Abstract:[Objective] Lycium ruthenicum is a halophyte and used to improve saline lands in northwest China. However, little is known about the bacterial community structural dynamics with growth stage.[Methods] We investigated the dynamics of rhizosphere bacterial community structure in three growth stages using Illumina MiSeq high-throughput sequencing. [Results] We obtained a total of 317467 16S rDNA reads, corresponding to 7028 bacterial/archaeal operational taxonomic units. The alpha diversity was higher in the rhizosphere than in bulk soil. The diversity and richness of rhizosphere bacteria were much lower in senescence stage than that in vegetative and flowering/fruiting stages. The relative abundances of Proteobacteria and Acidobacteria gradually decreased, whereas the abundance of Cyanobacteria increased along with growth cycle. The phylum Firmicutes abundance was significantly higher in senescence stage than in other stages. The abundant genera composition also changed with growth stage. Seventeen genera (i.e. Corynebacterium, Acidovorax, Elizabethkingia, Albirhodobacter and Pseudomonas) were abundant at vegetative stage; Sixteen bacterial genera were enriched in flowering/fruiting stage, including Rhodoligotrophos, Geminicoccus, Gracilimonas and Thioprofundum. Four bacterial genera, Exiguobacterium, Citrobacter, Acinetobacter and Pseudomonas, were abundant in senescence stage. In vegetative and flowering/fruiting stages, the rhizosphere bacterial community was of high similarity, and the similarities between rhizosphere communities were higher than that between rhizosphere and bulk soil communities. However, in senescence stage, the rhizosphere bacterial community composition was more different from the communities in previous stages, but turned to be more similar with that of bulk soil. [Conclusion] The rhizosphere bacterial community diversity and composition were changing with growth stage, and great difference was found between senescence stage and previous two stages. Plant growth stage had important effects on structuring the rhizosphere bacterial community of L. ruthenicum.

Abstract:[Objective] We isolated and screened endophytic and rhizosphere bacteria with 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase from halophyte Limonium sinense (Girard) Kuntze collected from Jiangsu coastal area and investigated their diversity and plant growth promoting potential. [Methods] Strains were obtained from inner tissues and rhizosphere soils using pure culture cultivation method and identified by 16S rRNA gene sequencing and phylogenetic analysis. Their potential plant growth promoting index of nitrogen fixation, phosphate solubilization, indoleacetic acid (IAA) production and NaCl tolerance ability were evaluated. [Results] Eighteen strains with ACC deaminase were obtained and 13 of them exhibited more than 20 nmol α-KA/(mg Pr·h) ACC deaminase activity. Nine isolates produced IAA, 11 had nitrogen fixation ability and 7 of them had phosphate solubilization ability. Most of the isolates could grow under 0%-13% NaCl. The results of 16S rRNA sequencing showed that these strains belonged to seven genera, with Arthrobacter as the most predominant genus. Among them, strain KLBMP 5180 was found to be a potential novel species of the genus Arthrobacter. [Conclusion] The halophyte plants Limonium sinense (Girard) Kuntze located in the area of coastal shoal contain a variety of symbiotic bacteria with ACC deaminase as well as the source of novel species. Some of them had good research prospect in the future.

Abstract:[Objective] This study aimed to describe the composition of the endophytic bacterial communities in Salicornia europaea root, and to examine how endophytic bacteria vary across host growth periods. [Methods] PCRbased Roche FLX 454 pyrosequencing was applied to reveal the diversity and succession of endophytic bacteria. [Results] A total of 20363 partial 16S rRNA gene sequences were obtained. These sequences revealed huge amount of operational taxonomic units (OTUs), that is, 552-941 OTUs in a root sample. Endophytes in roots mainly comprised four phyla, among which Proteobacteria was the most represented, followed by Firmicutes, Actinobacteria, and Bacteroidetes. Gammaproteobacteria was the most abundant class of Proteobacteria, followed by Betaproteobacteria of this phylum. Genus Azomonas, Serratia, Pantoea, Serpens, Pseudomonas, Halomonas, and Kushneria were shared by all growth stages. Gammaproteobacteria increased during the five stages. The dominant bacterial genera during five periods were related to Delftia, Kushneria, Serratia, Pantoea, Erwinia, respectively. Five libraries contained 2108 unique OTUs with 5 OTUs in common. The greatest number of OTUs was detected during flowering stage. Endophytic bacteria diversity was reduced during fruiting stage. A combination of soil pH, average monthly temperature and soil salt concentration has significant effects on the endophytic bacterial community structure during the five stages. [Conclusion] As a whole, the diversity of endophytic bacteria was high inroot of Salicornia europaea. The distribution of endophytic bacteria showed obvious dynamic changes, and the host growth stages determined the endophytic bacterial community.

Abstract:[Objective] We studied the diversity of endophytic bacterial communities in different species of halophytes growing in the same saline habitat, and analyzed the effect of rhizosphere soil physicochemical properties on endophytic bacterial communities. [Methods] PCR-based Roche FLX 454 pyrosequencing was applied to reveal the diversity of endophytic bacteria. [Results] Endophytic bacterial communities of the 16 species of halophytes mainly included 4 phyla, which were Proteobacteria, Tenericutes, Actinobacteria and Firmicutes. In terms of plant species classification, colonial differences existed among plant species at perspectives of composition of bacterial taxa; in the case of plant genus level, endophytic bacteria of different halophyte plant species but belonging to same plant genus exhibited similarity; as to plant family level, Actinobacteria and Proteobacteria comprised the main abundant phyla of the halophytes belonging to Chenopodiaceae; Proteobacteria comprised the main abundant phyla of the halophytes belonging to Zygophyllaceae; Tenericutes comprised the main abundant phyla of the halophytes belonging to Tamaricaceae; Proteobacteria, Fimicutes and Actinobacteria comprised the main abundant phyla of the halophytes belonging to Plumbaginaceae. The Cl- in rhizosphere soil has significant effect on endophytic bacterial community structure. Moreover, there is a strong correlation between bacterial community and the combination of Cl-, Mg2+ and total nitrogen. [Conclusion] Halophytes harbors diverse endophytic bacteria. In the same saline habitat, the distribution of endophytic bacteria showed host plant species-specific, and the Cl- in rhizosphere soil was one of the factors determined the endophytic bacterial community.

Abstract:[Objective] The Yellow River Delta is one of the most important estuary wetland ecosystems in the world. Suaeda glauca (SG), Glycine soja and Phragmites australis (GP) are three typical plants that play important roles in the ecosystem of this region. In this work, we compared the microbial community composition and functional genes of the rhizosphere soils of these typical halophytes with those of bulk soil of the barren wetland (BW) along the saline gradient in the Yellow River Delta. [Methods] Metagenome sequencing was used to analyze the composition and abundance of the microbial communities. COG (Clusters of Orthologous Groups) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analyses were used to determine the functional gene annotation of the predicted genes. [Results] The results demonstrated that Proteobacteria was the most abundant phylum in all samples. The relative abundance of Proteobacteria in the rhizosphere soils of SG and GP was 28.8% and 10.6% greater than that of the BW, respectively. In addition, Bacteroidetes, Actinobacteria and Gemmatimonadetes were detected as abundant species in the three samples. Sinorhizobium was an abundant species in the GP sample and may be responsible for nitrogen fixation in the rhizosphere soils. Sequence annotation indicated that the number of the predicted functional genes of BW was higher than that of SG and GP. Among them, amino acid metabolism, carbohydrate and energy metabolism, and inorganic ion transport and metabolism genes were abundant in the three samples. [Conclusion] This study demonstrated that different plants and soils have a coordinated effect on the soil microbial communities of the Yellow River Delta, and provided valuable insights on microbial resilience and their potential application on bioremediation of the coastal zone saline-alkali soils.