Evidence of Calcium Signaling and Modulation of the LmrS Multidrug Resistant Efflux Pump Activity by Ca2 + Ions in S. aureus

Abstract

Calcium ions (Ca 2+) play a pivotal role in eukaryote cell signaling and regulate many physiological functions. Although a similar role for Ca 2+ in prokaryotes has been difficult to demonstrate, there is increasing evidence for Ca 2+ as a cell regulator in bacteria. The purpose of this study was to investigate Ca 2+ signaling and the effect of Ca 2+ on the Staphylococcus aureus multidrug resistant efflux pump LmrS. We hypothesized that antibiotics act by increasing Ca 2+ concentrations, which in turn enhance the efflux activity of LmrS. These Ca 2+ transients were measured by luminometry in response to various antibiotics by using the photoprotein aequorin reconstituted within live bacterial cells. Efflux associated with LmrS was measured by the increase in fluorescence due to the loss of ethidium bromide (EtBr) from both S. aureus cells and from E. coli cells in which the lmrs gene of S. aureus was expressed. We found that addition of antibiotics to cells generated unique cytosolic Ca 2+ transients and that addition of CaCl 2 to cells enhanced EtBr efflux whereas addition of Ca 2+ chelators or efflux pump inhibitors significantly decreased EtBr efflux from cells. We conclude that antibiotics induce a Ca 2+ mediated response through transients in cytosolic Ca 2+ , which then stimulates LmrS efflux pump.

A Burkholderia thailandensis DedA Family Membrane Protein Is Required for Proton Motive Force Dependent Lipid A Modification

“…We have previously reported that overexpression of mdfA , a Na + -K + /H + antiporter of the major facilitator superfamily essential for alkaline tolerance in E. coli ( Lewinson et al, 2004 ), can compensate cell division defects and drug sensitivity of an E. coli strain lacking two partially redundant DedA family genes yqjA and yghB ( Kumar and Doerrler, 2014 ). In E. coli and S. aureus , alkaline pH was shown to induce calcium influx and cytoplasmic calcium accumulation compared to acidic pH ( Naseem et al, 2008 ; Nava et al, 2020 ). In light of these studies; it is possible that lower membrane potential of Δ dbcA at pH 7.5 is related to inefficient efflux of divalent cations at slightly alkaline pH.…”

An interbacterial lipase toxin with an unprecedented reverse domain arrangement defines a new class of type VII secretion system effector

“…TelC is dependent on Ca 2+ ions for activity, as are many lipases including most previously characterised staphylococcal enzymes 10,50 . Calcium is abundant in the cell wall of staphylococci but is buffered in the cytoplasm at low micromolar levels 51,52 and we speculate that the concentration is too low to support intracellular TslA activity. In support of an extracellular activity for TslA, S. aureus coproduces an extracellular immunity lipoprotein, TilA for self-protection, which binds to TslA with a low nanomolar Kd.…”

The ctpF Gene Encoding a Calcium P-Type ATPase of the Plasma Membrane Contributes to Full Virulence of Mycobacterium tuberculosis

“…When Mtb is phagocytosed by macrophages, tubercle bacilli then face an approximately 4-fold increase of the intraphagosomal Ca 2+ concentration at 24 h post-infection [ 15 , 57 ]. Cells respond to different environmental stimuli by transient changes in the cytosolic Ca 2+ concentration, which are useful to transmit information and to trigger cellular events according to the speed, timing and magnitude of the metal signal [ 26 , 58 ]. Some bacteria detect and respond to different environmental stimuli using two-component systems and Ca 2+ sensors, which transduce signals through phosphorylation events and protein–protein interactions and thereby regulate transcription and translation processes [ 27 , 59 ].…”