Biology subjects

Alteio, L.

Publications and source records attributed to Alteio, L..

3 recordsLinked to original sources

bioRxiv2024

Strong family- and guild-specific responses of arbuscular mycorrhizal fungi to long-term deficiencies and imbalances of N, P and K

O_LIMany agroecosystems face nitrogen (N), phosphorus (P) or potassium (K) deficiencies due to imbalanced or insufficient nutrient replenishment after plant biomass harvest. How this affects the symbiosis between plants and arbuscular mycorrhizal fungi (AMF), and the abundance of exploration-based AMF guilds (i.e., rhizophilic, edaphophilic, ancestral) remains largely unknown. C_LIO_LIWe studied a 70-year nutrient-deficiency experiment in a managed grassland in central Austria, where aboveground biomass was harvested three times annually. N, P and K were fully, partially, or not replenished, causing long-term nutrient deficiencies and imbalances. We analysed AMF communities in soil and roots by DNA/RNA amplicon sequencing and fatty-acid biomarkers, alongside soil and plant community properties. C_LIO_LISoil AMF communities were affected by N and P deficiencies, while root AMF communities were most susceptible to K deficiency, showing a 50% biomass reduction. We observed distinct guild- and family-specific responses: The edaphophilic guild declined with N deficiency, while the rhizophilic guild decreased with P and K deficiencies. Families within each guild, particularly in the ancestral guild, showed differential responses, indicating complementary nutrient specializations at the family level. C_LIO_LIOur findings underscore the previously unrecognized role of K deficiency in AMF symbiosis and suggest the existence of nutrient-related functional subgroups within exploration-based AMF guilds. C_LI

ecology↗

bioRxiv2024

Distinct microbial communities are linked to organic matter properties in millimetre-sized soil aggregates

Soils provide essential ecosystem services and represent the most diverse habitat on Earth. It has been suggested that the presence of various physico-chemically heterogenous microhabitats supports the enormous diversity of microbial communities in soil. However, little is known about the relationship between microbial communities and their immediate environment at the micro- to millimetre-scale. In this study, we examined whether bacteria, archaea, and fungi organise into distinct communities in individual 2-millimetre-sized soil aggregates and compared them to communities of homogenized bulk soil samples. Furthermore, we investigated their relationship to their local environment by concomitantly determining microbial community structure and physico-chemical properties from the same individual aggregates. Aggregate-communities displayed exceptionally high beta-diversity, with 3-4 aggregates collectively capturing more diversity than their homogenized parent soil core. Up to 20-30% of ASVs (particularly rare ones) were unique to individual aggregates selected within a few centimetres. Aggregates and bulk soil samples showed partly different dominant phyla, indicating that taxa that are potentially driving biogeochemical processes at the small scale may not be recognized when analysing larger soil volumes. Microbial community composition and richness of individual aggregates were closely related to aggregate-specific carbon and nitrogen content, carbon stable-isotope composition, and soil moisture, indicating that aggregates provide a stable environment for sufficient time to allow co-development of communities and their environment. We conclude that the soil microbiome is a metacommunity of variable subcommunities. Our study highlights the necessity to study small, spatially coherent soil samples to better understand controls of community structure and community-mediated processes in soils.

ecology↗

bioRxiv2023

Bacteria face trade-offs in the decomposition of complex biopolymers

Although depolymerization of complex carbohydrates is a growth-limiting bottleneck for microbial decomposers, we still lack understanding about how the production of different types of extracellular enzymes affect individual microbes and in turn the performance of whole decomposer communities. In this work we use a theoretical model to evaluate the potential trade-offs faced by microorganisms in biopolymer decomposition which arise due to the varied biochemistry of different depolymerizing enzyme classes. We specifically consider two broad classes of depolymerizing extracellular enzymes, which are widespread across microbial taxa: exo-enzymes that cleave small units from the ends of polymer chains and endo-enzymes that act at random positions generating degradation products of varied sizes. Our results demonstrate a fundamental trade-off in the production of these enzymes, which is independent of systems complexity and which appears solely from the intrinsically different temporal depolymerization dynamics. As a consequence, specialists that produce either exo- or only endo-enzymes limit their growth to high or low substrate conditions, respectively. Conversely, generalists that produce both enzymes in an optimal ratio expand their niche and benefit from the synergy between the two enzymes. Finally, our results show that, in spatially-explicit environments, consortia composed of endo- and exo-specialists can only exist under oligotrophic conditions. In summary, our analysis demonstrates that the (evolutionary or ecological) selection of a depolymerization pathway will affect microbial fitness under low- or high substrate conditions, with impacts on the ecological dynamics of microbial communities. It provides a possible explanation why many polysaccharide degraders in nature show the genetic potential to produce both of these enzyme classes. Author summaryThe decomposition of polysaccharides by microbes is a key process in the global carbon cycle. It requires the joint action of a variety of microbially-produced extracellular enzymes. They can be broadly classified into endo-enzymes, that act in the middle of polymers, and exo-enzymes, that cleave units from polymer ends. Little is known about the benefits for microbes producing a certain enzyme type and the interplay between enzyme producing strategies in mixed communities. This hampers our comprehensive understanding of decomposition in terrestrial and marine ecosystems and thus limits the prediction of decomposition processes, for example in a changing climate. Based on theoretical modelling, we revealed a fundamental trade-off in the action of these enzymes. While exo-enzymes are more efficient at high substrate conditions, endo-enzymes perform better when substrate is low. Generalists producing both enzymes expand their ecological niche of substrate availability compared to specialists only producing one of the two types. Complementary specialists only co-exist in oligotrophic conditions. We conclude that producing enzymes for specific steps within polymer degradation represents relevant ecological strategies for microbes in decomposer communities.

microbiology↗