Technical note: LFNS-SMOD-0.4

smod Smart Measuring Optical Device

™  

Abstract

The SMODTM or Smart Measuring Optical Device, is a sensor that monitors cell growth

in situ by measuring the Optical Density

(OD600) of the culture and transfers real-time

data to a Windows PC. The device and data are managed by the SMOD Control

Software (v1.0).

In this technical note we demonstrate the

reproducibility of the data produced by the

SMOD and describe how growth curves can

be generated using the SMOD.

Authors Grand, R. S., Saraswat, M., Lifeonics Ltd.

Keywords Optical Density monitoring (OD600),

Data consistency, Growth curves, Growth rate determination, Mutant

strain analysis.

Copyright © 2016, Lifeonics Ltd.

Effortless growth curves with the SMOD

Copyright © 2015, Lifeonics Ltd.

Introduction

Different microorganisms or microorganisms

grown under different conditions have varied

growth rates. Commonly, to determine the

growth rate of a microorganism, a growth curve is generated. To do this, a cell culture

is inoculated with a low number of cells and

the Optical Density (OD600) of the culture is

measured at regular intervals over many hours. This is a time consuming task that

requires the researcher to be present for

many hours to measure the OD600. The Smart Measuring Optical Device (SMODTM)

provides a long awaited solution to this task

by measuring the OD600 of a culture in situ,

in real-time and transmitting the data wirelessly to a PC, automatically creating a

growth curve and freeing up researchers

time.  

How the SMOD he lps to

generate growth curves? Many parameters alter the growth rate of

microorganisms such as growth medium

(Figure 3), temperature and mutations (Figure 4). For many procedures the growth

rate of microorganisms needs to be

determined. For example, to be able to estimate how long it will take for a culture to

reach a specific OD600 or to compare the

g r o w t h r a t e b e t w e e n d i f f e r e n t

microorganism strains. The conventional way to produce a growth curve requires a

researcher to take samples of a cell culture

at regular intervals over many hours and measure the OD600 in a bench top

spectrophotometer. This has a number of

issues. First, monitoring multiple cultures at

once is a time consuming process. Second, once cultures reach high ODs they need to

be diluted to be accurately measured in a

bench top spectrophotometer. Third, as a

result of the first two issues, the culture cannot be monitored at short time intervals

(e.g. every 10 minutes) because the

researcher would have to continually take measurements. This would frequently

interrupt the culturing process (e.g. shaking

speed and cause fluctuations in incubation

temperature) because the incubator is opened every time a sample(s) is taken,

resulting in high variability between

measurements. The use of the SMOD elevates these issues by enabling the OD600

of many cultures to be monitored in parallel

and to high OD600 without the need for

culture dilution. Furthermore, because the measurements are taken in situ, the culturing

process is not interrupted and the

measurements can be taken at shorter time intervals (as frequent as every 10 minutes).

As a result the SMOD delivers highly

reproducible data (Figures 1 - 2), generates

clean growth curves and enables the precise determination of growth rate (Figures 1 - 4).

Conclusion

D e t e r m i n i n g t h e g r o w t h r a t e o f microorganisms is a common technique

used to estimate how long organisms take

to reach a particular growth phase or to

compare the growth of different organisms. This is a time consuming and laborious task

that no one enjoys. With the SMOD - the lab

is in the sample - enabling real-time, continuous monitoring of culture growth

without interrupting the culturing process.

This provides an effortless method to

determine the growth rate of any microorganism grown in a suspension

culture.

Copyright © 2016, Lifeonics Ltd.

Figure 2. Optical density measurements taken by SMODs in separate Yeast cultures are highly reproducible. The growth of three separate Yeast (Schizosaccharomyces pombe) cell cultures in YES medium was monitored with the SMOD over-night. Cells were grown at a constant temperature (300C) with agitation (200rpm) and the average Optical Density (OD600) measurements of the three SMODs is graphed with the standard deviation (Black). Also shown is the average temperature of the cultures as measured by the SMOD with the standard deviation (Blue).

Figure 1. Optical density measurements taken by two SMODs in the same Escherichia coli culture are highly reproducible. The growth of E. coli cells in LB medium was monitored by two SMODs in the same culture to determine the reproducibility of the Optical Density measurements between SMODs. Cells were grown at a constant temperature (370C) with agitation (200rpm) and the average Optical Density (OD600) measured by the two SMODs is graphed with the standard deviation (Black). Also shown is the average temperature of the cultures as measured by the SMOD with the standard deviation (Blue).

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Copyright © 2016, Lifeonics Ltd.

Figure 4. The SMOD can be used to quantifying the difference in growth rate between different mutant strains. Two Wild-type (Black) and Mutant (Red) Yeast (Schizosaccharomyces pombe) cell cultures were grown in YES medium and the OD600 was monitored with the SMOD. Cells were grown at a constant temperature (300C) with agitation (200rpm) and the average Optical Density (OD600) measurements of two replicates is graphed with the the standard deviation (Black and Red). Also shown is the average temperature of the cultures as measured by the SMOD with the standard deviation (Blue).

Figure 3. The SMOD can be used to determine the difference in growth rate when cell are grown in different medium. Escherichia coli cells were grown in LB medium without (Black) and with (Red) MgSO4 and the OD600 was monitored with the SMOD. Cells were grown at a constant temperature (370C) with agitation (200rpm) and the Optical Density (OD600) measurements are plotted (Black and Red). Also shown are the temperatures of the cultures as measured by the SMOD (light and dark Blue).

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