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Chapter 14 Fungi Importance of Fungi Together with Heterotrophic bacteria Ecological decomposers Decomposing fruit- Rhizopus Root-rot fungus- white mycelial causes disease in living trees Acts as decomposers on dead plants Root rot Ouch!!! Fungi • Composed of Hyphae • Heterotrophic absorbers Characteristics of Fungi • Composed of Hyphae Fungal filaments= “Cobwebby” strands of subterranean “white stuff” Mycelium Fungi form important symbiotic relationships • 80% of all vascular plants species from mutually beneficial associations called mycorrhizae between roots and fungi • Plant nutrition • Lichens form symbiotic relationship with fungi, algal, or cyanobacterial cells • Fungi and insects • Endophytes- fungi live in plants produce toxic that protect host Four phyla of fungi • Chytridiomycota • Zygomycota • Ascomycota next week lecture • Basidiomycota next week lecture Chars of Fungi • All have cell wall • Cell wall composed of polysaccharide- chitin • Chitin more resistant to microbial degradation than cellulose All Fungi Heterotrophic Absorbers • Unable to engulf small microorganisms • Secrete enzymes and absorb smaller molecules •Absorb food mostly at or near the growing tips of their hyphae Fungi obtain their food • Either as Saprophytes or • As mutualistic symbionts Some • Obtain energy through fermenation producing ethyl alcohol from glucose (i.e. yeast) Fungi Store energy • Polysaccharide • Glycogen • Lipids Fungi reproduce both sexually and asexually • Reproduce through the formation of spores that are produced sexually or asexually • Most are nonmotile spores • Some are dry and small and airborne • Some are slimy and stick to the bodies of insects and other arthropods • Some propel into airphototropism Common method of asexual reproduction in fungi • By means of spores • Either produced in sporangia – The sporangium is a saclike structure, the entire contents of which are converted into one or more spores Asexual reproduction • Or • Hyphal cells called conidiogenous cells – Spores produced by conidiogenous cells occur singly or in chains called conidia Asexual repro • Some Reproduce by fragmentation of their hyphae Sexual reproduction • Three distinct phases • First two are phases of fertilization (syngamy) – Plasmogamy- the fusion of protoplasts – Karyogamy- the fusion of nuclei (some don’t fuse forming a dikaryon) Divide by mitosis Give rise to gametes by differentiation gametangia 4 Spores The last phase is meiosis • Sexual reproduction results in the formation of specialized spores such as zygospores, ascospores, basidiospores. Zygospores • Zygospores • Asexual and sexual reproduction (by means of haploid spores) • Sexually producing zygospores require two compatible species Zygomycetes: Phylum Zygomycota • Live on decaying plant and animal matter in soil • Some are parasites of plants, insects or small soil animals • Others form symbiotic relationshipsendomycorrhizea- with plants occasionally cause infection in animals • Rhizopus stolonifer- best known zygomycetes Life cycle of Rhizopus stolonifer Gametangia the gamete producing structures are in the Process of producing a zygospore Zygospore develops within the thick walled zygosporangium
