It is saprophytic fungus and grows vegetative fruits, meat and many other moist and dead organic substratums. Fungus is also called green or blue mould.
Thallus of Penicillium has branched pale coloured mycelium and thin walled hyphae. Hyphae are separate and each cell is uni or multi nucleate.
Reproduction: Penicillium reproduces by asexual and sexual methods.
(1) Asexual Reproduction: It takes place by conidia or conidiospores which are developed on conidiospores. The conidiospores are branched separate and consist of multinucleate cells. On the terminal ends of the branches of conidiospore the bottle like sterigmata are produced. They are uni-nucleate and bear uni-nucleate conidia in basigenous chains. Each conidial chain has hundred or more conidia. Each conidium is uni-nucleate and green, on liberation the conidia get dispersed and on getting suitable media and appropriate condition for germination, they germinate by producing germ tubes which develop into new mycelia.
(2) Sexual Reproduction: It takes place rarely. Penicillium may be homothallic or heterothallic i.e. sex organs may arise either from the same or different mycelia.
Male and female sex organs are known as Antheridia or ascogonia.
Ascogonium (female organ) is an elongated uni-nucleate structure when young. It arises as a short erect protuberance from ordinary cell of mycelium. It elongates and its nucleus divides to form 32 or 64 daughter nuclei. Ascogonium in this stage is an elongated tubular non septate and multinucleate structure. Antheridium also arises as a branch from mycelium called antheridial branch. It becomes spirally coiled around ascogonium. Antheridium is uni-nucleate in beginning and remains uni-nucleate always. The apical part of antheridial branch swells slightly and then cut off from rest of the hypha by a cross wall, the club shaped terminal uni-nucleate cell thus cut off and is called antheridium.
Dikaryotizaion or Plasmogamy:
Tip of antheridium comes in contact water lateral wall of ascogonium, the wall gets dissolved and two protoplast come in contact.
Ascogonial nuclei arrange themselves in pairs (dikaryons and ascogonium) get divided into a number of cells. Each cell contains a pair of nuclei called ukaryon.
Each bi-nucleate cell of ascogonium is called Ascus mother cell in which karyogamy takes place. This fusion nucleus undergoes meiosis, to form ascospores. These sexual structures become surrounded by vegetative fungal hyphae and a fruiting body called ascocarp or cleistothercium develops. Pear shaped asi soon dissolve and release ascospores into cleistotherium. Ascospores liberated free and germinate to form new mycelium.
Economic Importance of Penicillium:
It spoils many food stuffs and other goods like furniture and leather goods. Some species cause dangerous disease in man and animals.
Penicillium is also very useful for human kind. The wonder drug Penicillia is extracted from species P. notatum and P. crysogenum. Some species produce organic acids such as citric, fumric, oxalic and gallic acids. Some species are used in making cheese.
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