Question

81 Exercise 7: Selective and Differential Growth Medium and Tests Questions 1. What elements are important to consider when recording data about the growth of an organism? 2. What are some ways that cause the same bacteria to grow differently in different conditions? 3. List the types of growth patterns in broth. There are four dikprent type broth = Pellicle, Sediment, and flocculent ok growth uniform fine pattin in turbidity 4. List the types of growth patterns or colony morphology in an agar slant. 5. What is pigment? Is a white colony pigmented?

Answer 1

Ans 1:  The growth of microorganisms is influenced by various physical and chemical factors of their environment.  Physical factors- Temperature, pH, osmotic pressure, hydrostatic pressure and radiation.  Chemical factors- Oxygen, carbon, nitrogen, phosphorus, sulfur, etc.

Ans 2: Basically the way through which same bacteria can adapt to the new conditions is through modification at genetic level. In bacteria there are 3 modes for doing so; Transformation is the method in which bacteria intake the genetic element of dead bacteria from the environment. in transfection when bacteriphages attack bacteria some part of bacterial genoe incorporated in the genome of the phage. After the lysis of the bacteria when this phage attacks some other bacteria its genome along wth the part of the genome of the previous bacteria gets incorporated inside the new bacterial genome. The thrid and the last way is through physical contact which is called conjugation; the physical contact is because of the pilli present on the surface of bacteria. One bacteria acts as donor and one acts as recepient. So because of the change at genetic level the same bacteria grows differently under different conditions.

Ans 4:  Categories of colony growth and appearance include:

• shape
• margin or edge
• elevation or depression
• color
• texture

Colony shapes:

• round, circular
• irregular
• punctiform (tiny, pinpoint)

Margin/Edge:

• Entire (smooth, no irregularities)
• Undulate (wavy)
• Lobate (lobed)
• Filamentous
• Rhizoid (branched)
• Swarming
• Spreading
• "Feet" (ex: Candida albicans yeast)
• Double zone of hemolysis
• Complete zone of hemolysis (beta)
• Partial zone of hemolysis (alpha)
• No hemolysis (gamma)

Colony Elevations/Depressions:

• Convex (rounded)
• Concave (depressed/sunken in)
• Flat
• Raised
• Pulvinate (very convex)
• Umbonate (raised in the center)
• Target-shaped

Colony Textures:

• Dull
• Shiny
• Mucoid (slimy)
• Dry
• Crusty
• Friable
• Moist
• Rough
• Smooth
• Crumbly
• Sticky
• Stringy
• Molar Tooth
• Powdery

Colony Color/Pigment Production:

• White
• Cream/Buff
• Purple
• Gray
• Yellow
• Red
• Green/Blue-Green
• Pink/Rose
• Orange
• Black centers

Optical Properties:

• Opaque
• Transparent
• Translucent
• Shiny
• Dull/Matte

Colony Scent/Odor:

• Flowery
• Fruit-like
• Bleach
• Ammonia
• Malodorous
• Putrid.

Ans 5: A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.

Yes, it is considered as pigmented because white color colonies are also being able to differentiated from the others.