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Microbial Life

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Microbial Life Chapter 13 – PowerPoint PPT presentation

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Title: Microbial Life


1
Microbial Life
  • Chapter 13

2
Characteristics of Microbes
  • Prokaryotic cells
  • Smaller
  • Lack special structures such as a nucleus and
    organelles
  • All prokaryotic cells are microorganisms
  • Some microorganisms are eukaryotic
  • Viruses?

3
Microorganisms
4
Microorganisms are diverse and widespread
0
  • Pathogens
  • causing disease
  • Normal / indigenous flora
  • decomposing dead skin cells
  • supplying essential vitamins,
  • guarding against pathogenic organisms
  • Saprobes
  • In soil
  • decompose dead organisms, sustaining chemical
    cycles

5
Microbiology
  • The study of organisms (microorganisms or
    microbes) too small to be seen without
    magnification
  • This includes
  • Bacteria
  • Viruses
  • Fungi
  • Protozoa
  • Algae
  • Helminthes

6
Bacteria
7
Bacteria
  • Single-celled organisms
  • Various shapes
  • Cocci
  • Bacilli
  • Spiral shapes
  • Cellular
  • Lack membrane-enclosed cellular structures
  • Widely distributed in nature

8
Generalized structure of a prokaryotic cell
9
Appendages
  • Flagella
  • rotates 360o
  • 1-2 or many distributed over entire cell
  • Fimbriae
  • adhesion
  • Pili
  • made of pilin protein
  • found only in Gram negative cells
  • Functions
  • joins bacterial cells for DNA transfer
    (conjugation)
  • Adhesion
  • to form biofilms and microcolonies

10
The Cell Envelope
  • External covering outside the cytoplasm
  • Composed of few basic layers
  • glycocalyx
  • cell wall
  • Gram positive
  • Gram negative
  • cell membrane
  • Maintains cell integrity

11
Chromosome
  • single, circular, double-stranded DNA molecule
  • contains all the genetic information required by
    a cell
  • DNA is tightly coiled around a protein
  • dense area called the nucleoid

12
Plasmids
  • small circular, double-stranded DNA
  • stable extrachromosomal DNA elements that carry
    nonessential genetic information
  • duplicated and passed on to offspring
  • replicate independently from the chromosome

13
Endospores
  • resting, dormant cells
  • produced by some G genera
  • resistance linked to high levels of calcium
    certain acids
  • longevity verges on immortality
  • 25 to 250 million years
  • pressurized steam at 120oC for 20-30 minutes will
    destroy

14
Viruses
15
Viruses
  • Acellular
  • Composed of nucleic acid and a few proteins
  • Requires electron microscope for viewing

16
General Structure of Viruses
  • Capsids
  • All viruses possess
  • Constructed from identical subunits called
    capsomers
  • made of protein
  • Structural types
  • helical
  • Continuous helix of capsomers forming a
    cylindrical nucleocapsid
  • icosahedral
  • 20-sided with 12 corners
  • vary in the number of capsomers

17
General Structure of Viruses
  • Viral envelope
  • mostly animal viruses
  • acquired when virus leaves host cell
  • Protects the nucleic acid when the virion is
    outside the host cell
  • spikes
  • exposed proteins on the outside of the envelope
  • essential for attachment of the virus to the host
    cell
  • Naked
  • composed only of a nucleocapsid
  • Enveloped
  • surrounded by an envelope

18
Nucleic acids
  • Viral genome
  • either DNA or RNA but never both
  • Number of genes varies for each type of virus
  • few to hundreds
  • DNA viruses
  • usually double stranded (ds)
  • may be single stranded (ss)
  • circular or linear
  • RNA viruses
  • usually single stranded
  • may be double stranded
  • Segmented versus nonsegmented

19
6 Steps in Viral Replication
  1. adsorption
  2. penetration
  3. replication
  4. assembly
  5. maturation
  6. release

20
Fungi
21
Fungi
  • Yeasts and molds
  • Single-celled, microscopic
  • Mushrooms
  • Multicellular, macroscopic
  • Cell nucleus and other cellular structures
  • Absorb nutrients from their environment
  • Saprobes
  • Widely distributed in water and soil
  • Thermal dimorphism
  • grow as molds at 30C and as yeasts at 37C

22
Fungal Organization - Mold
  • Fungal Cell Structure
  • Hyphae
  • Mycelium
  • Conidia / spores
  • Sexual and asexual reproduction
  • Cell walls contain chitin
  • Energy reserve is glycogen
  • Nonmotile
  • Produce wind-blown spores
  • Grow toward food source

23
Fungal Organization
  • Yeasts
  • Soft, uniform texture and appearance
  • Unicellular (bicellular)
  • False hyphae
  • Beta-glycan cell wall structure

24
Protozoa
25
Protozoa
  • 100,000 species
  • _at_ 25 are important pathogens
  • Some spread by insect vectors
  • Vary in shape, lack a cell wall
  • Most are unicellular
  • Colonies are rare
  • Obtain food by engulfing or ingesting smaller
    organisms and plant material
  • Most are harmless, free-living in a moist habitat

26
Protozoa
  • Exist as trophozoite
  • motile feeding stage
  • cyst
  • Dormant resting stage when conditions are
    unfavorable for growth and feeding
  • All reproduce asexually, mitosis or multiple
    fission
  • Many also reproduce sexually

27
Protozoan Classification
  • Simple grouping is based on method of motility,
    reproduction, and life cycle
  • Mastigophora
  • primarily flagellar motility
  • Sarcodina
  • primarily ameba
  • Ciliophora
  • Cilia
  • Apicomplexa
  • motility is absent except male gametes

28
Algae
29
Algae
  • Unicellular to multicellular
  • Macroalgae
  • Microalgae
  • Have a nucleus and many membrane-enclosed
    cellular structures
  • Photosynthesize their own food
  • Widely distributed in fresh and salt water
  • Important source of food for other organisms

30
Algae Diversity
  • Diatoms
  • single-celled
  • silica shell
  • Euglenophyta
  • single-celled
  • photosynthesis
  • Dinoflagellata
  • flagella and can move
  • usually photosynthetic
  • sometimes phosphorescent
  • plankton
  • Chrysophyta
  • silica in their cell wall
  • found in fresh water
  • Phaeophyta
  • contains many familiar seaweeds.
  • Rhodophyta
  • red pigments
  • contains many types of seaweed
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