Thursday, April 26, 2012

Applications Thursday: Bacterial Growth Measurements in a Microplate Reader

Scientists have cultured micro-organisms for many years in liquid media, measuring cell proliferation in a cuvette using the absorbance at 600nm. The use of microplates in formats up to 96 well has provided the means to measure multiple conditions simply and easily in the appropriate microplate reader. The advent of microplate readers with temperature control and shaking options has provided researchers with the possibility of long term studies requiring no user interaction, other than to load the plate and analyze the data. Microplate readers that offer the capacity to read in multiple modes, absorbance, fluorescence and luminescence, provide further flexibility in the potential experiments that can be performed by enabling the assessment of gene expression or cell activity in relation to growth, for example.

Microbes that have no specific atmospheric requirements for growth will be happy in the standard environment of the microplate reader. Those requiring more specific oxygen or carbon dioxide conditions may grow but not in a representative or healthy manner, potentially compromising the experiment. The Atmospheric Control Unit (ACU) from BMG LABTECH provides the researcher with a system that uniquely enables control of both the oxygen and carbon dioxide concentrations in an independent manner.

Microbes that have been demonstrated to grow well in the BMG LABTECH readers without the need for gas control are: E.coli (AN207), Salmonella enteric (AN140), Vibrio fischeri (AN199), Candida albicans (AN189), and Corynebacterium glutamicum (AN125).

However, more fastidious microbes require elevated CO2 levels as clearly shown with Neisseria meningitides (AN155) that thrive in a 5% CO2 environment. In addition,  Campylobacter jejuni has even more stringent requirements for healthy growth,  42°C with 7% O2 and 10% CO2 (AN 217), with similar stringent growth requirements for Helicobacter.

The ability to effectively grow microbes in optimum conditions allows for the possibility to design experiments to investigate many parameters, including antibiotic resistance minimum inhibitory concentrations. The design of the ACU allows the researcher to simply define the O2 and CO2 concentrations required, without the need to change gases or to use expensive premixed gases on different days for different microbes.

Here is a list of the Bacterial Growth Applciation Notes mentioned above:
AN 207: Assessing Microbial Metabolism Using A Simple ‘Mix & Measure’ Oxygen Consumption Assay
AN 140: High-Throughput Determination of Bacterial Growth Kinetics using a FLUOstar OPTIMA
AN 199: Monitoring Bacterial Cell-to-Cell Communication “Quorum sensing” Using FLUOstar OPTIMA
AN 189: High-Throughput Method for Dual Assessment of Antifungal Activity and Growth Kinetics Using a FLUOstar Omega
AN 125: Monitoring of Microbial Growth Curves by Laser Nephelometry
AN 155: Growth of Neisseria meningitidis in the FLUOstar OPTIMA with Microprocessor Controlled Gas Vent
AN 217: Growth of Campylobacter using BMG LABTECH's FLUOstar Omega equipped with ACU

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