Microbial communities play a vital role in biogeochemical cycles, allowing the biodegradation of a wide range of pollutants. The composition of the community and the interactions between its members affect degradation rate and determine the identity of the final products. Here, we demonstrate the application of sequencing technologies and metabolic modeling approaches towards enhancing biodegradation of atrazine-a herbicide causing environmental pollution. Treatment of agriculture soil with atrazine is shown to induce significant changes in community structure and functional performances. Genome-scale metabolic models were constructed for Arthrobacter, the atrazine degrader, and four other non-atrazine degrading species whose relative abundance in soil was changed following exposure to the herbicide. By modeling community function we show that consortia including the direct degrader and non-degrader differentially abundant species perform better than Arthrobacter alone. Simulations predict that growth/degradation enhancement is derived by metabolic exchanges between community members. Based on simulations we designed endogenous consortia optimized for enhanced degradation whose performances were validated in vitro and biostimulation strategies that were tested in pot experiments. Overall, our analysis demonstrates that understanding community function in its wider context, beyond the single direct degrader perspective, promotes the design of biostimulation strategies.These authors contributed equally:

No abstract

Despite a growing knowledge of nutrient limitation for mangrove species and how mangroves adapt to low nutrients, there is scant information about the relative importance of N:P ratio and leaf phenolics variability in determining nutrient conservation. In this study, we evaluated possible nutrient conservation strategies of a mangrove Rhizophora stylosa under nutrient limitation. 1. The leaf nutrient concentrations of R. stylosa changed with season, with the highest N concentration in winter and the highest P concentration in spring for both mature and senescent leaves. Leaf N and P concentrations decreased significantly during leaf senescence. Based on N:P ratios R. stylosa forest was N-limited. Accordingly, the nitrogen resorption efficiency (NRE) was significantly higher than phosphorus resorption efficiency (PRE) for the R. stylosa leaves during leaf senescence. The NRE and PRE both reached the highest in the autumn. Average N and P concentrations in the senescent leaves were 0.15% and 0.06% for R. stylosa, respectively, indicating a complete resorption of N and an incomplete resorption of P. There was a significant negative correlation between nitrogen resorption proficiency (NRP) and NRE, meanwhile phosphorus resorption proficiency (PRP) and PRE correlation was also highly significantly. 2. R. stylosa leaves contained relatively high tannin level. Total phenolics, extractable condensed tannins and total condensed tannins contents increased during leaf senescence, and changed between seasons. The lowest concentrations of total phenolics, extractable condensed tannins and total condensed tannins occurred in summer, total phenolics concentrations were inversely related to nitrogen or phosphorus concentrations. 3. Our results confirmed that resorption efficiency during leaf senescence depends on the type of nutrient limitation, and NRE was much higher than PRE under N-limited conditions. R. stylosa forest developed several nutrient conservation strategies in the intertidal coastline surroundings, including high nitrogen resorption efficiency, low nutrient losses and high tannins level.Program for New Century Excellent Talents in University [NCET- 070725]; Fujian Province Universit

No abstract

Changes in the N and P concentrations, N:P ratios, and tannin content in Casuarina equisetifolia branchlets across a coastal gradient were studied at Chishan Forestry Center of Dongshan County, Fujian Province, China. (1) Total phenolics and protein precipitation capacity in young branchlets was significantly higher than in mature and senescent branchlets across a coastal gradient; extractable condensed tannin content was higher in young and mature branchlets than in senescent branchlets. Whereas proteinbound condensed tannins increased with senescence, fiberbound condensed tannins fluctuated without a consistent pattern; (2) N and P concentrations at various stages of branchlet development across a coastal gradient followed the same order: young branchlets [ mature branchlets [ senescent branchlets; N:P ratio of young branchlets was the lowest, and increased with maturity and senescence across a coastal gradient; phosphorus resorption efficiency was significantly higher than nitrogen resorption efficiency among corresponding coastal gradients in response to P deficiency (high N:P ratio), but nutrient resorption efficiency was influenced by coastal gradients; (3) significant linear relationships between total phenolics and nutrient contents indicated that polyphenolics had a potential effect on nutrient cycling.