Silver ions cause oscillation of bacterial length of Escherichia coli

Abstract

Silver (Ag) in various forms have recently gained broad interest and been revisited due to their promising antimicrobial effects. Here we report our study on the morphological dynamics of live bacteria when subjected to Ag + ions. Using time-lapse microscopy, we observed oscillations of cell-length for a large fraction of bacteria exposed to 60 μ M of Ag + ions. In addition, we found that the responses of bacteria to Ag + ions were heterogeneous. We quantified the oscillations of cell-length with power spectral density, which appeared different from that of bacteria growing in the absence of Ag + ions. Furthermore, a model similar to the predator-prey argument was developed to understand the observed oscillations of cell-length upon exposure to Ag + ions. This model not only successfully produced the oscillations but also explained the observed heterogeneity in the bacterial responses to Ag + ions.

Antimicrobial silver inhibits bacterial movement and stalls flagellar motor

“…indicating Ag + -treatment led to lower bacterial motility. We also note that the radii slightly 208 increased for longer treatment time, implying possible recovery of the bacteria as reported by 209 our previous results [6,15]. The slower motion of bacteria caused by Ag + ions was further visualized in Fig.…”

“…33 34 42 towards understanding the antimicrobial mechanism of Ag, suggesting that Ag caused 43 multidirectional damages to bacteria, including DNA damage, membrane disruption, free radical 44 generation (ROS), and loss of ATP production [7,9, 10, 11, 12, 13]. However, various aspects of 45 the antimicrobial mechanism of Ag remain elusive, especially that the temporal resolution for 46understanding the Ag-caused damages in bacteria Ag is still limited [7, 14,15]. This includes how 47 silver affects the motility of bacteria, which is tightly coupled to bacterial virulence [16].…”

“…understanding the Ag-caused damages in bacteria Ag is still limited [7, 14,15]. This includes how 47 silver affects the motility of bacteria, which is tightly coupled to bacterial virulence [16].…”

“…Bacterial strain and growth 102 103 An E. coli K12-derived strain from Refs. [15,23,30,31] was used in this study. The strain has been 104 used in previous investigations of the antimicrobial activities of Ag + ions and AgNPs [15,23,31].…”

“…[15,23,30,31] was used in this study. The strain has been 104 used in previous investigations of the antimicrobial activities of Ag + ions and AgNPs [15,23,31]. 105 This strain has the hns gene knocked out from the chromosomal DNA, but supplemented with a 106 plasmid encoding for the H-NS protein fused to mEos3.2 fluorescent protein[32] and for 107 resistance to kanamycin and chloramphenicol [15,23,30,31] Measurements in the swimming and tethering assays were done at room temperature using 120 phase contrast microscopy on an Olympus IX-73 inverted microscope equipped with a 100´, 121 NA=1.25 phase-contrast, oil-immersion objective (Olympus) and an EMCCD camera (Andor 122 Technology).…”