Pseudogracilibacillus endophyticus sp. nov., a moderately thermophilic and halophilic species isolated from plant root.

A Gram-stain-positive strain, designated DT7-02T, was isolated from the surface-sterilized root of Oenotherabiennis (evening primrose) and subjected to taxonomic characterization. Cells of DT7-02T were slender rod-shaped, motile by means of flagella, and oxidase- and catalase-positive. The colonies were circular, pinkish-yellow, opaque, glistering and 1-2 mm in diameter. The strain was moderately thermophilic and halophilic, as growth occurred at 20-44 °C (optimum 40 °C), pH 7-10 (optimum pH 8-9) and in the presence of 0-8 % of NaCl (optimum 4 %) in tryptic soy broth. The analysis of 16S rRNA gene sequences indicated that the strain represented a member of the genus Pseudogracilibacillus of the family Bacillaceae, and the sequence similarity was 96.5 % with Pseudogracilibacillus auburnensis P-207T and 95.9 % with Pseudogracilibacillus marinus NIOT-bflm-S4T. Other related taxa were Ornithinibacillus contaminans DSM 22953T and Sinibacillus soli KCTC 33117T, with 16S rRNA gene sequence similarities of 95.4 and 94.3 %, respectively. The major cellular fatty acids of DT7-02T were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0. The DNA G+C content was 35.1 mol%, and the respiratory quinone was MK-7. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol and phosphatidylethanolamine. The combination of chemotaxonomic properties enabled differentiation of DT7-02T from the other two species of the genus Pseudogracilibacillus. The results of phylogenetic, phenotypic and chemotaxonomic analyses demonstrate that strain DT7-02T (=KCTC 33854T=JCM 31192T) merits recognition as representing a novel species of the genus Pseudogracilibacillus, for which the name Pseudogracilibacillusendophyticus sp. nov. is proposed.

Hydrocarbon degradation potential and plant growth-promoting activity of culturable endophytic bacteria of Lotus corniculatus and Oenothera biennis from a long-term polluted site.

Many endophytic bacteria exert beneficial effects on their host, but still little is known about the bacteria associated with plants growing in areas heavily polluted by hydrocarbons. The aim of the study was characterization of culturable hydrocarbon-degrading endophytic bacteria associated with Lotus corniculatus L. and Oenothera biennis L. collected in long-term petroleum hydrocarbon-polluted site using culture-dependent and molecular approaches. A total of 26 hydrocarbon-degrading endophytes from these plants were isolated. Phylogenetic analyses classified the isolates into the phyla Proteobacteria and Actinobacteria. The majority of strains belonged to the genera Rhizobium, Pseudomonas, Stenotrophomonas, and Rhodococcus. More than 90% of the isolates could grow on medium with diesel oil, approximately 20% could use n-hexadecane as a sole carbon and energy source. PCR analysis revealed that 40% of the isolates possessed the P450 gene encoding for cytochrome P450-type alkane hydroxylase (CYP153). In in vitro tests, all endophytic strains demonstrated a wide range of plant growth-promoting traits such as production of indole-3-acetic acid, hydrogen cyanide, siderophores, and phosphate solubilization. More than 40% of the bacteria carried the gene encoding for the 1-aminocyclopropane-1-carboxylic acid deaminase (acdS). Our study shows that the diversity of endophytic bacterial communities in tested plants was different. The results revealed also that the investigated plants were colonized by endophytic bacteria possessing plant growth-promoting features and a clear potential to degrade hydrocarbons. The properties of isolated endophytes indicate that they have the high potential to improve phytoremediation of petroleum hydrocarbon-polluted soils.