Vanessa Nessner Kavamura

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 β-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.

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.

Analysis of bacterial composition in marine sponges reveals the influence of host phylogeny and environment

ABSTRACT Bacterial communities associated with sponges are influenced by environmental factors; however, some degree of genetic influence of the host on the microbiome is also expected. In this work, 16S rRNA gene amplicon sequencing revealed diverse bacterial phylotypes based on the phylogenies of three tropical sponges (Aplysina fulva, Aiolochroia crassa and Chondrosia collectrix). Despite their sympatric occurrence, the studied sponges presented different bacterial compositions that differed from those observed in seawater. However, lower dissimilarities in bacterial communities were observed within sponges from the same phylogenetic group. The relationships between operational taxonomic units (OTUs) recovered from the sponges and database sequences revealed associations among sequences from unrelated sponge species and sequences retrieved from diverse environmental samples. In addition, one Proteobacteria OTU retrieved from A. fulva was identical to sequences previously reported from A. fulva specimens collected along the Brazilian coast. Based on these results, we conclude that bacterial communities associated with marine sponges are shaped by host identity, while environmental conditions seem to be less important in shaping symbiont communities. This is the first study to assess bacterial communities associated with marine sponges in the remote St. Peter and St. Paul Archipelago using amplicon sequencing of the 16S rRNA gene. &NA; Graphical Abstract Figure. Linking sponge phylogeny to associated bacteria.

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.

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

ABSTRACT 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.

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.

The role of species turnover in structuring bacterial communities in a local scale in the cactus rhizosphere

Background and aimsCereus jamacaru is a native cactus in the semiarid biome caatinga able to withstand long periods of drought. Here, we studied the rhizosphere microbiome of this cactus to understand how precipitation affects the assembly of bacterial communities from the taxonomical and functional perspectives.MethodsWe selected three C. jamacaru plants in the caatinga biome, sampled the rhizosphere soil from the same plants during rainy and dry seasons and performed shotgun sequencing from total DNA isolated from rhizosphere using Ion Torrent technology.ResultsAcidobacteria, Actinobacteria and Proteobacteria showed increase in relative abundance during the rainy season when compared to dry season. Five major functional groups were significantly different, including differences in amino acids and derivatives, carbohydrates, protein metabolism, respiration, and RNA metabolism. Taxonomically, the assembly of bacterial communities follows a neutral model.ConclusionsThe assembly of bacterial communities in the rhizosphere of C. jamacaru is affected by precipitation resulting in different taxonomical and functional community patterns during dry and rainy seasons. We attribute these differences on rhizosphere communities composition to dispersal limitation of microorganisms caused by low pore connectivity due to low water content in the soil, which leads to spatially isolate communities during the dry season.

Diversity and Technological Aspects of Microorganisms from Semiarid Environments

Semiarid environments are characterized by the low water availability throughout the year. Hence, its microbial inhabitants are selected to be capable to withstand this stressful setting. This selection process acts both over the community, making it less abundant and phylogenetically diverse, and over each population by making necessary for it to express features that protect them from heat and desiccation. From a biotechnological perspective, these can be explored, and several bioproducts such as enzymes, inoculants, polysaccharides, and many others could be generated. This chapter will explore how this economic potential can be tamed and used to generate technology and improve the lives on the rural areas of such environments.

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

ABSTRACT 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.