ABSTRACT
To explore food composition of Chinese mitten crab (Eriocheir sinensis) in rice-crab integrated ecosystem in saline-alkali land of the Yellow River Delta, we analyzed carbon and nitrogen stable isotope ratios (δ13C and δ15N) in the crab and that in food sources, including plants (Elodea, Potamogeton crispus, Ceratophyllum demersum, Lemna minor, Oryza sativa stem and leaf, rice grain), animals (benthos, zooplankton), organic debris and artificial feed (compound feed, corn meal) in Kenli District, Dongying, Shandong Province in June to October of 2020. Substantial differences in δ13C and δ15N were found among food sources. The δ13C and δ15N values of different food sources were in a range of -30.09--11.24 and 0.03-12.78, respectively, while those of the crab muscle were in range of -24.61--20.08 and 4.74-9.21, respectively, indicating diverse food sources for the crab. During the experiment, the contribution rate of different food sources followed the order: plant (46.7%-57.1%)>animal (21.5%-24.5%)>artificial feed (10.9%-21.3%)>organic detritus (7.1%-7.9%). It suggested that the natural bait of the paddy field could meet the feeding needs of Chinese mitten crabs in saline-alkali land. Even the crabs were fed with non-animal artificial feed, the contribution rates of the main food sources were not altered.
Subject(s)
Oryza , Rivers , Alkalies , Animals , Carbon Isotopes/analysis , Ecosystem , Nitrogen Isotopes/analysisABSTRACT
Antibiotic-resistant bacteria are a serious threat to human and animal health. Metabolite-enabled eradication of drug-resistant pathogens is an attractive strategy, and metabolite adjuvants, such as fumarate, are used for restoring the bactericidal ability of antibiotics. However, we show that metabolites in the TCA cycle increase the viability of Edwardsiella tarda against chloramphenicol (CAP), based on the survival assay of differential metabolites identified by LC-MS/MS. Furthermore, NADPH promotes CAP resistance in the CAP-resistant strain, while oxidants restore the bactericidal ability. Finally, we show that the intracellular redox state determines the sensitivity to CAP, and the total antioxidative capacity is decreased significantly in the antibiotic-resistant strain. Considering that the metabolites promote CAP resistance, metabolite adjuvants should be applied very cautiously. Overall, our research expands on the knowledge that the redox state is related to the bactericidal ability of CAP.
Subject(s)
Edwardsiella tarda , Fish Diseases , Animals , Anti-Bacterial Agents/pharmacology , Chloramphenicol/pharmacology , Chromatography, Liquid , Humans , Tandem Mass SpectrometryABSTRACT
The functional diversity of aquatic microbial communities in sea cucumber (Apostichopus japonicus) cultural ponds was examined in this paper. The Biolog plate technique and redundancy analysis (RDA) method were used to evaluate seasonal changes and their relationships with environmental factors. The results showed that both total amount and types of carbon sources utilized by microbes in the sea cucumber cultural ponds varied seasonally, and were the highest in summer and lowest in winter, with polymers being the main type of carbon sources. Principal component analysis revealed that the carbon utilization diversity of the microbial communities varied significantly over the seasonal courses. A total of 10 categories of carbon sources were significantly related to the principal component 1, among which were polymers, carbohydrates, carboxylic acids, amino acids, and amines. Significant seasonal changes were detected for all carbon utilization diversity indices of the microbial communities, including Shannon, McIntosh, Simpson, and S-E. However, seasonal variations were different among the microbial diversity indices. RDA analysis revealed that TP, NO(3-)-N, TN, and PO4(3-)-P were the critical environmental factors influencing the seasonal changes in functional diversity of aquatic microbial community in sea cucumber cultural ponds.
