INTRODUCTION
Microbiology
three
cardinal objectives, namely: characterization, classification, and identification. The entire
‘
microbial world’ enjoys the reputation for being an extremely complex and extraordinarily diversified
domain with respect to their morphological, physiological, and genetical characteristic features. In the
light of the said glaring facts, it became almost necessary to afford a broad and critical classification as
a means of bringing order to the puzzling diversity as well as variety of organisms in nature. Therefore,
once the characteristic features of the various microbes existing in this universe have been duly established,
one may compare it with other organisms quite conveniently in order to draw a line amongst their
similarities and dissimilarities in particular. It would be a lot easier task to segregate the microbes having
the same features and subsequently group them together under a specific classified head or group known
as
‘classification’.
Based upon the enormous volume of researches made in the study of microorganisms, one has to
know their
characteristics prior to their legitimate identification and classification. Because of the
extremely minute and microscopical size of the microorganism, it may not be quite feasible to carry out
an elaborated study of the
characteristics of a single microorganism. In order to circumvent the above
difficulties, one may conveniently study the
characteristics of a culture i.e., a population of microorganisms
or the propogation of microorganisms. Therefore, the meticulous investigation of the
characteristics
of a
culture comprising a host of microorganisms,* it is as good as exploring the characteristics
of a
single organism. Pure Culture [Axenic Culture] : It refers to a ‘culture’ that essentially be
composed of a single type of microorganism, irrespective of the number of individuals, in a surrounding
absolutely free of other living microbes (organisms). Summarily, the process of establishing the
‘characteristics’
of microorganisms is not only a cardinal prerequisite for
classification but also play a varietyof vital, indeed essential, roles in nature.
CHARACTERIZATION
The microorganisms may be broadly characterized into the following categories, namely:
(
i) Morphological characteristics
(
ii) Chemical characteristics
(
iii) Cultural characteristics
(
iv) Metabolic characteristics
(
v) Antigenic characteristics
(
vi) Genetic characteristics
(
vii) Pathogenicity, and
(
viii) Ecological characteristics.
The aforesaid categories of characteristics shall now be treated individually in the sections that
follow :