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Questions and Answers

What is colony size?

The diameter in millimeters of well isolated colonies. It may vary in size in different areas of the plate.

What is a punctiform (pinpoint) colony?

Colonies that are less than about 5 mm.

What does colony color refer to?

The color of bacterial and yeast colonies which can be light tan, cream-colored, or various other colors due to pigments.

Which of the following describes colony shape? (Select all that apply)

Filamentous Signup and view all the answers

What does elevation refer to in colony morphology?

How the colony rises away from the surface of the medium. Signup and view all the answers

What is a flat colony?

A flat colony lies completely flat along the surface of the medium. Signup and view all the answers

What is the difference between a raised colony and a convex colony?

A raised colony has its top above the medium but still parallel with the surface, while a convex colony curves across the top. Signup and view all the answers

What is a pulvinate colony?

A pulvinate colony is similar to convex but is higher off the plate. Signup and view all the answers

Define an umbonate colony.

An umbonate colony has a higher center than the edges. Signup and view all the answers

What characterizes a craterform colony?

A craterform colony has a depression in the center of the colony. Signup and view all the answers

Describe a hilly colony.

A hilly colony has an irregular surface with many elevations and depressions. Signup and view all the answers

What is referred to as the margin of a colony?

The margin is the edge of a bacterial colony. Signup and view all the answers

Which of the following describes an entire margin?

Smooth and with no irregularities Signup and view all the answers

What characterizes an undulate margin?

An undulate margin has a slightly wave edge. Signup and view all the answers

Define a lobate margin.

A lobate margin has large projections or lobes growing from the edge of the colony. Signup and view all the answers

What does an erose margin look like?

An erose margin has jagged, pointed projections on the edge. Signup and view all the answers

Describe a filamentous margin.

A filamentous margin has strand-like extensions into the agar. Signup and view all the answers

What does a curled colony look like?

A curled colony forms concentric rings of growth. Signup and view all the answers

What are optical properties in colony morphology?

Optical properties refer to how colonies differ in the way they transmit light. Signup and view all the answers

What are transparent colonies?

Transparent colonies are almost completely clear. Signup and view all the answers

What is the definition of translucent colonies?

Translucent colonies are not completely clear but permit some scattered light to get through. Signup and view all the answers

What are opaque colonies?

Opaque colonies completely block light transmission and are often heavily pigmented. Signup and view all the answers

What does texture refer to in colony morphology?

Texture refers to the smoothness or roughness of a colony. Signup and view all the answers

What characterizes smooth colonies?

Smooth colonies have a shiny surface and a slimy appearance called mucoid. Signup and view all the answers

What does a rough colony look like?

Rough colonies have a dull, rough appearance. Signup and view all the answers

What does filamentous refer to in texture?

Filamentous colonies appear to be a mass of small threads or fibers. Signup and view all the answers

Study Notes

Colony Morphology Overview

Colony Size: Refers to the diameter in millimeters of well-isolated colonies; can be influenced by space and nutrient availability.
Punctiform: Colonies with a size of less than 5 mm, often requiring magnification for further description.

Colony Color

Many bacteria and yeast exhibit light tan or cream-colored colonies.
Some species produce various pigments leading to colors like white, red, yellow, and purple.
Colonies can secrete soluble pigments that alter the color of the surrounding medium.

Colony Shape

Various shapes include circular, oval, spindle (tapered ends), irregular (asymmetrical), filamentous (fibrous), and rhizoid (root-like).

Elevation

Describes how a colony rises from the medium's surface; observed visually by tilting the plate.

Colony Elevation Types

Flat: Lies completely flat on the medium's surface.
Raised: Top is above the medium, yet parallel to the surface.
Convex: Curves at the top like a water drop.
Pulvinate: Similar to convex but higher off the plate.
Umbonate: Higher center with lower edges.
Craterform: Features a depression in the center, distinct from umbonate.
Hilly: Displays an irregular surface with various elevations and depressions.

Colony Margin Characteristics

Margin: The edge of a bacterial colony.
Entire: Smooth, without irregularities.
Undulate: Slightly wavy edge.
Lobate: Large projections or lobes from the edge.
Erose: Jagged, pointed projections along the edge.
Filamentous: Strand-like extensions into the agar.
Curled: Forms concentric growth rings.

Optical Properties

Colonies can vary in light transmission, observed by holding the petri dish up to the light.
Transparent: Almost completely clear.
Translucent: Not fully clear, allowing some light to pass through.
Opaque: Completely blocks light, often heavily pigmented.

Texture of Colonies

Refers to smoothness or roughness, observed by tilting the plate for light reflection.
Smooth: Shiny, with a slimy, mucoid appearance.
Rough: Dull and coarse texture.
Filamentous (texture): Appears as a mass of small threads or fibers.