The potato rhizosphere microbiota correlated to the yield of three different regions in Korea.

We examined potato rhizosphere bacterial and fungal communities across three regions: Cheongju, Pyeongchang, and Gangneung. These regions have varying soil and climate conditions, resulting in different yields. We found that precipitation was the main limiting factor in our study while soil physiochemical factors affect bacterial and fungal microbiota in correlation with yield. Both bacterial and fungal microbiota showed distinct patterns according to the regions. ASVs positively correlated with yield were predominantly found in the Pyeongchang region which also produced the highest yields, while ASVs negatively correlated with yield were associated with Gangneung where the lowest yields were observed. The greatest bacterial and fungal diversity was detected in Pyeongchang consisting of Propionibacteriales, Burkholderiales, and Vicinamibacteriales. Gangneung, on the other hand primarily belong to Sordariales, Mortierellales, Cystofilobasidiales, and Tremellales. The putative yield-negative ASVs detected in Gangneung may have been influenced by drought stress. This work has highlighted key bacterial and fungal taxa as well as core taxa that may potentially be associated with high and low yields of potato in relation to metadata which includes soil chemical and physical parameters as well as weather data. Taken together we suggest that this information can be used to assess site suitability for potato production.

Land Management and Microbial Seed Load Effect on Rhizosphere and Endosphere Bacterial Community Assembly in Wheat.

Microbial community ecology studies have traditionally utilized culture-based methodologies, though the advent of next-generation amplicon sequencing has facilitated superior resolution analyses of complex microbial communities. Here, we used culture-dependent and -independent approaches to explore the influence of land use as well as microbial seed load on bacterial community structure of the wheat rhizosphere and root endosphere. It was found that niche was an important factor in shaping the microbiome when using both methodological approaches, and that land use was also a discriminatory factor for the culture-independent-based method. Although culture-independent methods provide a higher resolution of analysis, it was found that in the rhizosphere, particular operational taxonomic units (OTUs) in the culture-dependent fraction were absent from the culture-independent fraction, indicating that deeper sequence analysis is required for this approach to be exhaustive. We also found that the microbial seed load defined the endosphere, but not rhizosphere, community structure for plants grown in soil which was not wheat adapted. Together, these findings increase our understanding of the importance of land management and microbial seed load in shaping the root microbiome of wheat and this knowledge will facilitate the exploitation of plant-microbe interactions for the development of novel microbial inoculants.

Higher phylogenetic diversity prevents loss of functional diversity caused by successive drying and rewetting cycles.

Microbial communities regulate nutrient cycling in soil, thus the impact of climate change on the structure and function of these communities can cause an imbalance of nutrients in the environment. Structural and functional changes of soil bacterial communities in two contrasting biomes in Brazil, the Atlantic Forest and the Tropical Dry Forest (Caatinga), were studied by simulating, in microcosms, rainfall and drought events. Soil samples were collected in three Brazilian states: Bahia, Pernambuco and São Paulo, in a total of four sampling sites. Analysis of 16S rRNA amplicon libraries revealed changes in microbial communities after three drying-rewetting cycles (60-30% water holding capacity). Alpha diversity indexes were obtained for bacterial communities, as well as the functional diversity index (Shannon) based on the activity of the following enzymes: acid and alkaline phosphatase, arylsulfatase, dehydrogenase, cellulase, amylase, urease and phytase. In general, the soils of Caatinga showed a decrease in the diversity indexes studied, conversely, however, the soils of Atlantic Forest were found to be more resistant during the drying-rewetting cycles. Functional diversity was significantly different for the two biomes, with a decrease in Caatinga soils, while Atlantic Forest samples demonstrated a greater stability of enzymatic activity. Further, the Atlantic Forest samples showed more resistance when compared to samples from Caatinga. The results found in this study have confirmed the hypothesis that biomes, independent of climate, when subjected to successive events of drought and rewetting exhibit structural and metabolic changes.

Draft Genome Sequence of Plant Growth-Promoting Drought-Tolerant Bacillus sp. Strain CMAA 1363 Isolated from the Brazilian Caatinga Biome.

The strain of Bacillus sp. CMAA 1363 was isolated from the Brazilian Caatinga biome and showed plant growth-promoting traits and ability to promote maize growth under drought stress. Sequencing revealed genes involved in stress response and plant growth promotion. These genomic features might aid in the protection of plants against the negative effects imposed by drought.

Dry Season Constrains Bacterial Phylogenetic Diversity in a Semi-Arid Rhizosphere System.

The rhizosphere is viewed as a deterministic environment led by the interaction between plants and microorganisms. In the case of semi-arid plants, this interaction is strengthened by the harshness of the environment. We tested the hypothesis that dry season represents a constraint on the bacterial diversity of the rhizosphere from semi-arid plants. To accomplish this, we sampled two leguminous species at five locations during the dry and rainy seasons in the Caatinga biome and characterised bacterial community structures using qPCR and 16S rRNA sequencing. We found that the main differences between seasons were due to reduced phylogenetic diversity caused by dryness. Variation partitioning indicated that environmental characteristics significant impacts in ß-diversity. Additionally, distance decay relationship and taxa area relationship indicate a higher spatial turnover at the rainy season. During the dry season, decreased bacterial abundance is likely due to the selection of resistant or resilient microorganisms; with the return of the rain, the sensitive populations start to colonise the rhizosphere by a process that is strongly influenced by environmental characteristics. Thus, we propose that the reduction of PD and strong influence of environmental parameters on the assemblage of these communities make them prone to functional losses caused by climatic disturbances.

Draft Genome Sequence of Bacillus sp. Strain CMAA 1185, a Cellullolytic Bacterium Isolated from Stain House Lake, Antarctic Peninsula.

The aim of this study was to report the genome sequence of the cellulolytic Bacillus sp. strain CMAA 1185, isolated from Stain House Lake, Antarctica.

Functional congruence of rhizosphere microbial communities associated to leguminous tree from Brazilian semiarid region.

Semiarid environments are characterized by the uneven spread of rain throughout the year. This leads to the establishment of a biota that can go through long periods without rain. In order to understand the dynamics of rhizosphere microbial communities across these contrasting seasons in Caatinga, we used the Ion Torrent platform to sequence the metagenome of the rhizosphere of a native leguminous plant (Mimosa tenuiflora). The annotation indicated that most abundant groups detected were the Actinobacteria and Proteobacteria, and the dominant functional groups were carbohydrate and protein metabolisms, and that in the wet season, the communities carried carbohydrate and amino acid metabolisms.The major differences observed between seasons were higher abundance of genes related to carbohydrate and amino acid metabolisms in the rainy season, indicating that the populations present might be better adapted to a higher abundance of organic matter. Besides, no clear separation of samples was detected based on their taxonomic composition whereas the functional composition indicates that samples from the rain season are more related. Altogether, our results indicate that there is al arge functional stability in these communities mostly due to the selection of features that aid the biota to endure the dry season and blossom during rain.

Effects of different osmolarities on bacterial biofilm formation.

Biofilm formation depends on several factors. The influence of different osmolarities on bacterial biofilm formation was studied. Two strains (Enterobacter sp. and Stenotrophomonas sp.) exhibited the most remarkable alterations. Biofilm formation is an important trait and its use has been associated to the protection of organisms against environmental stresses.

Effects of different osmolarities on bacterial biofilm formation

Biofilm formation depends on several factors. The influence of different osmolarities on bacterial biofilm formation was studied. Two strains (Enterobacter sp. and Stenotrophomonas sp.) exhibited the most remarkable alterations. Biofilm formation is an important trait and its use has been associated to the protection of organisms against environmental stresses.

Microbial community biogeographic patterns in the rhizosphere of two Brazilian semi-arid leguminous trees.

Arid environments are regular and well distributed over all continents and display drought characteristics whether full-time or seasonal. This study aims to characterize how the microbial communities of the rhizosphere of two leguminous trees from the Brazilian semi-arid biome the Caatinga are geographically and seasonally shaped, as well as the factors driving this variation. With that purpose, the soil rhizosphere from two leguminous trees (Mimosa tenuiflora and Piptadenia stipulacea (Benth.) Ducke) were sampled in two different seasons: rainy and drought at five different sites. Assessment of bacterial and archaeal communities occurred by T-RFLP analysis of 16S rRNA and archaeal amoA genes. By these means, it was observed that the seasons (wet and dry periods) are the factors that most influence the composition of the microbial community from both analyzed plants, except for the results obtained from the CCA applied to Archaeas. Furthermore, soil physical-chemical factors also had a significant influence on the community and indicated a geographical pattern of the bacterial community. It was not possible to observe significant modifications in the composition in relation to the plant species. We have seen that soil characteristics and rainfall were the factors that most influenced the microbial composition. Also, the bacterial community had a significant correlation with soil characteristics that indicates that these rhizosphere communities might be selected by environmental characteristics. Furthermore, the data suggest that climate plays a key role in structuring the microbial community of this biome.

Screening of Brazilian cacti rhizobacteria for plant growth promotion under drought.

Drought is one of the major problems worldwide. The search for new and efficient microorganisms, from unexplored environments, to be used in association with plants to alleviate the negative effects imposed by water stress, is an interesting alternative. Thus, cacti-associated bacteria from the Brazilian semi-arid region were isolated based on their ability to grow in medium with reduced water availability. Strains were tested for the production of exopolysaccharides (EPS), as well as in vitro plant growth promotion traits. A great proportion of the isolates belong to the genus Bacillus. From a total of forty-eight bacteria, 65% were able to grow in medium with reduced water availability (0.919Aw), exopolysaccharide production was observed for 65% of the strains. The production of indole acetic acid (IAA) exceeding 51µgmL(-1) was observed for 4% and the high solubilization of Ca-P was verified for 6% of the isolates. No strain was able to produce hydrogen cyanide (HCN), 71% produced ammonia and 79% showed a halo of carboxymethyl cellulose (CMC) degradation. Zea mays L. growth promotion under water stress (30% of field capacity) was achieved by two strains of Bacillus spp. This is the first report to describe cacti-associated bacteria from Brazilian semi-arid with plant growth-promoting abilities.

Biotechnological strategies applied to the decontamination of soils polluted with heavy metals.

Soils have been submitted to several contaminants that vary in concentration and composition. Heavy metals can be widely spread and accumulated in those environments due to some inappropriate actions. In this present review some remediation techniques to remediate soils are presented, focusing on the use of plants that are capable of surviving in soils with heavy metals along with the function of some microorganisms in the restoration process.