title: Extracting iron and manganese from bacteria with ionophores - a mechanism against competitors characterized by increased potency in environments low in micronutrients.
abstract: To maintain their metal ion homeostasis, bacteria critically depend on membrane integrity and controlled ion translocation. Terrestrial Streptomyces species undermine the function of the cytoplasmic membrane as diffusion barrier for metal cations in competitors using ionophores. Although the properties of the divalent cation ionophores calcimycin and ionomycin have been characterized to some extent in vitro, their effects on bacterial ion homeostasis, the factors leading to bacterial cell death, and their ecological role are poorly understood. To gain insight into their antibacterial mechanism, we determined the metal ion composition of the soil bacterium Bacillus subtilis after treatment with calcimycin and ionomycin. Within 15 min the cells lost approximately half of their cellular iron and manganese content whereas calcium levels increased. The proteomic response of B. subtilis provided evidence that disturbance of metal cation homeostasis is accompanied by intracellular oxidative stress, which was confirmed with a ROS-specific fluorescent probe. B. subtilis showed enhanced sensitivity to the ionophores in medium lacking iron or manganese. Furthermore, in the presence of ionophores bacteria were sensitive to high calcium levels. These findings suggest that divalent cation ionophores are particularly effective against competing microorganisms in soils rich in available calcium and low in available iron and manganese.
authors: Biology of Microorganisms, Ruhr University Bochum, Bochum, Germany.
authors: Nadja
authors: N
authors: Raatschen
authors: Michaela
authors: M
authors: Wenzel
authors: Lars Ingo
authors: LI
authors: Ole Leichert
authors: Petra
authors: P
authors: Düchting
authors: Ute
authors: U
authors: Krämer
authors: Julia Elisabeth
authors: JE
authors: Bandow
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001412:Bacillus subtilis / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D001426:Bacterial Proteins / Q000032:analysis / Q000378:metabolism; D000001:Calcimycin / Q000737:chemistry; D002118:Calcium / Q000378:metabolism; D061207:Calcium Ionophores / Q000494:pharmacology; D004463:Ecology; D006706:Homeostasis; D015759:Ionomycin / Q000737:chemistry; D007476:Ionophores / Q000737:chemistry / Q000494:pharmacology*; D007501:Iron / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D008345:Manganese / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D018977:Micronutrients / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D020543:Proteome / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012988:Soil Microbiology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D061207:Calcium Ionophores; D007476:Ionophores; D018977:Micronutrients; D020543:Proteome; D017382:Reactive Oxygen Species; D000001:Calcimycin; D008345:Manganese; D015759:Ionomycin; D007501:Iron; D002118:Calcium