Vibrio palustris sp. nov. and Vibrio spartinae sp. nov., two novel members of the Gazogenes clade, isolated from salt-marsh plants (Arthrocnemum macrostachyum and Spartina maritima).

Two bacterial strains, EAod9T and SMJ21T, isolated from salt-marsh plants, were determined to be related to species of the genus Vibriofrom from 16S rRNA sequence comparisons. Their closest phylogenetic relatives are members of the Gazogenes clade, Vibrio mangrovi and Vibrio rhizosphaerae , which show the greatest similarity to the SMJ21TrRNA sequence (97.3 and 97.1 %, respectively), while EAod9T had less than 97.0 % similarity to any other species of the genus Vibrio. Both strains share the basic characteristics of the genus Vibrio, as they are Gram-stain negative, motile, slightly halophilic, facultatively anaerobic bacteria. In addition, they are oxidase-negative and unable to grow on TCBS Agar; they grow between 15 to 26 °C, pH 6 to 8 and in up to 10 % (w/v) total salinity. They produce indol, are positive in the Voges-Proskauer test and are negative for arginine dihydrolase, lysine and ornithine decarboxylases. Strain SMJ21T is aerogenic and red-pigmented, due to prodigiosin production, while strain EAod9T ferments glucose without gas and is not pigmented. The major cellular fatty acids of both novel strains were C16 : 1ω7c/C16 : 1ω6c and C16 : 0. WGSobtained for both strains, along with the other five members of the clade, allowed the determination of ANI indexes and in silico estimations of DDH values, which confirmed that the two strains represent two novel species of the genus Vibrio: Vibriopalustris sp. nov. (with EAod9T=CECT 9027T=LMG 29724T as the proposed type strain) and Vibrio spartinae sp. nov. (with SMJ21T=CECT 9026T=LMG 29723T as the proposed type strain).

Marinomonas spartinae sp. nov., a novel species with plant-beneficial properties.

Two strains of Gram-stain-negative, chemo-organotrophic, aerobic and halophilic gammaproteobacteria, isolated from within the stem and roots of Spartina maritima in salt marshes from the south Atlantic Spanish coast, were found to represent a novel species in the genus Marinomonas through phylogenetic analysis of their 16S rRNA genes and phenotypic characterization. 16S rRNA gene sequences of the two strains shared < 96.2% similarity with other Marinomonas species, with Marimonas alcarazii being the most similar in sequence. They required sodium ions for growth, were able to thrive at low (4 °C) temperatures and at salinities of 12-15%, were unable to hydrolyse any tested macromolecule except casein, and grew with different monosaccharides, disaccharides, sugar alcohols, organic acids and amino acids. The novel species differed from other Marinomonas species in the use of several sole carbon sources, its temperature and salinity ranges for growth, ion requirements and cellular fatty acid composition, which included C16:0, C16:1 and C18:1 as major components and C10:0 3-OH, C12:0 and C12:0 3-OH as minor components. The name Marinomonas spartinae sp. nov. is proposed, with SMJ19T (=CECT 8886T=KCTC 42958T) as the type strain.

Moving closer towards restoration of contaminated estuaries: Bioaugmentation with autochthonous rhizobacteria improves metal rhizoaccumulation in native Spartina maritima.

Spartina maritima is an ecosystem engineer that has shown to be useful for phytoremediation purposes. A glasshouse experiment using soil from a metal-contaminated estuary was designed to investigate the effect of a native bacterial consortium, isolated from S. maritima rizhosphere and selected owing to their plant growth promoting properties and multiresistance to heavy metals, on plant growth and metal accumulation. Plants of S. maritima were randomly assigned to three soil bioaugmentation treatments (without inoculation, one inoculation and repeated inoculations) for 30 days. Growth parameters and photosynthetic traits, together with total concentrations of several metals were determined in roots and/or leaves. Bacterial inoculation improved root growth, through a beneficial effect on photosynthetic rate (AN) due to its positive impact on functionality of PSII and chlorophyll concentration. Also, favoured intrinsic water use efficiency of S. maritima, through the increment in AN, stomatal conductance and in root-to-shoot ratio. Moreover, this consortium was able to stimulate plant metal uptake specifically in roots, with increases of up to 19% for As, 65% for Cu, 40% for Pb and 29% for Zn. Thus, bioaugmentation of S. maritima with the selected bacterial consortium can be claimed to enhance plant adaptation and metal rhizoaccumulation during marsh restoration programs.

Endophytic Cultivable Bacteria of the Metal Bioaccumulator Spartina maritima Improve Plant Growth but Not Metal Uptake in Polluted Marshes Soils.

Endophytic bacterial population was isolated from Spartina maritima tissues, a heavy metal bioaccumulator cordgrass growing in the estuaries of Tinto, Odiel, and Piedras River (south west Spain), one of the most polluted areas in the world. Strains were identified and ability to tolerate salt and heavy metals along with plant growth promoting and enzymatic properties were analyzed. A high proportion of these bacteria were resistant toward one or several heavy metals and metalloids including As, Cu, and Zn, the most abundant in plant tissues and soil. These strains also exhibited multiple enzymatic properties as amylase, cellulase, chitinase, protease and lipase, as well as plant growth promoting properties, including nitrogen fixation, phosphates solubilization, and production of indole-3-acetic acid (IAA), siderophores and 1-aminocyclopropane-1-carboxylate (ACC) deaminase. The best performing strains (Micrococcus yunnanensis SMJ12, Vibrio sagamiensis SMJ18, and Salinicola peritrichatus SMJ30) were selected and tested as a consortium by inoculating S. maritima wild plantlets in greenhouse conditions along with wild polluted soil. After 30 days, bacterial inoculation improved plant photosynthetic traits and favored intrinsic water use efficiency. However, far from stimulating plant metal uptake, endophytic inoculation lessened metal accumulation in above and belowground tissues. These results suggest that inoculation of S. maritima with indigenous metal-resistant endophytes could mean a useful approach in order to accelerate both adaption and growth of this indigenous cordgrass in polluted estuaries in restorative operations, but may not be suitable for rhizoaccumulation purposes.