Search Results (4)

A combined anaerobic–anoxic–oxic moving bed biofilm reactor (A²O-MBBR) constructed wetlands process was used to treat low carbon-to-nitrogen (C/N) simulated sewage. The results showed that the removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP) by this process were 94.06%, 94.40%, 67.11%, and 84.57%, respectively, and the concentrations of COD, NH₄⁺-N, TN, and TP in the effluent were lower than the Class I-A standard of GB18918-2002. In the anoxic zone, NH₄⁺-N had an inhibitory effect on phosphorus uptake via phosphorus-accumulating organisms (PAOs). The highest community diversity was observed in the anoxic zone sludge at 24 d. During the water-quality-shock loads stage, microbial community diversity decreased in a combined A²O-MBBR constructed wetlands reactor. At the phylum level, bacteria within the mature activated sludge were dominated by Proteobacteria, while Planctomycetes bacteria were the dominant species in the constructed wetlands. At the genus level, Tolumonas spp. were the dominant species in the 12 d and 24 d constructed wetlands and the anaerobic zone, with relative abundance percentages ranging from 20.24 to 33.91%. In the water-quality-shock loads stage, they were replaced by denitrifying bacteria such as Herbaspirillum spp. Unclassified_Burkholderiales was the dominant species in the constructed wetlands, with a relative abundance of 33.09%. Full article

Endophytic persistence of inoculated plant growth promoting bacteria (PGPB) involves interaction with the host plant and the host’s indigenous endophytic bacterial communities. This study investigated the persistence of Methylobacterium oryzae CBMB20 into the rice endosphere together with the impact of inoculation on the diversity and community structure of the root and shoot bacterial endophytes in Oryza sativa L. spp. indica cv. IR29. Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis of the root and shoot showed that M. oryzae CBMB20 was able to integrate and persist in the rice endosphere without causing drastic shifts in bacterial endophytic diversity and community composition. The bacterial communities in the root and shoot are very similar to the seeds of IR29, suggesting that most of them are seed-borne. The root endosphere bacterial communities of inoculated and uninoculated IR29 plants are more diverse compared to the shoots in terms of richness and diversity indices. The dominant bacterial T-RFs of the root endosphere of IR29 belong to Microbacterium, Delftia, Pseudomonas, Xanthomonas and Stenotrophomonas, Herbaspirillum, Enterobacter, and Sphingomonas, as observed in the three restriction enzyme T-RFLP profiles. Bacterial clades identified as Curtobacterium, Enterobacter, Stenotrophomonas, and Xanthomonas were distinctly observed in both the root and shoot communities, and these bacterial groups are also the dominant endophytes of the shoot endosphere. This study showed that Methylobacterium oryzae CBMB20 could persist and incorporate into the endophytic bacterial community of the endosphere without causing long-term antagonistic interactions with its host plant and with the native microbiota. Full article

Herbaspirillum seropedicae is an endophytic bacterium that can fix nitrogen and synthesize phytohormones, which can lead to a plant growth-promoting effect when used as a microbial inoculant. Studies focused on mechanisms of action are crucial for a better understanding of the bacteria-plant interaction and optimization of plant growth-promoting response. This work aims to understand the underlined mechanisms responsible for the early stimulatory growth effects of H. seropedicae inoculation in maize. To perform these studies, we combined transcriptomic and proteomic approaches with physiological analysis. The results obtained eight days after inoculation (d.a.i) showed increased root biomass (233 and 253%) and shoot biomass (249 and 264%), respectively, for the fresh and dry mass of maize-inoculated seedlings and increased green content and development. Omics data analysis, before a positive biostimulation phenotype (5 d.a.i.) revealed that inoculation increases N-uptake and N-assimilation machinery through differentially expressed nitrate transporters and amino acid pathways, as well carbon/nitrogen metabolism integration by the tricarboxylic acid cycle and the polyamine pathway. Additionally, phytohormone levels of root and shoot tissues increased in bacterium-inoculated-maize plants, leading to feedback regulation by the ubiquitin-proteasome system. The early biostimulatory effect of H. seropedicae partially results from hormonal modulation coupled with efficient nutrient uptake-assimilation and a boost in primary anabolic metabolism of carbon–nitrogen integrative pathways. Full article

The genus Herbaspirillum includes several strains isolated from different grasses. The identification of non-coding RNAs (ncRNAs) in the genus Herbaspirillum is an important stage studying the interaction of these molecules and the way they modulate physiological responses of different mechanisms, through RNA–RNA interaction or RNA–protein interaction. This interaction with their target occurs through the perfect pairing of short sequences (cis-encoded ncRNAs) or by the partial pairing of short sequences (trans-encoded ncRNAs). However, the companion Hfq can stabilize interactions in the trans-acting class. In addition, there are Riboswitches, located at the 5′ end of mRNA and less often at the 3′ end, which respond to environmental signals, high temperatures, or small binder molecules. Recently, CRISPR (clustered regularly interspaced palindromic repeats), in prokaryotes, have been described that consist of serial repeats of base sequences (spacer DNA) resulting from a previous exposure to exogenous plasmids or bacteriophages. We identified 285 ncRNAs in Herbaspirillum seropedicae (H. seropedicae) SmR1, expressed in different experimental conditions of RNA-seq material, classified as cis-encoded ncRNAs or trans-encoded ncRNAs and detected RNA riboswitch domains and CRISPR sequences. The results provide a better understanding of the participation of this type of RNA in the regulation of the metabolism of bacteria of the genus Herbaspirillum spp. Full article