2.3微生物学PPT.ppt

2、生活史 无性繁殖阶段:菌丝体(营养体)在适宜的条件 下产生无性孢子,无性孢子萌发形成新的菌丝 体,多次重复。 有性繁殖阶段:在发育后期,在一定条件下,在 菌丝体上分化出特殊性器官(细胞),质配、核 配、减数分裂后形成单倍体孢子,再萌发形成 新的菌丝体。 有一些霉菌,至今尚未发现其生活史中有 有性繁殖阶段，这类真菌称为半知菌. 四、霉菌的代表属 根霉属（Rhizopus） 毛霉属（Mucor） 曲霉属（Aspergillus） 青霉属（Penicillinm） 根霉（Rhizopus) 毛霉（Mucor) 曲霉(Aspergillus) 青霉（Penicillum): 青霉分生孢子 * 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 o