High quality draft genome sequence of the type strain of Pseudomonas lutea OK2(T), a phosphate-solubilizing rhizospheric bacterium

Macronutrients-availing microbiomes: biodiversity, mechanisms, and biotechnological applications for agricultural sustainability

Nitrogen, phosphorus, and potassium are the three most essential micronutrients which play major roles in plant survivability by being a structural or non-structural component of the cell. Plants acquire these nutrients from soil in the fixed (NO3¯, NH4+) and solubilized forms (K+, H2PO4- and HPO42-). In soil, the fixed and solubilized forms of nutrients are unavailable or available in bare minimum amounts; therefore, agrochemicals were introduced. Agrochemicals, mined from the deposits or chemically prepared, have been widely used in the agricultural farms over the decades for the sake of higher production of the crops. The excessive use of agrochemicals has been found to be deleterious for humans, as well as the environment. In the environment, agrochemical usage resulted in soil acidification, disturbance of microbial ecology, and eutrophication of aquatic and terrestrial ecosystems. A solution to such devastating agro-input was found to be substituted by macronutrients-availing microbiomes. Macronutrients-availing microbiomes solubilize and fix the insoluble form of nutrients and convert them into soluble forms without causing any significant harm to the environment. Microbes convert the insoluble form to the soluble form of macronutrients (nitrogen, phosphorus, and potassium) through different mechanisms such as fixation, solubilization, and chelation. The microbiomes having capability of fixing and solubilizing nutrients contain some specific genes which have been reported in diverse microbial species surviving in different niches. In the present review, the biodiversity, mechanism of action, and genomics of different macronutrients-availing microbiomes are presented.

Genome assembly, comparative genomics, and identification of genes/pathways underlying plant growth-promoting traits of an actinobacterial strain, Amycolatopsis sp. (BCA-696)

The draft genome sequence of an agriculturally important actinobacterial species Amycolatopsis sp. BCA-696 was developed and characterized in this study. Amycolatopsis BCA-696 is known for its biocontrol properties against charcoal rot and also for plant growth-promotion (PGP) in several crop species. The next-generation sequencing (NGS)-based draft genome of Amycolatopsis sp. BCA-696 comprised of ~ 9.05 Mb linear chromosome with 68.75% GC content. In total, 8716 protein-coding sequences and 61 RNA-coding sequences were predicted in the genome. This newly developed genome sequence has been also characterized for biosynthetic gene clusters (BGCs) and biosynthetic pathways. Furthermore, we have also reported that the Amycolatopsis sp. BCA-696 produces the glycopeptide antibiotic vancomycin that inhibits the growth of pathogenic gram-positive bacteria. A comparative analysis of the BCA-696 genome with publicly available closely related genomes of 14 strains of Amycolatopsis has also been conducted. The comparative analysis has identified a total of 4733 core and 466 unique orthologous genes present in the BCA-696 genome The unique genes present in BCA-696 was enriched with antibiotic biosynthesis and resistance functions. Genome assembly of the BCA-696 has also provided genes involved in key pathways related to PGP and biocontrol traits such as siderophores, chitinase, and cellulase production.

Characterization of endophytic bacteria isolated from root nodules of lentil in intercropping with durum wheat

Legumes improve soil fertility by interacting symbiotically with nitrogen-fixing rhizobia allocated in root nodules. Some bacterial endophytes can coexist with rhizobia in nodules and might help legumes by enhancing stress tolerance, producing hormones stimulating plant growth, and increasing plant nutrient intake. Twenty-six bacterial endophytes from Lens culinaris root nodules cultivated in intercropping with Triticum durum were identified and characterized molecularly and biochemically. Potential plant growth-promoting strains have been selected according to the indole acetic acid and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase production, and for their inorganic phosphate solubilization ability. The presence of genes associated to ACC deaminase and nitrogenase was evaluated. Six selected strains were grown with varying NaCl and polyethylene glycol concentrations to test their salt and osmotic stress tolerance. Priestia megaterium 11NL3 and Priestia aryabhattai 19NL1, resulted to be tolerant to salinity and osmotic stress, were tested on four genotypes of T. durum seeds in different stress conditions. The effect of strain inoculation on seed germination, vigor, and root-to-shoot ratio varied depending on the type of stress and on the durum wheat genotypes. For future research, it will be necessary to test the selected bacterial strains at different plant phenological stages and to clarify the mechanisms involved in the different outcomes of plant-microbe interactions.

Complete genome analysis of sugarcane root associated endophytic diazotroph Pseudomonas aeruginosa DJ06 revealing versatile molecular mechanism involved in sugarcane development

Sugarcane is an important sugar and bioenergy source and a significant component of the economy in various countries in arid and semiarid. It requires more synthetic fertilizers and fungicides during growth and development. However, the excess use of synthetic fertilizers and fungicides causes environmental pollution and affects cane quality and productivity. Plant growth-promoting bacteria (PGPB) indirectly or directly promote plant growth in various ways. In this study, 22 PGPB strains were isolated from the roots of the sugarcane variety GT42. After screening of plant growth-promoting (PGP) traits, it was found that the DJ06 strain had the most potent PGP activity, which was identified as Pseudomonas aeruginosa by 16S rRNA gene sequencing. Scanning electron microscopy (SEM) and green fluorescent protein (GFP) labeling technology confirmed that the DJ06 strain successfully colonized sugarcane tissues. The complete genome sequencing of the DJ06 strain was performed using Nanopore and Illumina sequencing platforms. The results showed that the DJ06 strain genome size was 64,90,034 bp with a G+C content of 66.34%, including 5,912 protein-coding genes (CDSs) and 12 rRNA genes. A series of genes related to plant growth promotion was observed, such as nitrogen fixation, ammonia assimilation, siderophore, 1-aminocyclopropane-1-carboxylic acid (ACC), deaminase, indole-3-acetic acid (IAA) production, auxin biosynthesis, phosphate metabolism, hydrolase, biocontrol, and tolerance to abiotic stresses. In addition, the effect of the DJ06 strain was also evaluated by inoculation in two sugarcane varieties GT11 and B8. The length of the plant was increased significantly by 32.43 and 12.66% and fresh weight by 89.87 and 135.71% in sugarcane GT11 and B8 at 60 days after inoculation. The photosynthetic leaf gas exchange also increased significantly compared with the control plants. The content of indole-3-acetic acid (IAA) was enhanced and gibberellins (GA) and abscisic acid (ABA) were reduced in response to inoculation of the DJ06 strain as compared with control in two sugarcane varieties. The enzymatic activities of oxidative, nitrogen metabolism, and hydrolases were also changed dramatically in both sugarcane varieties with inoculation of the DJ06 strain. These findings provide better insights into the interactive action mechanisms of the P. aeruginosa DJ06 strain and sugarcane plant development.

Genomic Landscape Highlights Molecular Mechanisms Involved in Silicate Solubilization, Stress Tolerance, and Potential Growth-Promoting Activity of Bacterium Enterobacter sp. LR6

Silicon (Si) is gaining widespread attention due to its prophylactic activity to protect plants under stress conditions. Despite Si's abundance in the earth's crust, most soils do not have enough soluble Si for plants to absorb. In the present study, a silicate-solubilizing bacterium, Enterobacter sp. LR6, was isolated from the rhizospheric soil of rice and subsequently characterized through whole-genome sequencing. The size of the LR6 genome is 5.2 Mb with a GC content of 54.9% and 5182 protein-coding genes. In taxogenomic terms, it is similar to E. hormaechei subsp. xiangfangensis based on average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH). LR6 genomic data provided insight into potential genes involved in stress response, secondary metabolite production, and growth promotion. The LR6 genome contains two aquaporins, of which the aquaglyceroporin (GlpF) is responsible for the uptake of metalloids including arsenic (As) and antimony (Sb). The yeast survivability assay confirmed the metalloid transport activity of GlpF. As a biofertilizer, LR6 isolate has a great deal of tolerance to high temperatures (45 °C), salinity (7%), and acidic environments (pH 9). Most importantly, the present study provides an understanding of plant-growth-promoting activity of the silicate-solubilizing bacterium, its adaptation to various stresses, and its uptake of different metalloids including As, Ge, and Si.

Antibiotic Resistant Pseudomonas Spp. Spoilers in Fresh Dairy Products: An Underestimated Risk and the Control Strategies

Microbial multidrug resistance (MDR) is a growing threat to public health mostly because it makes the fight against microorganisms that cause lethal infections ever less effective. Thus, the surveillance on MDR microorganisms has recently been strengthened, taking into account the control of antibiotic abuse as well as the mechanisms underlying the transfer of antibiotic genes (ARGs) among microbiota naturally occurring in the environment. Indeed, ARGs are not only confined to pathogenic bacteria, whose diffusion in the clinical field has aroused serious concerns, but are widespread in saprophytic bacterial communities such as those dominating the food industry. In particular, fresh dairy products can be considered a reservoir of Pseudomonas spp. resistome, potentially transmittable to consumers. Milk and fresh dairy cheeses products represent one of a few "hubs" where commensal or opportunistic pseudomonads frequently cohabit together with food microbiota and hazard pathogens even across their manufacturing processes. Pseudomonas spp., widely studied for food spoilage effects, are instead underestimated for their possible impact on human health. Recent evidences have highlighted that non-pathogenic pseudomonads strains (P. fluorescens, P. putida) are associated with some human diseases, but are still poorly considered in comparison to the pathogen P. aeruginosa. In addition, the presence of ARGs, that can be acquired and transmitted by horizontal genetic transfer, further increases their risk and the need to be deeper investigated. Therefore, this review, starting from the general aspects related to the physiological traits of these spoilage microorganisms from fresh dairy products, aims to shed light on the resistome of cheese-related pseudomonads and their genomic background, current methods and advances in the prediction tools for MDR detection based on genomic sequences, possible implications for human health, and the affordable strategies to counteract MDR spread.

Draft genome sequence of a cold-adapted phosphorous-solubilizing Pseudomonas koreensis P2 isolated from Sela Lake, India

The draft genome sequence of a cold-adapted phosphorus-solubilizing strain Pseudomonas koreensis P2 isolated from the Sela Lake contains 6,436,246 bp with G + C content of 59.8%. The genome sequence includes 5743 protein coding genes, 68 non-protein coding genes, 1007 putative proteins, 5 rRNA genes, 64 tRNAs and two prophage regions in 40 contigs. Besides these, genes involved in phosphate solubilization, siderophore production, iron uptake, heat shock and cold shock tolerance, multidrug resistance and glycine-betaine production were also identified.

Genome-based evolutionary history of Pseudomonas spp

Pseudomonas is a large and diverse genus of Gammaproteobacteria. To provide a framework for discovery of evolutionary and taxonomic relationships of these bacteria, we compared the genomes of type strains of 163 species and 3 additional subspecies of Pseudomonas, including 118 genomes sequenced herein. A maximum likelihood phylogeny of the 166 type strains based on protein sequences of 100 single-copy orthologous genes revealed thirteen groups of Pseudomonas, composed of two to sixty three species each. Pairwise average nucleotide identities and alignment fractions were calculated for the data set of the 166 type strains and 1224 genomes of Pseudomonas available in public databases. Results revealed that 394 of the 1224 genomes were distinct from any type strain, suggesting that the type strains represent only a fraction of the genomic diversity of the genus. The core genome of Pseudomonas was determined to contain 794 genes conferring primarily housekeeping functions. The results of this study provide a phylogenetic framework for future studies aiming to resolve the classification and phylogenetic relationships, identify new gene functions and phenotypes, and explore the ecological and metabolic potential of the Pseudomonas spp.

Hymenobacter jeollabukensis sp. nov., isolated from soil

A Gram-stain-negative, non-motile, rod-shaped, aerobic bacterial strain, designated 1-3-3-8^T, was isolated from soil and characterized taxonomically using a polyphasic approach. Comparative 16S rRNA gene sequence analysis showed that strain 1-3-3-8^T belongs to the family Cytophagaceae of phylum Bacteroidetes and is most closely related to Hymenobacter paludis KBP-30^T (96.8% similarity), Hymenobacter ocellatus Myx2105^T (96.8%), Hymenobacter coalescens WW84^T (95.6%), and Hymenobacter deserti ZLB-3^T (95.4%). The G + C content of the genomic DNA of strain 1-3-3-8^T was 63.6 mol%. The isolate contained C_15:0 iso (28.4%), summed feature 4 (C_17:1 anteiso B/C_17:1 iso I; 18.9%), and C_15:0 anteiso (17.6%) as major fatty acids, MK-7 as the predominant respiratory quinone, and sym-homospermidine as the predominant polyamine. The major polar lipids were phosphatidylethanolamine and an unidentified lipid. The phenotypic and chemotaxonomic data supported the affiliation of strain 1-3-3-8^T with the genus Hymenobacter. The DNA-DNA relatedness between strain 1-3-3-8^T and H. paludis KCTC 32237^T and H. ocellatus DSM 11117^T were 24.5 and 27.4% respectively, clearly showing that the isolate is not related to them at the species level. Overall, the novel strain could be differentiated from its phylogenetic neighbors on the basis of several phenotypic, genotypic, and chemotaxonomic features. Therefore, strain 1-3-3-8^T represents a novel species of the genus Hymenobacter, for which the name Hymenobacter jeollabukensis sp. nov. has been proposed. The type strain is 1-3-3-8^T (= KCTC 52741^T = JCM 32192^T).

Spirosoma pomorum sp. nov., isolated from apple orchard soil

A Gram-negative, motile, rod-shaped, aerobic bacterial strain, designated S7-2-11^T, was isolated from apple orchard soil from Gyeongsangnam-do Province, Republic of Korea, and was characterized taxonomically using a polyphasic approach. 16S rRNA gene sequence analysis indicated that strain S7-2-11^T belongs to the family Cytophagaceae in phylum Bacteroidetes, and is closely related to Spirosoma luteolum 16F6E^T (94.2% identity), Spirosoma knui 15J8-12^T (92.7%), and Spirosoma linguale DSM 74^T (91.0%). The G + C content of the genomic DNA of strain S7-2-11^T was 49.8 mol%. Strain S7-2-11^T contained summed feature 3 (C_16:1 ω7c/C_16:1 ω6c; 35.1%), C_16:1 ω5c (22.4%), C_15:0 iso (13.9%), and C_17:0 iso 3-OH (10.6%) as major cellular fatty acids, and MK-7 as the predominant respiratory quinone. The main polar lipids were phosphatidylethanolamine, an unidentified aminophospholipid, and two unidentified polar lipids. Phenotypic and chemotaxonomic data supported the affiliation of strain S7-2-11^T with the genus Spirosoma. The results of physiological and biochemical tests showed the genotypic and phenotypic differentiation of the isolate from recognized Spirosoma species. On the basis of its phenotypic properties, genotypic distinctiveness, and chemotaxonomic features, strain S7-2-11^T represents a novel species of the genus Spirosoma, for which the name Spirosoma pomorum sp. nov. is proposed. The type strain is S7-2-11^T (= KCTC 52726^T = JCM 32130^T).

Larkinella knui sp. nov., isolated from soil

A Gram-stain-negative, motile by gliding, rod-shaped, aerobic bacterium, designated 15J6-3T6^T, was isolated from a soil sample collected from Jeju Island, South Korea, and characterized taxonomically using a polyphasic approach. Comparative 16S rRNA gene sequence analysis showed that strain 15J6-3T6^T belongs to the family Cytophagaceae and is related to Larkinella harenae 15J9-9^T (93.9 % similarity), Larkinella arboricola Z0532^T (93.6 %), Larkinella bovis M2TB15^T (93.3 %), and Larkinella insperata LMG 22510^T (93.3 %). The DNA G+C content of strain 15J6-3T6^T was 50.6 mol%. The detection of phosphatidylethanolamine and an unidentified polar lipid as major polar lipids, menaquinone-7 as the predominant quinone, and C16 : 1ω5c, iso-C15 : 0, and iso-C17 : 0 3-OH as the major fatty acids also supports the affiliation of the isolate to the genus Larkinella. Based on its phenotypic properties and phylogenetic distinctiveness, we propose that strain 15J6-3T6^T should be classified in the genus Larkinella as a representative of a novel species, for which the name Larkinella knui sp. nov. is proposed. The type strain is 15J6-3T6^T (=KCTC 42998^T=JCM 31989^T).

Spirosoma flavus sp. nov., a novel bacterium from soil of Jeju Island

A novel, Gram-staining negative, yellow pigmented bacterial strain, designated 15J11-2^T, was isolated from soil sample on Jeju Island, Republic of Korea. The strain was subjected to a taxonomic study using a polyphasic approach. The strain was able to grow at temperature range from 10°C to 30°C, pH 7-8, and in presence of 0-1% (w/v) NaCl. Comparative 16S rRNA gene sequence analysis showed that strain 15J11-2^T belongs to the genus Spirosoma and levels of 16S rRNA gene sequence similarity ranged from 91.5% to 89.8%. The genomic DNA G + C content of strain 15J11-2^T was 46.0 mol%. The isolate contained phosphatidylethanolamine and an unidentified aminophospholipid as the main polar lipids, menaquinone MK-7 as the predominant respiratory quinone, and summed feature 3 (C_16:1 ω6c/C_16:1 ω7c; 39.4%), C_16:1 ω5c (27.1%), and C_16:0 (13.0%) as the major fatty acids, which supported the affiliation of strain 15J11-2^T to the genus Spirosoma. The results of physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain 15J11-2^T from recognized Spirosoma species. On the basis of its phenotypic properties, genotypic distinctiveness, chemotaxonomic features, strain 15J11-2^T represents a novel species of the genus Spirosoma, for which the name Spirosoma flavus sp. nov. is proposed. The type strain is 15J11-2^T (= KCTC 52026^T = JCM 31998^T).