Contrasted Reactivity to Oxygen Tensions in Frankia sp. Strain CcI3 throughout Nitrogen Fixation and Assimilation

Reconciling the irreconcilable is a primary struggle in aerobic nitrogen-fixing bacteria. Although nitrogenase is oxygen and reactive oxygen species-labile, oxygen tension is required to sustain respiration. In the nitrogen-fixing Frankia, various strategies have been developed through evolution to control the respiration and nitrogen-fixation balance. Here, we assessed the effect of different oxygen tensions on Frankia sp. strain CcI3 growth, vesicle production, and gene expression under different oxygen tensions. Both biomass and vesicle production were correlated with elevated oxygen levels under both nitrogen-replete and nitrogen-deficient conditions. The mRNA levels for the nitrogenase structural genes (nifHDK) were high under hypoxic and hyperoxic conditions compared to oxic conditions. The mRNA level for the hopanoid biosynthesis genes (sqhC and hpnC) was also elevated under hyperoxic conditions suggesting an increase in the vesicle envelope. Under nitrogen-deficient conditions, the hup2 mRNA levels increased with hyperoxic environment, while hup1 mRNA levels remained relatively constant. Taken together, these results indicate that Frankia protects nitrogenase by the use of multiple mechanisms including the vesicle-hopanoid barrier and increased respiratory protection

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

<em>Blastococcus brunescens</em> sp. nov., a member of the <em>Geodermatophilaceae </em>isolated from sandstone collected from the Sahara Desert in Tunisia

\ua9 2024 The Authors.The taxonomic position of strain BMG 8361T, isolated from sandstone collected in the Sahara Desert of Southern Tunisia, was refined through a polyphasic taxonomic investigation. Colonies of BMG 8361T were pale-orange coloured, irregular with a dry surface and produced a diffusible pink or brown pigment depending on media. The Gram-positive cells were catalase-positive and oxidase-negative. The strain exhibited growth at 10–40\ub0C and pH values ranging from 5.5 to 9.0, with optima at 28–35\ub0C and pH 6.5–8.0. Additionally, BMG 8361T demonstrated the ability to grow in the presence of up to 1% NaCl (w/v) concentration. The peptidoglycan of the cell wall contained meso-diaminopimelic acid, glucose, galactose, xylose, ribose, and rhamnose. The predominant menaquinones consisted of MK-9(H4) and MK-9. The main polar lipids were phosphatidylcholine, phosphatidylinositol, glycophosphatidylinositol, diphosphatidylglycerol, phosphatidylethanolamine, and two unidentified lipids. Major cellular fatty acids were iso-C16:0, iso-C16:1 h, and C17:1 ω8c. Phylogenetic analyses based on both the 16S rRNA gene and whole-genome sequences assigned strain BMG 8361T within the genus Blastococcus. The highest pairwise sequence similarity observed in the 16S rRNA gene was 99.5% with Blastococcus haudaquaticus AT 7-14T. However, when considering digital DNA–DNA hybridization and average nucleotide identity, the highest values, 48.4 and 86.58%, respectively, were obtained with Blastococcus colisei BMG 822T. These values significantly undershoot the recommended thresholds for establishing new species, corroborating the robust support for the distinctive taxonomic status of strain BMG 8361T within the genus Blastococcus. In conjunction with the phenotyping results, this compelling evidence leads to the proposal of a novel species we named Blastococcus brunescens sp. nov. with BMG 8361T (=DSM 46845T=CECT 8880T) as the type strain

<em>Blastococcus carthaginiensis</em> sp. nov., isolated from a monument sampled in Carthage, Tunisia

A comprehensive polyphasic investigation was conducted to elucidate the taxonomic position of an actinobacterium, designated BMG 814T, which was isolated from the historic ruins of Carthage city in Tunisia. It grew as pink-orange pigmented colonies and displayed versatile growth capabilities, thriving within a temperature range of 20-40 \ub0C, across a pH spectrum ranging from pH 5.5 to 10 and in the presence of up to 4 % NaCl. Chemotaxonomic investigations unveiled specific cell components, including diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, glycophosphatidylinositol, an unidentified aminoglycophospholipid, six unidentified aminolipids, two unidentified phospholipids and one unidentified lipid in its polar lipid profile. Furthermore, galactose, glucose and ribose were identified as the primary cell-wall sugars. Major menaquinones identified were MK-9(H4), MK-9(H2) and MK-9, while major fatty acids comprised iso-C15 : 0, iso-C16 : 0, C17 : 1 ω8c and C18 : 1 ω9c. Through phylogenetic analysis based on the 16S rRNA gene sequence, the strain was positioned within the genus Blastococcus, with Blastococcus capsiensis BMG 804T showing the closest relationship (99.1 %). In light of this, draft genomes for both strains, BMG 814T and BMG 804T, were sequenced in this study, and comparative analysis revealed that strain BMG 814T exhibited digital DNA-DNA hybridization and average nucleotide identity values below the recommended thresholds for demarcating new species with all available genomes of type strains of validly names species. Based on the polyphasic taxonomy assessment, strain BMG 814T (=DSM 46848T=CECT 8878T) was proposed as the type strain of a novel species named Blastococcus carthaginiensis sp. nov

Permanent improved high-quality draft genome sequence of Nocardia casuarinae strain BMG51109, an endophyte ofactinorhizal root nodules of Casuarina glauca

Here, we report the first genome sequence of aNocardiaplant endophyte, N. casuarinaestrain BMG51109, isolated fromCasu-arina glaucaroot nodules. The improved high-quality draft genome sequence contains 8,787,999 bp with a 68.90% GC contentand 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

Evaluation des performances et gestion optimale des bassins solaires

SIGLECNRS T 59280 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc