Life Cycle of Fungi

5 Key excerpts on "Life Cycle of Fungi"

• 

  eBook - ePub

  Fungi, Algae, and Protists

  • Britannica Educational Publishing, Kara Rogers(Authors)
  • 2010(Publication Date)
  • Britannica Educational Publishing

    (Publisher)

  CHAPTER 2Life Cycle and Ecology of Fungi and Lichens

  T he abundance and wide distribution of fungi in nature are a reflection of reproductive success and adaptation to various ecological niches. Reproduction may be either asexual or sexual. In asexual life cycles, fungi are haploid (containing one set of chromosomes), and they may use fragmentation, budding, fission, or spores to produce offspring. In sexually reproducing forms, a diploid stage occurs, in which the nuclei of the haploid sex cells fuse together, facilitating the recombination of genetic material. This provides an opportunity for the emergence of genetic variation between individuals of the same species, thereby improving species adaptation to the immediate environment. Certain species of fungi are very highly adapted to their habitats, requiring specific nutrients or temperature ranges for growth. Other species, however, are less tailored to their surroundings. These fungi often are able to assimilate a wide variety of organic substances and are relatively indifferent to other ecological factors such as temperature.

  REPRODUCTIVE PROCESSES OF FUNGI

  Following a period of intensive growth, fungi enter a reproductive phase by forming and releasing vast quantities of spores. Spores are usually single cells produced by fragmentation of the mycelium or within specialized structures (sporangia, gametangia, sporophores, etc.). Spores may be produced either directly by asexual methods or indirectly by sexual reproduction. Sexual reproduction in fungi, as in other living organisms, involves the fusion of two nuclei that are brought together when two sex cells (gametes) unite. Asexual reproduction, which is simpler and more direct, may be accomplished by various methods.

  Sir Alexander Fleming (b. Aug. 6, 1881, Lochfield Farm, Darvel, Ayrshire, Scot.—d. March 11,1955, London, Eng.)

  Scottish bacteriologist Sir Alexander Fleming was best known for his discovery of penicillin. Fleming had a genius for technical ingenuity and original observation. His work on wound infection and lysozyme, an antibacterial enzyme found in tears and saliva, guaranteed him a place in the history of bacteriology. But it was his discovery of penicillin in 1928, which started the antibiotic revolution, that sealed his lasting reputation. Fleming was recognized for this achievement in 1945, when he received the Nobel Prize for Physiology or Medicine, along with Australian pathologist Howard Walter Florey and British biochemist Ernst Boris Chain, both of whom isolated and purified penicillin.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Molds, Mushrooms, and Medicines

  Our Lifelong Relationship with Fungi

  • Nicholas P. Money, Nicholas Money(Authors)
  • 2024(Publication Date)
  • Princeton University Press

    (Publisher)

  The colony of branching hyphae is a mycelium. When this mycelium has grown over a large area and absorbed enough food, it reverses direction and flows to the sur- face, where the threads merge to form mushrooms. Mushrooms with gills are the fruit bodies or sex organs of fungi that mist the air with spores. As the urge to reproduce becomes an imperative, the fungus moves from belowground to aboveground, changing its role from feeding to fruiting in the wondrous cycle of its life. But most fungi never form a mushroom and are microscopic through- out their feeding and reproductive stages. These include aquatic fungi that swim in ponds, with tailed cells that resemble animal sperm; molds with stalks hung with sparkling spores that look like miniature chande- liers; and 1,500 species of yeasts. Yeasts include the species used in brew- ing and baking, whose Latin name is Saccharomyces cerevisiae, and I n t e r ac t i ng 5 another fungus, called Candida albicans, that lives on everyone and is best known, unfortunately, for its irritating nature as the vaginal yeast.2 (Latin names are kept to a bare minimum in this book, but some of the fungi are best known through their Latin names, and others are so ob- scure that they have never been given a common name.) Unlike fungi that grow as thin threads, which we call molds, yeasts develop as single rounded cells and produce buds, or daughter cells, on their surface. MAKING SENSE OF THE MYCOBIOME The entire human body is affected by fungi. Yeasts populate the skin and crowd around the hair follicles on the scalp; other species live in the ear canals, nasal passages, and mouth; and fungi swarm in the digestive and reproductive systems. The fungi are as small as the cells of our tissues and only become visible when they grow in such profusion that they form patches and pastes on the surface of the skin.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Fungi

  Biology and Applications

  • Kevin Kavanagh(Author)
  • 2005(Publication Date)
  • Wiley

    (Publisher)

  Examples of dimorphic fungi, which live in both a yeast and filamentous form, are also discussed to highlight unique features and variations on themes within the fungi. 2.2 Fungal life cycles 2.2.1 Ascomycete yeast (Saccharomyces cerevisiae) S. cerevisiae is an extremely well studied organism, with a clearly defined and experimentally manipulable life cycle. The life cycle of yeast involves mitotically propagating haploid forms of two distinct mating types, and a diploid form that can either grow vegetatively or be induced into a meiotic developmental path- way through manipulation of the nutrient conditions of the growth medium. The cellular pathways regulating processes such as mitotic proliferation, cell recognition and mating, meiosis and sporulation have been extensively studied on a molecular level, and are generally well understood. Mitotic growth of yeast cells involves budding (Figures 2.1, 2.6). During this process growth of the cell is directed to a specific location on the surface of the mother cell, and a new cell is formed somewhat like blowing up a balloon through a hole in the mother cell. This involves highly polarized growth of the developing daughter cell, implicating both the actin and microtubule-based cytoskeletal networks, and is tightly coordinated with the cell cycle. This coor- dination ensures that the daughter cell receives a complete copy of the genetic material. Both haploid and diploid cells divide by the budding process, although there are subtle differences in the choice of the sites of bud emergence between haploids and diploids. In addition, some diploid cells can also modify the coor- dination of the cell cycle and polarized growth to switch to a pseudohyphal growth mode. In this growth pattern individual cells are more elongated, and the budding pattern leads to the formation of chains of cells rather than compact colonies characteristic of the true budding mode. Genetic analysis is highly developed in S. cerevisiae.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  The Fungal Population

  An Advanced Treatise

  • G. C. Ainsworth, Alfred S. Sussman, G. C. Ainsworth, Alfred S. Sussman(Authors)
  • 2013(Publication Date)
  • Academic Press

    (Publisher)

  Ecology SAPROBIC FUNGI AND THEIR HABITATS This page intentionally left blank CHAPTER 1 The Ecology of Terrestrial Fungi DAVID PARK 1 Department of Botany Manchester University Manchester, England I. INTRODUCTION It is widely recognized that in the field of ecology there are fundamental principles that apply to most organisms, including man as well as micro-organisms. Workers investigating a particular type of organism can define processes and formulate principles of application to ecology generally. Conversely work in a restricted field can often benefit from the application of ideas deriving from work on very different organisms. In many ways the ecology of fungi demonstrates these generalities and has great similari-ties to that of other groups; it has sometimes confirmed work in other fields and sometimes contributed to it. Fungi, because of their small size and their rapid activity permit a study on a smaller scale than do many more traditional ecological materials, and they can be particularly useful in this role. However, partly because fungi have certain special features of somatic morphology, of physiology and of genetics, as described in earlier accounts in these volumes, there are some important ways in which their ecology differs from that of higher plants and animals, and these differences will carry most of the emphasis in this account. The large surface : volume ratio inherent in the hyphal growth form gives a large contact with the environment and greatly affects fungal biology. Ecologists studying root systems of higher plants have sometimes been impressed with the surface : volume ratio there, but in filamentous, and even more in unicellular, fungi the surface for contact with the environ-ment is extremely high in relation to the total mass of protoplasm. Not only is the area of contact large, but there is no great distance between any point in the protoplasm itself and the environment.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Ecology of Saprotrophic Basidiomycetes

  • Lynne Boddy, Juliet Frankland, Pieter van West(Authors)
  • 2007(Publication Date)
  • Academic Press

    (Publisher)

  All rights reserved. 79 with other fungi and bacteria. Changes in the seasonal pattern of fruiting in the UK can be detected from field records made in the last 50 years, and while not all species behave in the same way, mean first fruiting date is now significantly earlier and mean last fruiting date is now significantly later, which results in an extended fruiting season. Significant numbers of species that previously only fruited in autumn now also fruit in spring. Such analyses show that relatively simple field observations of fungi can detect climate change, and that fungal responses are sufficiently sensitive to react to the climate change that has already occurred by adapting their pattern of development. Unfortunately, though it is possible to deduce the decisive steps in development that are open to influence, the molecular controls that normally regulate those steps remain unknown. Extensive genomic analysis shows that sequences crucial to multicellular development in animals or plants do not occur in fungal genomes, so we are ignorant of the basic control processes of fungal multicellular developmental biology. 1. INTRODUCTION We use the term fruit bodies to encompass all the structures that develop from fungal mycelia to produce and distribute spores or other propagules, including basidiomata—the structures that release sexual spores (meiospores) in Basidi-omycota, as well as a range of structures that produce asexual spores (mito-spores) and some somatic (vegetative) structures, such as stromata and sclerotia, that can survive adverse conditions. Obviously, the phrase encompasses a very wide range of organs but their common feature is that they are multicellular, and their shape and form emerge as a result of a sequence of developmental adjust-ments. That is, they exhibit a characteristic pattern of morphogenesis.

  Sign up to read

  Learn more about book