Permanent draft genome sequence of Bradyrhizobium vignae, strain ISRA 400, an elite nitrogen-fixing bacterium, isolated from the groundnut growing area in Senegal.

A new Bradyrhizobium vignae strain called ISRA400 was isolated from groundnut (Arachis hypogaea L.) root nodules obtained by trapping the bacteria from soil samples collected in the Senegalese groundnut basin. In this study, we present the draft genome sequence of this strain ISRA400, which spans approximatively 7.9 Mbp and exhibits a G+C content of 63.4%. The genome analysis revealed the presence of 48 tRNA genes and one rRNA operon (16S, 23S, and 5S). The nodulation test revealed that this strain ISRA400 significantly improves the nodulation parameters and chlorophyll content of the Arachis hypogaea variety Fleur11. These findings suggest the potential of Bradyrhizobium vignae strain ISRA400 as an effective symbiotic partner for improving the growth and productivity of groundnut crop.

Root Nodule Microsymbionts of Native Coriaria myrtifolia in Algeria.

Coriaria myrtifolia occurs as natural flora of warm temperate climates of northern Algeria which commonly found in hedges, forest and ravine edges. This actinorhizal species was known to establish a mutualistic symbiosis with members of phylogenetic cluster 2 (including strains associated to Coriaria spp., Ceanothus, Datiscaceae, and Dryadoideae) within the genus Frankia. Attempts to isolate C. myrtifolia microsymbionts from native plants growing in 4 locations in Algeria permitted to only recover asymbiotic Frankia strains (unable to reestablish nodulation and to fix nitrogen) from phylogenetic cluster 4 and several non-Frankia actinobacteria including members of Micrococcus, Micromonospora, Nocardia, Plantactinospora, and Streptomyces genera. The biodiversity of Frankia microsymbionts of C. myrtifolia root nodules was assessed using PCR-amplification followed by partial nucleotide sequencing of glnA1 (glutamine synthetase type 1) gene. On the 12 different glnA1 gene sequences obtained in this study, 9 were detected for the first time, and were mainly closelyrelated to Mediterranean genotypes previously described in the Grand Maghreb countries (Morocco and Tunisia) and in Europe (France) but without clear separations from other cluster 2 genotypes.

High-Quality Genome Sequences of Six Actinobacterial Strains Isolated from Granite, Granodiorite, and Tourmaline Rock Surfaces Sampled from Tamil Nadu, India, and New England, United States.

Here, we announce four contiguous and two high-quality draft genome sequences of six actinobacterial strains (Blastococcus, Georgenia, Nocardioides, Allobranchiibius, Yimella, and Williamsia) that were isolated from rock samples obtained from Indian historical ruins and colonial building stones in New England, United States. These new sequences expand the genome datasets recovered from stone-dwelling microbes and will allow the prediction of their potential role in the stone microbiome.

Effect of actinorhizal root exudates on the proteomes of Frankia soli NRRL B-16219, a strain colonizing the root tissues of its actinorhizal host via intercellular pathway.

Frankia and actinorhizal plants exchange signals in the rhizosphere leading to specific mutual recognition of partners and nitrogen-fixing nodule organogenesis. Frankia soli strain NRRL B-16219, from the Elaeagnus specificity group, colonizes the root tissues of its actinorhizal host through direct intercellular penetration of root epidermis cells and cortex. Here, we studied the early proteogenomic response of strain NRRL B-16219 to treatment with root exudates from compatible Elaeagnus angustifolia, and incompatible Ceanothus thyrsiflorus and Coriaria myrtifolia, host plants grown in nitrogen depleted hydroponic medium. Next-generation proteomics was used to identify the main Frankia proteins differentially expressed in response to the root exudates. No products of the nod genes present in B-16219 were detected. Proteins specifically upregulated in presence of E. angustifolia root exudates include those connected to nitrogen fixation and assimilation (glutamate synthetase, hydrogenase and squalene synthesis), respiration (oxidative phosphorylation and citric acid cycle pathways), oxidative stress (catalase, superoxide dismutase, and peroxidase), proteolysis (proteasome, protease, and peptidase) and plant cell wall degrading proteins involved in the depolymerization of celluloses (endoglucanase, glycosyltransferase, beta-mannanases, glycoside hydrolase and glycosyl hydrolase). Proteomic data obtained in this study will help link signaling molecules/factors to their biosynthetic pathways once those factors have been fully characterized.

Alone Yet Not Alone: Frankia Lives Under the Same Roof With Other Bacteria in Actinorhizal Nodules.

Actinorhizal plants host mutualistic symbionts of the nitrogen-fixing actinobacterial genus Frankia within nodule structures formed on their roots. Several plant-growth-promoting bacteria have also been isolated from actinorhizal root nodules, but little is known about them. We were interested investigating the in planta microbial community composition of actinorhizal root nodules using culture-independent techniques. To address this knowledge gap, 16S rRNA gene amplicon and shotgun metagenomic sequencing was performed on DNA from the nodules of Casuarina glauca. DNA was extracted from C. glauca nodules collected in three different sampling sites in Tunisia, along a gradient of aridity ranging from humid to arid. Sequencing libraries were prepared using Illumina NextEra technology and the Illumina HiSeq 2500 platform. Genome bins extracted from the metagenome were taxonomically and functionally profiled. Community structure based off preliminary 16S rRNA gene amplicon data was analyzed via the QIIME pipeline. Reconstructed genomes were comprised of members of Frankia, Micromonospora, Bacillus, Paenibacillus, Phyllobacterium, and Afipia. Frankia dominated the nodule community at the humid sampling site, while the absolute and relative prevalence of Frankia decreased at the semi-arid and arid sampling locations. Actinorhizal plants harbor similar non-Frankia plant-growth-promoting-bacteria as legumes and other plants. The data suggests that the prevalence of Frankia in the nodule community is influenced by environmental factors, with being less abundant under more arid environments.

Draft Genome Sequence for Frankia sp. Strain BMG5.11, a Nitrogen-Fixing Bacterium Isolated from Elaeagnus angustifolia.

Frankia sp. strain BMG5.11, which was isolated from Elaeagnus angustifolia nodules, is able to infect other actinorhizal plants, including Elaeagnaceae, Rhamnaceae, Colletieae, Gymnostoma, and Myricaceae Here, we report the 11.3-Mbp draft genome sequence of Frankia sp. strain BMG5.11, with a G+C content of 69.9% and 9,926 candidate protein-encoding genes.

Draft genome sequence of the symbiotic Frankia sp. strain BMG5.30 isolated from root nodules of Coriaria myrtifolia in Tunisia.

Frankia sp. strain BMG5.30 was isolated from root nodules of a Coriaria myrtifolia seedling on soil collected in Tunisia and represents the second cluster 2 isolate. Frankia sp. strain BMG5.30 was able to re-infect C. myrtifolia generating root nodules. Here, we report its 5.8-Mbp draft genome sequence with a G + C content of 70.03% and 4509 candidate protein-encoding genes.

Frankia asymbiotica sp. nov., a non-infective actinobacterium isolated from Morella californica root nodule.

The taxonomic status of strain M16386T, a nitrogen-fixing but non-nodulating isolate from Morella californica, was established on the basis of a polyphasic approach. The strain grows as branched hyphae, with vesicles and non-motile productive multilocular sporangia. It metabolizes short fatty acids, TCA cycle intermediates and carbohydrates as carbon sources, and fixes nitrogen in the absence of combined nitrogen source in the growth media. Chemotaxonomic traits of strain M16386T are consistent with its affiliation to the genus Frankia. The characteristic diamino acid in the cell wall is meso-diaminopimelic acid. Strain M16386T contains phosphatidylinositol, phosphatidylglycerol, diphosphatidylglycerol, glycophospholipid and phospholipid as polar lipids; MK-9(H4) and MK-9(H6) as the predominant menaquinones; iso-C16 : 0 and C17 : 1ω8c as major fatty acids; and galactose, glucose, mannose, rhamnose and ribose as whole-cell sugars. Strain M16386T showed 98.2 % 16S rRNA gene sequence similarity with its closest phylogenetic neighbour, Frankia inefficaxDSM 45817T. Based on these results, strain M16386T (=DSM 100626T=CECT 9040T) is designated the type strain of a novel species of the genus Frankia,for which the name Frankia asymbiotica sp. nov. is proposed.

Proteogenomics data for deciphering Frankia coriariae interactions with root exudates from three host plants.

Frankia coriariae BMG5.1 cells were incubated with root exudates derived from compatible (Coriaria myrtifolia), incompatible (Alnus glutinosa) and non-actinorhizal (Cucumis melo) host plants. Bacteria cells and their exoproteomes were analyzed by high-throughput proteomics using a Q-Exactive HF high resolution tandem mass spectrometer incorporating an ultra-high-field orbitrap analyzer. MS/MS spectra were assigned with two protein sequence databases derived from the closely-related genomes from strains BMG5.1 andDg1, the Frankia symbiont of Datisca glomerata. The tandem mass spectrometry data accompanying the manuscript describing the database searches and comparative analysis (Ktari et al., 2017, doi.org/10.3389/fmicb.2017.00720) [1] have been deposited to the ProteomeXchange with identifiers PXD005979 (whole cell proteomes) and PXD005980 (exoproteome data).

Host Plant Compatibility Shapes the Proteogenome of Frankia coriariae.

Molecular signaling networks in the actinorhizal rhizosphere select host-compatible Frankia strains, trigger the infection process and eventually the genesis of nitrogen-fixing nodules. The molecular triggers involved remain difficult to ascertain. Root exudates (RE) are highly dynamic substrates that play key roles in establishing the rhizosphere microbiome. RE are known to induce the secretion by rhizobia of Nod factors, polysaccharides, and other proteins in the case of legume symbiosis. Next-generation proteomic approach was here used to decipher the key bacterial signals matching the first-step recognition of host plant stimuli upon treatment of Frankia coriariae strain BMG5.1 with RE derived from compatible (Coriaria myrtifolia), incompatible (Alnus glutinosa), and non-actinorhizal (Cucumis melo) host plants. The Frankia proteome dynamics were mainly driven by host compatibility. Both metabolism and signal transduction were the dominant activities for BMG5.1 under the different RE conditions tested. A second set of proteins that were solely induced by C. myrtifolia RE and were mainly linked to cell wall remodeling, signal transduction and host signal processing activities. These proteins may footprint early steps in receptive recognition of host stimuli before subsequent events of symbiotic recruitment.

Permanent Draft Genome Sequences of Three Frankia sp. Strains That Are Atypical, Noninfective, Ineffective Isolates.

Here, we present draft genome sequences for three atypical Frankia strains (lineage 4) that were isolated from root nodules but are unable to reinfect actinorhizal plants. The genome sizes of Frankia sp. strains EUN1h, BMG5.36, and NRRL B16386 were 9.91, 11.20, and 9.43 Mbp, respectively.

Permanent Improved High-Quality Draft Genome Sequence of Nocardia casuarinae Strain BMG51109, an Endophyte of Actinorhizal Root Nodules of Casuarina glauca.

Here, we report the first genome sequence of a Nocardia plant endophyte, N. casuarinae strain BMG51109, isolated from Casuarina glauca root nodules. The improved high-quality draft genome sequence contains 8,787,999 bp with a 68.90% GC content and 7,307 predicted protein-coding genes.

Permanent Draft Genome Sequence of Nocardia sp. BMG111209, an Actinobacterium Isolated from Nodules of Casuarina glauca.

Nocardia sp. strain BMG111209 is a non-Frankia actinobacterium isolated from root nodules of Casuarina glauca in Tunisia. Here, we report the 9.1-Mbp draft genome sequence of Nocardia sp. strain BMG111209 with a G + C content of 69.19% and 8,122 candidate protein-encoding genes.