Microbial assembly adapted to low-P soils in three subtropical forests by increasing the maximum rate of substrate conversion of acid phosphatases but not by decreasing the half-saturation constant
2022
Mori, Taiki | Wang, Senhao | Zhang, Wei | Mo, Jiangming
It is hypothesized that microbes (and plant roots) in tropical soils adapt to a low-phosphorus (P) environment by lowering the Kₘ, which represents the affinity with substrates, of the phosphatase assembly (at the community level), and thus P fertilization increases Kₘ. However, the hypothesis has not yet been tested, partly due to the difficulty of measuring Kₘ in ecosystems, where elevated organic and inorganic P through P fertilization can lead to an overestimation of the Kₘ values through competitive inhibition. However, a lack of response of apparent Kₘ (ᵃᵖᵖKₘ) to P fertilization can be interpreted as a lack of support for the hypothesis. The present study demonstrated that 10-year P fertilization in a primary forest and a secondary forest did not affect ᵃᵖᵖKₘ, although ᵃᵖᵖKₘ was slightly elevated by P fertilization in a planted forest. Meanwhile P fertilization clearly reduced the ᵃᵖᵖVₘₐₓ (apparent Vₘₐₓ) of phosphatases in the primary and secondary forests. Our result suggested that microbes (and plants) in tropical forests adapt to the P-poor environment through increasing the phosphatase abundance, but not through reducing the Kₘ of the phosphatase assembly (at the community level).
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