Symbiosis

Bacterial-fungal interactions (BFIs) which have important ramifications for the biology of the interacting partners have been demonstrated extensively. Here we show for the first time that diverse bacterial symbionts occur in insect-pathogenic fungi. We firstly detected the bacterial symbionts by fluorescence in situ hybridization in combination with confocal laser scanning microscopy in Pandora neoaphidis. We also compared P. neoaphidis with the closely related species, P. nouryi, and found that 26 OTUs of bacterial symbionts covered taxonomically six classes in bacterial lineage, most were member of Gammaproteobacteria. To make inferences about the vertical transmission of bacterial symbionts, we compared their diversity in the hyphae and primary conidia of one isolate. Nine OTUs were identified and classified into four classes. Although the frequency of class Gammaproteobacteria was higher than other classes, the Shannon-Weiner diversity index was similar. Additionally, to understand the relationship between fungal virulence and bacterial symbiont diversity within fungi, we compared the predictive 16s rRNA clone library and the virulence of two genetically comparable isolates with different diversities of symbionts (F98028+ and F98028−). Conclusively, our study revealed the diversity of potential bacterial symbionts found inside insect-fungal structures through 16s rRNA clone library construction, and the potential impact between P. neoaphidis virulence and diversity in the bacterial symbionts harbored within their hyphae and conidia.

The unicellular green alga Oophila amblystomatis forms a symbiosis with embryos of the spotted salamander Ambystoma maculatum. The discovery of intracellular invasion of some host cells by the symbiont has raised questions about benefits for the symbiont or the host, including the possibility of vertical symbiont transmission. To determine the provenance of algal cells that reproduce inside individual egg capsules I collected female salamanders from two different ponds in 2019 and 2021 and induced them to oviposit in custom-manufactured bins containing either autoclaved or non-autoclaved pond water. In both years, algae accumulated in all egg masses oviposited in non-autoclaved water. In 2019 no algae accumulated in egg masses oviposited in autoclaved water and in 2021 a few egg capsules in two egg masses from two different bins accumulated algae near the end of the experiment. For the 2021 experiment, I used PCR with Oophila-specific primers and PacBio sequencing of the 18S rRNA gene to confirm that green egg capsules contained Oophila sp; there was no evidence of algal DNA in capsules from egg masses having no visible algae. These results support previous evidence that algae are derived from pond water, but the appearance of algae in 2021 in egg masses laid in autoclaved water suggests that additional sources of algae are possible.

Fungi are often overlooked in microbiome research and, as a result, little is known about the mammalian mycobiome. Although frequently detected in vertebrate guts and known to contribute to digestion in some herbivores, whether these eukaryotes are a persistent part of the mammalian gut microbiome remains contentious. To address this question, we sampled fungi from wild woodrats (Neotoma spp.) collected from 25 populations across the southwestern United States. For each animal, we collected a fecal sample in the wild, and then re-sampled the same individual after a month in captivity on a controlled diet. We characterized and quantified fungi using three techniques: ITS metabarcoding, shotgun metagenomics and qPCR. Wild individuals contained diverse fungal assemblages dominated by plant pathogens, widespread molds, and coprophilous taxa primarily in Ascomycota and Mucoromycota. Fungal abundance, diversity and composition differed between individuals, and was primarily influenced by animal geographic origin. Fungal abundance and diversity significantly declined in captivity, indicating that most fungi in wild hosts came from diet and environmental exposure. While this suggests that these mammals lack a persistent gut mycobiome, natural fungal exposure may still impact fungal dispersal and animal health.

In the present study, we identified the fungal community, including yeasts, in the mycangium of the ambrosia beetle, Xylosandrus crassiusculus (Coleoptera: Curculionidae) and observed the fungal diversity in the mycangia at different times during the dispersal season of beetles. The results showed that the fungal community in the mycangia of X. crassiusculus was dominated by Ambrosiella roeperi, which is regarded as a primary ambrosia fungus. The fungal diversity in the mycangia was influenced by the timing of beetle sampling during the flight dispersal season, with more diverse fungal communities in the late dispersal season. The composition of auxiliary fungi differed significantly among individuals in this study as well as between this study and other studies, indicating that the auxiliary fungi were likely influenced by factors such as locality and seasons.

An investigation was undertaken to assess the community structure of ectomycorrhizal (ECM) fungi on naturally regenerating European larch (Larix decidua Mill.) seedlings grown under forest conditions. The sites examined were in two managed monoculture larch forests, differentiated by soil chemistry and mature tree density. Morphological and molecular analyses revealed a total of 22 fungal taxa. From detected ECM fungal taxa, 13 were noted at Site I and 13 at Site II. Only four taxa were found in both sites (Russula ochroleuca, Thelephora terrestris, Lactarius tabidus and Paxillus involutus). The most abundant species at Site I (lower mineral concentration, high tree density) was Hydnotrya tulasnei (25.7 %), followed by Pseudotomentella tristis, Tomentella sublilacina and Russula puelaris. At Site II (higher mineral concentration, low tree density) the dominant fungal symbiont of larch seedlings was clearly Wilcoxina mikolae, which accounted for 74 % of mycorrhizal tips. The less abundant species comprised T. terrestris, L. tabidus, Xerocomus pruinatus and R. ochroleuca. The analysis of similarity (ANOSIM) and non-metric multidimensional scaling (NMDS) ordination clearly separated the ECM fungal assemblages in the two sites tested. Because our study sites were differentiated by many factors, it is not easy to distinguish one factor in particular to explain the differences observed between the ECM communities at Sites I and II. The results obtained significantly increase our knowledge about the diversity of the ECM fungi hosted by L. decidua. The large number of ECM fungi detected was the first observation showing these fungi as symbiotic partners of European larch.

The use of growth-promoting and potentially nitrogen-fixing (N) bacteria in corn is a viable alternative to increase grain yield, reduce costs and environmental risks. However, the role of Azospirillum brasilense in the process of N utilization by plants needs to be better understood for its efficient use. Thus, the objective of this study was to evaluate the responses of inoculation with A. brasilense in corn cultivated in succession to cover crops associated with doses of mineral N. Two experiments were carried out in Augusto Pestana and Santa Maria (Rio Grande do Sul, Brazil), growing maize in succession to winter crops (black oats and forage radish), under doses of mineral N in top dressing (0, 75, 150 and 225 kg of N ha− 1), associated with A. brasilense inoculation. It was found that corn inoculation under black oat responded better to N rates applied to the thousand seed weight (TSW), grain yield (GY) (Augusto Pestana) and relative chlorophyll content (RCC) (Santa Maria). This was not evidenced when on forage radish residue, which quadratically adjusted the variables regarding N doses. In Santa Maria, the yield components were influenced by the interaction between the predecessor crop and the N dose, with a linear response to N doses when under black oat, obtaining isolated positive effects of inoculation for TSW and GY. It was concluded that the effect of inoculation of corn with A. brasilense is affected by residue from previous crops and N dose, with greater N demand in succession to black oat.

Finger millet is an important food crop that grows in arid and semi-arid parts of Africa and Asia and serve as a staple food source for millions of people. However, compared to other major crops, finger millet gives lower yield. For major crops high yield has been achieved through the introduction of improved varieties coupled with an intensive use of synthetic agrochemicals, often at the expense of the environment. In recent years endophytes received attention because of their potential to increase crop yield without massive application of synthetic chemicals. In this study seeds collected from three finger millet growing regions of Ethiopia contained a high load of bacterial endophytes. But no fungal endophytes were isolated from any of the samples. Based on their 16S rRNA gene sequence the isolates were identified as members of the genera Pantoea, Pseudomonas, Enterobacter, Sphingobacterium, Microbacterium, and Curtobacterium. A significant number of the isolates produced indole-3-acetic acid (IAA), were able to grow on nitrogen free medium, solubilized phosphate, and produced hydrogen cyanide. The most interesting observation was that the different genera showed restricted occurrence to a specific geographic location. Differences in plant growth promotion capacity based on the geographic location from which the isolates were obtained was also observed. Therefore, location specific differences in the distribution of the different taxonomic groups and their difference in plant growth promotion capacity could have important practical implication for the selection of the best microbial inoculants to improve plant growth and crop yield.