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.
Few studies have evaluated the trophic level in tropical caves, and none related the microbial biomass dynamics in the immobilization of carbon and nitrogen. Here, four tropical caves of Terra Ronca ...State Park, Brazil, were studied: Angélica, São Bernardo, Terra Ronca I, and Terra Ronca II caves. Physical, chemical, and microbiological parameters (microbial biomass and respiration) were estimated in the dry and wet seasons. São Bernardo, Terra Ronca I, and Terra Ronca II caves presented higher nitrogen and microbial biomass nitrogen (MBN) values in the wet season than in the dry season. On the other hand, the Angélica cave showed larger amounts of nitrogen and lower MBN values in the dry season. These results indicate that caves can be adjusted in two ecological theories known as “stoichiometric decomposition” and “microbial nitrogen mining”—to the effects of nutrient availability on organic matter decomposition. The caves studied showed different environmental dynamics in relation to organic matter decomposition, which allows them to be considered unique and possess specific characteristics. Microbial biomass dynamics can be an important parameter to evaluate the availability of nutrients and ecological dynamics of the trophic network in subterranean environments.
Microbial biomass shows different decomposition patterns among tropical caves, which could be interpreted by two theories: stoichiometric decomposition and microbial nitrogen mining. Our results indicate that nutrient flow and ecological dynamics, such as microbial parameters related to decomposition processes, cannot be generalized to all subterranean environments.
Many orchid species are endangered due to anthropogenic pressures such as habitat destruction and overharvesting, meanwhile, all orchids rely on orchid mycorrhizal fungi (OMF) for seed germination ...and seedling growth. Therefore, a better understanding of this intimate association is crucial for orchid conservation. Isolation and identification of OMF remain challenging as many fungi are unculturable. In our study, we tested the efficiency of both culture-dependent and culture-independent methods to describe OMF diversity in multiple temperate orchids and assessed any phylogenetic patterns in cultivability. The culture-dependent method involved the cultivation and identification of single pelotons (intracellular hyphal coils), while the culture-independent method used next-generation sequencing (NGS) to identify root-associated fungal communities. We found that most orchid species were associated with multiple fungi, and the orchid host had a greater impact than locality on the variability in fungal communities. The culture-independent method revealed greater fungal diversity than the culture-dependent one, but despite the lower detection, the isolated fungal strains were the most abundant OMF in adult roots. Additionally, the abundance of NGS reads of cultured OTUs was correlated with the extent of mycorrhizal root colonization in orchid plants. Finally, this limited-scale study tentatively suggests that the cultivability character of OMF may be randomly distributed along the phylogenetic trees of the rhizoctonian families.
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.
Subterranean environments are oligotrophic. However, few studies have investigated the composition and function of their terrestrial mycobiota. This study examined the functional role of filamentous ...cave fungi in cellulose degradation. soil samples and dry sediment were collected in the surface epigean environment and two sites in the entrance and twilight zones inside Gruta do Catao in the Sao Desiderio karst area, state of Bahia, Brazil. Fungi were cultured from the samples, and the total organic carbon, culturable microorganisms, and carbon and nitrogen microbial biomasses were estimated. All fungal strains were evaluated for cellulase production in carboxymethylcellulose synthetic medium, and the enzymatic indices were estimated. We observed a significant difference (p < 0.05) in physical, chemical, and biological parameters between epigean soil and cave sediments by Tukey's test. We recovered a total of 20 isolates comprising the genera Aspergillus (50.0%), Pénicillium (25.0%), Talaromyces (10.0%), Trichoderma (5.0%), Purpureocillium (5.0%) and Scopulariopsis (5.0%). The majority of the isolates (90%) showed cellulolytic activity, which is a higher percentage compared to that normally reported in the literature for sediments. Thus there is a high probability that the filamentous fungi act in nutrient cycling, thereby contributing to the quality and maintenance of the cave ecosystem. These results indicate that parameters such as total organic carbon, biomass, and relative humidity that tend to differ between caves and epigean environments, provide selective pressures for microorganisms that use alternative sources of energy and nutrients.
We identified Basidiobolus fungi on geophilomorphan centipedes (Chilopoda) from caves of Southeast Brazil. Twelve specimens of centipedes of the family Geophilidae were examined, and two of them ...carried the secondary capilliconidia of Basidiobolus on their exoskeleton. The fungus uses the surface of the exoskeleton as a support for the asexual reproductive structure. In this manner, the host is used for the purpose of dispersing its spores. This study expands current knowledge of the diversity of arthropods used as host for the fungus, and in particular for Basidiobolus, living in cave habitats.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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.
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Previous issue date: 2014-02-11
Financiadora de ...Estudos e Projetos
The cave environments are oligotrophic and have specific characteristics that determine the native microbiota. Few studies have investigated the composition and function of soil microbiota of subterranean environments. This study aimed to expand the knowledge on the cave microbiota, discuss the functional role of the microbiota in these environments, isolate and select fungal strains with biotechnological potential for the degradation of cellulose. Soil epigean environment and two poins inside the cave Catão, São Desiderio BA, were sampled. The amount of total organic carbon, carbon and nitrogen in the microbial biomass and the microbial density was evaluated in the soil. All strains were evaluated for the activities of endoglucanase, β-glucosidase and total cellulase by submerged fermentation. Of these three strains of Aspergillus strains, one strain standard, and a Penicillium the process of solid state fermentation using wheat bran as substrate were selected. We observed a significant difference between epigeal and subterranean environment in relation to physical, chemical and biological soil parameters evaluated. We obtained 20 isolates belonging of the genus Aspergillus (SDC1.1, SDC 1.2, SDC 1.4, SDC 1.6, SDC 2.4, SDC 2.6, SDC 2.8, SDC 2.10, SDC 2.11, SDC 2.12), Penicillium (SDC 1.3, SDC 1.7, SDC 2.2, SDC 2.7, SDC2.9, SDC 2.13), Trichoderma (SDC 2.3), Scopulariopses (SDC 2.1) e Purpureocillium (SDC 2.5). Of all isolates showed 90% cellulolytic activity. During the submerged fermentation endoglucanase activity showed maximum values of 6.39 IU/mL in a strain of Aspergillus sp6 and maximum total cellulase activity was 1.7 IU/ml for Aspergillus sp8 strain. The strain Aspergillus sp6 showed maximum β- glucosidase activity of 13.67 IU/mL. Compared to solid-state fermentation, the Aspergillus sp6 and Aspergillus sp8 strains stood out compared to mutant strain Aspergillus niger 3T5B8, with values of endoglucanase and total cellulase activity higher whole with a lower protein content in their enzymatic extracts. From these resulados, we conclude that the cave environment presents singularities compared to epigean environment which probably allows you to select naturally microorganisms that use alternative sources for energy and nutrients.
Os ambientes cavernícolas são oligotróficos e possuem características específicas que determinam a microbiota local. Poucos estudos têm investigado a composição e funcionalidade da microbiota edáfica de ambientes subterrâneos. Este trabalho teve como objetivo ampliar o conhecimento sobre a microbiota cavernícola, discutir o papel funcional da microbiota nesses ambientes, isolar e selecionar linhagens fúngicas com potencial biotecnológico para a degradação de celulose. Foram coletadas amostras de solo do meio epígeo e de dois pontos no interior da caverna do Catão, São Desidério-BA. Nas amostras foram avaliadas as quantidades de carbono orgânico total, a densidade microbiana, carbono e nitrogênio da biomassa microbiana, bem como isoladas linhagens de fungos filamentosos. Todas as linhagens foram avaliadas quanto as atividades de endoglucanase, celulase total e β-glucosidases por meio de fermentação submersa. Dessas linhagens foram selecioandas três linhagens de Aspergillus, sendo uma linhagem padrão, e uma linhagem de Penicillium para o processo de fermentação em estado sólido, utilizando farelo de trigo como substrato. Observamos uma diferença significativa entre o meio epígeo e subterrâneo em relação aos parâmetros físicos, químicos e biológicos do solo avaliados. Obtivemos 20 isolados pertencentes aos gêneros Aspergillus (SDC1.1, SDC 1.2, SDC 1.4, SDC 1.6, SDC 2.4, SDC 2.6, SDC 2.8, SDC 2.10, SDC 2.11, SDC 2.12), Penicillium (SDC 1.3, SDC 1.7, SDC 2.2, SDC 2.7, SDC2.9, SDC 2.13), Trichoderma (SDC 2.3), Scopulariopses (SDC 2.1) e Purpureocillium (SDC 2.5). De todos os isolados 90% apresentaram atividade celulolítica. Durante a fermentação submersa a atividade endoglucanase apresentou valores máximos de 6,39 IU/mL em uma linhagem de Aspergillus sp6 e a atividade máxima de celulase total foi de 1,7 IU/mL para uma linhagem Aspergillus sp8. A linhagem Aspergillus sp6 apresentou atividade β-glucosidase máxima de 13,67 IU/mL. Em relação a fermentação em estado sólido, as linhagens Aspergillus sp6 e Aspergillus sp8 se destacaram em relação a linhagem padrão Aspergillus niger 3T5B8, com valores de atividade endoglucanase e celulase total superiores e com um menor conteúdo proteico em seus extratos enzimáticos. A partir desses resultados, concluímos que o ambiente cavernícola apresenta singularidades em relação ao meio epígeo e que provavelmente permite selecionar naturalmente microrganismos que utilizam fontes alternativas para obtenção de energia e nutrientes.
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