Relationship of Phytate, Phytate‐Mineralizing Bacteria, and Beta‐Propeller Phytase Genes along a Coastal Tributary to the Chesapeake Bay

Abstract

Core Ideas Positive correlation between phytate P, inorganic P, and PMB along the creek. Bacteria with BPP genes about four orders of magnitude higher in water than sediment. High inorganic P in the creek most likely derived partly from phytate degradation. Phytate is often the most common and recalcitrant form of organic P in soils. Given that extracellular phytase activities are attributed to soil microorganisms, the distribution and characterization of phytate‐mineralizing bacteria (PMB) and quantification of phytate genes across an environmental gradient can address questions related to the degree of relative recalcitrancy of phytate P and microbial response to phytate loading. In this study, we analyzed paired sediment and water samples from different sites along a stretch of East Creek, a coastal tributary to the Chesapeake Bay, for the abundance of PMB as well as β‐propeller phytase (BPP) genes, a gene for the most common of the phytase enzymes, using culture‐dependent and ‐independent methods. We found that a larger proportion of isolates from sites near the headwaters were PMB than at the mouth of the creek. Our quantitative polymerase chain reaction (qPCR) results show that the total number of bacteria (both with and without BPP genes) in water and sediment samples was highest at the agricultural headwaters but decreased significantly at wetland sites. Similarly, 16S rRNA‐normalized BPP copies show that the abundance of bacteria capable of phytate degradation was about four orders of magnitude higher in water than in sediment. These results probably indicate that the presence of phytate promotes the proliferation of phytate‐degrading microorganisms with a potentially higher rate of phytate degradation in water than in sediments. Overall, these results provide important insights into phytate loading and PMB abundance in a coastal tributary and P export to the Chesapeake Bay.