Biology Lab Quiz 1: Key Terms and Techniques in Microbial Colony Morphology

Agar

nutrient-containing media solidified with agar, a complex polysaccharide extracted from a multicellular red-purple algal species

what is the ideal gelling agent and why

agar, its nontoxic to most microbes

What are Broths

nutrient-containing liquids that allow cells to grow in 3 dimensions

purposes of broths

1. produces a large number of cells

2. observes cell arrangements

3. observes anaerobic metabolic processes

what is a pure culture

a collection of cells of a single strain or species growing in an environment free from contamination by any other living forms

what is colony morphology

refers to the characteristics of the visible growth of expanding populations of microbes on solid and semisolid media (traits you can see without a microscope: color, size, shape, elevation, surface features)

whole colony pictures

edge pictures

elevation pictures

streak plate method

a technique where you use your inoculating loop to drag and physically separate cells on the surface of an agar plate

pour plate method

cells are added to melted agar, the agar is then poured into a plate, and colonies will appear at points where the cells were trapped

dilutions are created by transferring loopfuls of cells from one tube to the next in a series

Why do streak plating and pour plating result in isolated colonies?

they allow you to physically separate cells on a solid medium which then allows them to divide and create colonies

what is a colony

a visible mass of cells, contains cells that are genetically identical clones

terms used to describe the whole colony in colony morphology

1. circular

2. irregular

3. rhizoid

terms used to describe the edge in colony morphology

1. entire

2. undulate

3. lobate

4. filamentous

terms used to describe the elevation in colony morphology

1. flat

2. raised

3. convex

4. umbonate