Question

Think About It... 1. Speculate about the results of the following errors in aseptic i culturing technique. Would pure culture be maintained? Would contamination occur? Why? • Placing caps on lab bench while performing transfer • Holding tubes at a 45° angle away from each other in the hand held in a TV shape Old culture tube is held in space nearest pointer in hand, rather than nearest ring finger: Tubes are held open while instrument is flamed: 2. What are the two main purposes of subculturing? 3. If you suspect that a broth culture is contaminated, what technique would you use to find out? What results would confirm a contamination had occurred?

Answer 1

1) Placing cap on lab bench while performing a transfer = Contamination can occur if the laminar hood or biosafety cabinet should not be wiped properly with 70% ethanol ..Using the laminar flow cabinet: Work well into the cabinet. That grating at the front of the hood is part of the air flow - it is not a clean area. Remind coworkers to avoid walking too fast near the hood when it is in use and avoid making fast movements in and out of the hood. Ensure that everything you need is in the hood before you begin.DO NOT pass anything over an open container that is meant to be kept sterile.

Holding tubes at 45 degree angle =No contamination sould not occur if we will held the tubes at 45 degree angle...but we should wear gloves...bare handed we should not handle the tubes

old culture tubes is held in space nearest pointer in hand rather then nearest ring finger ....yes its right and contamination will not occur

Tubes should remain close so that contamination can be avoided ...

2)  Two basic approaches are used: mechanical separation or chemical separation from the substratum.

3) For bacteria:...Look for shape moving around that are distinct from your cells.

For yeast and fungi:....Look for clumps, mats, budding (yeasts) and colonies on the surface of the media (fungi).

If your media contains phenol red: look for changes in the color of your media as this indicates pH changes. If it starts to go orange/yellow, you may have a problem (either contamination or you need to replenish your cell’s media supply more frequently).

Look for signs of turbidity or cloudiness of the media.