Ensifer Adhaerens Research Articles

Soil parameters drive the diversity of Citrus sinensis rhizosphere microbiota which exhibits a potential in plant drought stress alleviation

Plant associated microorganisms, particularly those exhibiting a plant growth promoting (PGP) effect, play an important role in plant nutrition and health and the adaptation to unfavorable climatic conditions, such as drought which threatens the productivity of agricultural crops. The selection of specific microbial populations in the soil habitats associated to plants depends upon the soil physico-chemical parameters besides the ‘rhizosphere effect’ played by each plant species through rhizodepositions. In this study, we investigated the community structure and PGP potential of the microbiota associated to Citrus sinensis plants located in different geographical regions of Tunisia. The bacteria community structure was correlated to soil physiochemical parameters and we identified potassium, carbon and organic matter content as drivers of the C. sinensis microbiota composition. The evaluation of the potential of selected bacteria as biofertilizer and bio-stimulator under drought stress was achieved through the phylogenetic and functional characterization of a large collection of bacterial strains isolated from the rhizosphere of C. sinensis. The strains were screened in vitro for putative plant growth promoting traits, and the six most promising isolates were tested in vivo on Solanum lycopersicum and Capsicum annuum model plants. The bacterized plants were cultivated under drought stress and compared with not bacterized and fully irrigated control plants. All the tested bacteria induced a significant increase in the number of leaves and in root biomass of both plant species compared to not inoculated plants. Our results highlighted that the strains Ensifer adhaerens S1B1.5 and Pseudomonas resinovorans S4R2.6 were, in particular, effective in promoting plant growth under water shortage, indicating them as promising strains for the development of sustainable biofertilizers suited for agriculture in arid and semi-arid regions characterized by water scarcity.

Calcite formation induced by Ensifer adhaerens, Microbacterium testaceum, Paeniglutamicibacter kerguelensis, Pseudomonas protegens and Rheinheimera texasensis.

A wide range of bacterial species are able to induce calcium carbonate precipitation. Using our own laboratory-preserved strains, we have newly discovered that Ensifer sp. MY11e, Microbacterium sp. TMd9a1, Paeniglutamicibacter sp. MSa1a, Pseudomonas sp. GTc3, and Rheinheimera sp. ATWe6 can induce the formation of calcite crystals on an agar medium. Type strains of their closely related species (Ensifer adhaerens, Microbacterium testaceum, Paeniglutamicibacter kerguelensis, Pseudomonas protegens, and Rheinheimera texasensis) could also induce calcite formation. Although the initial pH value of the agar medium was 6.1, the pH of the agar media containing calcite, induced by cultivation of the 10 bacterial strains, increased to 8.0-8.4. The ammonification (oxidative deamination) of amino acids may been responsible for this increase in pH. The crystals formed both on and around the bacterial colonies. Furthermore, when these strains (excepting two Microbacterium strains) were cultivated on a cellulose acetate membrane filter (0.20μm pore size) resting on the surface of the agar medium (i.e., in the membrane filter culture method), the crystals formed on the agar medium separate from the bacterial cells. These results indicate that the bacterial cells did not necessarily become nucleation sites for these crystals. We also investigated whether the studied strains could be applied to the biocementation of sand, and found that only two Ensifer strains were able to form large sand lumps.

Ensifer-Mediated Transformation (EMT) of Rice (Monocot) and Oilseed Rape (Dicot).

Ensifer adhaerens OV14 underpins the successful crop transformation protocol, termed Ensifer-mediated transformation (EMT). The adaptability and efficiency of EMT technology to successfully transform both monocot and dicots have been previously reported. To facilitate community users' transition to EMT, the modified rice and oilseed rape plants generated in this work were developed using EMT protocols that were grounded in standard Agrobacterium-mediated transformation (AMT) processes. Therefore, this chapter describes simple yet crucial steps involved in transferring the use of EMT of rice and oilseed rape for generation of fertile and independent transgenic lines.

EFFECT OF BACTERIAL ENDOPHYTES ISOLATED FROM THE CITRUS ON THE PHYSICAL PARAMETER OF BITTER GOURD (Momordica charantia L.)

Bacterial endophytes have a symbiotic relationship between different parts of the plant and could play an important role to improve plant health. The effects of endophytic bacterial communities in bitter gourd have not been studied yet in Pakistan. In the present study, ten different bacteria that belong to class Alpha, beta and gamma Proteobacteria as well as bacilli were injected into bitter gourd seedlings under glass house conditions and five weeks after physical parameters (SL, RL, leaf area, leaf number, wet and dry weight of plant, root and shoot ratio) were studied. According to results Azomonas agilis and Ensifer adhaerens give good results as compared to control for all parameters studied. These inoculants could be used as bio fertilizer for sustainable crop production system.

Safety and efficacy of vitamin B12 (in the form of cyanocobalamin) produced by Ensifer spp. as a feed additive for all animal species based on a dossier submitted by VITAC EEIG.

Cyanocobalamin is a synthetic form of vitamin B12 used in pharmaceuticals, supplements and as a food additive. It is intended to be used in feed for all animal species and categories. The European Commission asked EFSA for an opinion on the safety for the target animals, consumer, user and the environment and on the efficacy of cyanocobalamin produced by fermentation with Ensifer adhaerens strains SCM 2034 or CICC 11008s or Ensifer fredii strain CMCC (B) 70000. Since relevant data were not provided by the applicant that would allow a proper identification and characterisation of the production strains, the Additives and Products or Substances used in Animal Feed (FEEDAP) Panel cannot conclude on the safety of the use of vitamin B12 produced using E. adhaerens CICC 11008s and E. fredii CMCC (B) 70000 in animal nutrition for the target animals, the consumer, the user and the environment. Due to significant uncertainties on the identity and safety of the production strain E. adhaerens SCM 2034, including the presence of antibiotic resistance genes, the absence of viable cells of the production strain or their DNA in the product, the FEEDAP Panel cannot conclude on the safety of the use of vitamin B12, produced by E. adhaerens SCM 2034 in animal nutrition for the target species, consumers and the environment. Due to high endotoxin content, potential inhalation exposure when handling premixtures and reported irritancy for skin and eyes, vitamin B12 produced by E. adhaerens SCM2034 is considered to pose a risk to user safety. Vitamin B12 additives produced by Ensifer spp. are regarded as effective in meeting animals’ requirements.

Chemical characterization and potential application of exopolysaccharides produced by Ensifer adhaerens JHT2 as a bioemulsifier of edible oils

Bioemulsifiers are able to stabilize oil-in-water emulsions and are very important in several industrial processes, including food processing. In this study, a bioemulsifier produced by Ensifer adhaerens JHT2 was tested for its ability to emulsify edible oils (canola, corn, palm, olive and soy). Emulsification of soy and canola oils was detected, but the highest emulsification index (EI) was obtained when JHT2 culture supernatant was used for the emulsification of palm oil (EI=100%). Bioemulsifier production was evaluated using nine culture media and different NaCl concentrations (0.5 to 10%), pH (4 to 10) and temperatures (28 to 42°C). The highest emulsification activity was detected in the supernatants of JHT2 grown in trypticase soy broth containing 0.5–1.0% NaCl, pH6–7 and temperatures of 28–37°C. Characterization of the bioemulsifier produced by JHT2 revealed typical characteristics of exopolysaccharides (EPS), constituting a backbone of (1→4)-β-d-glucopyranosyl and (1→3)-β-D-galactopyranosyl alternating with (1→4)-α-d-mannopyranosyl units that branch from the structure at O-2. Side chains are composed of units of (1→6)-β-d-glucopyranosyl and 3-O-linked galactopyranosyl bearing a pyruvic acid acetal substitution at O-4 and O-6. Our results indicate that the EPS produced by Ensifer adhaerens JHT2 is a promising option for improving and maintaining stable emulsions in food prepared with edible oils.

Peroxidase production and ligninolytic potentials of fresh water bacteria Raoultella ornithinolytica and Ensifer adhaerens

Interest in novel ligninolytic bacteria has remained topical due to, in part, the maneuverability of the bacterial genome. Conversely, the fungal genome lacks the dexterity for similar maneuverability thus, posing challenges in the fungal enzyme yield optimization process. Some impact of this situation includes the inability to commercialize the bio-catalytic process of lignin degradation by fungi. Consequently, this study assessed some fresh water bacteria isolates for ligninolytic and peroxidase properties through the utilization and degradation of model lignin compounds (guaiacol and veratryl alcohol) and the decolourization of selected ligninolytic indicator dyes; Azure B (AZB), Remazol Brilliant Blue R (RBBR) and Congo Red (CR). Bacterial strains with appreciable ligninolytic and peroxidase production potentials were identified through 16S rDNA sequence analysis and the nucleotide sequences deposited in the GenBank. About 5 isolates were positive for the degradation of both guaiacol (GA) and veratryl alcohol (VA) thus, accounting for about 17% of the test isolates. Similarly, AZB, RBBR and CR were respectively decolorized by 3, 2 and 5 bacterial strains thus, accounting for 10%, 7% and 17% of the test isolates. Two of the test bacterial strains were able to decolourize AZB, RBBR and CR respectively and these bacterial strains were identified as Raoultella ornithinolytica OKOH-1 and Ensifer adhaerens NWODO-2 with respective accession numbers as KX640917 and KX640918. Upon quantitation of the peroxidase activities; 5250±0.00U/L was recorded against Raoultella ornithinolytica OKOH-1 and 5833±0.00U/L against Ensifer adhaerens NWODO-2. The ligninolytic and dye decolourization properties of Raoultella ornithinolytica OKOH-1 and Ensifer adhaerens NWODO-2 marks for novelty particularly, as dyes with arene substituents were decolourized. Consequently, the potentials for the industrial applicability of these test bacterial strains abound as there is a dearth of information on organisms with such potentials.

Gellertiella hungarica gen. nov., sp. nov., a novel bacterium of the family Rhizobiaceae isolated from a spa in Budapest.

A novel alphaproteobacterium, strain RAM11T, belonging to the family Rhizobiaceae was isolated from the pool water of a thermal bath in Budapest, Hungary. Based on the 16S rRNA gene sequence strain RAM11T shows the highest sequence similarity values to Ensifer adhaerens Casida A (97.44 %), to Ensifer (syn. Sinorhizobium) americanus CFNEI 156T (96.87 %) and to Rhizobium azooxidifex Po 20/26T (96.76 %). The new bacterium is strictly aerobic, its optimum growth occurs at 20-37 °C, between pH 7 and 9 and without NaCl. It is motile due to a single polar flagellum, capable of budding and forms rosettes in liquid culture. The major isoprenoid quinone of strain RAM11T is Q-10, the major cellular fatty acids are C18 : 1ω7c and 11-MeC18 : 1ω7c. The polar lipid profile contains phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylcholine, an unidentified aminolipid and an unidentified phospholipid. The G+C content of DNA of the type strain is 62.9 mol%. Strain RAM11T (=DSM 29853T=NCAIM B.02618T) is proposed as type strain of a new genus and species with the proposed name Gellertiella hungarica gen. nov., sp. nov.

Ensifer adhaerens for heavy metal bioaccumulation, biosorption, and phosphate solubilization under metal stress condition

Abstract In this study, a bacterial strain was recovered from the chickpea root surface and its heavy metal tolerance ability, bioaccumulation, biosorption, chromium reduction potential, and phosphate solubilization activity were determined. Bacterial strain (OS3) was molecularly characterized through 16S rRNA partial gene sequencing and confirmed strain sequences belonged to the Ensifer adhaerens , inveterate by the BLASTn and phylogenetic analysis and achived accession number from Genbank # HE681418.1. Strain OS3 was able to tolerate up to 250 µg/ml Cd, 500 µg/ml Cr, 800 µg/ml each of Cu and Zn and 1000 µg/ml Ni. Moreover, strain OS3 was able to bioaccumulate and biosorb varying concentrations of heavy metals and showed maximum accumulation of Ni (95%) and least accumulation of Pb (74%) at a temperature of 34 °C and pH 7. The Langmuir and Freundlich adsorption constants were evaluated from the isotherms with a correlation coefficient ( r 2 > 0.98). The strain reduced 200 µg/ml of Cr (VI) completely after 96 h growth at 35 °C. Apart from bioremedaition ability, bacterial strain OS3 expressed a significant inorganic phosphate (P) solubilizing activity and solubilized inorganic P upto 303 µg/ml with a 2.2 solubilization index. Also, strain OS3 demonstrated plant growth promoting traits even under metal stress and secreted IAA, siderophore, HCN and ammonia under in vitro conditions. This study demonstrated that E. adhaerens survived well, even when exposed to higher concentrations of heavy metals and retained plant growth promoting activities. The biosorption ability, chromium reducing potential and ability to secrete plant growth regulators makes this organisms an interesting choice for metal removal (bioremediation) and enhancing crop production even in metal polluted soils.

Use of overburden waste for London plane (Platanus × acerifolia) growth: the role of plant growth promoting microbial consortia

Abstract: Overburden waste dumps represent a huge threat to environmental quality. The reduction of their negative impact can be achieved by vegetation cover establishment. Usually, this action is complicated due to site-specific characteristics, such as nutrient deficiency, elevated metal concentration, low pH value, lack of moisture and lack of organic matter. Establishment of vegetation can be facilitated by inoculation with plant growth promoting bacteria (PGPB) which improve the physicochemical and biological properties of degraded substrates and make them more hospitable for plants. In this study we selected several strains based on the ability to produce ammonia, indole-3-acetic acid, siderophores and lytic enzymes, and to solubilize inorganic phosphates. This selection resulted in microbial consortia consisting of Serratia liquefaciens Z-I ARV, Ensifer adhaerens 10_ ARV, Bacillus amyloliquefaciens D5 ARV and Pseudomonas putida P1 ARV. The effects of PGPB consortia on one-year-old London plane (Platanus × acerifolia [Aiton] Willd.) seedlings replanted into overburden waste from Kolubara Mine Basin were examined. After seven months, inoculated seedlings were 32% higher with 45% wider root collar diameter and over 80% higher total dry biomass compared to uninoculated seedlings grown in Kolubara’s overburden. Inoculation resulted in higher amounts of total soluble proteins, higher chlorophyll and epidermal flavonoids content and higher total antioxidative capacity in the leaves. This study represents a successful search for effective PGPB strains and shows that microbial consortia have an important role in enhancing the growth of seedlings in nutrient deficient and degraded substrates such as overburden waste from open-pit coal mines. Positive response of London plane seedlings suggest that inoculation may help widening the opus of species for reforestation of post mining areas and speed up natural succession processes and recovery of degraded landscapes.

Ensifer collicola sp. nov., a bacterium isolated from soil in South Korea.

Strain Mol12T, which presented in the form of Gram-negative, motile, non-spore forming rod-shaped, was isolated from soil in South Korea and characterized to determine its taxonomic position. The strain grew at 20-30°C (optimum 30°C) and pH 7.0-10.0 (optimum pH 8.0) with 1% (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that the strain Mol12T was most closely related to Ensifer terangae LMG 7834T (96.78%), Rhizobium daejeonense KCTC 12121T (96.43%), Ensifer adhaerens Casida AT (96.28%). Chemotaxonomic data showed that the predominant fatty acids were Summed Feature 8 (C18:1 ω7c and/or C18:1 ω6c; 53.02%) and C18:1 ω7c 11-methyl (24.01%). Its complex polar lipid contained major amounts of diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE) and Q-10 as the predominant ubiquinone. The DNA G+C content of strain Mol12T was determined to be 60.9 mol%. Based on the phylogenetic, chemotaxonomic, and phenotypic data, strain Mol12T (=KCTC 42816T =JCM 31049T) ought to be classified as a type strain of a novel species, for which the name Ensifer collicola sp. nov. is proposed.

Hypersensitive Response of Plasmid-Encoded AHL Synthase Gene to Lifestyle and Nutrient by Ensifer adhaerens X097.

It is known that some bacteria, especially members of the family Rhizobiaceae, have multiple N-acyl homoserine lactones (AHL) synthase genes and produce multiple AHL signals. However, how bacteria selectively utilize these multiple genes and signals to cope with changing environments is poorly understood. Ensifer adhaerens is an important microorganism in terms of biotechnology, ecology and evolutionary. In this study, we investigated the AHL-based QS system of E. adhaerens X097 and its response to different lifestyles or nutrients. Draft genome sequence data indicated that X097 harbored three distinct AHL synthase genes (ensI1, 2, 3) and seven luxR homologs, which was different from other E. adhaerens strains. In vitro expression indicated that plasmid-encoded ensI1 and ensI2 directed production of multiple AHLs, while chromosome-encoded ensI3 only directed production of C14-HSL. Predicted three dimensional structure of EnsI3 was quite different from that of EnsI1 and EnsI2. X097 produced different AHL profiles in Luria-Bertani (LB) and NFB medium, under biofilm and planktonic lifestyle, respectively. Notably, expression of ensI1 and ensI2 but not ensI3 is hypersensitive to different lifestyles and nutrients. The hypersensitive response of plasmid-encoded AHL synthase genes to different culture conditions may shed a light on the phylogenetic development of AHL synthase genes in Rhizobiaceae family.

Ensifer-mediated Arabidopsis thaliana Root Transformation (E-ART): A Protocol to Analyse the Factors that Support Ensifer-mediated Transformation (EMT) of Plant Cells.

Ensifer adhaerens OV14, a soil borne alpha-proteobacteria of the Rhizobiaceae family, fortifies the novel plant transformation technology platform termed 'Ensifer-mediated transformation' (EMT). EMT can stably transform both monocot and dicot species, and the host range of EMT is continuously expanding across a diverse range of crop species. In this protocol, we adapted a previously published account that describes the use of Arabidopsis thaliana roots to investigate the interaction of A. thaliana and Agrobacterium tumefaciens. In our laboratory, we routinely use A. thaliana root explants to examine the factors that enhance the utility of EMT. In addition, the E-ART protocol can be used to study the transcriptional response of E. adhaerens and host plant following exposure to explant tissue, the transformability of different Ensifer adhaerens strains/mutants as well as testing the susceptibility of A. thaliana mutant lines as a means to decipher the mechanisms underpinning EMT.

Multi locus sequence analysis and symbiotic characterization of novel Ensifer strains nodulating Tephrosia spp. in the Indian Thar Desert

Phylogenetically diverse Ensifer strains associated with five species of Tephrosia growing in alkaline soils of semi-arid regions of the Thar Desert were characterized using multi locus sequence analysis. Based on 16S rRNA and four protein-coding housekeeping gene (recA, atpD, glnII and dnaK) sequences, the Tephrosia–Ensifer strains were genetically different from the type strains of Ensifer saheli, Ensifer kostiensis, Ensifer terangae (African origin) and Ensifer psoraleae (Asiatic origin). One strain, Ensifer sp. TL4, showed maximum similarity (99%) to Ensifer adhaerens LMG 20216T and formed a separate lineage close to it. Phylogenetic incongruence between sym and housekeeping genes was observed. The monophyletic origin of symbiotic genes from Asia in the Tephrosia–Ensifer strains from the Thar Desert suggests that they might have been acquired from a common ancestor and horizontally transferred. These novel strains are promiscuous, cross-nodulating some papilionoid crop species, mimosoid trees and the caesalpinioid Chamaecrista pumila. This study improves understanding of the distribution of Ensifer in unexplored and threatened alkaline arid regions of the Thar Desert and how this relates to other similar regions in the world.

Microbial Degradation of Polyhydroxyalkanoates with Different Chemical Compositions and Their Biodegradability.

The study addresses degradation of polyhydroxyalkanoates (PHA) with different chemical compositions-the polymer of 3-hydroxybutyric acid [P(3HB)] and copolymers of P(3HB) with 3-hydroxyvalerate [P(3HB/3HV)], 4-hydroxybutyrate [P(3HB/4HB)], and 3-hydroxyhexanoate [P(3HB/3HHx)] (10-12mol%)-in the agro-transformed field soil of the temperate zone. Based on their degradation rates at 21 and 28°C, polymers can be ranked as follows: P(3HB/4HB) > P(3HB/3HHx) > P(3HB/3HV) > P(3HB). The microbial community on the surface of the polymers differs from the microbial community of the soil with PHA specimens in the composition and percentages of species. Thirty-five isolates of bacteria of 16 genera were identified as PHA degraders by the clear zone technique, and each of the PHA had both specific and common degraders. P(3HB) was degraded by bacteria of the genera Mitsuaria, Chitinophaga, and Acidovorax, which were not among the degraders of the three other PHA types. Roseateles depolymerans, Streptomyces gardneri, and Cupriavidus sp. were specific degraders of P(3HB/4HB). Roseomonas massiliae and Delftia acidovorans degraded P(3HB/3HV), and Pseudoxanthomonas sp., Pseudomonas fluorescens, Ensifer adhaerens, and Bacillus pumilus were specific P(3HB/3HHx) degraders. All four PHA types were degraded by Streptomyces.

Draft Genome Sequence of Ensifer adhaerens M78, a Mineral-Weathering Bacterium Isolated from Soil.

Ensifer adhaerens M78, a bacterium isolated from soil, can weather potash feldspar and release Fe, Si, and Al from rock under nutrient-poor conditions. Here, we report the draft genome sequence of strain M78, which may facilitate a better understanding of the molecular mechanism involved in mineral weathering by the bacterium.

Capability of the plant-associated bacterium, Ensifer adhaerens strain OV14, to genetically transform its original host Brassica napus

Land plants exist in intimate associations with complex microbial communities across the phyllosphere, endosphere, and rhizosphere, with the latter inhabited by microbes that establish relationships with their host extending from parasitism to mutualism. For example, the rhizospheric Agrobacterium tumefaciens is pathogenic across a broad host range while its related rhizobia Sinorhizobium meliloti is an important symbiont of plants. Of interest, both species have a recorded capacity to genetically transform plant species with variable success. In this regard they have been recently joined by the rhizospheric non-pathogenic bacterium Ensifer adhaerens OV14, which has demonstrated an ability to genetically transform both dicots (Arabidopsis thaliana, Nicotiana tabaccum, and Solanum tuberosum) and monocot (Oryza sativa). The goal of this study was to investigate the potential of E. adhaerens strain OV14 to genetically transform Brassica napus, the host species from which it was isolated. By tailoring current A. tumefaciens-based protocols to suit the growth parameters of E. adhaerens strain OV14, here we report the successful transformation of the commercial B. napus cultivar Delight. The results indicated that co-cultivating 5 day old cotyledonary petiole explants with E. adhaerens strain OV14 (OD600nm = 0.8) for 5 days in the presence of 200 µM acetosyringone delivered transgenic plants of morphological equivalence to the original treated cv. Delight. A transformation frequency of 4.0 ± 0.2 % was attained based on stable integration patterns recorded for T1 individuals, which indicated transgene integrations of 1–3 copies/line. Segregation analysis based on the inheritance of the nptII transgene in the T2 generation showed Mendelian and non-Mendelian segregation patterns for the designated kanamycin resistance phenotype. To conclude, this practical study highlights the expanding host range of Ensifer-mediated transformation by confirming the ability of the symbiont Ensifer adhaerens OV14 to genetically engineer its original host.

Ensifer-mediated transformation: an efficient non-Agrobacterium protocol for the genetic modification of rice.

While Agrobacterium-mediated transformation (AMT) remains the most widely used technique for gene transfer in plants, interest exists for the use of non-Agrobacterium gene delivery systems due to freedom-to-operate issues that remain with AMT across several jurisdictions. In addition, the plant pathogenic mode of action of Agrobacterium tumefaciens significantly increases the costs to passage engineered cultivars through the regulatory process. Ensifer adhaerens (OV14) is a soil-related bacterium with the proven ability to genetically modify the model plant A. thaliana and the staple crop S. tuberosum (Wendt et al., Trans Res 21:567–578, 2012). While previous work was relevant for dicotyledonous species, in this study, the efficacy of Ensifer adhaerens (OV14)-mediated transformation (EMT) was determined on two japonica rice varieties, Curinga and Nipponbare, and the recalcitrant indica variety, IR64. The results indicated that E. adhaerens (OV14) exhibits infection efficiencies ranging between 50–70 %, 90–100 % and 90–95 % for Curinga, Nipponbare and IR64 respectively. Curinga and Nipponbare plants transformed with E. adhaerens (OV14) and A. tumefaciens (LBA4404 and EHA105) were regenerated achieving transformation efficiencies of 16 % and 26–32 % for Curinga and 7 and 4 % for Nipponbare respectively. Separately, the transformation of IR64 was only recorded via EMT (transformation efficiency ~1 %). Integration analyses conducted on 24 transgenic rice lines illustrated that T-DNA insertion occurred randomly throughout the rice genome for EMT (and AMT), with similar integration patterns in the rice genomic DNA observed for both bacterial species.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-015-1369-9) contains supplementary material, which is available to authorized users.

Characterization of the biosorption and biodegradation properties of Ensifer adhaerens: A potential agent to remove polychlorinated biphenyls from contaminated water

Ensifer adhaerens is a soil bacterium known for its potential to remove pollutants from the environment. We investigated the contributions of biosorption and biodegradation to the process of polychlorinated biphenyl (PCB) removal from water by living or heat-killed E. adhaerens with different incubation times. We examined the physicochemical properties of E. adhaerens, including its membrane surface moieties, extracellular polymeric substances, and defense-related enzyme activities. In addition, we measured the biosorption and biodegradation of different PCB congeners. We found that removal of PCBs by heat-killed E. adhaerens was attributed to biosorption only, while both biosorption and biodegradation were responsible for the dissipation of PCBs by live E. adhaerens. Biosorption initially plays a major role in PCB removal, but biodegradation becomes increasingly important with increased incubation time. The results of infrared spectroscopy analysis showed that bacterial lipids, proteins, and polysaccharides, which offer abundant binding sites, are responsible for the biosorption of PCBs. Biodegradation was correlated with loosely bound polysaccharides and defense-related enzyme activities that could increase the pollutant’s solubility and facilitate further degradation. The PCB congeners exhibited different biosorption and biodegradation patterns, and the patterns were correlated with the octanol–water partition coefficients (Kow) of the congeners. The more hydrophobic organic compounds tended to have higher biosorption, but lower biodegradation capacities. These results indicate that E. adhaerens-mediated biosorption and biodegradation of PCBs are dependent on the status of the strain, the incubation time, and the PCB congener present, and suggest guidelines for PCB removal from water.

Profiling antibiotic resistance and electro-transformation potential ofEnsifer adhaerensOV14; a non-Agrobacteriumspecies capable of efficient rates of plant transformation

Ensifer adhaerens OV14 underpins the successful crop transformation protocol termed Ensifer-mediated transformation but issues exist in regard to addressing the pleomorphic tendency of the bacterium in suboptimal conditions, identifying the optimal parameters for electrotransformation and defining the strain's antibiotic profile. Here, modifications made to growth medium composition addressed the pleomorphic trait of E. adhaerens OV14, delivering uniform E. adhaerens OV14 growth to ensure efficient rates of electroporation with plasmids up to 42.2 kb in size. Separately, 63 putative antibiotic resistance coding sequences were identified across the E. adhaerens OV14 genome, with testing confirming the strain's susceptibility to gentamicin (≥10 mg L(-1)), tetracycline (≥10 mg L(-1)), chloramphenicol (≥100 mg L(-1)) and cefotaxime (≥500 mg L(-1)) and resistance to ampicillin, paramomycin, streptomycin, spectinomycin, ticarcillin-clavulanate and kanamycin. Partial resistance against carbenicillin, rifampicin, hygromycin-B and neomycin was also recorded. Resistance to kanamycin was supported by seven independent nptII-like homologs located within the E. adhaerens OV14 genome. Transcriptional analysis of these targets highlighted two homologs (AHK42288 and AHK42618) whose transcription was significantly elevated within 2 h exposure to kanamycin and which in the case of AHK42288 was maintained out to 6 h post-exposure. In conclusion, our results have identified optimal conditions for the handling of E. adhaerens and have identified a future genome editing target (AHK42288) to negate the kanamycin-resistant phenotype of E. adhaerens.