The Impact of Intraspecies Variability on Growth Rate and Cellular Metabolic Activity of Bacteria Exposed to Rotating Magnetic Field

Abstract

Majority of research on the influence of magnetic fields on microorganisms has been carried out with the use of different species or different groups of microorganisms, but not with the use of different strains belonging to one species. The purpose of the present study was to assess the effect of rotating magnetic fields (RMF) of 5 and 50 Hz on the growth and cellular metabolic activity of eight species of bacteria: Staphylococcus aureus, Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella pneumoniae, Enterococcus faecalis, Enterobacter cloacae, Moraxella catarrhalis, and Bacillus cereus. However, contrary to the research conducted so far, each species was represented by at least four different strains. Moreover, an additional group of S. aureus belonging to a single clonal type but representing different biotypes was also included in the experiment. The results showed a varied influence of RMF on growth dynamics and cellular metabolic activity, diversified to the greatest extent in dependence on the bacterial strain exposed to the RMF and to a lesser extent in dependence on the frequency of the generated magnetic field. It was found that, with regard to the exposed strain of the same species, the effect exerted by the RMF may be positive (i.e., manifests as the increase in the growth rate or/and cellular metabolic activity) or negative (i.e., manifests as a reduction of both aforementioned features) or none. Even when one clonal type of S. aureus was used, the results of RMF exposure also varied (although the degree of differentiation was lower than for strains representing different clones). Therefore, the research has proven that, apart from the previously described factors related primarily to the physical parameters of the magnetic field, one of the key parameters affecting the final result of its influence is the bacterial intraspecies variability.

Regulatory and Enterotoxin Gene Expression and Enterotoxins Production in Staphylococcus aureus FRI913 Cultures Exposed to a Rotating Magnetic Field and trans-Anethole

“…The results of basic microbiological studies presented in this article were an extension of the previous studies in this area presented in the cited reference works [ 34 , 35 , 37 , 38 , 39 , 40 ]. The cited experimental studies were focused on the influence of the interaction between RMF and antibiotics, as well as the analysis of bacterial colony growth dynamics, the metabolic activity of cells, as well as genetic activity of selected bacterial species exposed to RMF.…”

The effects of rotating magnetic field and antiseptic on in vitro pathogenic biofilm and its milieu

“…There were also no statistically significant differences in the viability of RMF-exposed cells forming a biofilm on the specific (C, M, B) agar discs. In our previous studies, we showed that the RMF affected the cell viability of S. aureus and P. aeruginosa , but it has to be underlined that these studies were conducted for bacteria cultured in liquid cultures, during their phase of logarithmic growth 18 . In the present study, the exposed bacteria were immobilized on the surface of agar discs and anchored within the biofilm matrix.…”

“…The exposure of biofilm to the RMF was carried out using self-designed RMF bioreactors, described in our previous works 18 , 20 , 21 , and adopted for purposes of this research. One of the bioreactors was operated with the active RMF generator, while the second served as the control setup (without RMF).…”

“…ions of antimicrobials present in a medium) moving them accordingly to the magnetic field rotation 15 . Furthermore, we previously demonstrated that the RMF displays an impact (of various nature—from negative to positive one) on the growth, metabolic activity, and biofilm formation of several different strains and species of microorganisms 16 – 18 . In a separate line of investigation, we analyzed the combined effect of RMF and different antibiotics and antiseptics against S. aureus and P. aeruginosa biofilms in a standard microplate model 19 .…”

The efficacy of antiseptic agents against staphylococcal biofilm can be quantitatively assessed with the use of processed microscopic images

“…This assumption is valid not only because of the aforementioned activity mechanism of these antiseptics, but also because of the rheological phenomena occurring during antiseptics’ introduction, removal and subsequent laboratory stages of dye introduction and microplate well rinsing. As was observed, the measured thickness of staphylococcal biofilms differed not only between particular strains, showing explicitly the importance of intra-species variability [19] , but also within a single sample (well of a 24-well microplate). This thickness differentiation is meaningful, taking into consideration the activity of antiseptics against biofilm.…”