Actinomycetes: an unexplored microorganisms for plant growth promotion and biocontrol in vegetable crops.

Actinomycetes, a Gram positive bacteria, well reported as a source of antibiotics, also possess potential to control various plant pathogens, besides acting as plant growth promoting agent. Chemicals in different forms are extensively being used in vegetable farming, adversely affecting the environment and consumer health. Microbial agent like actinomycetes can substantially replace these harmful chemicals, and have now started finding a place as an important input in to farming practices. Only selected vegetable crops belonging to 11 different families have been explored with use of actinomycetes as biocontrol and plant growth promoting agent till now. It provides ample opportunities to vegetable researchers, to further explore with use of this very important group of microorganisms, in order to achieve even higher production level of safe vegetables. Mycostop and Actinovate are two actinomycetes based formulations globally available for use in vegetable farming as a substitute for chemical formulations. Present review article has summarized the literature available on use of actinomycetes in vegetable farming. Existing wide gap in knowledge, and potential thrust areas for future research have also been projected.

Vibrio palustris sp. nov. and Vibrio spartinae sp. nov., two novel members of the Gazogenes clade, isolated from salt-marsh plants (Arthrocnemum macrostachyum and Spartina maritima).

Two bacterial strains, EAod9T and SMJ21T, isolated from salt-marsh plants, were determined to be related to species of the genus Vibriofrom from 16S rRNA sequence comparisons. Their closest phylogenetic relatives are members of the Gazogenes clade, Vibrio mangrovi and Vibrio rhizosphaerae , which show the greatest similarity to the SMJ21TrRNA sequence (97.3 and 97.1 %, respectively), while EAod9T had less than 97.0 % similarity to any other species of the genus Vibrio. Both strains share the basic characteristics of the genus Vibrio, as they are Gram-stain negative, motile, slightly halophilic, facultatively anaerobic bacteria. In addition, they are oxidase-negative and unable to grow on TCBS Agar; they grow between 15 to 26 °C, pH 6 to 8 and in up to 10 % (w/v) total salinity. They produce indol, are positive in the Voges-Proskauer test and are negative for arginine dihydrolase, lysine and ornithine decarboxylases. Strain SMJ21T is aerogenic and red-pigmented, due to prodigiosin production, while strain EAod9T ferments glucose without gas and is not pigmented. The major cellular fatty acids of both novel strains were C16 : 1ω7c/C16 : 1ω6c and C16 : 0. WGSobtained for both strains, along with the other five members of the clade, allowed the determination of ANI indexes and in silico estimations of DDH values, which confirmed that the two strains represent two novel species of the genus Vibrio: Vibriopalustris sp. nov. (with EAod9T=CECT 9027T=LMG 29724T as the proposed type strain) and Vibrio spartinae sp. nov. (with SMJ21T=CECT 9026T=LMG 29723T as the proposed type strain).

Zunongwangia endophytica sp. nov., an endophyte isolated from the salt marsh plant, Halimione portulacoides, and emended description of the genus Zunongwangia.

Taxonomical analyses were performed on strain CPA58T, a novel isolate obtained from surface-sterilized aboveground tissues of the halophyte Halimione portulacoides, collected from a salt marsh in Ria de Aveiro, Portugal. The strain was Gram-stain-negative, rod-shaped, oxidase-negative and catalase-positive. Optimal growth was observed at 26 °C, at pH 6-8 and in the presence of 2 to 3 % (w/v) NaCl. Phylogenetic analyses, based on the 16S rRNA gene sequence, showed that strain CPA58T belongs to the genus Zunongwangia, with highest sequence similarities to both Zunongwangia profunda SM-A87T and Zunongwangia mangrovi P2E16T (96.5 %), followed by Zunongwangia atlantica 22II14-10F7T (95.9 %). The principal fatty acids were iso-C15 : 0, summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH) and iso-C17 : 0 3-OH. The major respiratory quinone was MK-6 and the DNA G+C content was 35.1 mol%. Phylogenetic and chemotaxonomic analyses clearly placed strain CPA58T in the genus Zunongwangia. However, 16S rRNA gene sequence analysis showed that the threshold for same species relatedness was not surpassed, and biochemical tests revealed diagnostic characteristics that differentiated this strain from other type strains of species of the genus Zunongwangia. Overall, the analyses showed that strain CPA58T represents a novel species within the genus Zunongwangia, for which the name Zunongwangia endophytica sp. nov. is proposed, with the type strain CPA58T (=CECT 9128T=LMG 29517T).

Kocuria salina sp. nov., an actinobacterium isolated from the rhizosphere of the halophyte Arthrocnemum macrostachyum and emended description of Kocuria turfanensis.

A novel, non-motile coccoid, Gram-positive and non-endospore forming bacterium, designated Hv14bT, was isolated from the rhizosphere of the halophyte Arthrocnemum macrostachyum. It was observed to be catalase positive and oxidase negative and able to hydrolyse starch. MK-8(H2) was identified as the dominant menaquinone and the major cellular fatty acids were anteiso-C15 : 0 and iso-C15 : 0. The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol and an unidentified glycolipid. The 16S rRNA genes showed the highest 16S rRNA sequence identity with K. polaris DSM 14382T, K. rosea DSM 20447T and K. turfanensis DSM 22143T. Based on the phenotypic and molecular features and DNA-DNA hybridization data, it is concluded that strain Hv14bT is proposed to represent a novel species in the genus Kocuria, Kocuria salina sp. nov., with the type strain Hv14bT=DSM 28714T=CECT 9229T.

Parapedobacter deserti sp. nov., an endophytic bacterium isolated from Haloxylon ammodendron stems.

Strain N5SSJ16T, a Gram-negative-staining, non-spore-forming, rod-shaped, non-motile bacterium, was isolated from Haloxylon ammodendron stems. The strain grew in the presence of 0-4 % (w/v) NaCl (optimum growth in the absence of NaCl), at pH 7-9 (optimum: pH 8) and at 12-50 °C. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain N5SSJ16T was related phylogenetically to Parapedobacter composti 4M40T (96.5 %) and Parapedobacter luteus 4M29T (95.9 %). The cellular fatty acids were iso-C15 : 0, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), summed feature 9 (C16 : 0 10-methyl and/or iso-C17 : 1ω9c) and iso-C17 : 0 3-OH. MK-7 was the respiratory quinone. The main polar lipids were phosphatidylethanolamine, unidentified aminophospholipid and two unknown lipids. The G+C content of the DNA was 45.8 mol%. On the basis of chemotaxonomic, phylogenetic and phenotypic evidence, strain N5SSJ16T represents a novel species of the genus Parapedobacter, for which the name Parapedobacter deserti sp. nov. is proposed. The type strain is N5SSJ16T (=ACCC 19928T=KCTC 52416T).

Microbacterium diaminobutyricum sp. nov., isolated from Halimione portulacoides, which contains diaminobutyric acid in its cell wall, and emended description of the genus Microbacterium.

Three actinobacterial strains were isolated from roots of the salt-marsh plant Halimione portulacoides collected in Ria de Aveiro, Portugal. Molecular typing using enterobacterial repetitive intergenic consensus ERIC-PCR fingerprinting showed the strains to be highly similar. Phylogenetic analyses based on the 16S rRNA gene sequence and multilocus sequence analysis (MLSA) using gyrB, rpoB, recA and ppk and 16S rRNA genes sequences showed that the strains represented a member of the genus Microbacterium, with Microbacterium lacus DSM 18910T as the closest phylogenetic relative. DNA-DNA hybridization between strain RZ63T and its closest relative was below 70 %, supporting the hypothesis that it represented a distinct genomic species. Chemotaxonomic analyses of the novel strains and their DNA G+C contents confirmed their affiliation to the genus Microbacterium, however, the peptidoglycan of RZ63T contained diaminobutyric acid as the diagnostic diamino acid. In addition, physiological and fatty acid analyses revealed differences between these strains and their phylogenetic relatives, reinforcing their status as a distinct species. Based on the physiological, genetic and chemotaxonomic characterisation it is proposed that the strains studied represent a novel species of the genus Microbacterium for which the name Microbacterium diaminobutyricum sp. nov. is proposed (type strain RZ63T=DSM 27101T=CECT 8355T).

Aurantimonas endophytica sp. nov., a novel endophytic bacterium isolated from roots of Anabasis elatior (C. A. Mey.) Schischk.

An orange-coloured, aerobic, motile, short-rod-shaped bacterial strain, designated EGI 6500337T, was isolated from the surface-sterilized root of a halophyte, Anabasis elatior (C. A. Mey.) Schischk, collected from Urumqi, Xinjiang province, north-west China. Growth occurred at 5-35 °C (optimum 30 °C), at pH 6.0-9.0 (optimum pH 7.0) and in the presence of 0-6 % (w/v) NaCl (optimum 0-1 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain EGI 6500337T formed a distinct lineage in the cluster that comprised the genera Aurantimonas and Aureimonas in the family Aurantimonadaceae. The 16S rRNA gene sequence of strain EGI 6500337T shared highest similarity with those of Aurantimonas coralicida DSM 14790T (97.15 %) and Aurantimonas manganoxydans DSM 21871T (97.15 %). Strain EGI 6500337T contained Q-10 as the dominant isoprenoid quinone. The major cellular fatty acids were C18 : 1ω7c and C19 : 0ω8c cyclo. The polar lipid profile of strain EGI 6500337T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine and phosphatidylethanolamine as major components, similarly to members of the genus Aurantimonas. The DNA G+C content of strain EGI 6500337T was 66.8 mol%. The level of DNA-DNA relatedness between strain EGI 6500337T and Aurantimonas coralicida DSM 14790T was 24.7±2.9 %. On the basis of the phylogenetic analysis, chemotaxonomic data and phenotypic characteristics, strain EGI 6500337T represents a novel species of the genus Aurantimonas, for which the name Aurantimonas endophytica sp. nov. is proposed. The type strain is EGI 6500337T (=KCTC 52296T=CPCC 100904T).

Desert Perennial Shrubs Shape the Microbial-Community Miscellany in Laimosphere and Phyllosphere Space.

Microbial function, composition, and distribution play a fundamental role in ecosystem ecology. The interaction between desert plants and their associated microbes is expected to greatly affect their response to changes in this harsh environment. Using comparative analyses, we studied the impact of three desert shrubs, Atriplex halimus (A), Artemisia herba-alba (AHA), and Hammada scoparia (HS), on soil- and leaf-associated microbial communities. DNA extracted from the leaf surface and soil samples collected beneath the shrubs were used to study associated microbial diversity using a sequencing survey of variable regions of bacterial 16S rRNA and fungal ribosomal internal transcribed spacer (ITS1). We found that the composition of bacterial and fungal orders is plant-type-specific, indicating that each plant type provides a suitable and unique microenvironment. The different adaptive ecophysiological properties of the three plant species and the differential effect on their associated microbial composition point to the role of adaptation in the shaping of microbial diversity. Overall, our findings suggest a link between plant ecophysiological adaptation as a "temporary host" and the biotic-community parameters in extreme xeric environments.

Frigoribacterium endophyticum sp. nov., an endophytic actinobacterium isolated from the root of Anabasis elatior (C. A. Mey.) Schischk.

A novel endophytic actinobacterium, designated EGI 6500707(T), was isolated from the surface-sterilized root of a halophyte Anabasis elatior (C. A. Mey.) Schischk collected from Urumqi, Xinjiang province, north-west China, and characterized using a polyphasic approach. Cells were Gram-stain-positive, non-motile, short rods and produced white colonies. Growth occurred at 10-45 °C (optimum 25-30 °C), at pH 5-10 (optimum pH 8) and in presence of 0-4% (w/v) NaCl (optimum 0-3%). The predominant menaquinone was MK-9. The diagnostic phospholipids were diphosphatidylglycerol and phosphatidylglycerol. The major fatty acids were anteiso-C(15 : 0), anteiso-C(17 : 0) and iso-C(16 : 0). The DNA G+C content of strain EGI 6500707(T) was 69.1 mol%. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain EGI 6500707(T) should be placed in the genus Frigoribacterium (family Microbacteriaceae , phylum Actinobacteria ), and that the novel strain exhibited the highest 16S rRNA gene sequence similarity to Frigoribacterium faeni JCM 11265(T) (99.1%) and Frigoribacterium mesophilum MSL-08(T) (96.5%). DNA-DNA relatedness between strain EGI 6500707(T) and F. faeni JCM 11265(T) was 47.2%. On the basis of phenotypic and chemotaxonomic characteristics, phylogenetic analysis and DNA-DNA relatedness data, strain EGI 6500707(T) represents a novel species of the genus Frigoribacterium , for which the name Frigoribacterium endophyticum sp. nov. is proposed. The type strain is EGI 6500707(T) ( = JCM 30093(T) = KCTC 29493(T)).

Microbacterium proteolyticum sp. nov. isolated from roots of Halimione portulacoides.

An endophytic actinobacterial strain RZ36T, isolated from roots of the salt-marsh plant Halimione portulacoides, was subjected to a polyphasic taxonomic characterization. 16S rRNA gene sequence analysis revealed that this strain belonged to the genus Microbacterium. The closest phylogenetic relative was Microbacterium hominis DSM 12509T, with a pairwise 16S rRNA gene sequence similarity of 98.8 %. The DNA-DNA hybridization value between strain RZ36T and M. hominis DSM 12509T was 16 %. The affiliation to the genus Microbacterium was corroborated by phenotypic and chemotaxonomic characteristics. The cell-wall peptidoglycan type was B2ß and the diagnostic diamino acid was ornithine. Whole-cell sugars detected were galactose, glucose, rhamnose, ribose and xylose. The major fatty acids were anteiso-C15 : 0 and iso-C16 : 0 and the major menaquinone was MK-11 (64 %). Main polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol and two unknown glycolipids. The genomic DNA G+C content was 69.7 mol%. Thus, on the basis of phenotypic, genotypic and chemotaxonomic data, strain RZ36T is considered to represent a novel species of the genus Microbacterium, for which the name Microbacterium proteolyticum sp. nov. (type strain RZ36T = DSM 27100T = CECT 8356T) is proposed.

Labedella endophytica sp. nov., a novel endophytic actinobacterium isolated from stem of Anabasis elatior (C. A. Mey.) Schischk.

A Gram-stain positive, yellow-coloured, aerobic, non-motile, catalase-positive and oxidase-negative, endophytic actinobacterium, designated strain EGI 6500705(T), was isolated from the surface-sterilized stem of a halophyte Anabasis elatior (C. A. Mey.) Schischk collected from Urumqi, Xinjiang province, north-west China. The organism had ornithine as the diagnostic cell-wall diamino acid. The major fatty acids were anteiso-C15:0, anteiso-C17:0 and iso-C16:0. The predominant menaquinones were MK-9, MK-10 and MK-11. The DNA G + C content of strain EGI 6500705(T) was 69.2 mol%. Phylogenetic analyses based on 16S rRNA gene sequence showed that strain EGI 6500705(T) is clearly affiliated with the genus Labedella and most closely related to Labedella gwakjiensis KCTC 19176(T), with 99.0 % sequence similarity. DNA-DNA relatedness between strain EGI 6500705(T) and L. gwakjiensis KCTC 19176(T) was 27.4 %. On the basis of phenophytic, chemotaxonomic and phylogenetic analysis, the strain EGI 6500705(T) represents a novel species of the genus Labedella, for which the name Labedella endophytica sp. nov. is proposed. The type strain is EGI 6500705(T) (=KCTC 29494(T) = CPCC 203961(T) = JCM 30092(T)).

[Community diversity of ammonia-oxidizing bacteria of three plants rhizosphere in Ebinur Lake wetland].

OBJECTIVE: In order to study the community diversity of rhizosphere soil ammonia-oxidizing bacteria, Halocnemum strobilaceum, Reed and Salicornia in Ebinur Lake Wetland were investigated. METHODS: The clone libraries of amoA gene were constructed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and phylogenetics were analyzed. To explore the community structure of rhizosphere amomonia-oxidizing bacteria, we combined rhizosphere physicochemical factors of the three plants. RESULTS: Phylogenetic analysis of the amoA gene fragments showed that all of AOB sequences from shrimp of three plants rhizosphere were affiliated with Nitrosomonas or Nitrosomonas-like phyla, Nitrosospira phyla was not discovered. Three plants rhizosphere composition includes 9 OTUs,12 OTUs and 7 OTUs respectively. Coverages of all libraries of the three plants rhizosphere were over 99% and strongly representative. The richness index, chao1 index, ACE index and Shannon index of the three libraries were as follows, Reed rhizosphere AOB was much higher than Halocnemum strobilaceum rhizosphere AOB, and Salicornia rhizosphere AOB was the lowest. CONCLUSION: This study provides a basis for understanding the community diversity and structure of rhizosphere soil ammonia-oxidizing bacteria in Ebinur Lake wetland.

Mercury-resistant bacteria from salt marsh of Tagus Estuary: the influence of plants presence and mercury contamination levels.

Mercury (Hg) contamination of aquatic systems has been recognized as a global, serious problem affecting both wildlife and humans. High levels of Hg, in particular methylmercury (MeHg), were detected in surface sediments of Tagus Estuary. MeHg is neurotoxic and its concentration in aquatic systems is dependent upon the relative efficiency of reduction, methylation, and demethylation processes, which are mediated predominantly by the microbial community, in particular mercury-resistant (HgR) bacteria. Plants in contaminated ecosystems are known to take up Hg via plant roots. Therefore, the aims of this study were to (1) isolate and characterize HgR bacteria from a salt marsh of Tagus Estuary (Rosário) and (2) determine HgR bacteria levels in the rhizosphere and, consequently, their influence in metal cycling. To accomplish this objective, sediments samples were collected during the spring season in an area colonized by Sacocornia fruticosa and Spartina maritima and compared with sediments without plants. From these samples, 13 aerobic HgR bacteria were isolated and characterized morphologically, biochemically, and genetically, and susceptibility to Hg compounds, Hg(2+), and MeHg was assessed by determination of minimal inhibitory concentration (MIC). Genetically, the mer operon was searched by polymerase chain reaction (PCR) and 16S rRNA sequencing was used for bacterial identification. Results showed that the isolates were capable of growing in the presence of high Hg concentration with MIC values for HgCl2 and MeHgCl in the ranges of 1.7-4.2 µg/ml and 0.1-0.9 µg/ml, respectively. The isolates from sediments colonized with Sacocornia fruticosa displayed higher resistance levels compared to ones colonized with Spartina maritima. Bacteria isolates showed different capacity of Hg accumulation but all displayed Hg volatilization capabilities (20-50%). Mer operon was found in two isolates, which genetically confirmed their capability to convert Hg compounds by reducing them to Hg(0). Thus, these results are the first evidence of the relevance of interaction between bacteria and plants in Hg cycling in Tagus Estuary.

Soil microbial diversity in the vicinity of desert shrubs.

Water and nutrient availability are the major limiting factors of biological activity in arid and semiarid ecosystems. Therefore, perennial plants have developed different ecophysiological adaptations to cope with harsh conditions. The chemical profile of the root exudates varies among plant species and this can induce variability in associated microbial populations. We examined the influence of two shrubs species, Artemisia sieberi and Noaea mucronata, on soil microbial diversity. Soil samples were collected monthly, from December 2006 to November 2007, near canopies of both shrubs (0-10-cm depth). Samples were used for abiotic tests and determination of soil bacterial diversity. No significant differences were found in the abiotic variables (soil moisture, total organic matter, and total soluble nitrogen (TSN)) between soil samples collected from under the two shrubs during the study period. No obvious differences in the Shannon-Weaver index, evenness values, or total phylogenetic distances were found for the soil microbial communities. However, detailed denaturing gradient gel electrophoresis (DGGE) clustering as well as taxonomic diversity analyses indicated clear shifts in the soil microbial community composition. These shifts were governed by seasonal variability in water availability and, significantly, by plant species type.

Microfungal-community diversity in Zygophyllum dumosum and Hammada scoparia root zones in the northern Negev Desert.

The soil dilution plate method was used to determine the influences of perennial shrubs on the species diversity and density of cultivable microfungal communities inhabiting the root zones of two perennial shrubs, Zygophyllum dumosum and Hammada scoparia, in the northern Negev Desert, Israel. Soil samples were collected under the canopies of shrubs and the open spaces between them (serving as control) from five depths (0-10, 10-20, 20-30, 30-40, and 40-50 cm) during the wet and dry seasons of 2010. Fifty-one species belonging to 31 genera were identified from Zygomycota, teleomorphic and anamorphic Ascomycota, including Coelomycetes. During the wet and dry seasons, 4-10 and 2-6 species were identified at different soil depths beneath perennial shrubs and in the open spaces, while the corresponding colony-forming units (CFUs) varied from 3071 to 27687 and from 3201 to 15247 g(-1) dry soil. More diverse microfungal communities were collected in the vicinity of perennial shrubs compared to the open spaces during the wet season, while a reverse trend was observed during the dry season. Further study is needed to provide insights into the correlation between compounds of litter and root exudates of perennial shrubs and microfungal-community structure by a combination of molecular and physiological tools.

Vertical distribution of microbial community functionality under the canopies of Zygophyllum dumosum and Hammada scoparia in the Negev Desert, Israel.

Patchy desert shrubs magnify the horizontal heterogeneities of carbon source and nutrient availability in an arid ecosystem, significantly affecting the abundance and activity of the soil microbial community. Since each shrub species develops special ecophysiological adaptations to the extreme harsh desert environments, previous studies elucidated that the effects of perennial shrubs on microbial diversity are unequal. The aim of the present study, conducted in the Negev Desert, Israel, was to illustrate the vertical changes of soil microbial community functionality in the root zone of perennial shrubs. Soil samples were collected from the 0-50 cm depth at 10-cm intervals under the canopy of Zygophyllum dumosum, Hammada scoparia, and from the open spaces between them, in the wet and dry seasons. Soil moisture and organic matter exhibited a significant (P<0.001) plant and depth dependence. The mean basal respiration rates and microbial biomass in soils collected beneath perennial shrubs were relatively higher than the control during the wet season, however, a contrasting trend was observed at some soil depths during the dry season. Relatively high abundance and activity of aromatic and carboxylic acid utilizers were observed in the vicinity of perennial shrubs, and the values recorded during the dry season were generally higher than the corresponding values during the wet season. In addition, a "mirror effect" in vertical changes of the community-level physiological profile was observed between Z. dumosum and H. scoparia. This study demonstrated the stratification of the functional aspects in soils under the canopy of perennial shrubs, thus indicating that the scattered distribution of vegetation not only causes horizontal heterogeneities of the microbial community in an arid system, but also that the ecophysiological adaptations developed by xerophytes regulate the abundance and saprotrophic functionality of microorganisms in the root zone.

Three novel chromanones with biological activities from the endophytic fungus Phomopsis CGMCC No. 5416.

Three undescribed chromanones (1-3) and two known chromanones (4 and 5) were isolated from the culture of endophytic fungus Phomopsis CGMCC No. 5416 from the stems of Achyranthes bidentata. Their structures were determined by spectroscopic analysis. Compounds 1 and 2 showed inhibitory activities against HIV-1 with IC50 values of 20.4 and 32.5 µg ml-1, respectively. Compounds 1-3 displayed moderate cytotoxicity with CC50 values of 36.5-79.3 µg ml-1 against A549, MDA-MB-231, and PANC-1 cell lines. Moreover, compound 3 can induce the early apoptosis of PANC-1 cancer cells with the apoptosis rate of 10.52%.

Reactive green dye remediation by Alternanthera philoxeroides in association with plant growth promoting Klebsiella sp. VITAJ23: A pot culture study.

Contamination of soil by textile effluent is a major threat found worldwide. These pollutants have diverse range of negative effects on the ecosystem, therefore restoration through cost effective biological strategy is the need of the hour. The aim of the current study was to enhance the decolourization of reactive green dye (RGD) using phytoremediation coupled with augmentation of effective bacteria to the rhizosphere. The isolate Klebsiella sp. VITAJ23 was isolated from textile effluent polluted soil and was assessed for its plant growth promoting traits (PGP) and the PGP functional genes were amplified. The soil was artificially polluted with RGD concentration ranging from 1000 to 3000 mg kg-1 and Alternanthera philoxeroides plantlets were planted in phyto and rhizoremediation treatments, the setup was maintained upto 60 d. The isolate VITAJ23 was augmented in the rhizoremediation setup and the morphological parameters were assessed at regular interval. There was a significant increase in the chlorophyll content as well as root and shoot length of the plant when treated with the bacterial suspension. Decolourization study revealed 79% removal of reactive green dye with an enhanced oxido-reductase enzyme activity in the setup bioaugmented with bacteria. The biodegraded metabolites were identified as 2-allylnapthalene, l-alanine, n-acetyl-and propenoic acid by GC-MS analysis and a plant-bacteria degradation pathway was predicted using computational tools. Inoculation of PGP-Klebsiella sp. VITAJ23 enhanced the rate of plant growth and dye degradation.

Latitudinal variation in soil biota: testing the biotic interaction hypothesis with an invasive plant and a native congener.

Soil biota community structure can change with latitude, but the effects of changes on native plants, invasive plants, and their herbivores remain unclear. Here, we examined latitudinal variation in the soil biota community associated with the invasive plant Alternanthera philoxeroides and its native congener A. sessilis, and the effects of soil biota community variation on these plants and the beetle Agasicles hygrophila. We characterized the soil bacterial and fungal communities and root-knot nematodes of plant rhizospheres collected from 22 °N to 36.6 °N in China. Soil biota community structure changed with latitude as a function of climate and soil properties. Root-knot nematode abundance and potential soil fungal pathogen diversity (classified with FUNGuild) decreased with latitude, apparently due to higher soil pH and lower temperatures. A greenhouse experiment and lab bioassay showed native plant mass, seed production, and mass of beetles fed native foliage increased with soil collection latitude. However, there were no latitudinal patterns for the invasive plant. These results suggest that invasive and native plants and, consequently, their herbivores have different responses to latitudinal changes in soil-borne enemies, potentially creating spatial variation in enemy release or biotic resistance. This highlights the importance of linking above- and below-ground multitrophic interactions to explore the role of soil biota in non-native plant invasions with a biogeographic approach.

Assessing the role of endophytic bacteria in the halophyte Arthrocnemum macrostachyum salt tolerance.

There is an increasing interest to use halophytes for revegetation of salt affected ecosystems, as well as in understanding their mechanisms of salt tolerance. We hypothesized that bacteria from the phyllosphere of these plants might play a key role in its high tolerance to excessive salinity. Eight endophytic bacteria belonging to Bacillus and closely related genera were isolated from phyllosphere of the halophyte Arthrocnemum macrostachyum growing in salty agricultural soils. The presence of plant-growth promoting (PGP) properties, enzymatic activities and tolerance towards NaCl was determined. Effects of inoculation on seeds germination and adult plant growth under experimental NaCl treatments (0, 510 and 1030 mM NaCl) were studied. Inoculation with a consortium including the best performing bacteria improved considerably the kinetics of germination and the final germination percentage of A. macrostachyum seeds. At high NaCl concentrations (1030 mM), inoculation of plants mitigated the effects of high salinity on plant growth and physiological performance and, in addition, this consortium appears to have increased the potential of A. macrostachyum to accumulate Na+ in its shoots, thus improving sodium phytoextraction capacity. Bacteria isolated from A. macrostachyum phyllosphere seem to play an important role in plant salt tolerance under stressing salt concentrations. The combined use of A. macrostachyum and its microbiome can be an adequate tool to enhance plant adaptation and sodium phytoextraction during restoration of salt degraded soils.