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European Bark Beetle Ips typographus is a secondary pest that affects dead and weakened spruce trees (Picea genus). Under certain environmental conditions, it has massive outbreaks, resulting in the attacks of healthy trees, becoming a forest pest. It has been proposed that the bark beetle’s microbiome plays a key role in the insect’s ecology, providing nutrients, inhibiting pathogens, and degrading tree defense compounds, among other probable traits yet to be discovered. During a study of bacterial associates from I. typographus, we isolated three strains identified as Pseudomonas from different beetle life stages. A polyphasic taxonomical approach showed that they belong to a new species for which the name Pseudomonas typographi sp nov. is proposed. Genome sequences show their potential to hydrolyze wood compounds and synthesize several vitamins; screening for enzymes production was verified using PNP substrates. Assays in Petri dishes confirmed cellulose and xylan hydrolysis. Moreover, the genomes harbor genes encoding chitinases and gene clusters involved in the synthesis of secondary metabolites with antimicrobial potential. In vitro tests confirmed the capability of the three P. typographi strains to inhibit several Ips beetles’ pathogenic fungi. Altogether, these results suggest that P. typographi aids I. typographi nutrition and resistance to fungal pathogens

Rapeseed (Brassica napus L.) is an important crop worldwide, due to its multiple uses, such as a human food, animal feed and a bioenergetic crop. Traditionally, its cultivation is based on the use of chemical fertilizers, known to lead to several negative effects on human health and the environment. Plant growth-promoting bacteria may be used to reduce the need for chemical fertilizers, but efficient bacteria in controlled conditions frequently fail when applied to the fields. Bacterial endophytes, protected from the rhizospheric competitors and extreme environmental conditions, could overcome those problems and successfully promote the crops under field conditions. Here, we present a screening process among rapeseed bacterial endophytes to search for an efficient bacterial strain, which could be developed as an inoculant to biofertilize rapeseed crops. Based on in vitro, in planta, and in silico tests, we selected the strain Pseudomonas brassicacearum CDVBN10 as a promising candidate; this strain produces siderophores, solubilizes P, synthesizes cellulose and promotes plant height in 5 and 15 days-post-inoculation seedlings. The inoculation of strain CDVBN10 in a field trial with no addition of fertilizers showed significant improvements in pod numbers, pod dry weight and shoot dry weight. In addition, metagenome analysis of root endophytic bacterial communities of plants from this field trial indicated no alteration of the plant root bacterial microbiome; considering that the root microbiome plays an important role in plant fitness and development, we suggest this maintenance of the plant and its bacterial microbiome homeostasis as a positive result. Thus, Pseudomonas brassicacearum CDVBN10 seems to be a good biofertilizer to improve canola crops with no addition of chemical fertilizers; this the first study in which a plant growth-promoting (PGP) inoculant specifically designed for rapeseed crops significantly improves this crop’s yields in field conditions.

Today there is an urgent need to find new ways to satisfy the current and growing food demand and to maintain crop protection and food safety. One of the most promising changes is the replacement of chemical fertilizers with biofertilizers, which include plant root-associated beneficial bacteria. This work describes and shows the use of B. halotolerans SCCPVE07 and R. laguerreae PEPV40 strains as efficient biofertilizers for escarole crops, horticultural species that are widely cultivated. An in silico genome study was performed where coding genes related to plant growth promoting (PGP) mechanisms or different enzymes implicated in the metabolism of phenolic compounds were identified. An efficient bacterial root colonization process was also analyzed through fluorescence microscopy. SCCPVE07 and PEPV40 promote plant development under normal conditions and saline stress. Moreover, inoculated escarole plants showed not only an increase in potassium, iron and magnesium content but also a significant improvement in protocatechuic acid, caffeic acid or kaempferol 3-O-glucuronide plant content. Our results show for the first time the beneficial effects in plant development and the food quality of escarole crops and highlight a potential and hopeful change in the current agricultural system even under saline stress, one of the major non-biological stresses

Symbiosis between microbes and insects has been raised as a promising area for understanding biological implications of microbe–host interactions. Among them, the association between fungi and bark beetles has been generally recognized as essential for the bark beetle ecology. However, many works investigating bark beetle bacterial communities and their functions usually meet in a common finding: Pseudomonas is a broadly represented genus within this holobiont and it may provide beneficial roles to its host. Thus, we aimed to review available research on this microbe–host interaction and point out the probable relevance of Pseudomonas strains for these insects, in order to guide future research toward a deeper analysis of the importance of these bacteria for the beetle’s life cycle

Pseudomonas is a large and diverse genus broadly distributed in nature. Its species play relevant roles in the biology of earth and living beings. Because of its ubiquity, the number of new species is continuously increasing although its taxonomic organization remains quite difficult to unravel. Nowadays the use of genomics is routinely employed for the analysis of bacterial systematics. In this work, we aimed to investigate the classification of species of the genus Pseudomonas on the basis of the analyses of the type strains whose genomes are currently available. Based on these analyses, we propose the creation of three new genera (Denitrificimonas gen nov. comb. nov., Neopseudomonas gen nov. comb. nov. and Parapseudomonas gen nov. comb. nov) to encompass several species currently included within the genus Pseudomonas and the reclassification of several species of this genus in already described taxa

BACKGROUND: There is an urgent need for a new sustainable way of satisfying the increasing demand for food worldwide. One of the main challenges is replacing chemical fertilizers with biofertilizers, which include plant root-associated beneficial microorganisms. The present study reports, for the first time, the effects of SCCPVE07 bacterial strain with respect to improving not only plant development, but also the nutritional content and bioactive compounds content of Coriandrum sativum L., one of the most economically important crops, even for plant growth under salinity stress. RESULTS: Innoculated coriander plants (C. sativum L.) showed an increase in potassium, carbon, calcium and iron content. A significant improvement in phenolic compounds contents was also observed. The contents of 5-O-caffeoylquinic acid, cinnamic acid, 4-methoxy-cinnamic acid hexoside, K-3-O rutinoside, Q-3-O-rutinoside, Q-3-O-glucoside and Q-3-O-glucuronide were sig nificantly enhanced. Moreover, an efficient bacterial root colonization and a noted growth promotion were demonstrated. Bacterial genome was sequenced and analysed. Gene coding related to Plant growth promotion (PGP) mechanisms and proteins involved in plant defence from salinity or in the metabolism of phenolic compounds, such as quercetin 2,3-dioxygenase and phenolic acid decarboxylase, were identified. CONCLUSION: The results obtained in the present study show, for the first time, the beneficial effects of the inoculation of a bacterial Bacillus halotolerans biofertilizer on coriander crops with respect to increasing the content in bioactive compounds and plant development.

The genus Agrobacterium was created a century ago by Conn who included it in the family Rhizobiaceae together with the genus Rhizobium. Initially, the genus Agrobacterium contained the non-pathogenic species Agrobacterium radiobacter and the plant pathogenic species Agrobacterium tumefaciens and Agrobacterium rhizogenes. At the end of the past century two new pathogenic species, Agrobacterium rubi and Agrobacterium vitis, were added to the genus. Already in the present century these species plus Agrobacterium larrymoorei were reclassified into genus Rhizobium. This reclassification was controversial and for a time both genus names were used when new species were described. Few years ago, after a taxonomic revision based on genomic data, the old species A. rhizogenes was maintained in the genus Rhizobium, the old species A. vitis was transferred to the genus Allorhizobium and several Rhizobium species were transferred to the genus Agrobacterium, which currently contains 14 species including the old species A. radiobacter, A. tumefaciens, A. rubi and A. larrymoorei. Most of these species are able to produce tumours in different plants, nevertheless the genus Agrobacterium also encompasses non-pathogenic species, one species able to nodulate legumes and one human pathogenic species. Taking into account that the species affiliations to five Agrobacterium genomospecies have not been determined yet, an increase in the number of species within this genus is expected in the near future.

Frass from the insect Tenebrio molitorcan be applied as an organic fertilizer due to its nutritional content. In this study insects were fed on different types of foodproducing excrement with different compositions. This allowed us to compare the potential effect of the excrement on plant growth promotion and to test its ability to increase tolerance to abiotic stresses such as drought, excess water and salinity. The best results were obtained when the insects were fed a diet low in fat andstarch content. Moreover, a microbiological study using the excrement produced showed that the presence of microorganisms improved plant growth parameters, inthe absence or presence of stress conditions. The analysis of the microbiome through massive parallel sequencing, as well as the analysis of the capacity of severalmicrobial isolates to promote plant growth, showed that several microorganisms present in the excrement are plant growth promoters (PGPs). Ourfindings indicatethat the frass produced by these insects, due to its nutritional content and associated microbiota, can be potentially used as a biofertilizer in organic farming.However, this potential dramatically varies according to the insect's diet. Further analyses should be performed to set the optimal time and amount of application forthe different aimed plant

Industrial synthetic dyes cause health and environmental problems. This work describes the isolation of 84 bacterial strains from the midgut of the Lasius niger ant and the evaluation of their potential application in dye bioremediation. Strains were identified and classified as judged by rRNA 16S. The most abundant isolates were found to belong to Actinobacteria (49%) and Firmicutes (47.2%). We analyzed the content in laccase, azoreductase and peroxidase activities and their ability to degrade three known dyes (azo, thiazine and anthraquinone) with different chemical structures. Strain Ln26 (identified as Brevibacterium permense) strongly decolorized the three dyes tested at different conditions. Strain Ln78 (Streptomyces ambofaciens) exhibited a high level of activity in the presence of Toluidine Blue (TB). It was determined that 8.5 was the optimal pH for these two strains, the optimal temperature conditions ranged between 22 and 37 °C, and acidic pHs and temperatures around 50 °C caused enzyme inactivation. Finally, the genome of the most promising candidate (Ln26, approximately 4.2 Mb in size) was sequenced. Genes coding for two DyP-type peroxidases, one laccase and one azoreductase were identified and account for the ability of this strain to effectively oxidize a variety of dyes with different chemical structures.

Antimicrobial resistance is a worldwide problem that threatens the effectiveness of treatments for microbial infection. Consequently, it is essential to study unexplored niches that can serve for the isolation of new microbial strains able to produce antimicrobial compounds to develop new drugs. Bark beetles live in phloem of host trees and establish symbioses with microorganisms that provide them with nutrients. In addition, some of their associated bacteria play a role in the beetle protection by producing substances that inhibit antagonists. In this study the capacity of several bacterial strains, isolated from the bark beetles Ips acuminatus, Pityophthorus pityographus Cryphalus piceae, and Pityogenes bidentatus, to produce antimicrobial compounds was analyzed. Several isolates exhibited the capacity to inhibit Gram-positive and Gram-negative bacteria, as well as fungi. The genome sequence analysis of three Pseudomonas isolates predicted the presence of several gene clusters implicated in the production of already described antimicrobials and moreover, the low similarity of some of these clusters with those previously described, suggests that they encode new undescribed substances, which may be useful for developing new antimicrobial agents. Moreover, these bacteria appear to have genetic machinery for producing antitumoral and antiviral substances. Finally, the strain IA19T showed to represent a new species of the genus Pseudomonas. The 16S rRNA gene sequence analysis showed that its most closely related species include Pseudomonas lutea, Pseudomonas graminis, Pseudomonas abietaniphila and Pseudomonas alkylphenolica, with 98.6, 98.5 98.4, and 98.4% identity, respectively. MLSA of the housekeeping genes gyrB, rpoB, and rpoD confirmed that strain IA19T clearly separates from its closest related species. Average nucleotide identity between strains IA19T and P. abietaniphila ATCC 700689T, P. graminis DSM 11363T, P. alkylphenolica KL28T and P. lutea DSM 17257T were

The growing interest in a healthy lifestyle and in environmental protection is changing habits regarding food consumption and agricultural practices. Good agricultural practice is indispensable, particularly for raw vegetables, and can include the use of plant probiotic bacteria for the purpose of biofertilization. In this work we analysed the probiotic potential of the rhizobial strain PEPV40, identified as Rhizobium laguerreae through the analysis of the recA and atpD genes, on the growth of spinach plants. This strain presents several in vitro plant growth promotion mechanisms, such as phosphate solubilisation and the production of indole acetic acid and siderophores. The strain PEPV40 produces cellulose and forms biofilms on abiotic surfaces. GFP labelling of this strain showed that PEPV40 colonizes the roots of spinach plants, forming microcolonies typical of biofilm initiation. Inoculation with this strain significantly increases several vegetative parameters such as leaf number, size and weight, as well as chlorophyll and nitrogen contents. Therefore, our findings indicate, for the first time, that Rhizobium laguerreae is an excellent plant probiotic, which increases the yield and quality of spinach, a vegetable that is increasingly being consumed raw worldwide.