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

Abstract

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.

Isolation of plant-growth-promoting and metal-resistant cultivable bacteria from Arthrocnemum macrostachyum in the Odiel marshes with potential use in phytoremediation

“…Concentration of metal(loids)s in tissues of A. macrostachyum and in rhizospheric soil collected in the estuary of the Odiel River was also measured (Table 1). Soil data were similar to those recently published by Mesa et al (2015a).…”

“…Halos in dark background were observed in bacteria with DNAsa activity. Chitinase activity was performed as described in Mesa et al (2015a). The plates were supplemented with 0.3 M NaCl.…”

“…Metals discharged in the marshes are introduced into the food chain, affecting all the inhabitants of the ecosystem (Álvarez-Rogel et al, 2004). An example of this sort of contamination is the joint estuary of the Odiel and Tinto rivers in Huelva (SW Spain), one of the most polluted areas in the world, because of the high concentration of metals (mainly As, Cu, Pb, and Zn) found in their sediments (Nelson and Lamothe, 1993;Sainz et al, 2004;Mesa et al, 2015a). For N100 years, intense mining activity took place in this area; recently, the beginning of industrialization of the region in the late 1960s has contributed to this contamination (Nelson and Lamothe, 1993;Davis et al, 2000).…”

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

“…They were non-fermentative and displayed the phenotypic features listed in Table 1 and the species description below. Both strains displayed plant growth-promoting abilities, as reported by Mesa et al (2015). …”

“…The plants were sampled in May 2013 from two marshy, saline environments in the estuaries of the rivers Odiel (SMJ19 T ) and Piedras (SMJ28), in Huelva, South Atlantic Spanish coast (378 109 35.20 N 68 559 59.20 W and 378 169 09.10 N 78 099 36.40 W). Isolation procedures were detailed by Mesa et al (2015). Briefly, surface-sterilized stems and roots of S. maritima were used.…”