BY MWEBAZA IVAN
Involves classification, nomenclature and identification
classification is the arrangement of organisms into groups
based on their mutual similarity or evolutional relatedness.
Nomenclature is the process of assigning names to a an
organism (and requires agreement for unambiguous usage of
Identification is the practical process of determining that a
particular isolate belongs to a given recognized group.(
microbiologists are usually concerned with this in practice)
DOMAINS OF LIFE
All life forms belong to three large groups/domains i.e.
Archaea, bacteria and eukarya (three domain system-
carl woese, 1977).
Have membrane bound organelles.
DNA is linear and found on x-somes in nucleus.
Transcription requires formation of mRNA and moves
outside of the nucleus.
Have glycerol fatty acyl diester membrane lipids.
classified as separate from Bacteria by Carl woese in
1977 basing on rRNA gene sequences,
considered as prokaryotes along side Bacteria.
Their transcription and translation enzymes are
more similar to those of eukaryotes than of bacteria.
Have isoprenoid glycerol diether or diglycerol
Have no membrane bound organelles,
Have single circular DNA.
Transcription and translation can be carried out
Have diacyl glycerol diester lipids in their membranes.
Importance of Bacterial taxonomy
Helps in predictions and frame hypotheses for further
research based on knowledge of similar organisms.
Easy communication among microbiologists
Organization of knowledge.
Classification of Bacteria
Bacteria are arranged into species, genera, families, orders
The species is the basic group.
A prokaryotic species is a collection of strains which share
many stable properties and differ significantly from other
It should have similar G+C composition and 70% or greater
similarity as judged by DNA hybridization.
Species should ideally be distinguishable phenotypically
from other species.
A strain is a popn of organisms which are considered
to have descended from a single organism as found in a
natural habitat, in primary culture and in sub cultures.
Strains in a species may differ slightly e.g. biovars ,
morphovars , serovars.
Type strain is the first strain studied and more fully x-
terized than other strains.
A type strain must remain with in the genus of which
it is the nomenclatural type, only those strains very
similar to the type species are included in the species.
Once taxonomically relevant x-tics have been collected, they
may be used to construct a classification:
Natural classification (developed by Linnaeus), considers
just the overall similarity/observable traits,basically
anatomical traits (phenetic classification).
Numerical (Adansonian) classification, some how related
to phenetic though information about the properties of
organisms is converted into numerical form and compared
using computer programms , similarity or matching
coefficients and dendograms are constructed .( Robert
Sokal and Peter H.A.Sneath)
Involves study of evolutionary r/ships among
groups of organisms which are discovered through
molecular sequencing data and morphological data
This considers the phenotype,genotype, molecular
sequences, evolutionary x-tics , and ecological
behaviors in classification of the organisms
The rules are set in International code for the
nomenclature of Bacteria.
Bacteria are named according to binomial system
developed by Carl Von Linne/Linnaeus
A species is designated with two latinized names i.e. genus
The first name is capitalized, second is not capitalized
Taxonomic names approved by the International
committee of systematic Bacteriology are considered
official and binding.
Bergey’s Manual of systematic Bacteriology contains the
accepted system of prokaryotic taxonomy
IDENTIFICATION OF MEDICALLY
Key parameters used:
Cell wall (rigid, flexible, or absent).
Intracellular or extracellular.
Shape of the organism.
Spore forming abilities.
Genetics. (rRNA sequences, hybridization, gene probes)
Cultural x-tics (diameter, outline, elevation,colour etc)
The ability to grow in absence or presence of oxygen
Acid fast e.g
Wall less e.g.
Microbiology 5th edition (Lansing M. Prescott)
Lange microbiology and immunology review 10th
edition (Warren Levinson)
Brocks biology of Microorganisms (Madigan,