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In recent years, there has been increasing interest in plant microbiota; however, despite medicinal plant relevance, very little is known about their highly complex endophytic communities. In this work, we report on the genomic and phenotypic characterization of the antimicrobial compound producer Rheinheimera sp. EpRS3, a bacterial strain isolated from the rhizospheric soil of the medicinal plant Echinacea purpurea. In particular, EpRS3 is able to inhibit growth of different bacterial pathogens (Bcc, Acinetobacter baumannii, and Klebsiella pneumoniae) which might be related to the presence of gene clusters involved in the biosynthesis of different types of secondary metabolites. The outcomes presented in this work highlight the fact that the strain possesses huge biotechnological potential; indeed, it also shows antimicrobial effects upon well-described multidrug-resistant (MDR) human pathogens, and it affects plant root elongation and morphology, mimicking indole acetic acid (IAA) action.

Understanding plant&ndash, microbe interactions is crucial for improving plants&rsquo, productivity and protection. Constraint-based metabolic modeling is one of the possible ways to investigate the bacterial adaptation to different ecological niches and may give insights into the metabolic versatility of plant pathogenic bacteria. We reconstructed a raw metabolic model of the emerging plant pathogenic bacterium Pectobacterium parmentieri SCC3193 with the use of KBase. The model was curated by using inParanoind and phenotypic data generated with the use of the OmniLog system. Metabolic modeling was performed through COBRApy Toolbox v. 0.10.1. The curated metabolic model of P. parmentieri SCC3193 is highly reliable, as in silico obtained results overlapped up to 91% with experimental data on carbon utilization phenotypes. By mean of flux balance analysis (FBA), we predicted the metabolic adaptation of P. parmentieri SCC3193 to two different ecological niches, relevant for the persistence and plant colonization by this bacterium: soil and the rhizosphere. We performed in silico gene deletions to predict the set of essential core genes for this bacterium to grow in such environments. We anticipate that our metabolic model will be a valuable element for defining a set of metabolic targets to control infection and spreading of this plant pathogen.

Background Klebsiella oxytoca DSM 29614 - isolated from acid mine drainages - grows anaerobically using Fe(III)-citrate as sole carbon and energy source, unlike other enterobacteria and K. oxytoca clinical isolates. The DSM 29614 strain is multi metal resistant and produces metal nanoparticles that are embedded in its very peculiar capsular exopolysaccharide. These metal nanoparticles were effective as antimicrobial and anticancer compounds, chemical catalysts and nano-fertilizers. Results The DSM 29614 strain genome was sequenced and analysed by a combination of in silico procedures. Comparative genomics, performed between 85 K. oxytoca representatives and K. oxytoca DSM 29614, revealed that this bacterial group has an open pangenome, characterized by a very small core genome (1009 genes, about 2%), a high fraction of unique (43,808 genes, about 87%) and accessory genes (5559 genes, about 11%). Proteins belonging to COG categories “Carbohydrate transport and metabolism” (G), “Amino acid transport and metabolism” (E), “Coenzyme transport and metabolism” (H), “Inorganic ion transport and metabolism” (P), and “membrane biogenesis-related proteins” (M) are particularly abundant in the predicted proteome of DSM 29614 strain. The results of a protein functional enrichment analysis - based on a previous proteomic analysis – revealed metabolic optimization during Fe(III)-citrate anaerobic utilization. In this growth condition, the observed high levels of Fe(II) may be due to different flavin metal reductases and siderophores as inferred form genome analysis. The presence of genes responsible for the synthesis of exopolysaccharide and for the tolerance to heavy metals was highlighted too. The inferred genomic insights were confirmed by a set of phenotypic tests showing specific metabolic capability in terms of i) Fe2+ and exopolysaccharide production and ii) phosphatase activity involved in precipitation of metal ion-phosphate salts. Conclusion The K. oxytoca DSM 29614 unique capabilities of using Fe(III)-citrate as sole carbon and energy source in anaerobiosis and tolerating diverse metals coincides with the presence at the genomic level of specific genes that can support i) energy metabolism optimization, ii) cell protection by the biosynthesis of a peculiar exopolysaccharide armour entrapping metal ions and iii) general and metal-specific detoxifying activities by different proteins and metabolites. Electronic supplementary material The online version of this article (10.1186/s12866-018-1330-5) contains supplementary material, which is available to authorized users.

We announce here the draft genome sequence of Arthrobacter sp. strain EpSL27, isolated from the stem and leaves of the medicinal plant Echinacea purpurea and able to inhibit human-pathogenic bacterial strains. The genome sequencing of this strain may lead to the identification of genes involved in the production of antimicrobial molecules.

Acinetobacter baumannii is a clinical threat to human health, causing major infection outbreaks worldwide. As new drugs against Gram-negative bacteria do not seem to be forthcoming, and due to the microbial capability of acquiring multi-resistance, there is an urgent need for novel therapeutic targets. Here we have derived a list of new potential targets by means of metabolic reconstruction and modelling of A. baumannii ATCC 19606. By integrating constraint-based modelling with gene expression data, we simulated microbial growth in normal and stressful conditions (i.e. following antibiotic exposure). This allowed us to describe the metabolic reprogramming that occurs in this bacterium when treated with colistin (the currently adopted last-line treatment) and identify a set of genes that are primary targets for developing new drugs against A. baumannii, including colistin-resistant strains. It can be anticipated that the metabolic model presented herein will represent a solid and reliable resource for the future treatment of A. baumannii infections.

Background In their natural environment, bacteria face a wide range of environmental conditions that change over time and that impose continuous rearrangements at all the cellular levels (e.g. gene expression, metabolism). When facing a nutritionally rich environment, for example, microbes first use the preferred compound(s) and only later start metabolizing the other one(s). A systemic re-organization of the overall microbial metabolic network in response to a variation in the composition/concentration of the surrounding nutrients has been suggested, although the range and the entity of such modifications in organisms other than a few model microbes has been scarcely described up to now. Results We used multi-step constraint-based metabolic modelling to simulate the growth in a complex medium over several time steps of the Antarctic model organism Pseudoalteromonas haloplanktis TAC125. As each of these phases is characterized by a specific set of amino acids to be used as carbon and energy source our modelling framework describes the major consequences of nutrients switching at the system level. The model predicts that a deep metabolic reprogramming might be required to achieve optimal biomass production in different stages of growth (different medium composition), with at least half of the cellular metabolic network involved (more than 50% of the metabolic genes). Additionally, we show that our modelling framework is able to capture metabolic functional association and/or common regulatory features of the genes embedded in our reconstruction (e.g. the presence of common regulatory motifs). Finally, to explore the possibility of a sub-optimal biomass objective function (i.e. that cells use resources in alternative metabolic processes at the expense of optimal growth) we have implemented a MOMA-based approach (called nutritional-MOMA) and compared the outcomes with those obtained with Flux Balance Analysis (FBA). Growth simulations under this scenario revealed the deep impact of choosing among alternative objective functions on the resulting predictions of fluxes distribution. Conclusions Here we provide a time-resolved, systems-level scheme of PhTAC125 metabolic re-wiring as a consequence of carbon source switching in a nutritionally complex medium. Our analyses suggest the presence of a potential efficient metabolic reprogramming machinery to continuously and promptly adapt to this nutritionally changing environment, consistent with adaptation to fast growth in a fairly, but probably inconstant and highly competitive, environment. Also, we show i) how functional partnership and co-regulation features can be predicted by integrating multi-step constraint-based metabolic modelling with fed-batch growth data and ii) that performing simulations under a sub-optimal objective function may lead to different flux distributions in respect to canonical FBA. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3311-0) contains supplementary material, which is available to authorized users.

One of the most promising, but still overlooked fields of microbiological research is represented by endophytic microorganisms, i.e., those organisms living in the tissues of host plants and/or in their rhizosphere (Rosenblueth and Martinez-Romero, 2006; Reinhold-Hurek and Hurek, 2011). These microbes are emerging as a new potential source of secondary metabolites and products, for exploitation in medicine, agriculture, and industry. From a biotechnological perspective, a controlled (engineered) colonization of plant's tissues by some bacteria may be desirable because of their ability to produce a variety of plant growth promoting (PGP) molecules, spanning from siderophores, nitrogenases, hormones, and so on. In addition, host-microbe interaction confers indirect advantage to the plant, resulting from the inhibition activity exerted by the associated microbial community toward potential pathogens. Moreover, in the field of medicine, there are examples of very well-known molecules derived by endophytes like antibiotics, antimycotics, and anticancer drugs. Also, it is still unknown if plant-associated bacteria may enhance (or be responsible for) some of the effects exerted by the extracts of medicinal plants (essential oils) (Kloepper and Ryu, 2006; Hardoim et al., 2008). In this regard, in October 2012, in Casola Valsenio (Italy), a collection of microorganisms was isolated from both internal tissues and the rhizospheric soil of the medicinal plant Echinacea purpurea, as reported in Chiellini et al. (2014). Among others, two strains sampled from the rhizosphere and belonging to Arthrobacter species were identified, i.e., Arthrobacter sp. EpRS66 and Arthrobacter sp. EpRS71. Based on their antibiotic resistance profile, reported in Mengoni et al. (2014), and on further tests performed on these two strains, they were selected as good candidates for genome sequencing analysis. The last, will constitute a resource to deeply investigate their genomic features and to perform comparative genomics analysis. Moreover, in the aim of new drugs discovery, the genome sequence will facilitate the identification of putative genes responsible for the production of bioactive compounds.

We report here the draft genome sequence of the Pseudomonas sp. TAA207 and Pseudomonas sp. TAD18 strains, isolated from Antarctic sediments during a summer campaign near coastal areas of Terra Nova Bay (Antarctica). Genome sequence knowledge allowed the identification of genes associated with the production of bioactive compounds and antibiotic resistance. Furthermore, it will be instrumental for comparative genomics and the fulfillment of both basic and application-oriented investigations.

We announce here the draft genome sequence of Pseudomonas sp. strain EpS/L25, isolated from the stem/leaves of the medicinal plant Echinacea purpurea . This genome will allow for comparative genomics in order to identify genes associated with the production of bioactive compounds and antibiotic resistance.

We report here the draft genome sequence of the Flavobacterium sp. TAB 87 strain, isolated from Antarctic seawater during a summer campaign near the French Antarctic station Dumont d'Urville (60°40′S, 40°01′E). It will allow for comparative genomics and the fulfillment of both fundamental and application-oriented investigations. It allowed the recognition of genes associated with the production of bioactive compounds and antibiotic resistance.

To date, more than 50 enzymes are known to contain Mo and most of them occur in prokaryotes while only six were found in eukaryotes. In all organisms studied so far, the Mo-cofactor is synthesized by a highly conserved biosynthetic pathway that can be divided into four steps, each producing a specific biochemical intermediate. Different nomenclatures were introduced for genes and gene products involved in Mo-co formation according to the organism they belong. On the basis of the active site structure and catalytic function, molybdenum-dependent enzymes can be grouped into two categories: bacterial nitrogenases and pterin-based enzymes. Human and plants Mo-co deficiency are also described.

Nitrogen fixation is the most important input of biologically available nitrogen in Earth's ecosystems and is a metabolic ability possessed only by some Prokaryotes. To date four classes of nitrogenase enzymes have been characterized. Three nitrogenases are homologous enzymes with similar protein subunit composition and metal cofactor structure; these are the Mo-nitrogenase, V-nitrogenase, and Fe-only nitrogenase. How these three systems evolved and which of them first appeared on Earth is still under debate. The best studied system is the Fe-Mo-co based although several comparative analyses have been performed in past years.

Molybdenum and tungsten share several atomic properties. Hence, in order to distinguish them, microorganisms have evolved discriminating systems either at the level of metal insertion into the cofactor or during the possible interplay of molybdo-enzyme specific chaperones when incorporating the cofactor. Several different Mo transport systems have been identified in Prokaryotes and Eucaryotes with their relatively different regulation and storage systems.

The distribution of life on Earth is constrained by the distribution of 20 bio-essential nutrients. Particularly, the availability of those elements required as cofactor might have influenced the timing of origin and evolution of metabolic pathways. Since the amount of bio-available Mo strongly changed during evolution to form anoxic to oxygenic environments, it is interesting to speculate about the appearance of Mo containing enzymes in relation to other metals with similar chemical characteristics.

Rhodopseudomonas palustris strain 42OL was isolated in 1973 from a sugar refinery waste treatment pond. The strain has been prevalently used for hydrogen production processes using a wide variety of waste-derived substrates, and cultured both indoors and outdoors, either freely suspended or immobilized. R. palustris 42OL was suitable for many other applications and capable of growing in very different culturing conditions, revealing a wide metabolic versatility. The analysis of the genome sequence allowed to identify the metabolic pathways for hydrogen and poly-β-hydroxy-butyrate production, and confirmed the ability of using a wide range of organic acids as substrates.