Chapter 5 Microbial Nutrition and Culture cont’d Siti Sarah Jumali (ext 2123) Room 3/14 [email_address]

Food Preservation Temperatures

Patterns of Oxygen Use

Plasmolysis

Responses to Salt

The Great Salt Lake in Utah

Types of Culture Media Type of Media Purpose Chemically Defined Growth of chemoheterotrophs and photoautotrophs: microbiological assays Complex Growth of most chemoheterotrophic organisms Reducing Growth of obligate anO2 Selective Suppresion of unwanted microbes; encouraging desired microbes Differential Differentiation of colonies of desired microbes from others Enrichment Similar to selective media but designed to increase numbers of desired microbes to detectable levels.

Three species of Candida can be differentiated in mixed culture when grown on CHROMagar Candida plates

Identification of urinary tract pathogens with differential media (CHROMagar)

The Streak Plate Method uses agar plates to prepare pure cultures

The Streak Plate Method Figure 6.11

Anaerobic Jar Figure 6.6

To culture obligate anaerobes, all molecular oxygen must be removed and kept out of medium. Agar plates are incubated in sealed jars containing chemical substances that remove oxygen and generate carbon dioxide or water

Anaerobic Transfer

An Anaerobic Chamber Figure 6.7

CHAPTER 6: MICROBIAL GROWTH

Binary Fission

Binary Fission

Thin section of the bacterium Staphylococcus , undergoing binary fission

Budding in Yeast

Synchronous growth : A hypothetical situation in which the number of cells in a culture would increase in a stair-step pattern, dividing together at the same rate Nonsynchronous growth : A natural situation in which an actual culture has cell dividing at one rate and other cells dividing at a slightly slower rate

Microbes growing continuously in a chemostat

Plate Counts Figure 6.17

2) Counting Bacteria by Membrane Filtration

The Petroff-Hausser Counting Chamber

Direct Microscopic Count

Counting colonies using a bacterial colony counter

Bacterial colonies viewed through the magnifying glass against a colony-counting grid

Which of these plates would be the correct one to count? Why? Countable number of colonies (30 to 300 per plate )

Turbidity

Turbidity The less light transmitted, the more bacteria in sample.

Biosafety Level 4 (BSL-4) Laboratory

Questions?