Effects of hexavalent chromium on intestinal histology and microbiota in Bufo gargarizans tadpoles.

Chromium is detrimental heavy metal pollutants and can enter and affect aquatic organisms. In our experiment, B. gargarizans embryos were chronically exposed in different concentrations of Cr (VI) (0, 13, 104, and 416 µg Cr6+ L-1) until reached Gosner stage 38. We measured morphological parameters of the body and intestine of B. gargarizans tadpoles, and examined alteration of intestinal tissue. Furthermore, we analyzed the intestinal microbial community of B. gargarizans tadpoles using 16S rRNA gene amplicon sequencing. Our research demonstrated that Cr (VI) exposure caused alteration of intestinal tissue structure in 416 µg Cr6+ L-1 treatment groups. Total body length, body wet weight, intestinal length and wet weight of B. gargarizans tadpoles were significantly declined at 416 µg Cr6+ L-1. In addition, 16S rRNA gene sequencing revealed that Cr (VI) exposure significantly altered the intestinal microbiota diversity and composition, and perturbed the community structure of the microbiota. As for the intestinal microbiota, at the phylum level, Fusobacteria significantly changed in all Cr (VI) treated groups. Saccharibacteria and TM6_Dependentiae were detected only in the high dose exposure groups. At the genus level, Aeromonas was significantly decreased in Cr (VI) treated groups. According to the results of functional prediction, Cr (VI) exposure affected metabolism and increased risk of disease by inducing the alterations of intestinal microbiota structure. Taken together, the present study provide a new framework elucidating the toxic effects Cr (VI) exposure on B. gargarizans tadpoles associated with intestinal histology and microbiota.

[Influence of nitrogen forms ratio on growth and photosynthetic characteristics in Prunella vulgaris].

OBJECTIVE: The effects of different nitrogen forms on the growth and photosynthetic characteristics of Prunella vulgaris were observed. METHOD: Water culture experiments were carried out to observe the effects of NH4+: NO3- ratios(100:0, 75: 25, 50:50, 25:75, 0:100 in mmol x L(-1)) on the growth and photosynthetic characteristics of P. vulgaris. RESULT: The leaf area, fresh biomass and P(n) of these cultivars increased with the increasing of NH4(+) -N: NO3(-) -N ratios, and they were found to be the highest in 25: 75 NH4(+) -N: NO3)-) -N. However, they decreased with the increasing NH4(+) -N: NO3(-) -N ratio further. P. vulgaris had a minimum leaf area, biomass, chlorophyll content and P(n) in pure ammonium group. The biggest chlorophyll and carotenoid contents were found in the ratios of NH4(+) -N to NO3(-) -N of 50: 50. CONCLUSION: The results indicated that properly increasing nitrate proportion could promote the growth and photosynthesis of P. vulgaris.