Lee Hyeseung, Chang Yun C, Nardone Glenn, Kwon-Chung Kyung J
Laboratory of Clinical Infectious Diseases, NIAID, NIH, Bethesda, MD 20892, USA.
Mol Microbiol. 2007 May;64(3):591-601. doi: 10.1111/j.1365-2958.2007.05666.x.
Cryptococcus neoformans is a pathogenic yeast that causes life-threatening meningoencephalitis and grows well on mycological media regardless of inoculum size. Interestingly, a deletion of the global repressor TUP1 in C. neoformans uncovered a density-dependent growth phenotype reminiscent of the quorum-sensing phenomenon. An inoculum size of lower than 10(3) cells of the tup1Delta strain failed to form colonies on agar media while inocula of 10(5)-10(6) cells per plate formed a lawn. This phenotype, expressed as the inability to grow at low cell densities, was rescued by the culture filtrate from a high cell density tup1Delta culture and the active molecule in this culture filtrate was identified to be an oligopeptide composed of 11 amino acids. Activity assays, using a synthetic version of the peptide with strains harbouring a deletion of the corresponding gene, proved that the oligopeptide functioned as an autoregulatory molecule responsible for the density-dependent phenotype. Although a density-dependent growth phenotype has been reported in several species of Ascomycetes, no peptide has been reported to function as an autoregulator in the Kingdom Fungi. The identification of an 11-mer peptide as an autoregulatory molecule in C. neoformans suggests that a diverse mechanism of cell-to-cell communication exists in the Kingdom Fungi.
新型隐球菌是一种致病性酵母，可引发危及生命的脑膜脑炎，且无论接种量大小，在真菌培养基上均能良好生长。有趣的是，新型隐球菌中全局阻遏因子TUP1的缺失揭示了一种密度依赖性生长表型，类似于群体感应现象。tup1Δ菌株接种量低于10³个细胞时无法在琼脂培养基上形成菌落，而每平板接种10⁵ - 10⁶个细胞则形成菌苔。这种表现为在低细胞密度下无法生长的表型，可被来自高细胞密度tup1Δ培养物的培养滤液挽救，并且该培养滤液中的活性分子被鉴定为一种由11个氨基酸组成的寡肽。使用该肽的合成版本对缺失相应基因的菌株进行活性测定，证明该寡肽作为一种自调节分子，负责密度依赖性表型。尽管在几种子囊菌中已报道了密度依赖性生长表型，但在真菌界尚未有肽作为自调节因子发挥作用的报道。在新型隐球菌中鉴定出一种11聚体肽作为自调节分子，表明真菌界存在多种细胞间通讯机制。
