This document discusses various characteristics used to describe microbial colonies, including colony appearance, elevation, margins, optical density, color, and odor. Colony appearance can include cotton-like, dry and chalky, or have shapes like circular, filamentous, rhizoidal, dot-like, or irregular. Elevation describes the colony's depth over the agar surface as flat, raised, convex or umbonate. Margins, optical density, color, and odor are also used to identify microbial colonies. Certain microbes produce characteristic smells like an earthy odor from actinomycetes or fruity smell from fungi.

1. Vivek kumar
MSc MICROBIOLOGY
Bangalore University

3.  COLONY APPEARENCE –
 Many fungi produces colonies which are similar
to cotton wool. The molds produce colonies which
on aging develop to a dry chalky apperances.
They may be circular, filamentous ,rhizoidal
,punctiform(dot like),irregular or spindle shape.
 .

4.  COLONY ELEVATION –This form is used to
describe the depth of the colony developed
by microbes. A colony may be flat (thin film
over the agar surface), raised , convex or
umbonate.

5.  COLONY MARGINS
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7.  OPTICAL DENSITY-The colony may be
transparent or translucent(foggy in
appearance) or opaque (not permitting
light to pass through).
 COLONY COLOUR –Many microbes
develop colonies which are pigmented. Such
coloured substances are either water soluble
or insoluble. The soluble pigments diffuses
out in the medium.

8.  COLONY ODOUR- Some microbes produce
a characteristics smell which sometimes
helps in identifying microbes.
 The actinomycetes produce an earthy odour
which is quite often experienced after a first
shower or rain.
 Many fungi produce fruity smell while E.coli
produces a faecal odour.