Morphological and physiological changes in Lentilactobacillus hilgardii cells after cold plasma treatment

Abstract

Atmospheric cold plasma (ACP) inactivation of Lentilactobacillus hilgardii was investigated. Bacteria were exposed to ACP dielectric barrier discharge with helium and oxygen as working gases for 5, 10, and 15 min. The innovative approach in our work for evaluation of bacterial survival was the use in addition to the classical plate culture method also flow cytometry which allowed the cells to be sorted and revealed different physiological states after the plasma treatment. Results showed total inhibition of bacterial growth after 10-min of ACP exposure. However, the analysis of flow cytometry demonstrated the presence of 14.4% of active cells 77.5% of cells in the mid-active state and 8.1% of dead cells after 10 min. In addition, some of the cells in the mid-active state showed the ability to grow again on culture medium, thus confirming the hypothesis of induction of VBNC state in L .hilgardii cells by cold plasma. In turn, atomic force microscopy (AFM) which was used to study morphological changes in L. hilgardii after plasma treatment at particular physiological states (active, mid-active, dead), showed that the surface roughness of the mid-active cell (2.70 ± 0.75 nm) was similar to that of the control sample (2.04 ± 0.55 nm). The lack of considerable changes on the cell surface additionally explains the effective cell resuscitation. To the best of our knowledge, AFM was used for the first time in this work to analyze cells which have been sorted into subpopulations after cold plasma treatment and this is the first work indicating the induction of VBNC state in L. hilgardii cells after exposure to cold plasma.

The Biological Responses of Staphylococcus aureus to Cold Plasma Treatment

“…In this study, DNA and protein leakage were observed, particularly with prolonged cold plasma treatment of 30 and 60 min, indicating the effectiveness of cold plasma in causing cell lysis. Similar findings have been observed in cold plasma treatment of E. coli [43], Pseudomonas aeruginosa [44], and Lentilactobacillus hilgardii [45]. However, the treatment duration required for the detection of DNA and protein is longer for Gram-positive bacteria, such as S. aureus, possibly due to the thicker cell wall.…”

Comparison of the Effect of Cold Plasma with Conventional Preservation Methods on Red Wine Quality Using Chemometrics Analysis

“…The inactivating effect of cold plasma on microorganisms has already been well-documented by numerous authors. Both its direct effect on microbial cells [ 39 , 40 ] and its contribution to the microbiological safety of food products have been analyzed [ 41 , 42 , 43 ]. The findings available in the literature correspond with ours and indicate that the effectiveness of cold plasma treatment depends on the numerous parameters of the process as well as the food matrix that is subjected to the preservation process.…”

Atmospheric and Room Temperature Plasma (ARTP) Mutagenesis Improved the Anti-MRSA Activity of Brevibacillus sp. SPR20

“…Generally, plasma treatment mainly changes cell structures (pore formation and cell break) and cell growth. This structural change can be explained by the oxygen and nitrogen species induced by the plasma, promoting the oxidation of lipids and proteins of the cell membrane and causing various changes in cellular characteristics [31]. Interestingly, the SPR20 mutant had similar morphology and cell growth compared to its wild-type cells.…”

“…Previous studies demonstrated that Gram-positive bacteria were more resistant to plasma than Gram-negative cells and showed no morphological changes after plasma treatment. Gram-positive species lacked an outer membrane but had a thicker murein layer, giving them higher strength and rigidity [31,35].…”