title: Characterization of arsenic-resistant bacteria from the rhizosphere of arsenic hyperaccumulator Pteris vittata.
abstract: Arsenic hyperaccumulator fern Pteris vittata L. produces large amounts of root exudates that are hypothesized to solubilize arsenic and maintain a unique rhizosphere microbial community. Total heterotrophic counts on rich or defined media supplemented with up to 400 mmol/L of arsenate showed a diverse arsenate-resistant microbial community from the rhizosphere of P. vittata growing in arsenic-contaminated sites. Twelve bacterial isolates tolerating 400 mmol/L of arsenate in liquid culture were identified. Selected bacterial isolates belonging to different genera were tested for their resistance to osmotic and oxidative stresses. Results showed that growth was generally better under osmotic stress generated by arsenic than under that generated by NaCl or PEG 6000, demonstrating that arsenic detoxification metabolism also cross-protected bacterial isolates from arsenic-induced osmotic stress. After 32 h of growth, all arsenate at 1 mmol/L was reduced to arsenite by strains Naxibacter sp. AH4, Mesorhizobium sp. AH5, and Pseudomonas sp. AH21, but arsenite at 1 mmol/L remained unchanged. Sensitivity to hydrogen peroxide was similar to that in broad-host pathogen Salmonella enterica sv. Typhimurium wild type, except strain AH4. The results suggested that these arsenic-resistant bacteria are metabolically adapted to arsenic-induced osmotic or oxidative stresses in addition to the specific bacterial system to exclude cellular arsenic. Both these adaptations contribute to the high arsenic resistance in the bacterial isolates.
authors.affiliation: Soil and Water Science Department, University of Florida, Gainesville, 32601, USA.
authors.forename: Anhui
authors.initials: A
authors.lastname: Huang
authors.forename: Max
authors.initials: M
authors.lastname: Teplitski
authors.forename: Bala
authors.initials: B
authors.lastname: Rathinasabapathi
authors.forename: Lena
authors.initials: L
authors.lastname: Ma
mesh_terms: D053502:Arsenate Reductases / Q000235:genetics / Q000378:metabolism; D001151:Arsenic / Q000378:metabolism / Q000633:toxicity*; D001419:Bacteria / Q000145:classification* / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D018407:Bacterial Physiological Phenomena; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D044822:Biodiversity; D024881:Drug Resistance, Bacterial; D008969:Molecular Sequence Data; D009997:Osmotic Pressure; D018384:Oxidative Stress; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology*; D032495:Pteris / Q000378:metabolism / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012989:Soil Pollutants / Q000378:metabolism / Q000633:toxicity*
chemical_list: D001426:Bacterial Proteins; D012336:RNA, Ribosomal, 16S; D012989:Soil Pollutants; D053502:Arsenate Reductases; D001151:Arsenic