Sp. Nov., a Novel Plant Growth-promoting Bacterium Used in Heavy Metal Polluted Soils As a Phytoremediation Tool

Strain EAR8 is a root endophyte isolated from plants collected from the Odiel marshes, Huelva (Spain). It presented plant growth-promoting properties and improved the plant growth and heavy metal accumulation in polluted soils playing an important role in phytoremediation strategies. Phenotypically, strain EAR8 cells were Gram-positive, aerobic and non-motile rods with terminal oval endospores and non-swollen sporangia which form beige, opaque, butyrous, raised and irregular colonies with undulate margins. The strain was able to grow between 15-45 °C, at pH 6.0-9.0 and tolerated 0-25 % NaCl (w/v) showing optimal growth conditions on trypticase soy agar plates supplemented with 2.5 % NaCl (w/v) at pH 7.0 and 37 °C for 24 h. Chemotaxonomic analyses showed that the isolate has -diaminopimelic acid as the peptidoglycan in the cell wall and MK-7 as the major respiratory quinone. The predominant fatty acids were anteiso-C and iso-C and the polar lipid profile was composed of diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. Phylogenetic analyses based on the whole proteomes of closest sequenced relatives confirmed that strain EAR8 is affiliated to the genus and forms a clade with 15-1 with maximum support. Genome analyses showed that EAR8 has indole-3-acetic acid and siderophore biosynthesis and transporters genes and genes related to resistance against heavy metals. Phenotypic and phylogenomic comparative studies suggested that strain EAR8 is a new representative of the genus and the name sp. nov. is proposed. Type strain is EAR8 (=CECT 9072=DSM 103900).