Taxonomy
govern) refers to the science or discipline that essentially deals with the logical arrangement of
living things into categories. It may also be defined as
‘the laws and principles of classification of living
organisms’.
Aristotle
—in fact, was the first ever taxonomist in the fourth century BC who painstakingly and
meticulously categorized the so-called
‘living objects’ in the universe into almost 500 well defined
species of plant and animal kingdoms.
Carolus Linnaeus
(1735 – 1759) — a renowned Swedish botanist, virtually named a relatively
much larger segment of plants and animals and classified them with great skill and wisdom into the two
predominant kingdoms, namely :
Plantae and Animalia. In reality, Carolus was instrumental in devising
the unique
‘Binomial Scheme of Nomenclature’.
Ernst H Haeckel
— in the year 1866 logistically segregated the ‘microorganisms’ from the
existing plant and animal kingdoms. It was Ernst who first and foremost introduced the new terminology
Protist
exclusively reserved for the microorganisms. He subsequently coined another term Protista to
specifically and categorically include algae (microscopic), fungi, and protozoa thereby forming a ‘
third
kingdom
’.
Comments
: (1) There was disapproval with regard to the inclusion of both bacteria and fungi
together in the aforesaid kingdom
Protista.
(2) Bearing in mind the recent advances in the domain of
‘Cell Biology’, profuse objections
were raised pertaining to the two or three kingdom classification schemes as
encountered in Protista.
Robert H Whittaker (1969)
— duly put forward a most scientific, plausible, and logical systemof classification of the living organisms which was widely accepted by the modern microbiologists
across the world. However, Robert’s system articulately recognizes the
five kingdoms applicable to all
living things, namely:
Monera, Protista, Fungi, Animalia, and Plantae.
Monera —
predominantly includes bacteria and cyanobacteria.
Protista
— essentially comprises of eukaryotes and protozoa.
Fungi
— specifically belongs to the organisms attached to the kingdom of fungi.
Animalia and Plantae
— particularly include the traditional animals and plants.
It is, however, pertinent to mention here some of the main terminologies, one may frequently
come across in the proper and elaborated description of the
taxonomy of microorganisms, such as:
(
a) Species – i.e., the fundamental rank in the classification system; (b) genus – i.e., clubbing together
of two or more
species ; (c) family – i.e., the collection of genera; (d) order – i.e., the collection of
families
with identical characteristic features ; (e) class – i.e., the arranging together of order ; (f) phylum
(or
division) – i.e., grouping together of classes; and (g) kingdom – i.e., collection of two or more
phyla
.
Taxon,
also known as the basic taxonomic group represents the species i.e., a collection of
strains with almost similar characteristic features. In usual practice, the
microbial species invariably
comprise of a specialized typical strain termed as the
type strain, along with all other strains which are
regarded very much identical to the
type strain so as to justify their logical inclusion in the species. In
other words, the
type strain is symbolized and designated to be the permanent reference specimen for
the species. However, it may be stressed that it is not necessarily always the particular strain which
happens to be most characterwise typical of all the strains strategically included in the
species, whereas
it is essentially the specific strain to which all the rest of the strains should be critically compared to
ascertain, whether they do have a close resemblance sufficient enough to belong to the same
species.
The above glaring statement of facts pertaining to the
type strains are extremely vital and important;
and, therefore, specialized and particular attention need to be given to their genuine and regular maintenance
as well as preservation. The following are
two world famous reference collection centres locatedin USA and UK, namely:
(
a) American Type Culture Collection (ATCC), Rockville, Maryland, USA, and
(
b) National Collection of Type Cultures (NCTC), UK.
Interestingly, one may critically observe that the various
strains strategically present very much
within
species may differ slightly from one another in three prominent manners, namely:
(
a) Biovars: These are variant bacterial strains and are duly characterized by biochemical or
physiological characteristics
.
(
b) Morphovars: These are variants within a species defined by variation in morphological
characteristics
.(c) Serovars: These are variants within a species defined by variation in serological reactions.