Mitigating sediment cadmium contamination through combining PGPR Enterobacter ludwigii with the submerged macrophyte Vallisneria natans.

Sediment cadmium contamination poses risks to aquatic ecosystems. Phytoremediation is an environmentally sustainable method to mitigate cadmium contamination. Submerged macrophytes are affected by cadmium stress, but plant growth-promoting rhizobacteria (PGPR) can restore the health status of submerged macrophytes. Herein, we aimed to reduce sediment cadmium concentration and reveal the mechanism by which the combined application of the PGPR Enterobacter ludwigii and the submerged macrophyte Vallisneria natans mitigates cadmium contamination. Sediment cadmium concentration decreased by 21.59% after submerged macrophytes were planted with PGPR, probably because the PGPR colonized the rhizosphere and roots of the macrophytes. The PGPR induced a 5.09-fold increase in submerged macrophyte biomass and enhanced plant antioxidant response to cadmium stress, as demonstrated by decreases in oxidative product levels (reactive oxygen species and malondialdehyde), which corresponded to shift in rhizosphere metabolism, notably in antioxidant defence systems (i.e., the peroxidation of linoleic acid into 9-hydroperoxy-10E,12Z-octadecadienoic acid) and in some amino acid metabolism pathways (i.e., arginine and proline). Additionally, PGPR mineralized carbon in the sediment to promote submerged macrophyte growth. Overall, PGPR mitigated sediment cadmium accumulation via a synergistic plantmicrobe mechanism. This work revealed the mechanism by which PGPR and submerged macrophytes control cadmium concentration in contaminated sediment.

Submerged macrophyte restoration enhanced microbial carbon utilization in shallow lakes.

Submerged macrophytes are integral to the functioning of shallow lakes through their interaction with microorganisms. However, we have a limited understanding of how microbial communities in shallow lakes respond when macrophytes are restored after being historically extirpated. Here, we explored the interactions between prokaryotic communities and carbon utilization in two lakes where submerged macrophytes were restored. We found restoration reduced total carbon in sediment by 8.9 %-27.9 % and total organic carbon by 16.7 %-36.9 % relative to control treatment, but had no effects on carbon content in the overlying water. Sediment microbial communities were more sensitive to restoration than planktonic microbes and showed enhanced utilization of simple carbon substrates, such as Tween 40, after restoration. The increase in carbon utilization was attributed to declines in the relative abundance of some genera, such as Saccharicenans and Desertimonas, which were found weakly associated with the utilization of different carbon substrates. These genera likely competed with microbes with high carbon utilization in restored areas, such as Lubomirskia. Our findings highlight how restoring submerged macrophytes can enhance microbial carbon utilization and provide guidance to improve the carbon sequestration capacity of restored shallow lakes.

Three coralloid species of the genus Trechispora (Trechisporales, Basidiomycota) in China: two newly discovered taxa and one reported for the first time.

Two new species of Trechispora indigenous to southern China, T.laxa and T.tongdaoensis, are described and illustrated, and the first record of T.khokpasiensis in China is reported. Molecular phylogenetic analyses of the concatenated nuclear rDNA ITS1-5.8S-ITS2 and nuclear large subunit sequences supported the inclusion of the three species within the Trechispora clade, together with species formerly classified in Scytinopogon. The new species are similar in micromorphology to species of Trechispora (as traditionally circumscribed) but are distinguished by having coralloid basidiomata. A key to the known coralloid Trechispora species in China is provided.

Temperature-mediated microbial carbon utilization in China's lakes.

Microbes play an important role in aquatic carbon cycling but we have a limited understanding of their functional responses to changes in temperature across large geographic areas. Here, we explored how microbial communities utilized different carbon substrates and the underlying ecological mechanisms along a space-for-time substitution temperature gradient of future climate change. The gradient included 47 lakes from five major lake regions in China spanning a difference of nearly 15°C in mean annual temperatures (MAT). Our results indicated that lakes from warmer regions generally had lower values of variables related to carbon concentrations and greater carbon utilization than those from colder regions. The greater utilization of carbon substrates under higher temperatures could be attributed to changes in bacterial community composition, with a greater abundance of Cyanobacteria and Actinobacteriota and less Proteobacteria in warmer lake regions. We also found that the core species in microbial networks changed with increasing temperature, from Hydrogenophaga and Rhodobacteraceae, which inhibited the utilization of amino acids and carbohydrates, to the CL500-29-marine-group, which promoted the utilization of all almost carbon substrates. Overall, our findings suggest that temperature can mediate aquatic carbon utilization by changing the interactions between bacteria and individual carbon substrates, and the discovery of core species that affect carbon utilization provides insight into potential carbon sequestration within inland water bodies under future climate warming.

[Effects of supernatant of cord blood CD3AK cells on proliferation, differentiation and apoptosis of HL-60 cells].

OBJECTIVE: The study was to investigate the impact of cord blood CD(3)AK cell culture supernatant (CS) on proliferation, differentiation and apoptosis of HL-60 cells. METHODS: HL-60 cells were treated with different concentrations of CS (10%, 15%, 20%) for 3 days, 6 days and 9 days, and the same cells of control group were not treated with CS. The growth of induced cells was assessed with Trypan blue staining and cell counting with cytometer. The differentiation marker CD(11b) on the cell surface and cell-cycle was analyzed by flow cytometry (FCM), cell morphology (Wright-Giemsa staining) and NBT test to determine the extent of differentiation. Meanwhile, the changes of the apoptosis of the cells induced by 20% CS at different time points (3, 6 and 9 days) were analyzed by TUNNEL-POD, and the apoptotic characteristics of cells were observed. RESULTS: The growth of HL-60 cell was inhibited as CS-inducing time and the dose of CS increased. At the same time, but HL-60 cell number in G(0)/G(1) phase of cell-cycle increased, but HL-60 cell number in S phase decreased compared with untreated group. The HL-60 cells induced by 20% CS for 9 days showed that (52.7 +/- 1.8)% of cells were at G(0)+G(1) phase and (43.8 +/- 1.1)% were at S phase (P < 0.05), which demonstrated that HL-60 cells induced by 20% CS underwent G(0)/G(1) phase cell-cycle arrest. The volume of the differentiated cells was enlarged gradually as CS-inducing time prolonged. After 3 days the differentiating cells began to express differentiating marker CD(11b) on the cell surface and the nuclei morphology of the differentiated cells was also changed and NBT-stained cells increased in number with the increased dose of CS increased. Three days after induction by 20% CS, the induced cells began to show signs of apoptosis and the apoptotic percentage of induced cells gradually increased with CS-induction time. The rate of apoptosis of cells was (33.3 +/- 2.3)% at 9 days (P < 0.01). CONCLUSION: CS could not only inhibit the growth of HL-60 cells but also induce the differentiation and apoptosis in HL-60 cells.