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.

Isolation and screening of new fungal strains from extreme and understudied environments, such as caves, is a promising approach to find higher yields enzyme producers. Cellulolytic fungal strains isolated from a Brazilian cave were evaluated for their enzymatic production after submerged (SmF) and solid-state fermentation (SSF). After SmF, three strains were selected for their high enzymatic activities: Aspergillus ustus for endoglucanase (4.76 U/mg), Talaromyces bruneus for β-glucosidase (11.71 U/mg) and Aspergillus sp. (CBMAI 1926) for total cellulase (1.70 U/mg). After SSF, these strains, showed better yields compared to the reference strain Aspergillus niger 3T5B8. Aspergillus sp. (CBMAI 1926) stood out as a new species that expressed activity of total cellulases (0.10 U/mg) and low protein concentration (0.44 mg/mL). In conclusion, these isolated strains have a more efficient and promising cellulolytic enzyme complex that can be used in fermentation and saccharification processes with a lower protein concentration and a higher enzymatic activity than the reference strain. Therefore, beside the new genetic material characterized, our study highlights the benefits of cave extreme environments exploitation to find new potentially valuable strains.

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.

Orchid mycorrhizal fungi (OMF) from the rhizoctonia aggregate are generally considered to be soil saprotrophs, but their ability to utilize various nutrient sources has been studied in a limited number of isolates cultivated predominantly in liquid media, although rhizoctonia typically grow on the surface of solid substrates. Nine isolates representing the key OMF families (Ceratobasidiaceae, Tulasnellaceae and Serendipitaceae), sampled in Southern France and the Czech Republic, were tested for their ability to utilize carbon (C), nitrogen (N) and phosphorus (P) sources in vitro in both liquid and solid media. The isolates showed significant inter- and intra-familiar variability in nutrient utilization, most notably in N sources. Isolates produced generally larger amounts of dry biomass on solid medium than in liquid one, but some isolates showed no or limited biomass production on solid medium with particular nutrient sources. The largest amount of biomass was produced by isolates from the family Ceratobasidiaceae on most sources in both medium types. The biomass production of Tulasnellaceae isolates was affected by their phylogenetic relatedness on all sources and medium types. The ability of isolates to utilize particular nutrients in a liquid medium but not a solid one should be considered when optimizing solid media for symbiotic orchid seed germination and in understanding of OMF functional traits under in situ conditions.

Premise: Despite the high functional importance of endophytes, we still have limited understanding of the biotic and abiotic factors that influence colonization of plant hosts along major ecological gradients and lack quantitative estimates of their colonization extent. In this study, we hypothesized that the developmental stage of the ecosystem will affect the levels of bacterial and fungal endophytic assemblages in the foliar endosphere.Methods: We quantified levels of bacterial and fungal endophytes in leaves of four plant hosts at four stages of vegetation succession using an optimized qPCR protocol with bacteria‐specific 16S and fungi‐targeting primers.Results: (1) The ecosystem developmental stage did not have a significant effect on the colonization levels of bacterial or fungal endophytes. (2) Colonization levels by bacterial and fungal endophytes were governed by different mechanisms. (3) Endophytic colonization levels and their relationship to foliar tissue stoichiometry were highly host specific.Conclusions: Quantifying colonization levels is important in the study of endophytic ecology, and the fast, relatively low‐cost qPCR‐based method can supply useful ecological information, which can significantly enhance the interpretation potential of descriptive data generated, for example, by next‐generation sequencing.