Microwaves and Electrochemistry

Dale, Sara E. C.; Compton, Richard G.; Marken, Frank

doi:10.1002/9783527651313.ch12

Cited by 1 publication

(1 citation statement)

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“…S1 in the supplemental material) has many advantages compared to conventional (convection) heating. A dielectric material (i.e., aqueous medium) is directly heated by MW energy rather than by heat transfer through a material (i.e., vessel wall) (17). This process makes MW heating faster and more efficient than convection heating methods.…”

Section: Discussionmentioning

confidence: 99%

Differences in Physical and Biochemical Properties of Thermus scotoductus SA-01 Cultured with Dielectric or Convection Heating

Cockrell

Fitzgerald

Cusick

et al. 2015

Appl Environ Microbiol

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A thermophile, Thermus scotoductus SA-01, was cultured within a constant-temperature (65°C) microwave (MW) digester to determine if MW-specific effects influenced the growth and physiology of the organism. As a control, T. scotoductus cells were also cultured using convection heating at the same temperature as the MW studies. Cell growth was analyzed by optical density (OD) measurements, and cell morphologies were characterized using electron microscopy imaging (scanning electron microscopy [SEM] and transmission electron microscopy [TEM]), dynamic light scattering (DLS), and atomic force microscopy (AFM). Biophysical properties (i.e., turgor pressure) were also calculated with AFM, and biochemical compositions (i.e., proteins, nucleic acids, fatty acids) were analyzed by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the fatty acid methyl esters extracted from cell membranes. Here we report successful cultivation of a thermophile with only dielectric heating. Under the MW conditions for growth, cell walls remained intact and there were no indications of membrane damage or cell leakage. Results from these studies also demonstrated that T. scotoductus cells grown with MW heating exhibited accelerated growth rates in addition to altered cell morphologies and biochemical compositions compared with oven-grown cells. The term "extremophile" was first presented in 1974 by R. D. MacElroy to describe organisms that require extreme growth environments (or environments having conditions that humans cannot tolerate) (1). Since that time, thousands of extremophilic organisms have been identified in all three domains of the phylogenetic tree (Bacteria, Archaea, and Eukarya). These diverse organisms are further classified based on the environment in which they thrive. For example, thermophiles, like Thermus aquaticus, grow at high temperatures (Ͼ60°C) (2) while psychrophiles, e.g., Cryomyces antarcticus, prefer low temperatures (Ͻ15°C) (3). Members of the Acidobacteria phylum grow well in acidic environments (pH Ͻ 5) (4, 5) and are referred to as acidophiles. Barophiles or piezophiles such as Shewanella benthica require high pressures (Ͼ10 MPa) (6, 7), and halophiles like Halomonas spp. thrive in high-salt environments (up to 30%, wt/vol) (8). Some extremophiles thrive under multiple extreme conditions and are termed "polyextremophiles." For example, Natranaerobius thermophilus is an obligate anaerobic alkalithermophile that grows best at 55°C, 3.5 M Na ϩ , and pH 9.5 (9). The investigations of microbial communities that populate extreme environments such as hydrothermal vents and the Mariana trench have advanced our understanding of molecular and physiological responses underlying extremophile growth, survivability, and adaptation.Over the years, the effects of low-frequency (3-to 300-GHz) radiation, or microwave (MW) radiation, on living microorganisms have been studied (see Fig. S1 in the supplemental material). However, ther...

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Section: Discussionmentioning

confidence: 99%