BACTERIOLOGY THIRD LECTURE (A)
(DR. PETER)
WHITTAKER’S
KINGDOM CONCEPT
This is a
more recent and comprehensive system of classification, it is called the five
kingdom classification scheme proposed by R-H Whittaker in 1969. This
classification is based on three level cellular organizations. This care up in
order to accommodate three principle mode of nutrition: photosynthesis,
Absorption and ingestion.
On the basis
of the above characteristics the procaryotes are placed in the kingdom Monera
because they lack the ingestive mode of nutrition. The Unicellular Eucaryotic
micro-organisms are placed in the kingdom Protista: the nutritional types are
represented in the kingdom.
Fig1.1 Image of a
simplified representation of Whittaker’s five kingdom system
As it can be seen in the diagram, the Whittaker’s
classifications the nutritional mode is continuous, the mode of nutrition of
the micro algae is photosynthetic, and that of protozoa is ingestive and the
mode of nutrition in some other protist is Absorptive with some overlap to the
photosynthetic and ingestive mode.
The multicellular and multinucleoids eucaryotic organism are
classified in the kingdom plantae (multicellular green plants and higher Algae)
multicellular animals are classified nin the kingdom Animalia and the
multinucleoids higher fungi in the kingdom fungi their varying nutritional mode
leads to a more diversified cellular classification.
Microorganisms
are found in 3 of the 5 kingdom, Monera (bacteria and Cyanobacteria) Protist
(Micro algae and Protozoa) Fungi (Yeast and molds).
DIFFERENCE
BETWEEN GRAM +VE AND GRAM –VE BACTERIA
S/N
|
GRAM –VE
|
GRAM +VE
|
1.
|
They are
constant in their gram reaction
|
They
show variation in their gram reaction i.e. Gram variable
|
2.
|
Less
susceptible to penicillin antibiotics
|
They are
susceptible to penicillin antibiotics
|
3.
|
They are
more susceptible to disintegration by mechanical means and or enzyme
treatment
|
They are
less susceptible to disintegration by mechanical means or enzyme treatment
|
4.
|
They are
more susceptible to Streptomycin antibiotics
|
They are
less susceptible to Streptomycin antibiotics
|
5.
|
DAP is
found in all Gram-VE cells. Gram-VE cells lacks L-lysine
|
Most
Gram+VE cells possess L-lysine
|
6.
|
Contain
less amount of peptidoglycan
|
90% of
Gram+VE cell is made up of peptidoglycan
|
7.
|
Teichoic
acid is absent
|
Teichoic
acid is present
|
8.
|
Wall
made up of large amount of lipids
|
Contain less
amounts of lipids, contain more polysaccharides.
|
9.
|
Iodine –
Crystal violet complex extractable by alcohol which is an organic solvent
|
Iodine –
Crystal violet complex not extractable by alcohol
|
10.
|
Cross
linkage in the formation of the peptidoglycan is by direct peptide linkage of
the amino acid group of DAP to the carboxyl group of the terminal D-alanine.
|
CLASSIFICATION
OF MICRO – ORGANISM
1.
Intuitive method
2.
Adamsonian or Numerical method
3.
International classification
4.
DNA Homology
5.
Ribosomal RNA sequencing/Ribosomal
oligonucleotide cataloging.
CLASSIFICATION
OF TAXONOMY OF BACTERIA
Taxonomy is
the systematic arrangement of organism in groups, these groups or categories are
called Taxon such classification is done according to definite scheme.
Scientist name
are given to organism. Taxon offer adequate study. Publication of description
and other describe formalities.
Systematic
naming of organism is called nomenclature and scientist name are given by
scientist after mutual agreement e.g. the specie Lactobacillus. Plantarum was publish by the famous Swedish Botanist
Carl Linnaeus in 1753 representing the first biological classification that
shows the Binomial System (2 Names) of Nomenclature, from this is clear there
are two basic/features in the scheme-genus and the specie. These are now
accepted as the unit of classification in taxonomy.
However, with
bacterial the concept of specie is very difficult to define unlike the higher
plants and Animals, this is because there is no precise and universally
accepted definition of bacteria. This problem of defining bacteria species is
further complicated by the lack of apparent biological and evolution
relationship between bacteria and their living organization.
The minute
nature or size of bacterial cell of only a few character upon which to base a
classification because of this bacteriology have been compelled to used
secondary characteristics such as biochemical and physiological properties of
classification.
REAL
DIFFICULTY OF BACTERIA CLASSIFICATION
1.
There is no natural or phylogenetic
classification of bacteria (no form of bacteria is more complex than the other
bacteria on revolution) i.e. there is no evolutional trend in bacteria.
2.
There is lack of authentic cultures and
standardized procedure.
3.
Alteration of a gene (they are the most
primitive of all existing cells here they are amenable to mutation) this
mutation causes a number of problems.
Micro-organism or bacteria with some
character today may lose such character, the following today as can be seen in serrating
marcescens. This wild type of this organism produce a brilliant red pigment
called prodigiosm whereas the rare white colonies of this organization whereas
the rare white colonies are different from the red pigment producing colonies
phenotypically but all the same physiological and biochemically.
In some
instances the white colonies may revert to the red colonies producing red
pigments this is called reverse mutation, such a sudden inheritable charge in
phenotype is known as mutation, it may occur naturally or spontaneously or the
change may be induced artificially by man using chemical or physical agent, the
chemical agent are called mutagens and include among others acridine, dyes,
ethylmethyl sulphunate, mustard gas, X-rays, UV rays.
UNITS
OF CLASSIFICATION
SPECIE
In bacteriology
the specie is a single kind of bacterium all in the individual cell or
identical or nearly so. In actuality this identity of cell rarely exists this
is because in any culture of a single species, mutant strains will be found in
any different characteristics. Although these cells may show some staining
similarities but some minute biochemical change would have taken place. Usually
the differences are not extreme and they represent only temporary fluctuation
from principal types. When two bacteria have one or well-marked morphological difference
and exhibit important metabolic or other different between them that are
constant, the two may be regarded as distinct specie.
GENUS
A genus is ideally
a group of specie all of which bear different resemblance to one another to be
considered closely related and easily distinguishable for members of other
groups of genera. The boundary of some genera are sharply define by as few as 3
characteristics e.g. for;
1.
It is aerobic
2.
It forms endospores
3.
They are rods
For clostridium we have……
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BACTERIOLOGY STM311