Wednesday, July 15, 2020

A Dedicated Solution for Microbial Growth Analysis

The global microbiome is composed of the microorganisms such as bacteria, algae, and fungus that surround us and are foundational to the world we live in. While microbiologists have been studying microorganisms for centuries, we are barely starting to understand the complexity and diversity, of microbes as a tool and as an agent in the pathophysiology of disease. The growth characteristics of microbes are some of their most commonly studied phenotypic traits and are used for a wide variety of applications, including screening for new antibiotics, characterization of new microbial isolates, and interrogating clones for the bioremediation of toxic waste or wastewater treatment.

Microbial growth is traditionally measured using optical density measurements—most often taken at 600 nm-- as a proxy for turbidity. Originally, these were conducted growing the microbes in an Erlenmeyer flask with shaking incubators, and then measuring the optical density of the suspension in a 1 cm cuvette with a spectrophotometers over time to get a kinetic analysis of the microbial growth. These studies provide robust data on the lag time, log phase, and the time to reach the stationary phase of growth, but are typically laborious, requiring multiple samples from each culture during a 6-, 12-, 24- or even 72-hour time course.

These 3 phenotypic characteristics are used to understand microbial growth and the difference between microbial samples.

The use of multi-well microtiter plates in incubated microplate readers has greatly increased throughput and automated the data acquisition steps. However, microplate readers have some constraints when it comes to microbial growth analysis. In normal aerobic growth conditions, accurate growth measurements require efficient mixing of the samples and controlled incubation temperatures. Also, as the plates require constant shaking and incubation, growth analyses are limited to one plate per instrument.

Mixing is critical to delivering accurate results in two ways. One is to keep the samples properly aerated so dissolved oxygen is not a limiting factor to the growth conditions. The second is to maintain cell suspension. Inconsistently suspended cells can lead to artifacts in the turbidity measurements. Surface tension in the small diameter wells makes it difficult to get proper mixing of microbial samples in microtiter plates. As efficient mixing to provide aeration and to maintain cell suspension are critical to proper microbial cell growth, this limitation have restricted researchers ability to fully realize the throughput and automation aspects of microplate readers. The rigorous shaking required to break the surface tension in microwells can also take a toll on the mechanics of many plate readers.

The other critical element to microbial growth is temperature. Microorganisms are very temperature sensitive. Fluctuations and gradations in incubation temperatures will result in inconsistent growth and have a negative effect on growth analyses in microplate readers, causing erroneous results, and edge or plate effects. Without proper temperature control in microplate readers, the results are variable and unreliable.

The LogPhase™ 600 is the first microplate reader dedicated to microbial growth analysis, addressing the constraints of microplate readers for these assays. The shaking profile of the LogPhase 600 has been tuned, in both the shaking speed and amplitude, to rigorously shake samples assuring proper aeration and suspension of the samples. The shaking mechanism has been designed from the ground up with limited mechanical connections and a robust motor, followed by painstaking testing to make sure this instrument delivers a lifetime of robust performance for microbial growth analyses. The incubation chamber has also been carefully designed with 11 independent thermistors to measure and adjust temperature of the incubation chamber to ascertain consistent temperature conditions across all four plates the reader can measure in a single run. With only one application in mind, LogPhase 600 delivers the highest data quality, reliably, four microplates at a time.

Tell us about your microbial growth studies and learn more about BioTek’s LogPhase 600 here.

By: BioTek Instruments, JD Herlihy, Product Manager

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