16S rDNA Profiling to Reveal the Influence of Seed-Applied Biostimulants on the Rhizosphere of Young Maize Plants

In an open field trial on two agricultural soils in NW Italy, the impact of two seed-applied biostimulants on the rhizosphere bacterial community of young maize plants was evaluated. The 16S rDNA profiling was carried out on control and treated plant rhizosphere samples collected at the 4-leaf stage and on bulk soil. In both soils, the rhizospheres were significantly enriched in Proteobacteria, Actinobacteria, and Bacteriodetes, while the abundances of Acidobacteria, Cloroflexi and Gemmatimonadetes decreased compared with bulk soil. Among the culturable bacteria genera that showed an increase by both biostimulants, most are known to be beneficial for nutrient uptake, such as Opitutus, Chryseolinea, Terrimonas, Rhodovastum, Cohnella, Pseudoduganella and the species Anaeromyxobacter dehalogenans; others are known to be involved in root growth, such as Niastella, Labrys, Chloroflexia and Thermomonas; or in plant defence, such as Ohtaekwangia, Quadrisphaera, Turneriella, and Actinoallomurus. Both biostimulants were also found to stimulate gen. Nannocystis, a potential biocompetitive agent against aflatoxigenic Aspergillus moulds. Under controlled conditions, both biostimulants enhanced the shoot and root biomass at the 4\u20135 leaf stage. We conclude that the biostimulants do not decrease the biodiversity of the microbial community rhizosphere of young maize plants, but stimulate rare bacterial taxa, some involved in plant growth and pathogen resistance, a result that may have implications in improving crop management

Comparison of Bacterial and Archaeal Microbiome in Two Bioreactors Fed with Cattle Sewage and Corn Biomass

The bacterial and archaeal communities of two full-scale biogas producing plants (P1 and P2), associated with a 999 kW cogeneration unit, both located in North Italy, were analyzed at start up and fully operating phases, by means of various molecular approaches: (i) Automated Ribosomal Intergenic Spacer Analysis; (ii) cloning and sequencing of PCR amplicons of archaeal genes 16Srrna and mcrA; (iii) 16S rDNA high throughput next generation sequencing. P1 and P2 use the same technology and both were fed with cattle manure and corn silage. During the study of P1 also the post digester (fed with pig manure) was analyzed. The aim of this research was to characterize the bacterial and archaeal communities in two very similar plants to profile the core microbiota. The results of this analysis highlighted that the two plants (producing comparable quantities of volatile fatty acids, biogas, and energy) differed in anerobic microbiota (Bacteria and Archaea). Notably the methanogenic community of P1 was dominated by the strict acetoclastic Methanosaeta (Methanothrix) (up to 23.05%) and the unculturable Candidatus Methanofastidiosum (up to 32.70%), while P2 was dominated by the acetoclastic, but more substrate-versatile, Methanosarcina archaeal genus (49.19%). The data demonstrated that the performances of plants with identical design, in similar operating conditions, yielding comparable amount of biogas (average of 7237 m3 day−1 and 7916 m3 day−1 respectively for P1 and P2), VFA (1643 mg L− 1 and 1634 mg L−1) and energy recovery (23.90–24 MWh day−1), depend on the stabilization of effective and functionally optimized methanogenic communities, but these communities aretaxonomically different in the two biodigesters

Simultaneous enumeration of Campylobacter jejuni and Salmonella enterica genome equivalents by melting curve analysis following duplex real time PCR in the presence of SYBR Green

Chicken meat and eggs contaminated with Salmonella enterica and Campylobacter jejuni are among the major causes of gastrointestinal infections in humans. Determining the numbers of these pathogens at various stages of the food supply chain is critical to the validation of steps designed to produce safer food. In the current study, duplex real time PCR in the presence of SYBR Green was carried out with DNA extracted from pure cultures of the two pathogens and from chicken meat samples spiked with them. The peak areas of derivative of dissociation curves (PADDC), obtained after 35 PCR cycles were calculated and plotted against known genome equivalents (GEs) in a standard curve. The method provided an estimation for the number of GEs in a 25 μL PCR sample when 102-105GEs were present, similar to those obtained with duplex qPCR based on TaqMan probes by other authors, but with reduced costs