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A new apparatus to induce lysis of planktonic microbial cells by shock compression, cavitation and spray

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ABSTRACT

Experiments were conducted on an aqueous growth medium containing cultures of Escherichia coli (E. coli) XL1-Blue, to investigate, in a single experiment, the effect of two types of dynamic mechanical loading on cellular integrity. A bespoke shock tube was used to subject separate portions of a planktonic bacterial culture to two different loading sequences: (i) shock compression followed by cavitation, and (ii) shock compression followed by spray. The apparatus allows the generation of an adjustable loading shock wave of magnitude up to 300 MPa in a sterile laboratory environment. Cultures of E. coli were tested with this apparatus and the spread-plate technique was used to measure the survivability after mechanical loading. The loading sequence (ii) gave higher mortality than (i), suggesting that the bacteria are more vulnerable to shear deformation and cavitation than to hydrostatic compression. We present the results of preliminary experiments and suggestions for further experimental work; we discuss the potential applications of this technique to sterilize large volumes of fluid samples.

No MeSH data available.


Schematic of the experimental apparatus used to subject E. coli to mechanical loading.
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RSOS160939F1: Schematic of the experimental apparatus used to subject E. coli to mechanical loading.

Mentions: In this study, a bespoke shock tube was developed to subject the bacterial cultures to shock compression followed by either fluid cavitation or ejection through a small hole (to which we refer, in this paper, as ‘spray’). The apparatus consisted of a stainless steel shock tube machined to a length of L = 1 m, outer diameter D = 150 mm and bore diameter d = 10 mm, as sketched in figure 1. It was closed at one end by a thin brass diaphragm of thickness h = 25.4 µm, clamped to the annular end of the tube by a bolted steel cap. The cap was machined with a central hole of diameter dc = 4 mm and length 10 mm to allow jet ejection of the liquid samples upon bursting of the brass diaphragm. To capture the ejected portion of the test sample, a circular cylindrical hollow chamber was machined from stainless steel and bolted onto the steel cap; a valve was included on the top face to vent air during the spray process.Figure 1.


A new apparatus to induce lysis of planktonic microbial cells by shock compression, cavitation and spray
Schematic of the experimental apparatus used to subject E. coli to mechanical loading.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383840&req=5

RSOS160939F1: Schematic of the experimental apparatus used to subject E. coli to mechanical loading.
Mentions: In this study, a bespoke shock tube was developed to subject the bacterial cultures to shock compression followed by either fluid cavitation or ejection through a small hole (to which we refer, in this paper, as ‘spray’). The apparatus consisted of a stainless steel shock tube machined to a length of L = 1 m, outer diameter D = 150 mm and bore diameter d = 10 mm, as sketched in figure 1. It was closed at one end by a thin brass diaphragm of thickness h = 25.4 µm, clamped to the annular end of the tube by a bolted steel cap. The cap was machined with a central hole of diameter dc = 4 mm and length 10 mm to allow jet ejection of the liquid samples upon bursting of the brass diaphragm. To capture the ejected portion of the test sample, a circular cylindrical hollow chamber was machined from stainless steel and bolted onto the steel cap; a valve was included on the top face to vent air during the spray process.Figure 1.

View Article: PubMed Central - PubMed

ABSTRACT

Experiments were conducted on an aqueous growth medium containing cultures of Escherichia coli (E. coli) XL1-Blue, to investigate, in a single experiment, the effect of two types of dynamic mechanical loading on cellular integrity. A bespoke shock tube was used to subject separate portions of a planktonic bacterial culture to two different loading sequences: (i) shock compression followed by cavitation, and (ii) shock compression followed by spray. The apparatus allows the generation of an adjustable loading shock wave of magnitude up to 300 MPa in a sterile laboratory environment. Cultures of E. coli were tested with this apparatus and the spread-plate technique was used to measure the survivability after mechanical loading. The loading sequence (ii) gave higher mortality than (i), suggesting that the bacteria are more vulnerable to shear deformation and cavitation than to hydrostatic compression. We present the results of preliminary experiments and suggestions for further experimental work; we discuss the potential applications of this technique to sterilize large volumes of fluid samples.

No MeSH data available.