title: Effects of the metalloid oxyanion tellurite (TeO32-) on growth characteristics of the phototrophic bacterium Rhodobacter capsulatus.
abstract: This work examines the effects of potassium tellurite (K2TeO3) on the cell viability of the facultative phototroph Rhodobacter capsulatus. There was a growth mode-dependent response in which cultures anaerobically grown in the light tolerate the presence of up to 250 to 300 microg of tellurite (TeO3(2-)) per ml, while dark-grown aerobic cells were inhibited at tellurite levels as low as 2 microg/ml. The tellurite sensitivity of aerobic cultures was evident only for growth on minimal salt medium, whereas it was not seen during growth on complex medium. Notably, through the use of flow cytometry, we show that the cell membrane integrity was strongly affected by tellurite during the early growth phase (< or =50% viable cells); however, at the end of the growth period and in parallel with massive tellurite intracellular accumulation as elemental Te0 crystallites, recovery of cytoplasmic membrane integrity was apparent (> or =90% viable cells), which was supported by the development of a significant membrane potential (Deltapsi = 120 mV). These data are taken as evidence that in anaerobic aquatic habitats, the facultative phototroph R. capsulatus might act as a natural scavenger of the highly soluble and toxic oxyanion tellurite.
authors.affiliation: Dipartimento di Biologia, Università di Bologna, Bologna, Italy. roberto.borghese@unibo.it
authors.forename: Roberto
authors.initials: R
authors.lastname: Borghese
authors.forename: Francesca
authors.initials: F
authors.lastname: Borsetti
authors.forename: Paola
authors.initials: P
authors.lastname: Foladori
authors.forename: Giuliano
authors.initials: G
authors.lastname: Ziglio
authors.forename: Davide
authors.initials: D
authors.lastname: Zannoni
mesh_terms: D000693:Anaerobiosis; D002463:Cell Membrane Permeability / Q000187:drug effects; D003470:Culture Media; D004579:Electron Transport; D005434:Flow Cytometry; D008027:Light; D008564:Membrane Potentials; D008826:Microbial Sensitivity Tests; D016354:Rhodobacter capsulatus / Q000187:drug effects* / Q000254:growth & development*; D013691:Tellurium / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D003470:Culture Media; C026899:potassium tellurate(IV); C026660:tellurous acid; D013691:Tellurium