Virus/Fungi/Bacteria

1. Introduction to Microbial
Diversity

2. Microorganisms
• decomposing organic waste – recycling vital elements
• performing photosynthesis
• producing ethanol, acetone, vinegar, cheese, bread etc.
• Insect pest control by bacteria
• producing insulin and many other drugs
• causing disease
Microorganisms contribute
organisms too small for naked eyes
Autotrophs – Heterotrophs

3. The sizes of prokaryotic cells relative to other cells and biomolecules
(logarithmic scale)

4. Landmarks in Microbiology

5. Microorganisms
1014and also about bacterial, fungal, and protozoan cells, which
represent thousands of microbial species (Normal flora).
The anaerobic bacteria that inhabit our intestines contribute to the
digestion of food, and they are also essential for proper development of
the gastrointestinal tract in infants.
Normal flora on the skin and elsewhere also help us by competing with
disease-causing microorganisms.
A normal human body contains about 1013 humancells

6. Microbial Diversity
• Viruses
• Bacteria
• Archaea
• Fungi
• Algae
• Protozoa

7. Viruses carry information in the form of nucleic
acid. Need host cells for replication, protein
packaging.
Viruses have a small genome, made up of a
single nucleic acid type—either DNA or RNA—
(ss or ds). The genome is packaged in a protein
coat, which in some viruses is further enclosed
by a lipid envelope.
In general, replication involves
1. Disassembly of the infectious virus particle
2. Replication of the viral genome,
3. Synthesis of the viral proteins by the host
cell translation machinery, and
4. Reassembly of these components into
progeny virus particles.
Viruses

9. Figure 24-14 Molecular Biology of the Cell (© Garland Science2008)

10. Bacteria
Most can be classified broadly by their shape as rods, spheres,spirals.
Gram-staining properties.

11. Their genomes are also small, typically between 1,000,000 and 5,000,000
nucleotide pairs (compared to 12,000,000 for yeast and more than
3,000,000,000 for humans).
Only a minority of bacterial species have the ability to cause disease in
humans. Some of those that do cause disease can only replicate inside the
body of their host and are called obligate pathogens.
Others replicate in an environmental reservoir such as water or soil and
only cause disease if they happen to encounter a susceptible host; these
are called facultative pathogens.

12. Many bacteria are normally harmless but have a latent ability to cause
disease in an injured or immuno-compromised host; these are called
opportunistic pathogens.
A small number of genes causes significant differences between a virulent
pathogenic bacterium and its closest nonpathogenic relative. Genes that
contribute to the ability of an organism to cause disease are called
virulence genes: proteins - factors.

13. Archaea
Unicellular prokaryotes•
• No peptidoglycan but pseudomurein
• Live in extreme environments
Methanogens (methane producing)
Extreme halophiles (salt liking)


 Extreme thermophiles (heat liking)
 Have specialized structures (flagella and pili) that often confer
critical capabilities.
In the past - archaebacteria
• Since have independent evolutionary history
• Differences in biochemistry - separate domain

14. nicellular yeasts, multicellular molds, and mushrooms)
mosses, ferns, conifers, and flowering plants)
Protists
Fungi (
u
(
Plants
Animals
Nomenclature
Designed by Carolus Linnaeus (1735), each living organism is assigned two
names which consist of a genus and a specific epithet, both of which are
underlined or italicized.
In 1978, Carl Woese gave a system of classification based on cellular
organization of organisms. It groups all organisms in three domains:
1. Bacteria (cell walls contain a protein–carbohydrate complex called
peptidoglycan)
Archaea2.
3. Eukarya,
(cell walls, if present, lack peptidoglycan)
which includes the following:
(slime molds, protozoa, and algae)•
•
•
• (sponges, worms, insects, and vertebrates)

15. Cell Type Prokaryotic Prokaryotic Eukaryotic
Cell Wall Varies in composition;
contains no Peptidoglycan
Containspeptidoglycan Varies in composition;
contains carbohydrates
Membrane Lipids Composed of branched
carbon chains attachedto
glycerol by etherlinkage
Composed of straight
carbon chains attachedto
glycerol by esterlinkage
Composed of straight
carbon chains attachedto
glycerol by esterlinkage
First Amino Acid in
Protein Synthesis
Methionine Formylmethionine Methionine
rRNA Loop that binds to
ribosomal protein
Lacking Present Lacking
Common Arm of tRNA Lacking Present Present
Table: Some Characteristics of Archaea, Bacteria, and Eukarya
Archaea Bacteria Eukarya
Tortora, G. J., Funke, B. R. and Case, C. L. 2004. Microbiology: an introduction 12th Edition, Pearson Education, USA.

16. Figure: A model of the origin of eukaryotes. Invagination of the plasma membrane
may have formed the nuclear envelope and endoplasmic reticulum. Similarities,
including rRNA sequences, indicate that endosymbiotic prokaryotes gave rise to
mitochondria and chloroplasts.
Tortora, G. J., Funke, B. R. and Case, C. L. 2004. Microbiology: an introduction 12th Edition, Pearson Education, USA.

17. Three domain system
Tortora, G. J., Funke, B. R. and Case, C. L. 2004. Microbiology: an introduction 12th Edition, Pearson Education, USA.

18. Figure. A tree of life including Archaea, Bacteria and Eukarya. Groups with asterisks are marine, or
include a large amount of marine organisms. (Figure adapted from Baldauf 2003 using the colouring
scheme of Barton et al. 2007 and the archaeal groups following Brochier-Armanet et al. 2008)

19. unicellular yeasts
pombe)
filamentous, multicellular molds
Fungi
Eukaryotes, heterotrophs
The fungal branch of the eukaryotic kingdom includes both
• (Saccharomyces cerevisiae and Schizosaccharomyces
• (like those found on moldy fruit orbread).
Most of the important pathogenic fungi exhibit dimorphism—the ability to grow
in either yeast or mold form. The yeast-to-mold or mold-to-yeast transition is
frequently associated with infection

20. Algae
Unicellular or Multicellular
Autotrophic organisms, ranging from unicellular
to multicellular forms.
Most are photosynthetic like plants, and "simple"
because they lack the many distinct cell and
organ types found in land plants.
Prokaryotic cyanobacteria are informally referred
to as blue-green algae, but now the term algae is
restricted to eukaryotic organisms.
The economic importance as soil fertilizer, as vitamin synthesizer and as food.
A few algae are known pathogens - to humans, mammals, aquatic animals,
and higher plants. A disease called protothecosis, which is caused by species
of green algae, affects humans and other mammals, especially those in
tropical countries.

21. Protozoa
Single-celled eukaryotes
More elaborate life cycles and mostly require the services of more than one host

22. Recommended Books:
1. Tortora, G. J., Funke, B. R. and Case, C. L. 2004. Microbiology: an introduction
12th Edition, Pearson Education, USA.
2. Black, J. G., 2005. Microbiology: principles and explorations, by 6th Edition,
J. Wiley & Sons, USA.
3. Talaro, K. P., 2006. Foundations in Microbiology: Basic Principles. McGraw
Hill. Publisher.