title: Diversity of endophytic Pseudomonas in Halimione portulacoides from metal(loid)-polluted salt marshes.
abstract: Phytoremediation assisted by bacteria is seen as a promising alternative to reduce metal contamination in the environment. The main goal of this study was to characterize endophytic Pseudomonas isolated from Halimione portulacoides, a metal-accumulator plant, in salt marshes contaminated with metal(loid)s. Phylogenetic analysis based on 16S rRNA and gyrB genes showed that isolates affiliated with P. sabulinigri (n = 16), P. koreensis (n = 10), P. simiae (n = 5), P. seleniipraecipitans (n = 2), P. guineae (n = 2), P. migulae (n = 1), P. fragi (n = 1), P. xanthomarina (n = 1), and Pseudomonas sp. (n = 1). Most of these species have never been described as endophytic. The majority of the isolates were resistant to three or more metal(loid)s. Antibiotic resistance was frequent among the isolates but most likely related to species-intrinsic features. Common acquired antibiotic resistance genes and integrons were not detected. Plasmids were detected in 43.6 % of the isolates. Isolates that affiliated with different species shared the same plasmid profile but attempts to transfer metal resistance to receptor strains were not successful. Phosphate solubilization and IAA production were the most prevalent plant growth promoting traits, and 20 % of the isolates showed activity against phytopathogenic bacteria. Most isolates produced four or more extracellular enzymes. Preliminary results showed that two selected isolates promote Arabidopsis thaliana root elongation. Results highlight the diversity of endophytic Pseudomonas in H. portulacoides from contaminated sites and their potential to assist phytoremediation by acting as plant growth promoters and as environmental detoxifiers.
authors.affiliation: Biology Department and CESAM, University of Aveiro, 3810-193, Aveiro, Portugal.
authors.forename: Jaqueline
authors.initials: J
authors.lastname: Rocha
authors.affiliation: Biology Department, CESAM and iBiMED, University of Aveiro, Aveiro, Portugal.
authors.forename: Marta
authors.initials: M
authors.lastname: Tacão
authors.affiliation: Biology Department, CESAM and iBiMED, University of Aveiro, Aveiro, Portugal.
authors.forename: Cátia
authors.initials: C
authors.lastname: Fidalgo
authors.affiliation: Biology Department and CESAM, University of Aveiro, 3810-193, Aveiro, Portugal. artur.alves@ua.pt.
authors.forename: Artur
authors.identifier: http://orcid.org/0000-0003-0117-2958
authors.initials: A
authors.lastname: Alves
authors.affiliation: Biology Department, CESAM and iBiMED, University of Aveiro, Aveiro, Portugal.
authors.forename: Isabel
authors.initials: I
authors.lastname: Henriques
mesh_terms: D027703:Amaranthaceae / Q000382:microbiology*; D017360:Arabidopsis; D001419:Bacteria / Q000235:genetics; D001673:Biodegradation, Environmental; D024881:Drug Resistance, Bacterial; D060026:Endophytes / Q000235:genetics*; D008670:Metals; D019216:Metals, Heavy / Q000633:toxicity*; D008826:Microbial Sensitivity Tests; D010802:Phylogeny; D063245:Plant Development; D018517:Plant Roots / Q000254:growth & development; D010957:Plasmids / Q000235:genetics; D011549:Pseudomonas / Q000201:enzymology / Q000235:genetics* / Q000528:radiation effects; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D012965:Sodium Chloride; D053833:Wetlands
chemical_list: D008670:Metals; D019216:Metals, Heavy; D012336:RNA, Ribosomal, 16S; D012965:Sodium Chloride
keywords: Endophytic; Halimione portulacoides; Metals; Phytoremediation; Plant growth promoters; Pseudomonas