbes and subsequent colonization.
Chemicals such as dimethylsuloniopropionate (DMSP) and 2,3-dihydroxypropane-1-sulfonate (DHPS) and metabolites such as sugars and amino acids are implicated in the mechanisms of action of both microbiomes.
Interactions between phytoplankton and bacteria in the phycosphere could be potentially important in low-nutrient regions of the ocean and an example of mutualism.
If enough organic matter is produced, the bacteria could potentially harm the phytoplankton by causing the water to become more acidic.
Seymour, Justin R., et al. “Zooming in on the Phycosphere: the Ecological Interface for Phytoplankton–Bacteria Relationships.” Nature Microbiology, vol.
Role of Rhizobium, a plant growth promoting bacterium, in enhancing algal biomass through mutualistic interaction.