Bacteria Colony Appearance Morphology

Topics: Bacteria, Escherichia coli, Microbiology Pages: 2 (517 words) Published: February 9, 2015
The following show expected colony appearances and morphologies (shapes) of Escherichia coli and Staphylococcus aureus. Note characteristics such as edges, color, and whether the colonies are rough or smooth in texture. For colony appearances of E. coli and S. aureus, scientists often describe what they look like on agar. This is not the microscopic view (for example, as with a slide) but a “naked eye” view of how the bacterial colonies look while growing on a medium. (This is one type of culture.) If it is just plain nutrient agar (like below) … and it depends on what kind of growth medium is used, the colors should be similar to the pictures below. (In these examples, the time after plating is different for the two samples, so be aware that the colonies in these photos are different sizes for a reason.) We will culture our bacteria for about 2-7 days. Characteristics are most visible if the bacteria are examined using a stereoscopic scope.

E. coli
Shape (form): circular
Margin: entire
Elevation: raised
Size: punctiform, small
Texture (surface): smooth
Appearance: shiny
Pigmentation: nonpigmented (colorless)
Optical property: translucent

S. aureus
Shape (form): circular
Margin: entire
Elevation: convex
Size: moderate, large
Texture (surface): rough
Appearance: shiny
Pigmentation: tan, golden yellow
Optical property: opaque

For all bacteria, they can be described
on the basis of these traits (how the
bacteria look) when grown on a medium,
poured and allowed to harden in a petri
dish. Characteristics of bacterial colonies
become one of the type of signatures;
keep in mind there are many ways that
bacteria can be identified. This is just one
of the ways that bacteria can be explored.

Here are how these particular bacteria are classified according to Bergy’s Manual of Systematic Bacteriology. (Remember there are 3 Domains and 5 Kingdoms of Life.)

E. coli
Domain: Bacteria
Phylum: Proteobacteria...
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