Potential of Bradyrhizobia inoculation to promote peanut growth and beneficial Rhizobacteria abundance

AIMS

To investigate the effects of three symbiotic Bradyrhizobium strains on peanut growth and on rhizobacterial communities in flowering and harvest stages in an organic farm, also to evaluate the role of plant development in influencing peanut rhizobacterial microbiota and correlations among the inoculants, rhizobacterial communities and plant growth.

METHODS AND RESULTS

Peanut seeds were inoculated with three individual Bradyrhizobium strains, plant growth performance was measured in two developmental stages and rhizobacterial communities were analysed by Illumina sequencing of rpoB gene amplicons from peanut rhizosphere. The three bradyrhizobial inoculants significantly increased the nodule numbers and aboveground fresh weight of peanut plants regardless of the different growth stages, and the pod yields were increased to some extent and significantly positively correlated with Bradyrhizobium abundances in rhizosphere. Principal coordinate analysis indicated that the rhizobacterial communities were strongly influenced by the inoculation and peanut developmental stages. The bradyrhizobia inoculation increased relative abundances of potentially beneficial bacteria in peanut rhizosphere, and also altered rhizobacterial co-occurrence association networks and important network hub taxa. Similarly, plant development also significantly influenced the structure, composition and co-occurrence association networks of rhizobacterial communities.

CONCLUSIONS

Bradyrhizobial inoculants increased peanut growth and yields, they and plant development affected the assembly of peanut rhizobacterial communities.

SIGNIFICANCE AND IMPACT OF THE STUDY

Rhizobial inoculants improved the host plant performance that might also be associated with the dynamic changes in rhizobacterial community except enhancing the biological nitrogen fixation and helps to profoundly understand the mechanism how rhizobia inoculants improve plant growth and yields.

Recent development and new insight of diversification and symbiosis specificity of legume rhizobia: mechanism and application

Currently, symbiotic rhizobia (sl., rhizobium) refer to the soil bacteria in α- and β-Proteobacteria that can induce root and/or stem nodules on some legumes and a few of nonlegumes. In the nodules, rhizobia convert the inert dinitrogen gas (N₂ ) into ammonia (NH₃ ) and supply them as nitrogen nutrient to the host plant. In general, this symbiotic association presents specificity between rhizobial and leguminous species, and most of the rhizobia use lipochitooligosaccharides, so called Nod factor (NF), for cooperating with their host plant to initiate the formation of nodule primordium and to inhibit the plant immunity. Besides NF, effectors secreted by type III secretion system (T3SS), exopolysaccharides and many microbe-associated molecular patterns in the rhizobia also play important roles in nodulation and immunity response between rhizobia and legumes. However, the promiscuous hosts like Glycine max and Sophora flavescens can nodulate with various rhizobial species harbouring diverse symbiosis genes in different soils, meaning that the nodulation specificity/efficiency might be mainly determined by the host plants and regulated by the soil conditions in a certain cases. Based on previous studies on rhizobial application, we propose a '1+n-N' model to promote the function of symbiotic nitrogen fixation (SNF) in agricultural practice, where '1' refers to appreciate rhizobium; '+n' means the addition of multiple trace elements and PGPR bacteria; and '-N' implies the reduction of chemical nitrogen fertilizer. Finally, open questions in the SNF field are raised to future think deeply and researches.

Grape berry surface bacterial microbiome: impact from the varieties and clones in the same vineyard from central China

AIMS

Bacterial microbiome on grape berry surface may play an important role in grape quality and health. This study aims to investigate the impact of grape varieties and clones on grape berry surface bacterial microbiome from the same vineyard.

METHODS AND RESULTS

High-throughput sequencing strategy was used to investigate the bacterial diversity and abundance on the grape surfaces of 12 clones belonging to six varieties grown in the same vineyard of Zhengzhou Fruit Research Institute in Henan Province. In total, 45 bacterial phyla and 933 genera were detected from all samples. Cyanobacteria, Proteobacteria and Firmicutes were the most abundant and prevalent phyla, while Bacteroidetes, Chloroflexi, Acidobacteria and Planctomycetes were grape clone specific phyla. The nonrank genus from phylum Cyanobacteria occupied 30-81% of grape clones from Italian Riesling (GRX), Cabernet Franc (PLZ), Pinot Blanc (BBN) and Riesling (LSL). Interestingly, Bacillus, Pseudomonas and Lactococcus were the only three prevalent genera found on all the clones. Furthermore, the predicted functional activities of grape surface bacterial communities varied according to the clones.

CONCLUSIONS

The present study revealed that in addition to the grape varieties, the variations in grape clone background may also affect the bacterial microbiome on grape surfaces which may ultimately determine their functional activities.

SIGNIFICANCE AND IMPACT OF THE STUDY

This research provides an important information for grape planting and wine fermentation that not only the grape varieties need to be paid attention but also grape clones from the specific variety need to be concerned.

Rhizobial biogeography and inoculation application to soybean in four regions across China

AIMS

The aim of the study was to survey rhizobial biogeography and to inoculate soybean with selected rhizobia in China to enhance symbiotic nitrogen fixation (SNF).

METHODS AND RESULTS

Biogeography, genetic diversity and phylogeny of soybean rhizobia were surveyed. Inocula were prepared and applied to soybean. Results showed that Bradyrhizobium elkanii and Ensifer fredii were widely distributed in acid and alkaline soils respectively. Available iron was detected as the first determinant for distribution of the two rhizobia and the soybean varieties did not greatly affect the rhizobial compatibility. Geographical latitude and precipitation in June were the main geographical and climatic factors affecting the rhizobial distribution. Inoculation with selected rhizobia increased the nodule number, fresh weight, occupation ratio, seed protein content and soybean yields.

CONCLUSIONS

Selection and application of effective soybean rhizobia across China according to biogeography were clarified to promote the SNF, thereby improving soybean yield.

SIGNIFICANCE AND IMPACT OF THE STUDY

Rhizobial diversity and biogeography were evaluated systematically in six sites across China. Available iron and soil pH are found to be the most important determinants for the distribution of soybean rhizobia. Inoculation to soybean enhances SNF, positively correlating to the increase in soybean yield and seed protein content.

Metabolic consequences of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women and the leading cause of anovulatory infertility. The prevalence of the syndrome ranges between 6 to 15% based on broader Rotterdam diagnostic criteria verses strict NIH diagnostic criteria.1 The condition is characterized by a combination of ovulatory dysfunction, hyperandrogenism and the presence of polycystic ovaries. PCOS has been associated with multiple metabolic alterations and consequences including impaired glucose tolerance, insulin resistance, hyperinsulinemia, type II diabetes, dyslipidemia, metabolic syndrome, obesity and subclinical cardiovascular disease. It remains unclear however if these associations lead to an increased risk of clinically significant long-term cardiovascular disease. Large prospective studies to date have not detected significant differences in overall cardiovascular morbidity and mortality in PCOS. The phenotypical variability in PCOS has made researching each of these associations challenging as different aspects of the syndrome may be contributing, opposing or confounding factors. The ability to detect significant differences in long-term cardiovascular outcomes may also be due to the variable nature of the syndrome. In this review, we attempt to describe a summary of the current literature concerning the metabolic alterations and cardiovascular consequences of polycystic ovary syndrome.

Innovative applications of immunisation registration information systems: example of improved measles control in Taiwan

Immunisation registry systems have been shown to be important for finding pockets of under-immunised individuals and for increasing vaccination coverage. The National Immunisation Information System (NIIS) was established in 2003 in Taiwan. In this perspective, we present the construction of the NIIS and two innovative applications, which were implemented in 2009, which link the NIIS with other databases for better control of measles. Firstly, by linking the NIIS with hospital administrative records, we are able to follow up contacts of measles cases in a timely manner to provide the necessary prophylaxis, such as immunoglobulin or vaccines. Since 2009, there have been no measles outbreaks in hospitals in Taiwan. Secondly, by linking the NIIS with an immigration database, we are able to ensure that young citizens under the age of five years entering Taiwan from abroad become fully vaccinated. Since 2009, the measles-mumps-rubella vaccine coverage rate at two years of age has increased from 96% to 98%. We consider these applications of the NIIS to be effective mechanisms for improving the performance of infectious disease control in Taiwan. The experience gained could provide a valuable example for other countries.

Genetic diversity of rhizobia associated with Desmodium species grown in China

AIMS

Desmodia are leguminous plants used as important forage and herbal medicine in China. Little information is available about the nodule bacteria of Desmodium species. To understand the genetic diversity of rhizobia associated with Desmodium species grown in China, isolates from temperate and subtropical regions were obtained and analysed.

METHODS AND RESULTS

A total of 39 rhizobial strains isolated from 9 Desmodium species grown in China were characterized by PCR-based 16S rDNA gene and 16S-23S rDNA intergenic spacer gene restriction fragment length polymorphism (RFLP) and 16S rRNA gene sequencing. The results showed high diversity among rhizobia symbiotic with Desmodium species. Most microsymbionts of Desmodium species belonged to Bradyrhizobium closely related to Bradyrhizobium elkanii, Bradyrhizobium japonicum and Bradyrhizobium yuanmingense. Several small groups or single strain were related to Rhizobium, Sinorhizobium or Mesorhizobium.

CONCLUSIONS

Desmodium species formed nodules with diverse rhizobia in Chinese soils.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results offered the first systematic information about the microsymbionts of desmodia grown in the temperate and subtropical regions of China.

Novel nitrogen-fixing acetic acid bacteria, Gluconacetobacter johannae sp. nov. and Gluconacetobacter azotocaptans sp. nov., associated with coffee plants

Diazotrophic bacteria were isolated, in two different years, from the rhizosphere and rhizoplane of coffee (Coffea arabica L.) plants cultivated in Mexico; they were designated as type DOR and type SAd isolates. They showed characteristics of the family Acetobacteraceae, having some features in common with Gluconacetobacter (formerly Acetobacter) diazotrophicus, the only known N2-fixing species of the acetic acid bacteria, but they differed from this species with regard to several characteristics. Type DOR isolates can be differentiated phenotypically from type SAd isolates. Type DOR isolates and type SAd isolates can both be differentiated from Gluconacetobacter diazotrophicus by their growth features on culture media, their use of amino acids as nitrogen sources and their carbon-source usage. These results, together with the electrophoretic mobility patterns of metabolic enzymes and amplified rDNA restriction analysis, suggested that the type DOR and type SAd isolates represent two novel N2-fixing species. Comparative analysis of the 16S rRNA sequences revealed that strains CFN-Cf55T (type DOR isolate) and CFN-Ca54T (type SAd isolate) were closer to Gluconacetobacter diazotrophicus (both strains had sequence similarities of 98.3%) than to Gluconacetobacter liquefaciens, Gluconacetobacter sacchari (similarities < 98%) or any other acetobacteria. Strain CFN-Cf55T exhibited low levels of DNA-DNA reassociation with type SAd isolates (mean 42%) and strain CFN-Ca54T exhibited mean DNA-DNA reassociation of 39.5% with type DOR isolates. Strains CFN-Cf55T and CFN-Ca54T exhibited very low DNA reassociation levels, 7-21%, with other closely related acetobacterial species. On the basis of these results, two novel N2-fixing species are proposed for the family Acetobacteraceae, Gluconacetobacter johannae sp. nov. (for the type DOR isolates), with strain CFN-Cf55T (= ATCC 700987T = DSM 13595T) as the type strain, and Gluconacetobacter azotocaptans sp. nov. (for the type SAd isolates), with strain CFN-Ca54T (= ATCC 70098ST = DSM 13594T) as the type strain.

Rhizobium yanglingense sp. nov., isolated from arid and semi-arid regions in China

A novel rhizobial group, cluster 9, defined in previous research [Tan, Z. Y., Wang, E. T., Peng, G. X., Zhu, M. E., Martinez-Romero, E. & Chen, W. X. (1999). Int J Syst Bacteriol 49, 1457-1469], was further characterized by determination of DNA base composition, whole-cell protein SDS-PAGE analysis, DNA-DNA hybridization, 16S rRNA gene sequencing and host specificity. These isolates were collected from the wild legumes Amphicarpaea trisperma, Coronilla varia and Gueldenstaedtia multiflora growing in arid and semi-arid regions in northwestern China. Isolates within cluster 9 grouped into a single cluster above a similarity level of 90.6% in a cluster analysis based on protein SDS-PAGE, and they were differentiated from defined rhizobial species. Comparative analysis of 16S rRNA gene sequences showed that isolate CCBAU 71623T, representing cluster 9, was most related to Rhizobium gallicum and Rhizobium mongolense. The DNA-DNA homologies were lower than 42.4% among cluster 9 and defined species, including R. gallicum and R. mongolense. These data indicated that cluster 9 was a unique genomic species. Isolates within this cluster could share their host plants. They could not nodulate Galega orientalis and Leucaena leucocephala and formed ineffective nodules on Phaseolus vulgaris. This group could also be differentiated from defined species by phenotypic characteristics. It is therefore proposed as a new species, Rhizobium yanglingense, with isolate CCBAU 71623 as the type strain.

Sinorhizobium meliloti associated with Medicago sativa and Melilotus spp. in arid saline soils in Xinjiang, China

Of 42 rhizobial isolates from Medicago sativa and Melilotus spp. growing in arid saline fields in Xinjiang, China, 40 were identified as Sinorhizobium meliloti by a polyphasic approach. However, diverse groups were obtained from these isolates in numerical taxonomy and SDS-PAGE of proteins. They could grow at pH 10.5 and were tolerant to 2.5-4.0% (w/v) NaCl.

Sesbania herbacea-Rhizobium huautlense Nodulation in Flooded Soils and Comparative Characterization of S. herbacea-Nodulating Rhizobia in Different Environments

The nodulation of S. herbacea was compared under flooded and non-flooded conditions in two different soils. One soil was from a flooded field in Sierra de Huautla, the native habitat of this legume, while the other soil was from a well-drained field in Cuernavaca, where rhizobia were found to nodulate the introduced S. herbacea plants. Nodulation of the plants was completely eliminated by flooding in the Cuernavaca soil, whereas nodules were obtained in the same soil under non-flooded conditions. In contrast, nodules were formed in Huautla soil under both flooded and non-flooded conditions. Most isolates, except isolate HS2, from Huautla soil and water were identified as R. huautlense by colony morphology, growth rate, PCR-RFLP of 16S rRNA genes, MLEE, cellular plasmid contents, and RFLP of nifH and nodDAB genes. Isolate HS2 was identified as Mesorhizobium sp. Isolates from Cuernavaca soil were different from R. huautlense in many aspects and were classified into five rDNA types within the genera Mesorhizobium, Rhizobium, and Sinorhizobium by PCR-RFLP of 16S rRNA genes. R. huautlense is a water Rhizobium species. Growth by denitrification under oxygen limitation or with ethanol was observed for R. huautlense bacteria but not for the isolates from Cuernavaca. In an interstrain nodulation competitive assay under both flooded and non-flooded conditions, R. huautlense strain S02 completely inhibited the nodulation of Mesorhizobium sp. Sn2, an isolate from Cuernavaca. From these results, we conclude that R. huautlense has the unique ability to nodulate S. herbacea not only in flooded soils, but in non-flooded soils as well.

Rhizobium etli bv. mimosae, a novel biovar isolated from Mimosa affinis

Fifty rhizobial isolates from root nodules of Mimosa affinis, a small leguminous plant native to Mexico, were identified as Rhizobium etli on the basis of the results of PCR-RFLP and RFLP analyses of small-subunit rRNA genes, multilocus enzyme electrophoresis and DNA-DNA homology. They are, however, a restricted group of lineages with low genetic diversity within the species. The isolates from M. affinis differed-from the R. etli strains that orginated from bean plants (Phaseolus vulgaris) in the size and replicator region of the symbiotic plasmid and in symbiotic-plasmid-borne traits such as nifH gene sequence and organization, melanin production and host specificity. A new biovar, bv. mimosae, is proposed within R. etli to encompass Rhizobium isolates obtained from M. affinis. The strains from common bean plants have been designated previously as R. etli bv. phaseoli. Strains of both R. etli biovars could nodulate P. vulgaris, but only those of bv. mimosae could form nitrogen-fixing nodules on Leucaena leucocephala.

Characterization of bacteria isolated from wild legumes in the north-western regions of China

Nodule isolates from 11 species of wild legumes in north-western China were characterized by numerical taxonomy, PCR-based 16S rRNA gene RFLP and sequence analyses, DNA-DNA hybridization, restriction patterns of nodDAB and nifH genes, and symbiotic properties. Based on the results of numerical taxonomy, most of the 35 new isolates were grouped into five clusters (clusters 7, 9, 12, 14 and 15). Clusters 7 and 12 were identified as Mesorhizobium amorphae and Agrobacterium tumefaciens, respectively, based on their high DNA homologies with the reference strains for these species, their 16S rRNA gene analysis and their phenotypic features. Results of 16S rDNA PCR-RFLP analysis showed that cluster 9 belonged to Rhizobium. Clusters 14 and 15 were identified as Mesorhizobium based on their moderately slow-growing, acid-producing characters and the high similarity of their 16S rDNA PCR-RFLP patterns to those of Mesorhizobium species. These two clusters were genomic species distinct from all described species based on analysis of DNA relatedness within this genus. The isolates in cluster 12 (Agrobacterium tumefaciens) failed to nodulate their original host and other selected hosts and they did not hybridize to nif or nod gene probes. The possibility of opportunistic nodulation of these isolates is discussed. Identical restriction patterns were obtained in the nif or nod gene hybridization studies from the three isolates within cluster 15, which were isolated from the same host species. The isolates from different host plants in each of clusters 9 and 14 produced different nodDAB RFLP patterns, but similar nifH RFLP patterns appeared (one band for each isolate). Different patterns were observed among different clusters from both the nod and nif gene hybridization studies. Crossnodulation was recorded among the isolates and the host plants in the same cluster and promiscuous properties were found among some of the hosts tested.

Diversity of rhizobia associated with Amorpha fruticosa isolated from Chinese soils and description of Mesorhizobium amorphae sp. nov

Fifty-five Chinese isolates from nodules of Amorpha fruticosa were characterized and compared with the type strains of the species and genera of bacteria which form nitrogen-fixing symbioses with leguminous host plants. A polyphasic approach, which included RFLP of PCR-amplified 16S rRNA genes, multilocus enzyme electrophoresis (MLEE), DNA-DNA hybridization, 16S rRNA gene sequencing, electrophoretic plasmid profiles, cross-nodulation and a phenotypic study, was used in the comparative analysis. The isolates originated from several different sites in China and they varied in their phenotypic and genetic characteristics. The majority of the isolates had moderate to slow growth rates, produced acid on YMA and harboured a 930 kb symbiotic plasmid (pSym). Five different RFLP patterns were identified among the 16S rRNA genes of all the isolates. Isolates grouped by PCR-RFLP of the 16S rRNA genes were also separated into groups by variation in MLEE profiles and by DNA-DNA hybridization. A representative isolate from each of these DNA homology groups had a separate position in a phylogenetic tree as determined from sequencing analysis of the 16S rRNA genes. A new species, Mesorhizobium amorphae, is proposed for the majority of the isolates, which belonged to a moderately slow- to slow-growing, acid-producing group based upon their distinct phylogenetic position, their unique electrophoretic type, their low DNA homology with reference strains representing the species within the genus Mesorhizobium and their distinct phenotypic features. Strain ACCC 19665 was chosen as the type strain for M. amorphae sp. nov.

Rhizobium huautlense sp. nov., a symbiont of Sesbania herbacea that has a close phylogenetic relationship with Rhizobium galegae

The nitrogen-fixing rhizobial symbionts of Sesbania herbacea growing in the nature reserve at the Sierra de Huautla, Mexico, were isolated and characterized. All 104 isolates together with the type strain for Rhizobium galegae, HAMBI 540T, had similar 16S rRNA genes as revealed by PCR-RFLP analysis. Similarity in the sequences of the 16S rRNA genes placed the isolates on a phylogenetic branch shared with R. galegae. Among 66 randomly selected isolates, three closely related electrophoretic alloenzyme types (ETs) were identified, which were distinct from 10 ETs distinguished among 23 strains of R. galegae. A new species Rhizobium huautlense, represented by the Sesbania isolate SO2T, is proposed based upon low estimates of DNA relatedness between our chosen type strain and the type strains for the other species, the dissimilarity of the nucleotide sequence of the 16S rRNA genes, and their distinct ETs compared with R. galegae. The description of R. huautlense is significant because in the reconstruction of the phylogeny at R. huautlense there was a shift in the node of the branch of Agrobacterium vitis relative to that of R. galegae. The revised phylogenetic tree would tend to indicate common ancestry between R. galegae and Rhizobium leguminosarum.

Phylogenetic and genetic relationships of Mesorhizobium tianshanense and related rhizobia

The genetic and phylogenetic relationships for strains of Mesorhizobium tianshanense and its relatives were compared by an analysis of the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins, DNA-DNA hybridization, and full 16S rRNA gene sequencing. The strains of M. tianshanense formed a cluster which was distinct from those of other rhizobium species in the clustering analysis of SDS-PAGE. DNA-DNA relatedness between A-1BS (type strain of M. tianshanense) and the type or reference strains for Mesorhizobium loti, M. huakuii, M. ciceri, M. mediterraneum, and cluster U, an unnamed rhizobial group, ranged from 4.4 to 43.8%. The phylogenetic analysis based on the 16S rRNA gene sequences showed that M. tianshanense was closely related to the Mesorhizobium phylogenetic branch and could be distinguished from the other four species in this branch. These results further confirmed that these bacteria constitute a distinct rhizobial species.

Rhizobium hainanense sp. nov., isolated from tropical legumes

A fast-growing rhizobial group isolated from leguminous plants in Hainan Province, a tropical region of China, is proposed as a new Rhizobium species on the basis of 16S rRNA gene sequencing. DNA-DNA hybridization, and phenotypic characterization. This new species belongs to the phylogenetic branch which includes Rhizobium leguminosarum. We propose the name Rhizobium hainanense sp. nov. for this species. The strain CCBAU 57015 (166) is the type strain; it has been deposited in the culture collection of Beijing Agricultural University, People's Republic of China.

A review of otolaryngologic aircrew disqualification in the Chinese Air Force, 1961-90

Otolaryngologic disease was the third most common medical cause of permanent grounding, accounting for 145 (12.2%) of 1,186 aircrew members permanently grounded for various medical reasons in the General Hospital of the Chinese Air Force, 1961-90. We reviewed the medical files of these 145 grounded aircrew members. Their mean age was 31.7 years, their mean flight time before grounding was 878.3 hours, and the mean course of disease from onset to disqualification for flying was 3.9 years. Nearly half of them flew in fighter aircraft and 91 (62.8%) were pilots. The most common otolaryngologic condition responsible for permanent grounding was barotitis media, followed by hearing loss, Ménière's disease, motion sickness, and vertigo. The information from this report demonstrated that the grounded aircrew members were likely to be young, and that the course of disease from onset to grounding was too long.

Histaminergic response to Coriolis stimulation: implication for transdermal scopolamine therapy of motion sickness

The blood levels of histamine and 5-hydroxytryptamine (5-HT) in 10 subjects, with or without administration of the transdermal therapeutic system of scopolamine (TTS-S), were measured following motion sickness (MS) induced by Coriolis stimulation. Histamine and 5-HT were assayed using the fluorometric method. The results demonstrated that the blood levels of histamine increased significantly following MS and were even higher in the subjects using TTS-S, but we found neither significant changes in the blood levels of 5-HT following MS nor any effect of TTS-S on it. The results suggest that histamine contributes to the development of MS, and scopolamine may exert its anti-MS action by affecting the histaminergic system as well as the acetylcholinergic system; there may not be a definite relation between 5-HT and the development of MS.