Seasonal Patterns Contribute More Towards Phyllosphere Bacterial Community Structure than Short-Term Perturbations.

Phyllosphere microorganisms are sensitive to fluctuations in wind, temperature, solar radiation, and rain. However, recent explorations of patterns in phyllosphere communities across time often focus on seasonal shifts and leaf senescence without measuring the contribution of environmental drivers and leaf traits. Here, we focus on the effects of rain on the phyllosphere bacterial community of the wetland macrophyte broadleaf cattail (Typha latifolia) across an entire year, specifically targeting days before and 1, 3, and 5 days after rain events. To isolate the contribution of precipitation from other factors, we covered a subset of plants to shield them from rainfall. We used targeted Illumina sequencing of the V4 region of the bacterial 16S rRNA gene to characterize phyllosphere community composition. Rain events did not have a detectable effect on phyllosphere community richness or evenness regardless of whether the leaves were covered from rain or not, suggesting that foliar microbial communities are robust to such disturbances. While climatic and leaf-based variables effectively modeled seasonal trends in phyllosphere diversity and composition, they provided more limited explanatory value at shorter time scales. These findings underscore the dominance of long-term seasonal patterns related to climatic variation as the main factor influencing the phyllosphere community.

Atrazine detoxification by intracellular crude enzyme extracts derived from epiphytic root bacteria associated with emergent hydrophytes.

The present study demonstrated atrazine detoxification by intracellular crude enzyme extracts of Pseudomonas spp. strains ACB and TLB. Indigenous bacterial protein-based remediation techniques could be an alternative to bioaugmentation which pose multiple challenges when applied to the field. Intracellular enzymes were extracted from strains ACB and TLB and their degradation potential of 10 mg L-1 was determined using Gas Chromatography; further, enzyme extracts were subjected to protein profiling studies. In span of 6 h, enzyme extracts of strain ACB showed maximum degradation at 30 °C and 40 °C (71%) and enzyme extracts of strain TLB showed maximum degradation at 40 °C (48%). Atrazine degradation by enzyme extracts of strain ACB showed maximum degradation at pH 7 (71%) and pH 6 (69%) in 6 h. Similarly, enzyme extracts of strain TLB showed maximal degradation at pH 6 (46%) in 6 h. The present study demonstrated, for the first time, efficient atrazine remediation by intracellular crude enzyme extracts from epiphytic root bacteria at a range of temperature and pH conditions. Protein profiling studies indicated that atrazine induced expression of CoA ester lyase and alkyl hydroperoxide reductase in the strains ACB and TLB respectively. Expressions of these proteins have never been associated with atrazine exposure.

Lysinimonas yzui sp. nov., isolated from cattail root soil from mine tailings.

A yellow-pigmented, Gram-stain-negative, aerobic, non-motile rod shaped, mesophilic bacterium, designated strain N7XX-4T, was isolated from cattail root grown on the mine tailings of Phoenix mountain, Tongling city, Anhui Province (PR China). Analysis of the 16S rRNA gene sequence revealed that the strain represented a novel member of the family Microbacteriaceae. The nearest phylogenetic neighbour was Lysinimonas kribbensis MSL-13T (97.8 % 16S rRNA gene sequence similarity). The most abundant fatty acid in whole cells of N7XX-4T was anteiso-C15 : 0 (29.9 %). The predominant menaquinones were MK-12(H2), MK-13(H2) and MK-11(H2). The peptidoglycan type of the isolate was B1δ with l-Lys as the diagnostic cell-wall diamino acid. On the basis of differences in phenotypic and genotypic characteristics, strain N7XX-4T (=CGMCC 1.16548T=DSM 106791T=JCM 32630T) is designated as the type strain of a novel species of the genus Lysinimonas, for which the name Lysinimonas yzui sp. nov. is proposed.

Nonomuraea typhae sp. nov., an endophytic actinomycete isolated from the root of cattail pollen (Typha angustifolia L.).

A novel endophytic actinomycete, designated strain p1410T, was isolated from the root of cattail pollen (Typha angustifolia L.) and characterized using a polyphasic approach. The strain had morphological characteristics and chemotaxonomic properties identical to those of members of the genus Nonomuraea. It produced spiral chains of spores on aerial mycelium as well as forming a pseudosporangium. Whole-cell hydrolysates contained meso-diaminopimelic acid, glucose, ribose and madurose. The menaquinones detected were MK-9(H2), MK-9(H4) and MK-9(H0). The major fatty acids were 10-methyl C17 : 0, iso-C16 : 0 and C17 : 0. The polar lipids were diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, hydroxyphosphatidylethanolamine, phosphatidylinositol mannoside and an unknown glycolipid. The DNA G+C content of the draft genome sequence, consisting of 11.4 Mbp, was 70.9 mol%. Phylogenetic analysis of 16S rRNA gene sequences showed that strain p1410T belongs to the genus Nonomuraea with the highest sequence similarity to Nonomuraea candida HMC10T (98.6 %), but phylogenetically clustered with Nonomuraea endophytica YIM 65601T (98.4 %) and Nonomuraea longicatena NRRL 15532T (98.3 %). Based on its phenotypic characteristics, DNA-DNA relatedness and average nucleotide identity, the strain is considered to represent a novel species of the genus Nonomuraea, for which the name Nonomuraea typhae sp. nov. is proposed. The type strain is p1410T (=CCTCC AA 2019044T=JCM 33461T).

Changes of root microbial populations of natively grown plants during natural attenuation of V-Ti magnetite tailings.

Mine tailings contain dangerously high levels of toxic metals which pose a constant threat to local ecosystems. Few naturally grown native plants can colonize tailings site and the existence of their root-associated microbial populations is poorly understood. The objective of this study was to give further insights into the interactions between native plants and their microbiota during natural attenuation of abandoned V-Ti magnetite mine tailings. In the present work, we first examined the native plants' potential for phytoremediation using plant/soil analytical methods and then investigated the root microbial communities and their inferred functions using 16 S rRNA-based metagenomics. It was found that in V-Ti magnetite mine tailings the two dominant plants Bothriochloa ischaemum and Typha angustifolia were able to increase available nitrogen in the rhizosphere soil by 23.3% and 53.7% respectively. The translocation factors (TF) for both plants indicated that B. ischaemum was able to accumulate Pb (TF = 1.212), while T. angustifolia was an accumulator of Mn (TF = 2.502). The microbial community structure was more complex in the soil associated with T. angustifolia than with B. ischaemum. The presence of both plants significantly reduced the population of Acinetobacter. Specifically, B. ischaemum enriched Massilia, Opitutus and Hydrogenophaga species while T. angustifolia significantly increased rhizobia species. Multivariate analyses revealed that among all tested soil variables Fe and total organic carbon (TOC) could be the key factors in shaping the microbial structure. The putative functional analysis indicated that soil sample of B. ischaemum was abundant with nitrate/nitrite reduction-related functions while that of T. angustifolia was rich in nitrogen fixing functions. The results indicate that these native plants host a diverse range of soil microbes, whose community structure can be shaped by plant types and soil variables. It is also possible that these plants can be used to improve soil nitrogen content and serve as bioaccumulators for Pb or Mn for phytoremediation purposes.

Characterization of Hydrocarbon-Degrading Bacteria in Constructed Wetland Microcosms Used to Treat Crude Oil Polluted Water.

Ten plant species were grown in constructed wetlands (CWs) to remediate water containing 2% (w/v) crude oil. The plant species with better growth and biomass production were Typha latifolia and Cyperus laevigatus, and they were significantly correlated (R2 = 0.91) with hydrocarbon degradation. From T. latifolia and C. laevigatus, 33 hydrocarbon-degrading bacterial strains were isolated from the rhizosphere, and root and shoot interiors. More diversified bacteria were found in the rhizosphere and endosphere of C. laevigatus than those of T. latifolia. The predominant cultural hydrocarbon-degrading bacteria were shown to belong to the genera Pseudomonas, Acinetobacter and Bacillus. In addition to genes involved in hydrocarbon degradation, most of the bacteria displayed multiple plant growth promoting (PGP) activities. This study suggests the importance of selecting suitable bacterial strains with hydrocarbon degradation and PGP activities for improving the efficacy of CWs used in remediating water contaminated with crude oil.

Taxonomic structure and function of seed-inhabiting bacterial microbiota from common reed (Phragmites australis) and narrowleaf cattail (Typha angustifolia L.).

The present study investigated the endophytic bacterial communities in the seeds of mature, natural common reed (Phragmites australis) and narrowleaf cattail (Typha angustifolia L.). Additionally, seed endophytic bacterial communities were compared with rhizospheric and root endophytic bacterial communities using Illumina-based sequencing. Seed endophytic bacterial communities were dominated by Proteobacteria (reed, 41.24%; cattail, 45.51%), followed by Bacteroidetes (reed, 12.01%; cattail, 10.41%), Planctomycetes (reed, 10.36%; cattail, 9.09%), Chloroflexi (reed, 8.72%; cattail, 6.45%), Thermotogae (reed, 5.43%; cattail, 6.11%), Tenericutes (reed, 3.63%; cattail, 3.97%) and Spirochaetes (reed, 3.32%; cattail, 3.90%). The dominant genera were Desulfobacter (reed, 8.02%; cattail, 8.96%), Geobacter (reed, 2.74%; cattail, 2.81%), Thiobacillus (reed, 2.71%; cattail, 2.41%), Sulfurimonas (reed, 2.47%; cattail, 2.31%), Methyloversatilis (reed, 2.29%; cattail, 2.05%) and Dechloromonas (reed, 1.13%; cattail, 1.48%). Obvious distinctions were observed among the respective rhizospheric, root endophytic and seed endophytic bacterial communities. Principal coordinate analysis with weighted UniFrac distance and the heat map analysis demonstrated that the seed endophytic bacterial communities were distinct assemblages rather than a subgroup of rhizobacterial communities or root endophytic bacterial communities. These results provide new information regarding endophytic bacteria associated with seeds of wetland plants and demonstrate a variety of genera that have a strong potential to enhance phytoremediation in the wetland ecosystem.

Assessing the Bacterial Community Structure in the Rhizoplane of Wetland Plants.

Plant-microorganism interaction in the rhizosphere is important for nutrient cycling, carbon sequestration in natural ecosystems, contaminant elimination and ecosystem functioning. Abundance of microbial communities and variation in species composition can be an imperative determinant of phytoremediation capability. In the present study we have assessed the bacterial community structure in the rhizoplane of wetland plants, Acorus calamus, Typha latifolia, and Phragmites karka using Terminal restriction fragment length polymorphism technique. The most dominant phylum, in the plants under study, was phylum Firmicutes, followed by Proteobacteria and Actinobacteria. Bacterial groups belonging to phylum Chloroflexi, Acidobacteria, Deferribacteres and Thermotogae also showed their presence in P. karka and T. latifolia but were absent in A. calamus. Diversity indices of bacterial community were assessed. The results of this study show the presence of bacterial phyla which play an important role in bioremediation of contaminants. Thus these plants can be used as potential candidates of phytoremediation.

Community Composition and Abundance of Anammox Bacteria in Cattail Rhizosphere Sediments at Three Phenological Stages.

The distribution of anammox bacteria in rhizosphere sediments of cattail (Typha orientalis) at different phenological stages was investigated. Results showed that the number of 16S rRNA gene copies of the anammox bacteria was considerably higher in the rhizosphere sediment than in the nonrhizosphere sediment and control sediment. The abundances of the anammox bacteria exhibited striking temporal variations in the three different cattail phenological stages. In addition, the Chao1 and Shannon H indexes of the anammox bacteria in cattail rhizosphere sediments had evident spatial and temporal variations at different phenological stages. Four anammox genera (Brocadia, Kuenenia, Jettenia, and a new cluster) were detected and had proportions of 34.18, 45.57, 0.63, and 19.62%, respectively. The CCA analysis results indicated that Cu, TN, Pb, and Zn were pivotal factors that affect anammox bacteria composition. The PCoA analysis results indicated that the community structure at the rhizosphere and nonrhizosphere sediments collected on July was relatively specific and was different from sediments collected on other months, suggesting that cattail can influence the community structures of the anammox bacteria at the maturity stage.

Effect of reclaimed water effluent on bacterial community structure in the Typha angustifolia L. rhizosphere soil of urbanized riverside wetland, China.

In order to evaluate the impact of reclaimed water on the ecology of bacterial communities in the Typha angustifolia L. rhizosphere soil, bacterial community structure was investigated using a combination of terminal restriction fragment length polymorphism and 16S rRNA gene clone library. The results revealed significant spatial variation of bacterial communities along the river from upstream and downstream. For example, a higher relative abundance of γ-Proteobacteria, Firmicutes, Chloroflexi and a lower proportion of ß-Proteobacteria and ε-Proteobacteria was detected at the downstream site compared to the upstream site. Additionally, with an increase of the reclaimed water interference intensity, the rhizosphere bacterial community showed a decrease in taxon richness, evenness and diversity. The relative abundance of bacteria closely related to the resistant of heavy-metal was markedly increased, while the bacteria related for carbon/nitrogen/phosphorus/sulfur cycling wasn't strikingly changed. Besides that, the pathogenic bacteria markedly increased in the downstream rhizosphere soil since reclaimed water supplement, while the possible plant growth-promoting rhizobacteria obviously reduced in the downstream sediment. Together these data suggest cause and effect between reclaimed water input into the wetland, shift in bacterial communities through habitat change, and alteration of capacity for biogeochemical cycling of contaminants.

Rhizosphere bacterial community of Typha angustifolia L. and water quality in a river wetland supplied with reclaimed water.

Wetland plant rhizosphere microorganisms play a significant role in the purification of ecological restoration of reclaimed water replenishment wetlands. In this study, water quality discriminant analysis indicated the wetland had a distinctive role in the purification of total nitrogen (TN), total phosphorus (TP), and nitrate (NO3 (-)) from reclaimed water, of which removal rates were 42.15, 47.34, and 28.56 % respectively. All the sequences of 16S ribosomal RNA (16S rRNA) gene clone library were affiliated with Proteobacteria (74.50 %), Bacteroidetes (6.54 %), Gemmatimonadetes (5.88 %), Chloroflexi (4.25 %), Chlorobi (2.94 %), Nitrospira (2.61 %), Acidobacteria (2.29 %), and Actinobacteria (0.98 %). Assessment of water quality purification and rhizosphere bacterial properties revealed that the major biogeochemical reactions were nitrogen, phosphorus, carbon, and sulfur cycles (33.70, 15.40, 14.40, and 4.90 %, respectively). In addition, approximately 5.90 and 4.60 % of the clones are closely related with the minor biogeochemical degradations of antibiotics and halogenated hydrocarbons, which were the typical characteristics of reclaimed water wetland different from freshwater wetlands. The finding of water quality discriminant is consistent with that of bacterial community, but the latter was a more powerful method than the former which reveals possible implications of wetland plant purification on the reclaimed water.

A Comparison of Anammox Bacterial Abundance and Community Structures in Three Different Emerged Plants-Related Sediments.

Quantitative polymerase chain reaction (qPCR) assays and 16S rRNA gene clone libraries were used to document the abundance, diversity and community structure of anaerobic ammonia-oxidising (anammox) bacteria in the rhizosphere and non-rhizosphere sediments of three emergent macrophyte species (Iris pseudacorus, Thalia dealbata and Typha orientalis). The qPCR results confirmed the existence of anammox bacteria (AMX) with observed log number of gene copies per dry gram sediment ranging from 5.00 to 6.78. AMX was more abundant in T. orientalis-associated sediments than in the other two plant species. The I. pseudacorus- and T. orientalis-associated sediments had higher Shannon diversity values, indicating higher AMX diversity in these sediments. Based on the 16S rRNA gene, Candidatus 'Brocadia', Candidatus 'Kuenenia', Candidatus 'Jettenia' and new clusters were observed with the predominant Candidatus 'Kuenenia' cluster. The I. pseudacorus-associated sediments contained all the sequences of the C. 'Jettenia' cluster. Sequences obtained from T. orientalis-associated sediments contributed more than 90 % sequences in the new cluster, whereas none was found from I. pseudacorus. The new cluster was distantly related to known sequences; thus, this cluster was grouped outside the known clusters, indicating that the new cluster may be a new Planctomycetales genus. Further studies should be undertaken to confirm this finding.

Uranium immobilization in an iron-rich rhizosphere of a native wetland plant from the Savannah River Site under reducing conditions.

The hypothesis of this study was that iron plaques formed on the roots of wetland plants and their rhizospheres create environmental conditions favorable for iron reducing bacteria that promote the in situ immobilization of uranium. Greenhouse microcosm studies were conducted using native plants (Sparganium americanum) from a wetland located on the Savannah River Site, Aiken, SC. After iron plaques were established during a 73-day period by using an anoxic Fe(II)-rich nutrient solution, a U(VI) amended nutrient solution was added to the system for an additional two months. Compared to plant-free control microcosms, microcosms containing iron plaques successfully stimulated the growth of targeted iron reducing bacteria, Geobacter spp. Their population continuously increased after the introduction of the U(VI) nutrient solution. The reduction of some of the U(VI) to U(IV) by iron reducing bacteria was deduced based on the observations that the aqueous Fe(II) concentrations increased while the U(VI) concentrations decreased. The Fe(II) produced by the iron reducing bacteria was assumed to be reoxidized by the oxygen released from the roots. Advanced spectroscopic analyses revealed that a significant fraction of the U(VI) had been reduced to U(IV) and they were commonly deposited in association with phosphorus on the iron plaque.

Plastic and terrestrial organic matter degradation by the humic lake microbiome continues throughout the seasons.

Boreal freshwaters go through four seasons, however, studies about the decomposition of terrestrial and plastic compounds often focus only on summer. We compared microbial decomposition of 13C-polyethylene, 13C-polystyrene, and 13C-plant litter (Typha latifolia) by determining the biochemical fate of the substrate carbon and identified the microbial decomposer taxa in humic lake waters in four seasons. For the first time, the annual decomposition rate including separated seasonal variation was calculated for microplastics and plant litter in the freshwater system. Polyethylene decomposition was not detected, whereas polystyrene and plant litter were degraded in all seasons. In winter, decomposition rates of polystyrene and plant litter were fivefold and fourfold slower than in summer, respectively. Carbon from each substrate was mainly respired in all seasons. Plant litter was utilized efficiently by various microbial groups, whereas polystyrene decomposition was limited to Alpha- and Gammaproteobacteria. The decomposition was not restricted only to the growth season, highlighting that the decomposition of both labile organic matter and extremely recalcitrant microplastics continues throughout the seasons.

Paenibacillus typhae sp. nov., isolated from roots of Typha angustifolia L.

A Gram-stain-positive, facultatively anaerobic and rod-shaped bacterium, designated strain xj7(T), was isolated from roots of Typha angustifolia L. growing in Beijing Cuihu Wetland, China. The isolate was identified as a member of the genus Paenibacillus based on phenotypic characteristics and phylogenetic inference. The novel strain was spore-forming, motile, catalase-positive and oxidase-negative. Optimal growth of strain xj7(T) occurred at 28-30 °C and pH 7.0-7.5. Diphosphatidylglycerol was the most abundant polar lipid and occurred along with phosphatidylglycerol, phosphatidylethanolamine, one unknown phospholipid and three unknown aminophospholipids. The diamino acid found in the cell-wall peptidoglycan was meso-diaminopimelic acid. The predominant isoprenoid quinone was MK-7. The major fatty acid components were anteiso-C15 : 0 (56.1 %), iso-C16 : 0 (9.1 %), C16 : 0 (8.0 %), iso-C14 : 0 (6.3 %) and iso-C15 : 0 (5.1 %). The G+C content of genomic DNA was 47.9 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain xj7(T) fell within the evolutionary radiation encompassed by the genus Paenibacillus, its closest neighbours were Paenibacillus borealis KK19(T) (97.5 %) and Paenibacillus durus DSM 1735(T) (97.1 %). However, the DNA-DNA relatedness values between strain xj7(T) and P. borealis KK19(T) and between strain xj7(T) and P. durus DSM 1735(T), were both 35 %. Based on phenotypic, chemotaxonomic and phylogenetic properties, strain xj7(T) is considered to represent a novel species of the genus Paenibacillus, for which the name Paenibacillus typhae sp. nov. is proposed. The type strain is xj7(T) ( = CGMCC 1.11012(T) = DSM 25190(T)).

Comparison of the diversity of root-associated bacteria in Phragmites australis and Typha angustifolia L. in artificial wetlands.

Common reed (Phragmites australis) and narrow-leaved cattail (Typha angustifolia L.) are two plant species used widely in artificial wetlands constructed to treat wastewater. In this study, the community structure and diversity of root-associated bacteria of common reed and narrow-leaved cattail growing in the Beijing Cuihu Wetland, China, were investigated using 16S rDNA library and PCR-denaturing gradient gel electrophoresis methods. Root-associated bacterial diversity was higher in common reed than in narrow-leaved cattail. In both plant species, the dominant root-associated bacterial species were Alpha, Beta and Gamma Proteobacteria, including the genera Aeromonas, Hydrogenophaga, Ideonella, Uliginosibacterium and Vogesella. Acidobacteria, Actinobacteria, Nitrospirae and Spirochaetes were only found in the roots of common reed. Comparing the root-associated bacterial communities of reed and cattail in our system, many more species of bacteria related involved in the total nitrogen cycle were observed in reed versus cattail, while species involved in total phosphorus and organic matter removal were mainly found in cattail. Although we cannot determine their nutrient removal capacity separately, differences in the root-associated bacterial communities may be an important factor contributing to the differing water purification effects mediated by T. angustifolia and P. australis wetlands. Thus, further work describing the ecosystem functions of these bacterial species is needed, in order to fully understand how effective common reed- and narrow-leaved cattail-dominated wetlands are for phytoremediation.

Influence of plants on microbial activity in a vertical-downflow wetland system treating waste activated sludge with high organic matter concentrations.

The rhizosphere is a key zone for pollutant removal in treatment wetlands; therefore, studies on microbial activity may provide helpful information for a better understanding of purification processes. We studied microbial activity in a vertical-downflow constructed wetland system treating waste activated sludge with high organic matter concentrations, under Mediterranean climate. The aims of the work were to study the influence of (i) the presence of plants, (ii) the plant species (Phragmites australis Cav., Typha latifolia L., Iris pseudacorus L.), and (iii) the plant growth stage (plant senescence and plant fast growing stage) on total respiration rate and phosphatase activity in the substrate (intented here as the solid support on which the plants grow). The presence of plants had a positive influence on microbial activity, since substrate respiration and both acid and alkaline phosphatase activity were always higher in planted than in unplanted mesocosms. Among the three tested species, Phragmites was the one that most stimulated both substrate respiration rate and phosphatase activity, followed by Typha and Iris. These differences of microbial activity between mesocosms were corresponding to differences of removal efficiency. Substrate respiration and phosphatase activity were of similar magnitude at the two growth stages, while the stimulating effect of plants seemed to have been delayed and microbial activity showed higher fluctuations at plant fast growing stage than at plant senescence.

Stimulated phytoextraction of metals from fly ash by microbial interventions.

Various combinations of fly ash tolerant bacteria isolated from the rhizospheric zone of Typha latifolia naturally growing on a fly ash dump site were tested for enhanced metal uptake by Brassica juncea grown in fly ash amended with press mud. After enrichment of the bacteria in a nutrient broth, they were subsequently applied to the rhizospheric zone of B. juncea in different combinations. When the metal analysis was done in the plants at their maturity, it was revealed that out of 11 bacterial consortia prepared from the different combinations of four bacterial strains, Micrococcus roseus NBRFT2 (MTCC 9018), Bacillus endophyticus NBRFT4 (MTCC 9021), Paenibacillus macerans NBRFT5 (MTCC 8912) and Bacillus pumilus NBRFT9 (MTCC 8913), a combination of NBRFT5, NBRFT4 and NBRFT9 (ST3) was found to have induced the highest metal accumulations as compared to other consortia. The bioaugmentation of the ST3 consortium enhanced Fe accumulation by 247%, Ni by 231% and Zn by 223% in B. juncea as compared to control plants. These values were found to be significantly higher than the other bacterial consortia. Bacteria were also found to produce siderophores which could enhance the metal uptake by plants through metal mobilization. Besides siderophores, bacteria are also known to produce protons, organic acids and enzymes which enhance the metal mobilization and boost the phytoextraction process. The translocation of metals from root to stem was invariably higher than from stem to leaf. Hence, ST3 was adjudged the best consortium to be used in the field application to accelerate the phytoextraction of metals from fly ash by B. juncea.

Phytoremediation of pharmaceutical-contaminated wastewater: Insights into rhizobacterial dynamics related to pollutant degradation mechanisms during plant life cycle.

Rhizobacterial dynamics, relating to pollutant degradation mechanisms, over the course of plant lifespan have rarely been reported when using phytoremediation technologies for pharmaceutical-contaminated wastewater treatment. This study investigated the rhizobacterial dynamics of Typha angustifolia in constructed wetlands to treat ibuprofen (IBP)-polluted wastewater throughout plant development from seedling, vegetative, bolting, mature, to senescent stages. It was found that conventional pollutant and IBP removals increased with plant development, reaching to the best performance at bolting or mature stage (removal efficiencies: 92% organics, 52% ammonia, 60% phosphorus and 76% IBP). In the IBP-stressed wetlands, the rhizobacterial diversity during plant development was adversely affected by IBP accompanied with a reduced evenness. The bacterial communities changed dynamically at different developmental stages and showed significant differences compared to the control wetlands (free of IBP). The dominant bacteria colonized in the rhizosphere was the phylum Actinobacteria, having a final relative abundance of 0.79 and containing a large amount of genus norank_o__PeM15. Positive interactions were evident among the rhizobacteria in IBP-stressed wetlands and the predicted functions of 16S rRNA genes revealed the potential co-metabolism and metabolism of IBP. The co-metabolism of IBP might be related to root exudates such as amino acid, lipid, fatty acid and organic acid. In addition, positive correlations between the organic compounds of interstitial water (bulk environment) and the rhizobacterial communities were observed in IBP-stressed wetlands, which suggests that the influence of IBP on bulk microbiome might be able to modulate rhizosphere microbiome to achieve the degradation of IBP via co-metabolism or metabolism.

Suppression of root-endogenous fungi in persistently inundated Typha roots.

Wetland soils are defined by anoxic and reducing conditions that impose biogeochemically hostile conditions on plant roots and their endogenous fungal communities. The cosmopolitan wetland plant Typha L. mitigates root-zone anoxia efficiently, such that roots of these plants may constitute fungal habitats similar to roots in subaerially exposed soils. Alternatively, fungi may compete with plant cells for limited oxygen in inundated roots. We hypothesized that extrinsic environmental factors may reduce fungal incidence and affect fungal community structure within inundated roots as compared with those in subaerially exposed soils. We sampled roots of Typha spp. plants across inundation gradients in constructed reservoirs; root subsamples were microscopically examined for fungal structures, and morphologically distinct fungal endophytes were cultured and isolated from surface-sterilized subsamples. We found that the incidence of fungal hyphae was suppressed for all types of vegetative mycelia when roots were inundated, regardless of depth, but that there were no obvious differences in community composition of fungi cultured from roots growing in inundated versus subaerially exposed soils. This suggests that the suppression of hyphae we observed in root samples did not result from changes in community composition. Instead, low hyphal incidence in inundated Typha roots may reflect germinal inhibition or unsuccessful initial colonization, possibly owing to plant-mediated redox dynamism in the surrounding soil. No variation was seen in the incidence of asexual spores, or chytridiomycetes, nor were there significant differences between geographically disparate sampling sites. Communities of root-endogenous fungi may therefore be influenced more strongly by external environmental factors than by the environments that plant roots comprise.