This document provides information on the classification and characteristics of microorganisms. It discusses the four main groups of microorganisms - viruses, bacteria, fungi, and protists. For each group, it describes their structure, reproduction methods, examples of important diseases or species, and how they are classified. The document also covers symbiotic relationships between microorganisms and plants.

1. UNIT 1:
BIODIVERSITY AND
THE CLASSIFICATION
OF MICRO-
ORGANISMS
(Campbell and Reece (2010),
Chapter 19, 6 p. 98, 28, 31, 43)

2. MICRO ORGANISMS
 Microorganisms are very small life
forms (ultramicroscopic)
 Microscope examination
 Microbiology: The study of micro-
organisms and their interactions with
the environment and other life forms.

3. IMPORTANT MICROORGANISMS:
 Groups:
 VIRUSES
 BACTERIA
 FUNGI
 PROTISTA

4. VIRUSES
 Are “substances” that cause diseases
and can be transmitted between
organisms.
 Acellular?????
 Obligated intracellular parasites??
 Outside the host – virus metabolically
inert.

5. All virus particles consist of two
parts :
 a central core of a nucleic acid strand
(DNA/RNA)
 surrounded by a protein covering called
a capsid.
nucleocapsid

6.  Some viruses - additional covering
external to the capsid – called the
envelope
 Virus with envelope - enveloped viruses
and those without it = naked viruses.
 Envelope can have accessory structures.

7.  The capsid consist of sub-units called
capsomeres.
 The capsomeres have perfect geometric
shapes.
 Depending on the shape and
arrangement of these capsomeres, two
types of capsids may be
identified, namely helical and

8.  Helical and Icosahedral capsids

9. What criteria are used to classify a
virus?
geometry of the virus,
whether they have envelopes
the identity of the organism they infect
transmission mode
the disease they cause
the type of nucleic acid.

10. Patterns of viral replication
1. The lytic cycle.
Viruses enter a cell, replicate, and then
cause the cell to burst, releasing new
viruses.
2. The lysogenic cycle.
Viruses enter a long term relationship with
their host cells. Their nucleic acid replicates
as the host cells multiply.
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12. DIFFERENCE BETWEEN LYTIC AND LYSOGENIC
CYCLES

13. The replication cycle of a
bacteriophage (T4)
• Bacteriophage: A virus that attacks bacteria cells.

14. HIV
• Retroviruses use reverse transcriptase to copy
their RNA genome into DNA
• HIV (human immunodeficiency virus) is the
retrovirus that causes AIDS (acquired
immunodeficiency syndrome)

15. HIV REPRODUCTION

16. BACTERIA
• Microscopic, unicellular prokaryote????.
• Most are heterotrophic but some are capable
to photosynthesize.
• With respect to their oxygen requirement –
3 types:
 aerobic ( need oxygen to survive)
 facultative (can survive with or without
oxygen)
 anaerobic (oxygen will kill these bacteria).

17. Structure of a bacterial cell
• Flagellum: motility of cell
• Pilli: help with conjugation
• Cell envelope: consist of the glycocalyx, cell wall and
plasma membrane – protection
• Slime capsule: protect against loss of water and
stomach/soil acids.
• Cell wall: consist of peptidoglycan – maintain shape of cell.
• Plasma membrane: selective barrier that allows
oxygen, nutrients and wastes through cell.
• Nucleoid: consist of DNA - form chromatic bodies/plasmids.
Genetic information for reproduction.
• Ribosomes: complexes that make proteins (rRNA)

19. Bacteria are classified according to
their shape and arrangement

20. Reproduction and life cycle of
bacteria
• They reproduce asexually by :
budding and/or
simple binary fission
• There is no mitosis.
• They generally gave a single chromosome.
• Genetic exchange may occur through
conjugation.

21. Budding of bacteria.
• Cell's genetic information is
duplicated, creating an identical copy or clone
of the original cell.
• As the new cell pinches off or buds from the
surface, a bud scar is produced.

22. Binary fission of bacteria

23. IMPORTANCE OF BACTERIA
ECONOMICALLY
• Sulphur oxidizing bacteria can break down
copper sulphide into copper sulphate for
copper oar mining.
• Fermentation bacteria is used to produce
cheese, yogurt, buttermilk…..
• Lactobacillus is used to make cheese.
• Vinegar is made when wine/cider is
fermented by acetic acid bacteria.

24. IMPORTANCE OF BACTERIA
AS PATHOGENS CAUSE DISEASES SUCH AS:
• Diphtheria: Bacteria affecting the pharynx –
transmitted through coughing or sneezing.
• Tuberculosis: Bacteria that attack the lungs –
transmitted through saliva
• Plague: Bacteria that infects the lymph nodes
– transmitted to man from flee bites (flees
come from rodents).

25. IMPORTANCE OF BACTERIA
ECOLOGICALLY
• Bacteria form part of the nitrogen cycle
(denitrifying -, nitrifying – and nitrogen-fixed
bacteria)
• Bacteria are also involved in the sulfur and
phosphorous cycles.
• Bacteria act as saprophytes – break down
complex organic molecules into simple inorganic
molecules.
• In rural areas bacteria is used in septic tanks to
help to dispose of sewage.

26. FUNGI (MYCOPHYTA)
• Fungi include moulds, mushrooms, yeast and
mutualistic organisms.
• Fungi are divided into macroscopic fungi and
microscopic fungi.
• Fungi are heterotrophs, but cannot ingest their
food, they absorb nutrients from the environment
outside of its body. They secrete enzymes into
their surrounding environment which digests the
food before absorption

27. YEAST
MOLDS
MUSHROOMS
PARASITIC FUNGI

28. FUNGI STRUCTURE
• Fungi have vegetative filaments called
hyphae, with or without cross walls/septa.
• Hyphae cell walls consist of fungal
chitin, surrounding a plasma membrane and
cytoplasm.
• The hyphae form an interwoven mass called the
mycelium which infiltrates the medium on which
it grows/lives.
• Coenocytic fungi have continuous cytoplasmic
masses with several nuclei.

29. FUNGI EXAMPLE: Rhizopus stolonifer
Kollumella

30. The hyphae can be named specifically
according to where they grow:
• Rhizoids penetrate the substrate,
• the stolon grows on the surface of the
substrate and
• the sporangiophore grows upright
and contains the sporangium which
contains the spores for asexual
reproduction.

31. Reproduction of fungi
 Fungi can reproduce asexually (during favourable
conditions) or sexually (during unfavourable
conditions).
 We will study the reproduction of the bread
mould: Rhizopus stolonifer ( Class Zygomycetes)

33. PROTISTA
Protists:
• are unicellular (one cell)
• are Eukaryotes ( have a definite nucleus and
membrane-bound organelles)
• all are surrounded by a cell membrane.
• Can move by means of flagella
(Euglena, Trypanosoma), cilia (Paramecium) or
pseudopodia (Amoeba)
• (most) have a contractile vacuole – stores water
and nutrients + involved in osmoregulation.
• Form a food vacuole after the intake of food.
• Are filled with cytoplasm: ectoplasm + endoplasm.

34. PROTISTA
Protists:
• Can feed:
• autotrophic (photosynthesize)
• Heterotrophic (depend on other organisms for
food)
• Or parasitic (feed on living organic material)
Gaseous exchange occurs through the cell
membrane – oxygen diffuse in the cell and carbon
dioxide diffuse out of the cell.

35. PROTOZOA (SUBKINGDOM OF PROTISTA)
Protozoa take in food by means of:
1. Phagocytosis: The process whereby
pseudopodia are formed around a food
particle, together with water and lysosomes to
form a food vacuole. The lysosomes secrete
hydrolytic enzymes to digest the food.
2. Pinocytosis: small particles are brought into
the cell—forming an invagination, and then
suspended within small vesicles that
subsequently fuse with lysosomes to
hydrolyze, or to break down, the particles

36. PROTOZOA
Protozoa take in food by means of:
PHAGOCYTOSIS

37. Reproduction: Sexual:
Types of gametes
1) Isogametes – one of a pair of gametes that
are morphologically the same
2) Anisogametes – gametes that are
morphologically different e.g. sperm and egg
3) Microgametes – male gametes
4) Macrogametes – female gametes

38. Reproduction: Sexual
1. Conjugation * Exchange of gametic nuclei
* Exchange of genetic material
2) Syngamy: * Fusion of anisogametes
(sperm & egg)
3) Autogamy * Fusion of haploid nuclei from
the same individual
* Fusion of isogametes

39. Protista is classified in the following
way:

40. CLASSIFICATION OF PROTISTA

41. Euglena – classification and traits
Kingdom: Protista
Subkingdom: Protozoa
Phylum: Sarcomastigophora
Subphylum: Mastigophora
Class: Phytomastigophorea (e.g.
Genus:Euglena
Characteristics:
* Have one/two flagella
* Have a spiral / crystalline rod inside flagella
* Cytoskeleton
* Autotrophs in sunlight and heterotrophs in the dark
engulfing food by phagocytosis

42. Long flagellum
Eyespot
Short flagellum
Contractile vacuole
Nucleus
Chloroplast
Plasma membrane
Light detector
Pellicle
Euglena (LM) 5 µm
Euglena

43. Classification and traits of Trypanosoma
Kingdom: Protista
Subkingdom: Protozoa
Phylum: Sarcomastigophora
Subphylum: Mastigophora
Class: Zoomastigophorea
Genus: Trypanosoma
Characteristics:
Cause African sleeping sickness in humans

44. Classification and traits of Trichomonas
Kingdom: Protista
Subkingdom: Protozoa
Phylum: Sarcomastigophora
Subphylum: Mastigophora
Class: Zoomastigophorea
Genus: Trichomonas
Characteristics:
Pathogen causing severe infection in human
females called vaginitis

45. Classification and traits of Amoeba
Kingdom: Protista
Subkingdom: Protozoa
Phylum : Sarcomastigophora
Subphylum: Sarcodina
Genus: Amoeba
Characteristics
* Fleshly Pseudopodia

46. Classification and traits of Plasmodium
Kingdom: Protista
Subkingdom: Protozoa
Phylum : Apicomplexa
Class: Sporozoea
Genus: Plasmodium
Characteristics
* Parasite that cause malaria in humans (primary host) –
mosquito’s are the intermediate hosts.
* One end, the apex, contains a complex of organelles
specialized for penetrating a host
* Have complex life cycle with asexual and sexual stages which
require two or more different hosts for completion

47. Life cycle of Plasmodium

48. Classification and traits of Paramecium
Kingdom: Protista
Subkingdom: Protozoa
Phylum: Ciliophora
Genus: Paramecium
Characteristics:
* Contains cillia
* Binucleated (micro and macronucleus)
* Asexual reproduction by binary fission

49. SYMBIOTIC RELATIONSHIPS OF
MICROORGANISMS WITH PLANTS
 Plants have mutualistic relationships with several groups
of bacteria that help make nitrogen more available.
 3 types of bacteria are important:
1. Nitrogen-fixing bacteria: converts atmospheric nitrogen
into ammonia which in the soil binds with a hydrogen ion
to for ammonium.
2. Ammonifying bacteria: decompose protein into
ammonia which in the soil binds with a hydrogen ion to
for ammonium.
3. Nitrifying bacteria: converts ammonium into nitrates
which can be absorbed by plants.

50. SYMBIOTIC RELATIONSHIPS OF E. coli
IN THE HUMAN BODY
 Escherichia coli commonly abbreviated E. coli
 It is a gram negative, rod-shaped bacterium that is
commonly found in the lower intestine of warm-blooded
organisms (endotherms).
 Most E. coli strains are harmless, but some serotypes can
cause serious food poisoning in humans.
 The harmless strains are part of the normal flora of the
gut, and can benefit their hosts by producing vitamin K
and by preventing the establishment of pathogenic
bacteria within the intestine

51. E.coli found in the human colon

52. DISEASES CAUSED BY MICROORGANISMS
Do research on the following diseases:
• HIV – viral disease
• Tuberculosis – bacterial disease
• Malaria – protista disease
• Thrush – fungal disease

53. WHAT SOULD I KNOW ABOUT THE
DISEASES?
 The genus name of the organism that causes the disease,
 the symptoms of the disease,
 what part of the body is affected by the disease
 possible treatment for the disease.
You do not have to hand this in, but there
will be questions in the exam and tests on
it.