Effects of Atmospheric Plasma Corona Discharges on Soil Bacteria Viability.

Yulia Lazra,Yelena Bormashenko,Irina Dubrovin,Rivka Cahan,Edward Bormashenko,Victor Multanen

doi:10.3390/microorganisms8050704

Yulia Lazra, Yelena Bormashenko + Show 4 more

Open Access

https://doi.org/10.3390/microorganisms8050704

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Journal: Microorganisms	Publication Date: May 11, 2020
Citations: 9	License type: CC BY 4.0

Affiliation: Ariel University

Abstract

Crop contamination by soil-borne pathogenic microorganisms often leads to serious infection outbreaks. Plant protection requires disinfection of agricultural lands. The chemical and the physical disinfection procedures have several disadvantages, including an irreversible change in the soil ecosystem. Plasma, the “fourth state of matter” is defined as an ionized gas containing an equal number of negatively and positively charged particles. Cold-plasma technology with air or oxygen as the working gas generates reactive oxygen species, which are found to efficiently eradicate bacteria. In this study, we examined the effect of atmospheric plasma corona discharges on soil bacteria viability. Soil that was exposed to plasma for 60 s resulted in bacterial reduction by two orders of magnitude, from 1.1 × 105 to 2.3 × 103 cells g−1 soil. Exposure for a longer period of 5 min did not lead to further significant reduction in bacterial concentration (a final reduction of only 2.5 orders of magnitude). The bacterial viability was evaluated using a colorimetric assay based on the bacterial hydrogenases immediately after exposure and at selected times during 24 h. The result showed no recovery in the bacterial viability. Plasma discharged directly on bacteria that were isolated from the soil resulted in a reduction by four orders of magnitude in the bacterial concentration compared to untreated isolated bacteria: 2.6 × 10−3 and 1.7 × 10−7, respectively. The plasma-resistant bacteria were found to be related to the taxonomic phylum Firmicutes (98.5%) and comprised the taxonomic orders Bacillales (95%) and Clostridiales (2%). To our knowledge, this is the first study of soil bacteria eradication using plasma corona discharges.

Highlights

Contamination of vegetables by fecal pathogenic bacteria is a severe problem that occurs from fertilizing soil with organic matter, such as poultry manure and cow dung
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The effects of atmospheric plasma corona discharges were examined on soil bacteria by exposing the soil to plasma for 30 and 60 s

Summary

Introduction

Contamination of vegetables by fecal pathogenic bacteria is a severe problem that occurs from fertilizing soil with organic matter, such as poultry manure and cow dung. Cold-plasma technology is already applied in a variety of processes, including modification of the surface properties of organic and synthetic materials [12], bacterial deactivation in sewage sludge [13], wastewater treatment [14], biofilm formation on plasma-treated wood waste for bioremediation of toxic pollutants [15], biofilm formation on plasma-treated carbon-cloth anodes in microbial electrolysis cells for hydrogen formation [16], and advanced treatment of agriculture seeds [17]. Cold atmospheric-pressure plasma has become an attractive technology for microbial inactivation in the food industry and agricultural production, since the microorganism eradication occurs at low temperatures. Low-pressure plasma treatment (voltage was 5.5 kV, argon gas flow rate was 0.5 L min−1) of Xanthomonas campestris (6.6 log colony-forming units (CFU) per seed) led to a decrease of these cruciferous seed-plant pathogenic bacteria by 3.9 log after 5 min of exposure and by 6.6 log after 40 min [25].

Viable Count Assay

Measurements of Soil Bacterial Viability

Statistics

Findings

Conclusions