环境微生物课件—真核微生物.pptVIP

* * * * * * * * * * * * 由气生菌丝顶端分化成特殊囊状结构—孢子囊（sporangium)形成的孢子。 产生孢子囊的菌丝称孢囊梗（sporangiophore) 1、孢囊孢子 由于生于孢子囊内，又叫内生孢子。 它是由气生菌丝顶端膨大形成特殊囊状结构—孢子囊，孢子囊逐渐长大，在囊中形成许多核，每一个核外包以原生质并产生细胞壁，形成孢囊孢子。带有孢子囊的梗称孢子囊梗，孢子囊梗伸入到孢子囊中的部分叫囊轴或中轴。孢子囊成熟后释放出孢子。例藻状菌纲毛霉目及水霉目一些属以这种方式繁殖. Zygomycete Asexual Reproduction Zygomycete fungal mycelium is coenocytic. At the onset of sporulation large amounts of aerial hyphae are produced. The tips of these aerial hyphae fill with cytoplasmic contents, and the nuclei undergo repeated mitosis. Around each of the nuclei cytoplasm and organelles collect, and by the formation of copious vesicles from the Golgi, each nucleus becomes isolated from the next by a plasma membrane. Within the spaces created by this cytoplasmic cleavage, spore walls begin to form, again by the fusion of Golgi vesicles containing cell wall monomers and enzymes with the spore membrane. A sporangium forms. As these events occur so there is considerable water uptake by the forming sporangium, and as the columella forms the structure comes under considerable turgor pressure. The large sporangia can contain up to 100,000 spores (Fig 3). ★This diagram is redrawn from Brackers original and shows the development of a sporangium through time. As nuclei undergo repeated mitosis so the Golgi produces membrane bound vesicles filled with spore wall building materials. These coalesce around the nuclei to form a spore. Eventually they are released. ★Not all sporangia are as large as this, there are many species with smaller, specialized sporangia, called sporangiola, merosporangia and some are almost conidial, forming single spored sporangia that are only distinguished from the conidium of the higher fungi by the possession of a double spore wall. We will look at some of these structures in the practical. * 3、节孢子（又称粉孢子） 它是由菌丝断裂形成的外生孢子。 当菌丝长到一定阶段，出现许多横膈膜，然后从横膈膜处断裂，产生许多孢子。孢子是成串的短柱状、筒状或两端钝圆的细胞。 例：白地霉 * 4、厚垣孢子 这类孢子具有很厚的壁，又叫厚壁孢子。 菌丝顶端或中间的个别细胞膨大、原生质浓缩、变圆，然后细胞壁加厚形成圆形、纺锤形或长方形的厚壁孢子。 厚垣孢子也是霉菌的休眠体，对热、干燥等不良环境抵抗