title: Arsenic precipitation by an anaerobic arsenic-respiring bacterial strain isolated from the polluted sediments of Orbetello Lagoon, Italy.
abstract: OBJECTIVE
  To isolate and characterize an anaerobic bacterial strain from the deeper polluted lagoon sediment able to use as electron acceptors [As(V)] and sulfate (SO4(2-)), using lactate as an electron donor.
  
  
  RESULTS
  Methods for isolation from polluted lagoon sediments included anaerobic enrichment cultures in the presence of As(V) and SO4(2-). Reduction of As(V) to As(III) was observed during the growth of the bacterial strain, and the final concentration of As(III) was lower than the initial As(V) one, suggesting the immobilization of As(III) in the yellow precipitate. The precipitate was identified by energy dispersive spectroscopy X-ray as arsenic sulfide. Scanning electron microscopy (SEM) revealed rod-shaped bacterial cells embedded in the precipitate, where net-like formations strictly related to the bacterial cells were visible. The surface of the precipitate showed the adhesion of bacterial cells, forming clusters. Transmission electron microscopy (TEM) also highlighted precipitates inside the bacterial cells and on their surface. Following 16S rRNA sequencing, the bacterial strain 063 was assigned to the genus Desulfosporosinus.
  
  
  CONCLUSIONS
  This study reports, for the first time, the isolation from the polluted lagoon sediments of a strain capable of respiring and using As(V) and SO4(2-) as electron acceptors with lactate as the sole carbon and energy source with the formation of an arsenic sulfide precipitate.
  
  
  CONCLUSIONS
  The identification of these properties provides novel insight into the possible use of the anaerobic strain in bioremediation processes and also adds to the knowledge on the biogeochemical cycling of arsenic.
authors.affiliation: Department of Chemistry, University of Siena, Siena, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Focardi
authors.forename: M
authors.initials: M
authors.lastname: Pepi
authors.forename: M
authors.initials: M
authors.lastname: Ruta
authors.forename: M
authors.initials: M
authors.lastname: Marvasi
authors.forename: E
authors.initials: E
authors.lastname: Bernardini
authors.forename: S
authors.initials: S
authors.lastname: Gasperini
authors.forename: S E
authors.initials: SE
authors.lastname: Focardi
mesh_terms: D000693:Anaerobiosis; D001151:Arsenic / Q000378:metabolism*; D001152:Arsenicals / Q000378:metabolism*; D001673:Biodegradation, Environmental; D004269:DNA, Bacterial / Q000235:genetics; D019015:Geologic Sediments / Q000382:microbiology*; D007558:Italy; D008969:Molecular Sequence Data; D010459:Peptococcaceae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012989:Soil Pollutants / Q000378:metabolism*; D013440:Sulfides / Q000378:metabolism*
chemical_list: D001152:Arsenicals; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012989:Soil Pollutants; D013440:Sulfides; C045816:arsenic trisulfide; D001151:Arsenic