CHAP 2: MICROBIAL GROUP

CHAP 2: MICROBIAL GROUP

1. FUNGUS

   • Types of fungi
     • chytrids (Chytridiomycota), zygote (Zygomycota), sac (Ascomycetes)   and club (Basidiomycetes).
   • Reproduction in the fungi
     • Sexual
       • On unfavorable condition to generate genetic diversity
     • Asexual
       • on stable condition to maximize production and the diversification is less urgent.
   • Ecological impact of fungi:
     • As spoiler
       • Decompose food, wood and etc.
     • As food
       • Food for a variety of animals, including humans.
     • As habitat modifier
       • Lichens inhabit inhospitable places make habitat suitable for life
     • As plant growth regulator
       • Mycorrhizae
     • As decomposer
       • - To reduce complex polysaccharides and proteins   simple organic compounds use by other  - Recycling carbon, nitrogen and other elements to the ecosystem
     • As pathogens
       • Causes athletes foot, ringworm, and yeast infection
   • Feeding forms of fungi
     • Saprobic heterotrophs
       • – feed on dead or decaying organic matter
     • Mutualistic heterotrophs
       • – feeding of or with a living host without damaging the host, both host and fungus benefit
     • Parasitic heterotrophs
       •  – feeding on living host at cost to the host
   • Grouping of fungi:
     • Lichen
       • association of a fungus and a photosynthetic symbiont resulting in a stable thallus
     • Mycorrhizae
       • Plant root and fungi

2. MOLDS

   • Three divisions
     • Acrasiomycota
       • o  individual amoeboid cells  (unicellular) feed phagocytically             o  plentiful of food, divide  by mitosis  and cytokinesis
       • Cellular slime molds
         • o  great interest to cell and developmental biologists o  provide a comparatively simple and easily manipulated system
     • Myxomycota
       • o  plasmodial (acellular) slime molds saprophytes              o  multinucleated         o  motile amoeboid mass called plasmodium o  phagocytosized dead material
     • Oomycota
       • o  finely branched filaments called hyphae  o  Decomposers in aquatic ecosystems
   • Ecological function of molds
     • As predator
       • Engulf bacteria 
     • As decomposer
       • Recycling of nutrients
     • As pathogen
       • Cause diseases in plants e.g. tobacco plants, potatoes, grapes
   • Distribution of molds

3. BACTERIA

   • Cellular organization
     • ·  DNA not enclosed in  membrane ·  Genome 1/1000 smaller than eucaryotic genome
     • Reproduction
       • Binary fission (Shorter generation time, quick evolution, higher mutation rate)
     • Nutrition
       • Photoautotrophs, Chemotrophs,  Autotrophs and Heterotrophs.
   • Ecological function of Procaryotes
     • Recycling of chemical components
       • - convert inorganic materials to organic materials through various biochemical cycles.
     • Symbiotic relationships
       • - Commensalism, parasitism and mutualism.
     • Bioremediation
       • - To remove detrimental pollutants from the environment

4. VIRUS

   • Ecological function
     • Mostly disease causing in human, animals and plants (HIV, smallpox, herpes simplex)
     • Biological warfare
   • Viral replication
     • Attachment/Absorption
     • Release
     • Replication
     • Penetration
     • Assembly
   • Virus vs other living cells
     • Presence of either DNA or RNA
     • Inability to carry out cell division as procaryotes and eucaryotes
     • Inability to reproduce independent of cells

5. Eucaryotic microbe : Algae (aquatic plant)

   • Distribution: i) primary aquatic -planktonic -benthic -neustonic ii) terrestrial -moist -endosymbionts
   • Nutritional : i) photoautotrophic ii) chemoheterotrophic
   • Reproduction i) Asexual reproduction ii) Sexual reproduction
   • Ecology: i) Disrupt higher links of local food web - Algae→die→sink to the bottom →stimulate the growth of decomposers (bacteria)→depletion of oxygen in deeper water layers→chemical changes, releasing toxic gases→kill other marine organisms ii) Production of neurotoxin by algae - Harmful to vetebrates but not to fishes - Accumulate in fishes or shellfishes - Red tide: caused by dinoflagellates →produces brevetoxins→respiratory irritation in human
   • Classification : >cell wall >flagella number and location >chlorophyll and pigments >morphology of cells habitat >reproductive structures >life history patterns

6. Protozoa

   • Nutrition: (Chemoheterotrophic) a. Holozoic nutrition -solid nutrients→ phagocytosis→ cytostome b. Saprozoic nutrition -Soluble nutrients→ pinocytosis, diffusion, carrier-mediated transport
   • Reproduction: Asexual: Binary fission • Nucleus→mitosis • Cytoplasm→ cytokinesis Sexual: Conjugation
   • Ecology: i) In the marine food chain - Zooplankton (protozoans) ingest phytoplankton and bacteria - Influence the C and N cycle in oceans - A link for primary production and higher levels in the food chain. ii)Interaction with higher organisms Parasitic relationship (cause harm to host) - Zooflagellate Trypanosoma→African Sleeping Sickness in humans - Sporozoans: Plasmodium causes Malaria