Apophysomyces jiangsuensis sp. nov., a Salt Tolerant and Phosphate-Solubilizing Fungus from the Tidelands of Jiangsu Province of China

Abstract

A newly isolated phosphate-solubilizing fungus from the topsoil of Spartina alterniflora habitats in Yancheng coastal salt marsh was cultivated. Scanning electron microscopy observation revealed that the sporangia are nearly spherical, peach-shaped, and the spores formed on the top of sporangia. The spores are ellipsoidal with raised white nubbins on the surface. Based on a polyphasic study and the genetic distance analysis referring to the sequence analysis of ITS (ITS1 + 5.8S + ITS2) and 28S rDNA (D1/D2 domains) genes, the novel species belongs to the genus Apophysomyces and is named as A. jiangsuensis. The optimum growth temperature and salinity of the new species were 28 °C and 1.15% NaCl, respectively. A study of its phosphate-solubilizing ability revealed that the fungus had an obvious decomposition effect on lecithin, Ca3(PO4)2, and AlPO3, respectively. The pH of the fermented liquid progressively decreased from 6.85 to 2.27 after 7 days of incubation, indicating that the low molecular weight organic acids excreted into the culture liquor were oxalic, succinic, and malic acids and a trace amount of citric acid. Among these, oxalic acid was the major organic acid, and its amount reached 652.5 mg/L. These results indicated that the main mechanism underlying the dissolved phosphorus was related to the secretion of large amounts of organic acids.