title: Isolation and characterization of yeasts associated with plants growing in heavy-metal- and arsenic-contaminated soils.
abstract: Yeasts were quantified and isolated from the rhizospheres of 5 plant species grown at 2 sites of a Mexican region contaminated with arsenic, lead, and other heavy metals. Yeast abundance was about 10(2) CFU/g of soil and 31 isolates were obtained. On the basis of the phylogenetic analysis of 26S rRNA and internal transcribed spacer fragment, 6 species were identified within the following 5 genera: Cryptococcus (80.64%), Rhodotorula (6.45%), Exophiala (6.45%), Trichosporon (3.22%), and Cystobasidium (3.22%). Cryptococcus spp. was the predominant group. Pectinases (51.6%), proteases (51.6%), and xylanases (41.9%) were the enzymes most common, while poor production of siderophores (16.1%) and indole acetic acid (9.67%) was detected. Isolates of Rhodotorula mucilaginosa and Cystobasidium sloffiae could promote plant growth and seed germination in a bioassay using Brassica juncea. Resistance of isolates by arsenic and heavy metals was as follows: As(3+) ≥ 100 mmol/L, As(5+) ≥ 30 mmol/L, Zn(2+) ≥ 2 mmol/L, Pb(2+) ≥ 1.2 mmol/L, and Cu(2+) ≥ 0.5 mmol/L. Strains of Cryptococcus albidus were able to reduce arsenate (As(5+)) into arsenite (As(3+)), but no isolate was capable of oxidizing As(3+). This is the first study on the abundance and identification of rhizosphere yeasts in a heavy-metal- and arsenic-contaminated soil, and of the reduction of arsenate by the species C. albidus.
authors.affiliation: a Laboratorio de Micología General y Médica, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas (ENCB), Instituto Politécnico Nacional (IPN), Prolongación de Carpio y Plan de Ayala s/n, 11340 Mexico City, Mexico.|b Laboratorio de Ecología Microbiana, Departamento de Microbiología, ENCB, IPN, 11340 Mexico City, Mexico.
authors.forename: Juan
authors.initials: J
authors.lastname: Ramos-Garza
authors.affiliation: a Laboratorio de Micología General y Médica, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas (ENCB), Instituto Politécnico Nacional (IPN), Prolongación de Carpio y Plan de Ayala s/n, 11340 Mexico City, Mexico.
authors.forename: Rafael
authors.initials: R
authors.lastname: Bustamante-Brito
authors.affiliation: c Laboratorio de Nematología Agrícola, Departamento de Parasitología, ENCB, IPN, 11340 Mexico City, Mexico.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Ángeles de Paz
authors.affiliation: c Laboratorio de Nematología Agrícola, Departamento de Parasitología, ENCB, IPN, 11340 Mexico City, Mexico.
authors.forename: Ma Gabriela
authors.initials: MG
authors.lastname: Medina-Canales
authors.affiliation: d Laboratorio de Microbiología Industrial, Departamento de Microbiología, ENCB, IPN, 11340 Mexico City, Mexico.
authors.forename: María Soledad
authors.initials: MS
authors.lastname: Vásquez-Murrieta
authors.affiliation: b Laboratorio de Ecología Microbiana, Departamento de Microbiología, ENCB, IPN, 11340 Mexico City, Mexico.
authors.forename: En Tao
authors.initials: ET
authors.lastname: Wang
authors.affiliation: a Laboratorio de Micología General y Médica, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas (ENCB), Instituto Politécnico Nacional (IPN), Prolongación de Carpio y Plan de Ayala s/n, 11340 Mexico City, Mexico.
authors.forename: Aída Verónica
authors.initials: AV
authors.lastname: Rodríguez-Tovar
mesh_terms: D001149:Arsenates / Q000378:metabolism; D001151:Arsenic / Q000032:analysis / Q000378:metabolism* / Q000494:pharmacology; D018053:Arsenites / Q000378:metabolism; D002176:Candida albicans / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism; D003454:Cryptococcus / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D018525:Germination; D007210:Indoleacetic Acids / Q000378:metabolism; D019684:Magnoliopsida / Q000254:growth & development / Q000382:microbiology; D019216:Metals, Heavy / Q000032:analysis / Q000378:metabolism* / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D010084:Oxidation-Reduction; D010802:Phylogeny; D058441:Rhizosphere; D012639:Seeds / Q000254:growth & development / Q000382:microbiology; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*
chemical_list: D001149:Arsenates; D018053:Arsenites; D007210:Indoleacetic Acids; D019216:Metals, Heavy; D012989:Soil Pollutants; C030737:indoleacetic acid; C015001:arsenite; D001151:Arsenic; C025657:arsenic acid
keywords: arsenic; levure; reduction; rhizosphere; rhizosphère; réduction; speciation; spéciation; yeast