Monthly Archives: June 2011

24 Jun

Simple Stain

Using a single stain to color a bacterial cell is commonly referred to as a simple stain.  The most common dyes for this type of stain are methylene blue, fuchsin, and crystal violet.  These dyes work well because they have positively … Continue reading

20 Jun


Equipment for homogenization is chosen based on the viscosity of the sample among other considerations.  But what is viscosity?  The IUPAC Gold book defines Apparent Viscosity as “The ratio of stress to rate of strain” and Dynamic Viscosity as ”the ratio of … Continue reading

14 Jun

Ultraviolet Irradiation

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UV irradiation has been known to break down microorganisms for over 100 years.  Ultraviolet light at short wavelengths, 254nm, breaks down the molecular bonds in the microorganism’s DNA.  The use of UV light for sterilization is referred to as UVGI, ultraviolet … Continue reading

10 Jun

Smear Preparation

Bacterial smear preparation is an integral technique in microbiology laboratories.  There are several objectives when preparing a smear.  The first is to make sure that the cells adhere to the microscope slide so that they do not get washed off … Continue reading

06 Jun


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When choosing a centrifuge, RPM and RCF are specifications which must be considered.  In centrifugation RPM is of course revolutions per minute.  RCF is relative centrifugal force and the unit of measure is times the earths gravitational force at sea level or … Continue reading

03 Jun

Pure Culture Technique

In natural environments bacteria exist as mixed populations.  This presents a challenge when trying to study a single species.  It is very rare to find a single species living in natural environments.  Robert Koch, a pioneer in medical microbiology, knew … Continue reading