A survey of the ecological variability within 52 populations of Schoenoplectus californicus (C.A. Mey.) Soják across its distributional range revealed that it is commonly found in nitrogen (N) ...limited areas, but rarely in phosphorus limited soils. We explored the hypothesis that S. californicus supplements its nitrogen demand by bacterial N2-fixation processes associated with its roots and rhizomes. We estimated N2-fixation of diazotrophs associated with plant rhizomes and roots from several locations throughout the species' range and conducted an experiment growing plants in zero, low, and high N additions. Nitrogenase activity in rhizomes and roots was measured using the acetylene reduction assay. The presence of diazotrophs was verified by the detection of the nifH gene. Nitrogenase activity was restricted to rhizomes and roots and it was two orders of magnitude higher in the latter plant organs (81 and 2032 nmol C2H4 g DW-1 d-1, respectively). Correspondingly, 40x more nifH gene copies were found on roots compared to rhizomes. The proportion of the nifH gene copies in total bacterial DNA was positively correlated with the nitrogenase activity. In the experiment, the contribution of fixed N to the plant N content ranged from 13.8% to 32.5% among clones from different locations. These are relatively high values for a non-cultivated plant and justify future research on the link between N-fixing bacteria and S. californicus production.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Utricularia are rootless aquatic carnivorous plants which have recently attracted the attention of researchers due to the peculiarities of their miniaturized genomes. Here, we focus on a novel aspect ...of Utricularia ecophysiology-the interactions with and within the complex communities of microorganisms colonizing their traps and external surfaces.
Bacteria, fungi, algae, and protozoa inhabit the miniature ecosystem of the Utricularia trap lumen and are involved in the regeneration of nutrients from complex organic matter. By combining molecular methods, microscopy, and other approaches to assess the trap-associated microbial community structure, diversity, function, as well as the nutrient turn-over potential of bacterivory, we gained insight into the nutrient acquisition strategies of the Utricularia hosts.
We conclude that Utricularia traps can, in terms of their ecophysiological function, be compared to microbial cultivators or farms, which center around complex microbial consortia acting synergistically to convert complex organic matter, often of algal origin, into a source of utilizable nutrients for the plants.
Is Biomass a Reliable Estimate of Plant Fitness? Younginger, Brett S; Sirová, Dagmara; Cruzan, Mitchell B ...
Applications in plant sciences,
2017-February, February 2017, 2017-Feb, 2017-02-00, 20170201, Letnik:
5, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The measurement of fitness is critical to biological research. Although the determination of fitness for some organisms may be relatively straightforward under controlled conditions, it is often a ...difficult or nearly impossible task in nature. Plants are no exception. The potential for long-distance pollen dispersal, likelihood of multiple reproductive events per inflorescence, varying degrees of reproductive growth in perennials, and asexual reproduction all confound accurate fitness measurements. For these reasons, biomass is frequently used as a proxy for plant fitness. However, the suitability of indirect fitness measurements such as plant size is rarely evaluated. This review outlines the important associations between plant performance, fecundity, and fitness. We make a case for the reliability of biomass as an estimate of fitness when comparing conspecifics of the same age class. We reviewed 170 studies on plant fitness and discuss the metrics commonly employed for fitness estimations. We find that biomass or growth rate are frequently used and often positively associated with fecundity, which in turn suggests greater overall fitness. Our results support the utility of biomass as an appropriate surrogate for fitness under many circumstances, and suggest that additional fitness measures should be reported along with biomass or growth rate whenever possible.
Despite rapid progress in plant–microbe interaction research within terrestrial environments, our knowledge of aquatic plant and macroalgae microbiome structure, function, and ecology remains scarce, ...even though these hosts are key players in structuring the lacustrine environments. Here, we used the co-occurring, fast-growing hosts
Hydrilla verticillata
(Hydrocharitaceae) and
Cladophora
spp. (Chlorophyta), which dominate the littoral zones of a nitrogen-limited, hard-water lake, Lake Atitlán (Guatemala). The aim of this study was: (1) to assess the structure of
Hydrilla
phyllosphere-associated and
Cladophora
filament-associated bacterial and fungal assemblages in the context of host specificity; (2) to predict microbial potential to contribute to biogeochemical cycling in the lake littoral; and (3) to compare the aquatic microbiome structure to available datasets from terrestrial ecosystems, using next-generation amplicon sequencing, co-occurrence network analysis, and N
2
-fixation activity measurements. We show that the microbiomes associated with the phyllosphere of aquatic macrophytes and macroalgal filaments are surprisingly similar, with taxonomic and functional complexity analogous to that of rhizospheric assemblages in terrestrial plants, and have a potential to efficiently recycle nutrients from organic matter. We suggest that especially the fungal associations with these hosts represent an untapped research area of microbial ecology that warrants further attention.
Summary
Heterotrophic nanoflagellates (HNF) and ciliates are major protistan planktonic bacterivores. The term HNF, however, describes a functional guild only and, in contrast to the morphologically ...distinguishable ciliates, does not reflect the phylogenetic diversity of flagellates in aquatic ecosystems. Associating a function with taxonomic affiliation of key flagellate taxa is currently a major task in microbial ecology. We investigated seasonal changes in the HNF and ciliate community composition as well as taxa‐specific bacterivory in four hypertrophic freshwater lakes. Taxa‐specific catalyzed reporter deposition‐fluorescence in situ hybridization probes assigned taxonomic affiliations to 51%–96% (average ±SD, 75 ± 14%) of total HNF. Ingestion rates of fluorescently labelled bacteria unveiled that HNF contributed to total protist‐induced bacterial mortality rates more (56%) than ciliates (44%). Surprisingly, major HNF bacterivores were aplastidic cryptophytes and their Cry1 lineage, comprising on average 53% and 24% of total HNF abundance and 67% and 21% of total HNF bacterivory respectively. Kinetoplastea were important consumers of bacteria during summer phytoplankton blooms, reaching 38% of total HNF. Katablepharidacea (7.5% of total HNF) comprised mainly omnivores, with changing contributions of bacterivorous and algivorous phylotypes. Our results show that aplastidic cryptophytes, accompanied by small omnivorous ciliate genera Halteria/Pelagohalteria, are the major protistan bacterivores in hypertrophic freshwaters.
Foliar endophytic bacteria and fungi are increasingly being recognized as important drivers of plant host phenotype—affecting a wide range of eco‐physiological processes. However, we are still ...lacking fundamental ecosystem‐level knowledge about the structure, function and inter‐species interactions in endophytic assemblages associated with plant hosts sharing a common life strategy or ecological specialization.
In this study, we chose two groups of plants with contrasting physiology as model systems: parasites and their hosts. We assessed whether plant life‐history strategy, namely differences in nutrient acquisition and accumulation, plays a role in structuring above‐ground microbiomes under field conditions.
We focused on the structure, colonization extent and potential function of foliar endophytic bacteria and fungi in three root hemiparasitic species (Orobanchaceae), one stem holoparasite (Convolvulaceae), and their potential host plants co‐occurring in species‐rich temperate grassland ecosystems. For this purpose, we combined next generation amplicon sequencing with quantitative real‐time PCR, chemical analyses of leaf tissue, and, in the case of bacteria, functional predictions using information deposited in available databases.
We found the foliar endophytic assemblages to be diverse, dominated by generalist taxa, but highly similar across all studied species. Despite of the highly contrasting leaf tissue chemistry in the parasitic and non‐parasitic plant species, the parasitic trophic mode did not induce systematic shifts in the diversity, composition or predicted biogeochemical function of the endophytic microbiomes under field conditions. However, compared to their potential hosts, leaves of both hemiparasitic and holoparasitic species harboured significantly lower fungal counts, estimated as ß‐actin gene copies ng DNA−1, which suggests that parasitic plants may possess mechanisms to regulate the extent of colonization by endophytic fungi.
A free Plain Language Summary can be found within the Supporting Information of this article.
Resumo
Bactérias e fungos endofíticos foliares são cada vez mais reconhecidos como importantes agentes ambientais para o fenótipo das plantas hospedeiras, afetando uma gama de processos ecofisiológicos. Contudo, ainda há uma lacuna no conhecimento ecossistêmico sobre a estrutura, função e interações interespecíficas das comunidades endofíticas e suas plantas hospedeiras que compartilham uma estratégia de vida comum ou uma especialização ecológica.
Nesse estudo dois grupos de plantas com fisiologias distintas foram escolhidas como modelo: plantas parasitas e seus hospedeiros. Nós avaliamos o quanto a estratégia de vida, sobretudo diferenças na aquisição e acumulação de nutrientes, desempenha um papel na estrutura dos microbiomas endofíticos foliares sob condições naturais.
Nós focamos na estrutura, colonização e potenciais funções ecológicas de batérias e fungos endofíticos foliares em três espécies de plantas hemiparasitas de raízes (Orobanchaceae), uma holoparasita de caule (Convolvulaceae), e seus prováveis hospedeiros co‐ocorrendo em ecossistemas de pradarias temperadas com grande diversidade biológica. Para isso, nós usamos sequenciamento de nova geração, PCR em tempo real, análises químicas dos tecidos foliares e, em particular para bactérias, o perfil funcional baseado em informações disponíveis em banco de dado.
Nós encontramos uma diversa comunidade endofítica foliar, dominada por táxons generalistas, mas muito similares em todas as espécies de plantas estudadas. Apesar do contraste na composição química foliar entre as plantas parasitas e não‐parasitas, o perfil trófico das plantas parasitas não induziu mudanças sistemáticas na diversidade, composição e potenciais funções biogeoquímicas dos microbiomas endofíticos em condições naturais. No entanto, as folhas de espécies hemiparasitas e holoparasitas, comparadas com seus potenciais hospedeiros, possuíam uma quantidade de fungos significativamente menor, estimada pelo número de cópias do gene ß‐actina por ng de DNA, o qual sugere que as plantas parasitas possuem um mecanismo para regular a colonização de fungos endofíticos.
A free Plain Language Summary can be found within the Supporting Information of this article.
The genus Tetrahymena (Ciliophora, Oligohymenophorea) probably represents the best studied ciliate genus. At present, more than forty species have been described. All are colorless, i.e. they do not ...harbor symbiotic algae, and as aerobes they need at least microaerobic habitats. Here, we present the morphological and molecular description of the first green representative, Tetrahymena utriculariae n. sp., living in symbiosis with endosymbiotic algae identified as Micractinium sp. (Chlorophyta). The full life cycle of the ciliate species is documented, including trophonts and theronts, conjugating cells, resting cysts and dividers. This species has been discovered in an exotic habitat, namely in traps of the carnivorous aquatic plant Utricularia reflexa (originating from Okavango Delta, Botswana). Green ciliates live as commensals of the plant in this anoxic habitat. Ciliates are bacterivorous, however, symbiosis with algae is needed to satisfy cell metabolism but also to gain oxygen from symbionts. When ciliates are cultivated outside their natural habitat under aerobic conditions and fed with saturating bacterial food, they gradually become aposymbiotic. Based on phylogenetic analyses of 18S rRNA and mitochondrial cox1 genes T. utriculariae forms a sister group to Tetrahymena thermophila.
A survey of the ecological variability within 52 populations of Schoenoplectus californicus (C.A. Mey.) Soj#225;k across its distributional range revealed that it is commonly found in nitrogen (N) ...limited areas, but rarely in phosphorus limited soils. We explored the hypothesis that S. californicus supplements its nitrogen demand by bacterial N.sub.2 -fixation processes associated with its roots and rhizomes. We estimated N.sub.2 -fixation of diazotrophs associated with plant rhizomes and roots from several locations throughout the species' range and conducted an experiment growing plants in zero, low, and high N additions. Nitrogenase activity in rhizomes and roots was measured using the acetylene reduction assay. The presence of diazotrophs was verified by the detection of the nifH gene. Nitrogenase activity was restricted to rhizomes and roots and it was two orders of magnitude higher in the latter plant organs (81 and 2032 nmol C.sub.2 H.sub.4 g DW.sup.-1 d.sup.-1, respectively). Correspondingly, 40x more nifH gene copies were found on roots compared to rhizomes. The proportion of the nifH gene copies in total bacterial DNA was positively correlated with the nitrogenase activity. In the experiment, the contribution of fixed N to the plant N content ranged from 13.8% to 32.5% among clones from different locations. These are relatively high values for a non-cultivated plant and justify future research on the link between N-fixing bacteria and S. californicus production.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We used oligotrophic, P-limited herbaceous wetlands of northern Belize as a model system, on which to document and explain how changes in nutrient content along a salinity gradient affect activities ...of extracellular enzymes involved in macrophyte decomposition. To determine what is more important for decomposition, the initial litter quality, or site differences, we used reciprocal litter placement in a combined “site quality” and “litter quality” experiment running from August 2003 to April 2004. The experiment was set up in long-term control and nutrient addition plots (P, N, and NP) established in 2001 in 15 limestone-based inland marshes with a wide range of water conductivities (200–6000
μS) and a uniform pH (7.0–7.7) dominated by emergent macrophytes,
Eleocharis spp. There were no differences among the plots in total sediment N and water NH
4–N, but total and KCl-extractable sediment P and water PO
4–P were significantly higher in P and NP plots throughout the duration of the experiment. The initial litter N content was slightly but significantly different between control and N plots versus P and NP plots (5.7 and 7.1
mg
g
−1, respectively). The difference was much bigger for litter P content, 0.1 and 0.7
mg
g
−1, respectively. Enzyme activities of alkaline phosphatase, leucine-aminopeptidase, arylsulfatase, and
β-glucosidase were measured fluorometrically in
Eleocharis litter in both the litterbag experiment and the naturally decomposing material. Total phospholipid fatty acid (PLFA) content in litter samples was used as a measure of microbial biomass present. Phosphatase always exhibited the highest activity of the enzymes studied, followed by leucine-aminopeptidase, arylsulfatase and
β-glucosidase. There were no significant differences between enzyme activities from litterbags and the unconfined litter. Phosphatase activity was significantly suppressed in P-addition plots under all salinity levels while the activities of the remaining enzymes were significantly higher in P-enriched plots. There was a strong correlation between decomposition coefficient
k-values and most of the enzymes as well as between the amount of PLFA and enzyme activities. PLFA, arylsulfatase, and litter C/P were the best predictors of
k-values.
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