A high abundance of Firmicutes in the intestine of chinese mitten crabs (Eriocheir sinensis) cultured in an alkaline region

The Chinese mitten crab (Eriocheir sinensis) is a popular aquaculture product in East Asia, especially in China. In the last decade, rice–crab co-culture has rapidly expanded in China. Under this model, crabs are raised in rice fields instead of in traditional aquaculture ponds. In this study, we cultured two varieties of Chinese mitten crabs (Changjiang and Liaohe) in an alkaline region in northwest China and used Illumina MiSeq sequencing to compare the intestinal bacterial alpha diversity and community structure between traditional and co-culture aquaculture models, between two crab varieties, and between female and male crabs. Significant variations in intestinal bacterial communities were found between crab varieties and between female and male crabs but not between aquaculture models. These results show that rice–crab co-culture operations did not obviously impact the crab intestinal bacterial community compared with traditional pond aquaculture. Firmicutes was the most abundant bacterial phylum in the crab intestines (78%, relative abundance). Three dominant operational taxonomic units (OTUs) represented 73.2% of Firmicutes sequences and 56.8% of all sequences. A dominant OTU assigned as Firmicutes that was negatively correlated with crab body length, width, and weight was found in the source water for the experimental area. The results of this study suggest that the aquaculture of Chinese mitten crabs in alkaline regions requires more study to improve cultivation techniques.

Study on pH Fluorescent Probe Based on Exocyclic Ring-Fused Boron Dipyrromethene Fluorophore

Compound d was prepared by the improved three-step synthetic route using cyclohexene as starting material. After treatment of d with excess LiAlH4 at high temperature, the obtained e was reacted with various kinds of aromatic aldehydes including 4-N, N-dimethylaminobenzaldehyde, 4-hydroxybenzaldehyde, 4-methoxybenzaldehyde, benzaldehyde and 4-formyl-benzo-15-crown-5, respectively, in the presence of CF3COOH and oxidated with DDQ, followed by treatment with NEt3 and BF3.Et2O to provide five kinds of BODIPY derivatives fused with exocyclic rings. Their absorption and fluorescence properties were investigated. The fluorometric titrations were performed to examine their responsive abilities to pH in CH3OH-H2O (1:1, V/V). The results indicate that BODIPY 1 and 2 can be applied as a fluorescent probe for pH sensing in the acid and alkaline region, respectively, and switching between the fluorescence “ON/OFF” states in BODIPY 1 or 2 can be repeated by modulation of protonation/deprotonation process without decomposition and formation of precipitates. Moreover, the design principle and sensing mechanism of two probes are also preliminarily discussed.