Effect of microwave radiation on Bacillus subtilis spores.

PAPER pubmed Journal of applied microbiology 2004 In vitro study Effect: mixed Evidence: Low

Read original paper → DOI: 10.1111/j.1365-2672.2004.02406.x PMID: 15546413 Evidence Lab

Abstract

AIMS: To compare the killing efficacy and the effects exerted by microwaves and conventional heating on structural and molecular components of Bacillus subtilis spores. METHODS AND RESULTS: A microwave waveguide applicator was developed to generate a uniform and measurable distribution of the microwave electric-field amplitude. The applicator enabled the killing efficacy exerted by microwaves on B. subtilis spores to be evaluated in comparison with conventional heating at the same temperature value. The two treatments produced a similar kinetics of spore survival, while remarkably different effects on spore structures were seen. The cortex layer of the spores subjected to conductive heating was 10 times wider than that of the untreated spores; in contrast, the cortex of irradiated spores did not change. In addition, the heated spores were found to release appreciable amounts of dipicolinic acid (DPA) upon treatment, while extracellular DPA was completely undetectable in supernatants of the irradiated spores. These observations suggest that microwave radiation may promote the formation of stable complexes between DPA and other spore components (i.e. calcium ions); thus, making any release of DPA from irradiated spores undetectable. Indeed, while a decrease in measurable DPA concentrations was not produced by microwave radiation on pure DPA solutions, a significant lowering in DPA concentration was detected when this molecule was exposed to microwaves in the presence of either calcium ions or spore suspensions. CONCLUSIONS: Microwaves are as effective as conductive heating in killing B. subtilis spores, but the microwave E-field induces changes in the structural and/or molecular components of spores that differ from those attributable only to heat. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides information on the effect of microwaves on B. subtilis spore components.

AI evidence extraction

At a glance

Study type

In vitro study

Effect direction

mixed

Population

Bacillus subtilis spores (in vitro)

Sample size

—

Exposure

microwave

Evidence strength

Low

Confidence: 74% · Peer-reviewed: yes

Main findings

Microwave exposure and conventional conductive heating at the same temperature produced similar spore survival kinetics. However, structural/molecular effects differed: conductive heating increased cortex layer width and was associated with detectable extracellular DPA, whereas irradiated spores showed no cortex change and no detectable extracellular DPA; measurable DPA decreased under microwaves only in the presence of calcium ions or spore suspensions.

Outcomes measured

Spore survival/killing efficacy
Spore cortex layer structural changes
Dipicolinic acid (DPA) release/detectability in supernatants
Measurable DPA concentration in solutions with/without calcium ions or spore suspensions

Limitations

Microwave frequency not reported in abstract
Exposure duration and dosimetry metrics (e.g., SAR) not reported in abstract
Sample size not reported in abstract
In vitro bacterial spore model; findings may not generalize beyond this system

View raw extracted JSON

{
    "study_type": "in_vitro",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Bacillus subtilis spores (in vitro)",
    "sample_size": null,
    "outcomes": [
        "Spore survival/killing efficacy",
        "Spore cortex layer structural changes",
        "Dipicolinic acid (DPA) release/detectability in supernatants",
        "Measurable DPA concentration in solutions with/without calcium ions or spore suspensions"
    ],
    "main_findings": "Microwave exposure and conventional conductive heating at the same temperature produced similar spore survival kinetics. However, structural/molecular effects differed: conductive heating increased cortex layer width and was associated with detectable extracellular DPA, whereas irradiated spores showed no cortex change and no detectable extracellular DPA; measurable DPA decreased under microwaves only in the presence of calcium ions or spore suspensions.",
    "effect_direction": "mixed",
    "limitations": [
        "Microwave frequency not reported in abstract",
        "Exposure duration and dosimetry metrics (e.g., SAR) not reported in abstract",
        "Sample size not reported in abstract",
        "In vitro bacterial spore model; findings may not generalize beyond this system"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "microwave radiation",
        "Bacillus subtilis",
        "spores",
        "conventional heating",
        "electric field",
        "dipicolinic acid",
        "calcium ions",
        "cortex layer",
        "killing efficacy"
    ],
    "suggested_hubs": []
}

AI can be wrong. Always verify against the paper.

AI-extracted fields are generated from the abstract/metadata and may be incomplete or incorrect. This content is for informational purposes only and is not medical advice.

Comments

No comments yet.