There is increasing interest in the use of beneficial microorganisms as alternatives to chemical pesticides and synthetic fertilisers in agricultural production. Application of beneficial ...microorganisms to seeds is an efficient mechanism for placement of microbial inocula into soil where they will be well positioned to colonise seedling roots and protect against soil-borne diseases and pests. However, despite the long history of inoculation of legume seeds with
Rhizobia
spp. and clear laboratory demonstration of the ability of a wide range of other beneficial microorganisms to improve crop performance, there are still very few commercially available microbial seed inoculants. Seed inoculation techniques used for research purposes are often not feasible at a commercial scale and there are significant technical challenges in maintaining viable microbial inocula on seed throughout commercial seed treatment processes and storage. Further research is needed before the benefits of a wide range of environmentally sensitive potential seed inoculants can be captured for use in agriculture, ecosystem restoration and bioremediation. There is no single solution to the challenge of improving the ability of seed inoculants to establish and function consistently in the field. Development of novel formulations that maintain the viability of both inoculant and seed during storage will result from multidisciplinary research in microbial and seed physiology and adjuvant chemistry.
A customised synthetic microbial community (SynCom) composed of carefully selected rhizosphere-competent bacterial strains improved rice growth, yield and resistance to soil acidity and Al toxicity.
The extent to which soil phosphorus (P) status affected the incidence of soil phosphate-solubilising bacteria (PSB) and their taxonomic abundance and diversity was examined at three long-term ...fertiliser trials (Whatawhata, Winchmore and Ballantrae) in New Zealand. Bacteria were isolated from rhizosphere (ryegrass and clover) and non-rhizosphere soils differing in P status. The P-solubilising phenotype was determined on agar supplemented with sparingly-soluble mineral phosphates (Ca2OH(PO4)3 and CaHPO4). The frequency of P-solubilisation in the bacterial population was significantly greater (P < 0.001) in soils of low-P status, demonstrating a selection pressure for this trait based on soil P availability. P-solubilising bacteria from high-P level soils and soils which had not received P fertiliser (nil-P soils) were identified based on 16S rRNA-gene sequence analysis. Across the samples, the P-solubilising community was very rich with 39 genera of PSB found, spanning 24 families and 4 phyla. At Ballantrae and Winchmore, the PSB composition differed (P < 0.05) across soil P status, which was associated with an alteration in abundance of Actinobacteria, Pseudomonadaceae and Moraxellaceae. The phylogenetic composition of PSB differed significantly (P < 0.05) between sites, however nearly half the families were common across all sites, constituting a ‘core community’ of P-solubilising bacteria for these New Zealand pasture soils. As the abundance and composition of P-solubilising bacteria are under strong selection pressure affected through farm management strategies, better understanding of their ecology provides the opportunity to increase the availability of soil P for plant-uptake.
► Ecology of P-solubilising bacteria (PBS) was studied in 3 long-term field sites. ► Soil P status affected frequency of occurrence of P-solubilisation trait. ► Thirty nine genera of P-solubilising bacteria were identified. ► The taxonomic composition of PSB varied with soil P status at 2 sites. ► Changes in PSB were in the Actinobacteria, Pseudomonadaceae and Moraxellaceae taxa.
Abstract
Low-molecular-weight organic compounds in root exudates play a key role in plant–microorganism interactions by influencing the structure and function of soil microbial communities. Model ...exudate solutions, based on organic acids (OAs) (quinic, lactic, maleic acids) and sugars (glucose, sucrose, fructose), previously identified in the rhizosphere of Pinus radiata, were applied to soil microcosms. Root exudate compound solutions stimulated soil dehydrogenase activity and the addition of OAs increased soil pH. The structure of active bacterial communities, based on reverse-transcribed 16S rRNA gene PCR, was assessed by denaturing gradient gel electrophoresis and PhyloChip microarrays. Bacterial taxon richness was greater in all treatments than that in control soil, with a wide range of taxa (88–1043) responding positively to exudate solutions and fewer (<24) responding negatively. OAs caused significantly greater increases than sugars in the detectable richness of the soil bacterial community and larger shifts of dominant taxa. The greater response of bacteria to OAs may be due to the higher amounts of added carbon, solubilization of soil organic matter or shifts in soil pH. Our results indicate that OAs play a significant role in shaping soil bacterial communities and this may therefore have a significant impact on plant growth.
To identify and synthesize qualitative literature on the experiences of participants and key stakeholders in dance programs for people living with Parkinson's disease. Synthesizing the available ...literature can generate new insights into participant experience to inform current and future programs.
Qualitative and mixed methods studies were identified via a systematic search of six databases: CINAHL, Web of Science, Scopus, SPORTDiscus, PsycInfo, and MEDLINE. Articles were synthesized using the meta-ethnographic method developed by Noblit and Hare (1988). Key concepts across studies were related via reciprocal translation, ultimately forming a line-of-argument synthesis.
26 articles met the inclusion criteria. Four interrelated, overarching themes were developed: (1) dance communities provide peer support and insight into living with Parkinson's, (2) feeling safe, accepted, and included in the dance experience, (3) overcoming dance-based challenges contributes to sense of achievement, confidence, and connectedness, and (4) dance participation is an opportunity to re-imagine oneself.
Participant experience is shaped by the instructor-participant relationship, the social environment of classes, and class difficulty level. In order to support participant experience, classes should be safe, supportive, and have an appropriate challenge-skill balance. These qualities facilitate creative immersion and the potential for personal and collective change.
Nitrification is a key process of the nitrogen (N) cycle in soil with major environmental implications. The recent discovery of ammonia-oxidizing archaea (AOA) questions the traditional assumption of ...the dominant role of ammonia-oxidizing bacteria (AOB) in nitrification. We investigated AOB and AOA growth and nitrification rate in two different layers of three grassland soils treated with animal urine substrate and a nitrification inhibitor dicyandiamide (DCD). We show that AOB were more abundant in the topsoils than in the subsoils, whereas AOA were more abundant in one of the subsoils. AOB grew substantially when supplied with a high dose of urine substrate, whereas AOA only grew in the Controls without the urine-N substrate. AOB growth and the amoA gene transcription activity were significantly inhibited by DCD. Nitrification rates were much higher in the topsoils than in the subsoils and were significantly related to AOB abundance, but not to AOA abundance. These results suggest that AOB and AOA prefer different soil N conditions to grow: AOB under high ammonia (NH₃) substrate and AOA under low NH₃ substrate conditions.
Abstract
The root-associated soil microbiome contributes immensely to support plant health and performance against abiotic and biotic stressors. Understanding the processes that shape microbial ...assembly in root-associated soils is of interest in microbial ecology and plant health research. In this study, 37 plant species were grown in the same soil mixture for 10 months, whereupon the root-associated soil microbiome was assessed using amplicon sequencing. From this, the contribution of direct and indirect plant effects on microbial assembly was assessed. Plant species and plant-induced changes in soil physicochemistry were the most significant factors that accounted for bacterial and fungal community variation. Considering that all plants were grown in the same starting soil mixture, our results suggest that plants, in part, shape the assembly of their root-associated soil microbiome via their effects on soil physicochemistry. With the increase in phylogenetic ranking from plant species to class, we observed declines in the degree of community variation attributed to phylogenetic origin. That is, plant-microbe associations were unique to each plant species, but the phylogenetic associations between plant species were not important. We observed a large degree of residual variation (> 65%) not accounted for by any plant-related factors, which may be attributed to random community assembly.
Laboratory gut bacterial communities are not representative for natural field conditions.
Aims The mechanisms by which rhizosphere bacteria increase the availability of mineral P precipitates for plant use are understudied. However, Paraburkholderia bryophila Ha185 is known to solubilize ...inorganic phosphate in vitro via a novel process. Therefore, this study aimed to demonstrate P solubilization by Ha185 in association with roots of perennial ryegrass (Lolium perenne L.). Methods We developed a gnotobiotic plant assay to assess P solubilization by Ha185 on ryegrass roots under various nutrient conditions. A green fluorescent protein (GFP)-tagged derivative of Ha185 was used in conjunction with fluorescent microscopy and confocal microscopy to visualize colonization of ryegrass roots. Results Ha185 solubilized mineral P (hydroxyapatite) in association with ryegrass roots and increased ryegrass growth by 20% under P-limited conditions. The GFP-tagged Ha185 strain colonized the rhizoplane and penetrated the primaiy root of ryegrass, possibly through "crack entry" at the point of lateral root emergence, but also by entering the epidermal cells via root hairs. Conclusions Ha185 supported ryegrass growth under P-limited conditions, indicating this strain may improve availability of soil P for uptake by ryegrass. Tools developed in this study have broad application in the study of rhizobacteria-plant interactions.
Nitrification inhibitors, such as dicyandiamide (DCD), have been shown to decrease leaching from urea- and ammonium-based fertilisers and from urine patches in grazed pastures. To date there have ...been few studies on effects of nitrification inhibitors on non-target soil microbiota. This pot trial examined the short-term effects of DCD on the activity and diversity of both target (ammonium-oxidising bacteria and archaea) and non-target soil microbial populations. Bovine urine at a rate equivalent to 600kgurine-Nha−1 with or without DCD at 30kgha−1 was applied to pots planted with perennial ryegrass. This rate of DCD was typical of the amount applied to pasture in New Zealand, although this annual rate may be spread over several applications carried out over 2–3 months. The single high rate application was used to provide a “worst case scenario” to assist detection of potential impacts of DCD application to non-target soil microflora. Treatments also included DCD alone and untreated control pots. Soil used was a Horotiu sandy loam and pots were maintained at 80% WHC in a controlled-environment room at 12°C/16h (day) and 8°C/8h (night). Soil mineral N, hot water extractable C and N concentrations, soil pH, microbial biomass C and N, and DCD persistence were measured at regular intervals. Diversity and composition of the overall soil bacterial community were analysed by serial analysis of ribosomal sequence tags (SARST). Effects on ammonium-oxidising bacterial and archaeal communities were monitored more closely by determining the size of these populations using real-time PCR and their transcriptional activity by comparing RNA-denaturing gradient gel electrophoresis (DGGE) profiles following RT-PCR of the amoA gene. Changes in soil pH and mineral N following application of urine in the pot trial reflected patterns typically demonstrated in the field. Application of DCD to soil did not change the diversity of the soil bacterial community, with the four predominant phyla (Proteobacteria, Actinobacteria, Acidobacteria and Firmicutes) remaining in proportions that were similar to control soils. In contrast, urine application to soil resulted in a significant increase in members of Firmicutes, some of which are relatively stress tolerant. In line with the SARST results, shifts in the structure of the active component of the general soil bacterial community were detected in the urine and urine+DCD treatments only, further suggesting DCD had little impact on the overall soil bacterial activity. In contrast the microbes targeted by DCD, the ammonium-oxidising bacteria, were significantly affected by DCD with reductions in population size and altered activity. Ammonium-oxidising archaea, however, showed no response to application of DCD to soil, and were only minimally affected by application of urine. The results suggest that application of DCD to pasture is a relatively benign intervention that has an important role to play in mitigating the environmental hazards imposed by ongoing land use intensification.
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