Food Habit Associated Mycobiota Composition and Their Impact on Human Health

Mycobiota is not only associated with healthy homeostasis in the human gut but also helps to adapt to the environment. Food habits, alcohol consumption, intake of probiotics, and contaminated food with a mycotoxin, often lead to the alteration in the mycobiota composition. Impaired immunity of the host may affect fungal symbiosis leading to mycosis. The human gut adapts to the commensalism fungi belonging to the phylum Ascomycota and Basidiomycota. Diet habits such as plant-or animal-based, phytoestrogens enriched plant products, fat-rich diets also influence the colonization of certain fungal species in the mammalian gut. Food habits or mycotoxin-contaminated food or fungal peptides have an impact on bacterial-fungal interaction and human health. The mycobiota population such as Fusarium, Humicola, Aspergillus, and Candida are altered due to alcohol intake in alcoholic liver disease. The role of associated gut mycobiota due to irregular bowel habits or lifestyle change has been observed in inflammatory bowel disease. In this review, it has been observed that Saccharomyces, Aspergillus, Fusarium, Cladosporium, Candida, and Malassezia were the common genus in the human mycobiota. Therefore, this study focused on how diet habits and alcohol intake, among others., influence mycobiota composition that may affect the human immune system or overall health.

Target of rapamycin, PvTOR, is a key regulator of arbuscule development during mycorrhizal symbiosis in Phaseolus

Target of rapamycin (TOR) is a conserved central growth regulator in eukaryotes that has a key role in maintaining cellular nutrient and energy status. Arbuscular mycorrhizal (AM) fungi are mutualistic symbionts that assist the plant in increasing nutrient absorption from the rhizosphere. However, the role of legume TOR in AM fungal symbiosis development has not been investigated. In this study, we examined the function of legume TOR in the development and formation of AM fungal symbiosis. RNA-interference-mediated knockdown of TOR transcripts in common bean (Phaseolus vulgaris) hairy roots notably suppressed AM fungus-induced lateral root formation by altering the expression of root meristem regulatory genes, i.e., UPB1, RGFs, and sulfur assimilation and S-phase genes. Mycorrhized PvTOR-knockdown roots had significantly more extraradical hyphae and hyphopodia than the control (empty vector) roots. Strong promoter activity of PvTOR was observed at the site of hyphal penetration and colonization. Colonization along the root length was affected in mycorrhized PvTOR-knockdown roots and the arbuscules were stunted. Furthermore, the expression of genes induced by AM symbiosis such as SWEET1, VPY, VAMP713, and STR was repressed under mycorrhized conditions in PvTOR-knockdown roots. Based on these observations, we conclude that PvTOR is a key player in regulating arbuscule development during AM symbiosis in P. vulgaris. These results provide insight into legume TOR as a potential regulatory factor influencing the symbiotic associations of P. vulgaris and other legumes.

Are ectomycorrhizal fungi actually adapting to 5 years of extreme summer drought in Middle European forests?

<p>Middle Europe’s forests face an increasing risk of recurring summer droughts. To explore the impact of such conditions, trees in a mature spruce-beech forest were exposed to five successive years of extreme summer drought during the Kranzberg Roof Experiment located in Bavaria (Grams et al. 2021, DOI: 10.1002/ecs2.3399).</p><p>Those trees (<em>Picea abies</em> and <em>Fagus sylvatica</em>) heavily depend on their ectomycorrhizal fungal symbiosis partners (ECMf) belowground. Thus, we set out to identify modes of compositional and functional adaptation in these communities.</p><p>We monitored ECMf communities via metabarcoding and analysed the functionality of morphotyped ectomycorrhizae via testing their enzyme activities.</p><p>To our surprise, most effects were quantitative throughout the whole period. Total enzyme activities strongly declined alongside the numbers of vital root tips of drought treated trees, while enzyme activities per surviving root tip remained remarkably similar to controls. Likewise, ECMf communities only experienced minor shifts that only slightly increased during the years, although different capacities for drought tolerance in ECMf have previously been hypothesised.</p><p>Summed up: Along with most tree individuals, their fungal partners showed a strong ability to resist the applied extreme drought scenario, at the cost of severely diminished capacities at the ecosystems level.</p><p>Speculatively, individual root tips could be seen as surviving insulae whose fungal communities only experienced indirect and moderated drought effects. Therefore, the ECM system may rather show an inherent resistance to drought, with observable qualitative adaptation requiring a still longer time-frame.</p>

Conserved and reproducible bacterial communities associate with extraradical hyphae of arbuscular mycorrhizal fungi

Extraradical hyphae (ERH) of arbuscular mycorrhizal fungi (AMF) extend from plant roots into the soil environment and interact with soil microbial communities. Evidence of positive and negative interactions between AMF and soil bacteria point to functionally important ERH-associated communities. To characterize communities associated with ERH and test controls on their establishment and composition, we utilized an in-growth core system containing a live soil–sand mixture that allowed manual extraction of ERH for 16S rRNA gene amplicon profiling. Across experiments and soils, consistent enrichment of members of the Betaproteobacteriales, Myxococcales, Fibrobacterales, Cytophagales, Chloroflexales, and Cellvibrionales was observed on ERH samples, while variation among samples from different soils was observed primarily at lower taxonomic ranks. The ERH-associated community was conserved between two fungal species assayed, Glomus versiforme and Rhizophagus irregularis, though R. irregularis exerted a stronger selection and showed greater enrichment for taxa in the Alphaproteobacteria and Gammaproteobacteria. A distinct community established within 14 days of hyphal access to the soil, while temporal patterns of establishment and turnover varied between taxonomic groups. Identification of a conserved ERH-associated community is consistent with the concept of an AMF microbiome and can aid the characterization of facilitative and antagonistic interactions influencing the plant-fungal symbiosis.

Species-Specific Interactions of Bacillus Innocula and Arbuscular Mycorrhizal Fungi Symbiosis with Winter Wheat

Arbuscular mycorrhizal (AM) fungi establish close interactions with host plants, an estimated 80% of vascular plant species. The host plant receives additional soil bound nutrients that would otherwise not be available. Other components of the microbiome, such as rhizobacteria, may influence interactions between AM fungi and the host plant. Within a commercial arable crop selected rhizobacteria in combination with AM fungi may benefit crop yields. The precise nature of interactions between rhizobacteria and AM fungi in a symbiotic relationship overall requires greater understanding. The present study aims to assess this relationship by quantifying: (1) AM fungal intracellular root structures (arbuscules) and soil glomalin as an indicator of AM fungal growth; and (2) root length and tiller number as a measure of crop growth, in response to inoculation with one of three species of Bacillus: B. amyloliquefaciences, B. pumilis, or B. subtilis. The influence of soil management, conventional (CT) or zero tillage (ZT) was a further variable evaluated. A significant (p < 0.0001) species-specific impact on the number of quantifiable AM fungal arbuscules was observed. The inoculation of winter wheat (Triticum aestivum) with B. amyloliquefaciences had a positive impact on AM fungal symbiosis, as indicated by an average of 3226 arbuscules per centimetre of root tissue. Bacillus subtilis increased root length significantly (p < 0.01) but decreased fungal symbiosis (p < 0.01). The inoculation of field soils altered the concentration of glomalin, an indicator of AM fungal growth, significantly (p < 0.00001) for each tillage treatment. The greatest increase was associated with B. amyloliquefaciences for both CT (p < 0.0001) and ZT (p < 0.00001). Bacillus subtilis reduced measured glomalin significantly in both tillage treatments (p < 0.0001 and p < 0.00001 for CT and ZT respectively). The interaction between rhizobacteria and AM fungi is variable, being beneficial or detrimental depending on species. This relationship was evident in both tillage treatments and has important implications for maximizing symbiosis in the crop plant-microbiome present in agricultural systems.