Departamento de Microbiología y Genética, Universidad de Salamanca, Salamanca, Spain.
Antimicrob Agents Chemother. 2012 Dec;56(12):6121-31. doi: 10.1128/AAC.00752-12. Epub 2012 Sep 10.
Aspergillus fumigatus has two chitin synthases (CSMA and CSMB) with a myosin motor-like domain (MMD) arranged in a head-to-head configuration. To understand the function of these chitin synthases, single and double csm mutant strains were constructed and analyzed. Although there was a slight reduction in mycelial growth of the mutants, the total chitin synthase activity and the cell wall chitin content were similar in the mycelium of all of the mutants and the parental strain. In the conidia, chitin content in the ΔcsmA strain cell wall was less than half the amount found in the parental strain. In contrast, the ΔcsmB mutant strain and, unexpectedly, the ΔcsmA/ΔcsmB mutant strain did not show any modification of chitin content in their conidial cell walls. In contrast to the hydrophobic conidia of the parental strain, conidia of all of the csm mutants were hydrophilic due to the presence of an amorphous material covering the hydrophobic surface-rodlet layer. The deletion of CSM genes also resulted in an increased susceptibility of resting and germinating conidia to echinocandins. These results show that the deletion of the CSMA and CSMB genes induced a significant disorganization of the cell wall structure, even though they contribute only weakly to the overall cell wall chitin synthesis.
烟曲霉有两个几丁质合酶（CSMA 和 CSMB），它们具有肌球蛋白马达样结构域（MMD），呈头对头排列。为了了解这些几丁质合酶的功能，构建并分析了单突变和双突变菌株。尽管突变体的菌丝生长略有减少，但所有突变体和亲本菌株的菌丝中总几丁质合酶活性和细胞壁几丁质含量相似。在分生孢子中，ΔcsmA 菌株细胞壁中的几丁质含量不到亲本菌株的一半。相比之下，令人惊讶的是，ΔcsmB 突变体菌株和 ΔcsmA/ΔcsmB 突变体菌株的分生孢子细胞壁几丁质含量没有任何修饰。与亲本菌株疏水性的分生孢子不同，由于存在覆盖疏水性表面-棒层的无定形物质，所有 csm 突变体的分生孢子都是亲水性的。CSM 基因的缺失也导致休眠和萌发分生孢子对棘白菌素的敏感性增加。这些结果表明，CSMA 和 CSMB 基因的缺失导致细胞壁结构的显著紊乱，尽管它们对细胞壁总几丁质合成的贡献很小。
