Tank bromeliad water: similar or distinct environments for research of bacterial bioactives?

Tank formation transforms nitrogen metabolism of an epiphytic bromeliad and its phyllosphere bacteria

PREMISE

Up to half of tropical forest plant species grow on other plants. Lacking access to soils, vascular epiphytes have unique adaptations for mineral nutrition. Among the most distinctive is the tank growth form of certain large bromeliads, which absorb nutrients that are cycled by complex microbial communities in water trapped among their overlapping leaf bases. However, tanks form only after years of growth by juvenile plants, which must acquire nutrients differently. Understanding how nutrient dynamics change during tank bromeliad development can provide key insights into the role of microorganisms in the maintenance of tropical forest biodiversity.

METHODS

We evaluated variations in plant morphology, growth, foliar nitrogen physiology, and phyllosphere bacterial communities along a size gradient spanning the transition to tank formation in the threatened species Tillandsia utriculata.

RESULTS

Sequential morphological and growth phases coincided with the transition to tank formation when the longest leaf on plants was between 14 and 19 cm. Before this point, foliar ammonium concentrations were very high, but after, leaf segments absorbed significantly more nitrate. Leaf-surface bacterial communities tracked ontogenetic changes in plant morphology and nitrogen metabolism, with less-diverse communities in tankless plants distinguished by a high proportion of taxa implicated in ureolysis, nitrogen fixation, and methanotrophy, whereas nitrate reduction characterized communities on individuals that could form a tank.

CONCLUSIONS

Coupled changes in plant morphology, physiology, and microbiome function facilitate the transition between alternative nutritional modes in tank bromeliads. Comparing bromeliads across life stages and habitats may illuminate how nitrogen-use varies across scales.

Diversity and putative metabolic function of prokaryotic communities in tank bromeliads along an elevation gradient in tropical Mexico

Tank bromeliads are unique canopy microhabitats that offer freshwater and organic nutrient-rich substrates in the Neotropics. In them it is possible to thoroughly characterize environmental factors and species composition of terrestrial and aquatic biota. Therefore, these plants have been used as natural models to study how communities are distributed and assembled. Here we used amplicon sequencing of the 16S rRNA gene and their functional annotations to study the diversity and metabolic potential of prokaryotic communities in tank bromeliads in five different forests along an elevation gradient in tropical Mexico. Furthermore, we analyzed the effects of vegetation type and environmental factors inside the tanks on prokaryotic composition. We found a high prokaryotic diversity in tank bromeliads along the elevation gradient. Prokaryotes commonly observed in acidic environments rich in organic carbon, and the potential pathogen Pasteurella multocida, were present in all samples, but few amplicon sequence variants were shared between forests. The prokaryotic composition was affected by forest type, and comparisons against null models suggest that it was shaped by non-neutral processes. Furthermore, prokaryotic community changes significantly covaried with tank water temperature, pH, and inorganic carbon. We found a high diversity of putative metabolic groups dominated by chemoheterotrophs and fermenters, but taxonomic groups involved in nitrogen and sulfur cycling were also present in all samples. These results suggest that tank bromeliads promote taxonomic and metabolic diversity of the prokaryotic community at a local and regional scale and play an important role in the biogeochemistry of forest canopies in the Neotropics.

Selective Bacterial Community Enrichment between the Pitcher Plants Sarracenia minor and Sarracenia flava

The interconnected and overlapping habitats present in natural ecosystems remain a challenge in determining the forces driving microbial community composition. The cuplike leaf structures of some carnivorous plants, including those of the family Sarraceniaceae, are self-contained ecological habitats that represent systems for exploring such microbial ecology questions. We investigated whether Sarracenia minor and Sarracenia flava cultivate distinct bacterial communities when sampled at the same geographic location and time. This sampling strategy eliminates many abiotic environmental variables present in other studies that compare samples harvested over time, and it could reveal biotic factors driving the selection of microbes. DNA extracted from the decomposing detritus trapped in each Sarracenia leaf pitcher was profiled using 16S rRNA amplicon sequencing. We identified a surprising amount of bacterial diversity within each pitcher, but we also discovered bacteria whose abundance was specifically enriched in one of the two Sarracenia species. These differences in bacterial community representation suggest some biotic influence of the Sarracenia plant on the bacterial composition of their pitchers. Overall, our results suggest that bacterial selection due to factors other than geographic location, weather, or prey availability is occurring within the pitchers of these two closely related plant species. This indicates that specific characteristics of S. minor and S. flava may play a role in fostering distinct bacterial communities. These confined, naturally occurring microbial ecosystems within Sarracenia pitchers may provide model systems to answer important questions about the drivers of microbial community composition, succession, and response to environmental perturbations. IMPORTANCE This study uses amplicon sequencing to compare the bacterial communities of environmental samples from the detritus of the leaf cavities of Sarracenia minor and Sarracenia flava pitcher plants. We sampled the detritus at the same time and in the same geographic location, eliminating many environmental variables present in other comparative studies. This study revealed that different species of Sarracenia contain distinct bacterial members within their pitchers, suggesting that these communities are not randomly established based on environmental factors and the prey pool but are potentially enriched for by the plants' chemical or physical environment. This study of these naturally occurring, confined microbial ecosystems will help further establish carnivorous pitcher plants as a model system for answering important questions about the development and succession of microbial communities.

Evaluation of wood degradation rates by Teredinidae (Mollusca: Bivalvia) in two ecologically distinct areas, and temperature and salinity influences on the cellulolytic activity of associated bacteria

Teredinidae (shipworms) is a family of marine wood-boring bivalves that has an important role in the degradation of wood through its symbiotic relationship with cellulolytic bacteria. To evaluate the rate of degradation of wood by teredinids in two sites with different oceanographic conditions in Rio de Janeiro State, Brazil, artificial structures composed of pine wood sheets were immersed in the ocean for three months at Arraial do Cabo in an area under the influence of upwelling, and at Ilha Grande Bay under tropical and oligotrophic influences. After the immersion period, teredinids were removed from the collectors, identified, and counted. Wood consumption by the teredinids was quantified by comparing the dry weights of the collectors before and after immersion. Associated bacteria were isolated and their cellulolytic activities evaluated at different temperatures and salinities. Two Teredinidae species were recorded: Bankia gouldi and Lyrodus floridanus. The highest wood degradation rate and enzymatic activities of the isolated bacterial strains were recorded at Arraial do Cabo, suggesting that upwelling influenced the activities of those species.

Mangrove soil as a source for novel xylanase and amylase as determined by cultivation-dependent and cultivation-independent methods

Xylanase and α-amylase enzymes participate in the degradation of organic matter, acting in hemicellulose and starch mineralization, respectively, and are in high demand for industrial use. Mangroves represent a promising source for bioprospecting enzymes due to their unique characteristics, such as fluctuations in oxic/anoxic conditions and salinity. In this context, the present work aimed to bioprospect xylanases from mangrove soil using cultivation-dependent and cultivation-independent methods. Through screening from a metagenomic library, three potentially xylanolytic clones were obtained and sequenced, and reads were assembled into contigs and annotated. The contig MgrBr135 was affiliated with the Planctomycetaceae family and was one of 30 ORFs selected for subcloning that demonstrated only amylase activity. Through the cultivation method, 38 bacterial isolates with xylanolytic activity were isolated. Isolate 11 showed an enzymatic index of 10.9 using the plate assay method. Isolate 39 achieved an enzyme activity of 0.43 U/mL using the colorimetric method with 3,5-dinitrosalicylic acid. Isolate 39 produced xylanase on culture medium with salinity ranging from 1.25 to 5%. Partial 16S rRNA gene sequencing identified isolates in the Bacillus and Paenibacillus genera. The results of this study highlight the importance of mangroves as an enzyme source and show that bacterial groups can be used for starch and hemicellulose degradation.

Seasonal Physiological Parameters and Phytotelmata Bacterial Diversity of Two Bromeliad Species (Aechmea gamosepala and Vriesea platynema) from the Atlantic Forest of Southern Brazil

The ecology of complex microhabitats remains poorly characterized in most tropical and subtropical biomes, and holds potential to help understand the structure and dynamics of different biodiversity components in these ecosystems. We assessed nutritional and metabolic parameters of two bromeliad species (Aechmea gamosepala and Vriesea platynema) at an Atlantic Forest site and used 16S rDNA metabarcoding to survey the microbial communities inhabiting their tanks. We observed that levels of some nutrients (e.g., nitrogen) varied across seasons consistently in both species, while others (e.g., phenolic compounds) presented considerable differences between the two bromeliads. In contrast, patterns of tank microbial diversity did not follow a similar temporal trend. There was extensive variation in microbial composition among samples, which included intra-specific differences but also some consistent differences between the two bromeliads. For example, Citrobacter, Klebsiella and Pantoea presented significantly different abundances in the two species. Interestingly, the dominant bacterial genera in both species included Pseudomonas and Enterobacter, which have been reported to include plant-beneficial species. Overall, our data contribute to the characterization of the nutritional status of Atlantic Forest bromeliads and the composition of their prokaryotic communities, laying the foundation for detailed investigations targeting the ecological interactions between these plants and their associated microbes.

Ecology and biotechnological potential of bacterial community from three marine sponges of the coast of Rio de Janeiro, Brazil

Marine sponges has been a large reservoir of microbial diversity, with the presence of many species specific populations as well as producing biologically active compounds, which has attracted great biotechnological interest. In order to verify the influence of the environment in the composition of the bacterial community present in marine sponges and biotechnological potential of bacteria isolated from these organisms, three species of sponges and the waters surrounding them were collected in different beaches of Rio de Janeiro, Brazil. The profile of the bacterial community present in sponges and water was obtained by PCR-DGGE technique and the biotechnological potential of the strains isolated by producing amylase, cellulase, protease and biosurfactants. The results showed that despite the influence of the environment in the composition of the microbial community, studied marine sponges shown to have specific bacterial populations, with some, showing potential in the production of substances of biotechnological applications.