Real-time monitoring of bacterial growth kinetics in suspensions using laser speckle imaging

Hadi Loutfi,Guy Le Brun,Mireille Kallassy,Fabrice Pellen,Roger Lteif,Marie Abboud,Bernard Le Jeune

doi:10.1038/s41598-019-57281-2

Hadi Loutfi, Guy Le Brun + Show 5 more

Open Access

https://doi.org/10.1038/s41598-019-57281-2

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Abstract

In microbiology, monitoring the growth of any microorganism in culture is important for studying and optimizing the growth kinetics, the biomass and the metabolite production. In this work, we show that laser speckle imaging is a reliable technique that can be used to perform real-time monitoring of bacteria growth kinetic in liquid culture media. Speckle parameters, specifically speckle grain size and the spatial contrast of the speckle images, and standard analytical parameters (optical density, pH and colony forming units) were measured during the culture of different strains of Bacillus thuringiensis. Our results show that both speckle grain size and spatial contrast decrease with bacterial growth. Furthermore, speckle parameters are sensitive to the fermentation conditions. Statistical analysis revealed a relatively high correlation between speckle and analytical parameters.

Highlights

In microbiology, monitoring the growth of any microorganism in culture is important for studying and optimizing the growth kinetics, the biomass and the metabolite production
Given that the geometrical dimension of the bacteria is larger than the optical wavelength (Bt are rod-shaped bacteria with an average length of 4.5 μm26), we assumed that a Mie scattering regime would occur, favoring forward scattering and we put the experimental setup in transmission[27]
One of the main advantages of the speckle method is the variation in speckle grain size with the concentration of Bacillus thuringiensis (Bt) cells

Summary

Introduction

In microbiology, monitoring the growth of any microorganism in culture is important for studying and optimizing the growth kinetics, the biomass and the metabolite production. Intoxication manifests itself by an almost immediate paralysis of the digestive tract, which leads to a cessation of food intake This allows spores that have been ingested at the same time as the crystals to germinate, and bacteria from this germination to multiply in the insect, causing sepsis[22]. Principal component analysis indicated a high correlation between speckle results and analytical parameters (optical density: OD, culture medium pH and colony forming units: CFU), and validates the capacity of speckle for monitoring the kinetic growth of bacterial concentration in a liquid culture

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