MICROORGANISMS AND FUNGI

1
MICROORGANISMS AND FUNGI

• Modern Biology
• Chapters 24-28
• Biology Exploring Life
• Chapters 16-18

2
Viruses

• Nonliving particlesabsence of
• Cellular organization
• Viruses have no cell membranes or cytoplasm.
• Growth
• Homeostasis
• Metabolism
• Reproduction
• Viruses are obligate intracellular parasites.

3
Viral Structure and Shape

• Nucleic acid (DNA or RNA) surrounded by a protein
  coat called a capsid
• Sometimes a lipid envelope with glycoprotein
  projections outside the capsid
• Taken from host cell membrane during viral
  replication
• Used for attachment to, and infection of, a host
  cell
• Icosahedral or helical

4
Classification of Viruses

• Adenoviruses
• DNA, icosahedral, non-enveloped
• Ex. Common cold
• Herpesviruses
• DNA, icosahedral, enveloped
• Ex. Herpes simplex, chickenpox
• Helical enveloped RNA viruses
• Ex. Influenza, rabies, measles, TMV (tobacco
  mosaic virus)

5
Classification of Viruses (continued)

• Retroviruses
• RNA, icosahedral, enveloped
• Reverse transcription
• Ex. HIV (human immunodeficiency virus)
• ViroidsNOT viruses
• RNA with no capsid
• PrionsNOT viruses
• Abnormal, clumping proteins with no associated
  nucleic acid
• Ex. Scrapie, mad cow disease

6
Lytic Cycle

• Virulent viruses
• Attachment
• Entry
• Replication
• Assembly
• Release

7
Lysogenic Cycle

• Temperate viruses
• Attachment
• Injection
• Integration (prophage or provirus)
• Cell multiplication
• Certain stimuli eventually trigger virulence.

8
Impact of Viruses

• Controlling viral diseases
• Antibioticsno!
• Vaccination
• Antiviral drugs enzyme inhibitors
• Ex. Acyclovir, AZT, protease inhibitors
• Genetic engineering

9
Kingdoms Archaebacteria and Eubacteria

• (Domains Archaea and Bacteria)

10
Cellular Organization

• Prokaryotic
• Polysaccharide cell wall
• Unicellular
• Three shapes
• Coccus
• Bacillus
• Spirillum

11
Cellular Organization (continued)

• Unicellular (continued)
• Often found in colonies
• Strepto-
• Staphylo-

12
Metabolism

• Food/energy source
• Autotrophic or heterotrophic
• Autotrophic (self-feeding)
• Photosynthetic (sunlight)
• Chemosynthetic (inorganic molecules)
• Heterotrophic (other-feeding)
• Parasitic (living organisms)
• Saprophytic (dead organisms)

13
Metabolism (continued)

• Digestion / energy release
• Cellular respiration (aerobicwith oxygen) and/or
  fermentation (anaerobicwithout oxygen)
• Facultative anaerobes can do either.
• By-products of fermentation
• Alcohol (ethanol)
• Lactic acid

14
Homeostasis

• Taxis
• Directional movement toward or away from various
  stimuli
• Endospore
• State of dormancy through which bacteria survive
  unfavorable conditions

15
Reproduction

• Asexualbinary fission
• Rapid
• Generation time 12-20 minutes
• Natural selection acts quickly to cause evolution
  in bacterial populations.

16
Heredity

• Bacteria in colonies are genetically identical
  offspring of one original cell.
• Plasmids
• Extra circles of DNA that carry certain bacterial
  genes
• May be exchanged between bacteria through
  appendages called pili (singular, pilus)

17
Archaebacteria

• Ancient bacteria
• Most likely ancestors of eukaryotic cells
• Harsh habitats
• Oxygen-poor swamps and marshes
• Extremely salty water
• Hot sulfur springs

18
Eubacteria

• True bacteria
• Normal habitats (especially warm, moist places)
• IntestinesE. coli bacteria help digest food.
• Underarmsbacterial waste products contribute to
  body odor.
• Respiratory systemsinus infections, strep
  throat, etc.
• May be beneficial or harmful

19
Kingdom Protista

• (Domain Eukarya)

20
Cellular Organization

• Eukaryotic
• Endosymbiotic theory Protists evolved from
  mutualistic associations of smaller bacteria
  living inside larger bacteria.
• Unicellularexcept algae

21
Metabolism

• Autotrophic or heterotrophic
• Unicellular autotrophic (plant-like) protists
• Phytoplankton
• Base of aquatic food chains
• Diatoms
• Silica shells ground for grit in toothpaste
• Dinoflagellates
• Red tides

22
Metabolism (continued)

• Multicellular autotrophic protists
• Red algae
• Brown algae (kelp)
• Green algae (seaweed)

23
Metabolism (continued)

• Heterotrophic (animal-like) protists
• Amoebae
• Plasmodium causes malaria.
• Protozoans
• Paramecium
• Giardia causes giardiasis.

24
Homeostasis

• Movement
• Cilia
• Flagella
• Pseudopods

25
Reproduction and Heredity

• Mitosis and/or meiosis
• Mitosisasexual
• Offspring are genetically identical to parent.
• Meiosisconjugation
• Two haploid protists join and recombine their
  DNA.
• Offspring exhibit genetic variation.

26
Kingdom Fungi

• (Domain Eukarya)

27
Cellular Organization

• Hyphae (singular hypha)
• Name given to the cells of fungi
• Eukaryotic
• Some hyphae are multinucleate.
• Multicellularexcept yeasts

28
Anatomy

• Two main body parts
• Mycelium
• Branched network of hyphae that extend and spread
  out into the substrate (food source) where a
  fungus is living
• Fruiting body
• Structure above the surface of the substrate
  where meiosis occurs to produce spores for sexual
  reproduction

29
Metabolism and Homeostasis

• Heterotrophic
• Absorption (absorptive nutrition)
• Hyphae in the mycelium secrete digestive enzymes
  into the substrate.
• Hyphae then absorb the liquefied food.
• Sessile
• Fungi are stationarypermanently attached to
  their substrate.
• Most growth occurs at the tips of hyphae in order
  to obtain more nutrients.
• Environmental conditions determine whether fungi
  will reproduce sexually or asexually.

30
Reproduction and Heredity

• Asexual and/or sexual
• Asexualmitosis
• Production of genetically identical hyphae
• Sexualmeiosis
• Production of spores that are dispersed by wind
  or water
• Classification based on type of spore producedin
  other words, mode of sexual reproduction