Planctomonas psychrotolerans sp. nov., isolated from rhizosphere soil of Suaeda salsa.

A psychrotolerant actinobacterium, designated strain J5903T, was isolated from an alkaline soil sample from the rhizosphere of Suaeda salsa collected in desertification land surrounding Jiuliancheng Nur in Hebei Province, PR China. Cells of the isolate were Gram-stain-positive, aerobic, non-motile and non-spore-forming cocci. Strain J5903T grew optimally at 20‒25 °C, at pH 7.0‒7.5 and with <1 % (w/v) NaCl. The cell-wall peptidoglycan type was B2γ with d-2,4-diaminobutyric acid and l-2,4-diaminobutyric acid as diagnostic amino acids. The muramyl residue was acetyl type. The menaquinones were MK-11, MK-12, MK-10 and MK-13. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and one unidentified glycolipid. The major whole-cell fatty acids were anteiso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0. The genomic DNA G+C content was 69.1 mol%. It shared the highest average nucleotide identity and digital DNA-DNA hybridization values with Planctomonas deserti 13S1-3T. Phylogenies based on genome sequence showed that strain J5903T and P. deserti 13S1-3T formed a robust cluster with high bootstrap support. Strain J5903T shared typical chemotaxonomic characteristics with P. deserti 13S1-3T. Combining the polyphasic taxonomic evidence, strain J5903T represents a novel species of the genus Planctomonas, for which the name Planctomonas psychrotolerans sp. nov. is proposed. The type strain is J5903T (=DSM 101894T=CGMCC 1.15523T).

Bradyrhizobium arachidis sp. nov., isolated from effective nodules of Arachis hypogaea grown in China.

Twenty-three bacterial strains isolated from root nodules of Arachis hypogaea and Lablab purpureus grown in five provinces of China were classified as a novel group within the genus Bradyrhizobium by analyses of PCR-based RFLP of the 16S rRNA gene and 16S-23S IGS. To determine their taxonomic position, four representative strains were further characterized. The comparative sequence analyses of 16S rRNA and six housekeeping genes clustered the four strains into a distinctive group closely related to the defined species Bradyrhizobium liaoningense, Bradyrhizobium yuanmingense, Bradyrhizobium huanghuaihaiense, Bradyrhizobium japonicum and Bradyrhizobium daqingense. The DNA-DNA relatedness between the reference strain of the novel group, CCBAU 051107(T), and the corresponding type strains of the five mentioned species varied between 46.05% and 13.64%. The nodC and nifH genes of CCBAU 051107(T) were phylogenetically divergent from those of the reference strains for the related species. The four representative strains could nodulate with A. hypogaea and L. purpureus. In addition, some phenotypic features differentiated the novel group from the related species. Based on all the results, we propose a new species Bradyrhizobium arachidis sp. nov. and designate CCBAU 051107(T) (=CGMCC 1.12100(T)=HAMBI 3281(T)=LMG 26795(T)) as the type strain, which was isolated from a root nodule of A. hypogaea and had a DNA G+C mol% of 60.1 (Tm).

Molecular diversity and phylogeny of rhizobia associated with Lablab purpureus (Linn.) grown in Southern China.

As an introduced plant, Lablab purpureus serves as a vegetable, herbal medicine, forage and green manure in China. In order to investigate the diversity of rhizobia associated with this plant, a total of 49 rhizobial strains isolated from ten provinces of Southern China were analyzed in the present study with restriction fragment length polymorphism and/or sequence analyses of housekeeping genes (16S rRNA, IGS, atpD, glnII and recA) and symbiotic genes (nifH and nodC). The results defined the L. purpureus rhizobia as 24 IGS-types within 15 rrs-IGS clusters or genomic species belonging to Bradyrhizobium, Rhizobium, Ensifer (synonym of Sinorhizobium) and Mesorhizobium. Bradyrhizobium spp. (81.6%) were the most abundant isolates, half of which were B. elkanii. Most of these rhizobia induced nodules on L. purpureus, but symbiotic genes were only amplified from the Bradyrhizobium and Rhizobium leguminosarum strains. The nodC and nifH phylogenetic trees defined five lineages corresponding to B. yuanmingense, B. japonicum, B. elkanii, B. jicamae and R. leguminosarum. The coherence of housekeeping and symbiotic gene phylogenies demonstrated that the symbiotic genes of the Lablab rhizobia were maintained mainly through vertical transfer. However, a putative lateral transfer of symbiotic genes was found in the B. liaoningense strain. The results in the present study clearly revealed that L. purpureus was a promiscuous host that formed nodules with diverse rhizobia, mainly Bradyrhizobium species, harboring different symbiotic genes.

Ensifer sojae sp. nov., isolated from root nodules of Glycine max grown in saline-alkaline soils.

Thirteen bacterial isolates from root nodules of soybean grown in saline-alkaline soils in the Chinese province of Hebei were identified as a unique group in the genus Ensifer based upon BOX-PCR patterns, sequencing analyses of 16S rRNA and housekeeping genes and DNA-DNA hybridization. Phenotypically, positive tests for acid production and negative results for reduction in litmus milk and sensitivity to 50 µg ampicillin ml(-1), as well as some other features, could differentiate the novel group from defined species of the Ensifer-Sinorhizobium group. The novel group had symbiotic gene sequences (nodC and nifH) that were identical or very similar to those of Ensifer (Sinorhizobium) fredii, and formed effective nodules with Glycine max (soybean), Vigna unguiculata and Glycine soja. Based upon the consensus of these analyses, a novel species, Ensifer sojae sp. nov., is proposed, with CCBAU 05684(T) ( = LMG 25493(T)  = HAMBI 3098(T)) as the type strain. The DNA G+C content of strain CCBAU 05684(T) was 60.9 mol% (T(m)).

Bradyrhizobium lablabi sp. nov., isolated from effective nodules of Lablab purpureus and Arachis hypogaea.

Five strains isolated from root nodules of Lablab purpureus and Arachis hypogaea grown in the Anhui and Sichuan provinces of China were classified as members of the genus Bradyrhizobium. These strains had identical 16S rRNA gene sequences which shared 99.48 %, 99.48 % and 99.22 % similarity with the most closely related strains of Bradyrhizobium jicamae PAC68(T), Bradyrhizobium pachyrhizi PAC48(T) and Bradyrhizobium elkanii USDA 76(T), respectively. A study using a polyphasic approach, including 16S rRNA gene RFLP, IGS-RFLP, BOX-PCR, comparative sequence analysis of the 16S-23S rRNA intergenic spacer (IGS) and the recA, atpD and glnII genes, DNA-DNA hybridization and phenotypic tests, showed that the five strains clustered into a coherent group that differentiated them from all recognized species of the genus Bradyrhizobium. Sequencing of nifH and nodC genes and cross-nodulation tests showed that the representative strains CCBAU 23086(T), CCBAU 23160 and CCBAU 61434, isolated from different plants, had identical nifH and nodC gene sequences and were all able to nodulate Lablab purpureus, Arachis hypogaea and Vigna unguiculata. Based upon these results, the name Bradyrhizobium lablabi sp. nov. is proposed for this novel species and strain CCBAU 23086(T) ( = LMG 25572(T) = HAMBI 3052(T)) is designated as the type strain. The DNA G+C mol% is 60.14 (T(m)).