Acoustic Emission Signal of Lactococcus lactis before and after Inhibition with NaN3 and Infection with Bacteriophage c2

Debasish Ghosh,John M Stencel,Fred Payne,Didem Ozevin,Clair D Hicks

doi:10.1155/2013/257313

Abstract

The detection of acoustic emission (AE) from Lactococcus lactis, ssp lactis is reported in which emission intensities are used to follow and define metabolic activity during growth in nutrient broths. Optical density (OD) data were also acquired during L. lactis growth at 32°C and provided insight into the timing of the AE signals relative to the lag, logarithmic, and stationary growth phases of the bacteria. The inclusion of a metabolic inhibitor, NaN3, into the nutrient broth eliminated bacteria metabolic activity according to the OD data, the absence of which was confirmed using AE data acquisition. The OD and AE data were also acquired before and after the addition of Bacteriophage c2 in L. lactis containing nutrient broths during the early or middle logarithmic phase; c2 phage m.o.i. (Multiplicity of infection) was varied to help differentiate whether the detected AE was from bacteria cells during lysis or from the c2 phage during genome injection into the cells. It is proposed that AE measurements using piezoelectric sensors are sensitive enough to detect bacteria at the amount near 104 cfu/mL, to provide real time data on bacteria metabolic activity and to dynamically monitor phage infection of cells.

Highlights

Periodic, vibrational motion of Saccharomyces cerevisiae yeast cell walls was observed using atomic force microscopy (AFM) [1, 2]
This paper reports on the application of piezoelectric-based sensors to determine whether acoustic emission (AE) is produced by Lactococcus lactis ssp. lactis C2 during growth in nutrient broths and whether changes in the AE accompany the exposure of L. lactis to a metabolic inhibitor and to a c2specific Bacteriophage
It was discovered that the presence or absence of metabolic activity by bacteria Lactococcus lactis ssp. lactis C2 could be detected by measuring acoustic signals from cultures using piezoelectric sensing elements attached to the outside of bacteria growth flasks

Summary

Introduction

Vibrational motion of Saccharomyces cerevisiae yeast cell walls was observed using atomic force microscopy (AFM) [1, 2]. The periodic vibrations were ascribed to forced, concerted cell wall motions caused by cellular metabolism and molecular motors such as kinesin, dynein, and myosin rather than to natural resonant cell wall oscillations. The range of work ((force) × (amplitude)) associated with cell wall motion in eukaryotes can be estimated to be between ∼20 × 10−20 J-to-30 × 10−18 J (2000 aJ-to-30 aJ). These values are well above the

Methods

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Conclusion