Project description:Giant panda are carnivorous bears which feed almost exclusively on plant biomass (i.e. bamboo). The potential contribution of its gut microbiome to lignocellulose degradation has been mostly investigated with cultivation-independent approaches. Recently, we reported on the first lab-scale cultivation of giant panda gut microbiomes and described their actual fermentation capacity. Fermentation of bamboo leaf using green dung resulted in a neutral pH, the main products being ethanol, lactate and H2. Fermentation of bamboo pith using yellow dung resulted in an acidic pH, the main product being lactate. Here, we cultivated giant panda gut microbiomes to test 1) the impact of mixed dung as inoculum; 2) the fermentation capacity of solid lignocellulose as opposed to organics-rich biofluids in the dung; 3) the artificial shift of pH from neutral to acidic on bamboo leaf fermentation. Our results indicate that i) gut microbiomes fermentation of solid lignocellulose contributes up to a maximum of 1/3 even in the presence of organics-rich biofluids; ii) alcohols are an important product of bamboo leaf fermentation at neutral pH; iii) aside hemicellulose, gut microbiomes may degrade plant cell membranes to produce glycerol; iv) pH, rather than portion of bamboo, ultimately determines fermentation profiles and gut microbiome assemblage.
Project description:Leaf metabolomes are constantly changing in response to biotic and abiotic conditions, alongside internal physiological processes. Additionally, the diversity of plant species in a surrounding community influences the leaf metabolome. However, it is rarely considered how these changes might affect the chemical composition of litter emissions, which can mediate interactions with the decomposer community. To study these effects, reproducible methods for trapping litter volatiles are essential, particularly for analyzing larger sample numbers and after longer storage periods. This study optimized and validated a solid-phase microextraction (SPME) method for analyzing small amounts of litter from Quercus petraea within a biodiversity ecosystem functioning experiment. The SPME optimization focused on the fiber material, extraction temperature, and duration of sampling. The final optimized method, using a PDMS/DVB fiber and 60-minute extraction at 70 degrees celsius, demonstrated a high reproducibility, with %RSD values ranging from 0.073 to 0.119% (intraday) and 0.115 to 0.169% (interday) for retention time, and 4.41 to 7.72% (intraday) and 7.67 to 11.0% (interday) for peak area. This makes it a reliable and reproducible approach for the collection and analysis of litter volatiles. After validation, this method was applied to test the hypothesis that oak leaf litter volatile profiles are influenced by the surrounding biodiversity. The results showed that the main compound classes in oak leaf litter were fatty acids and terpenoids. Furthermore, plot diversity level was negatively correlated with terpenoid emission rates. By detecting these changes in volatile composition, we gained further insights into how tree diversity affects litter chemistry, which may also impact the decomposer network.
Project description:We tested whether home field advantage at inter- and intra-specific levels alters microbial carbon transformations, using a multi-factorial design with microcosms of freshwater submerged leaf litter from two species (Alder and Hemlock) exposed to 'home' or 'away' communities of microbes isolated from decomposing leaf litter, as well as controls with no microbial community added. For all 'home', 'away' and control conditions for each species we also had high or low oxygen treatments. Samples were taken at day 0, 154, 257 and 354 and extracted with solid phase columns and methanol to provide extracted metabolites.