Purification and some characteristics of a recombinant dimeric rhizobium meliloti beta-galactosidase expressed in escherichia coli

Baohe pill decoction treats diarrhea induced by high-fat and high-protein diet by regulating lactase-producing bacteria in intestinal mucosa

Introduction

This study aimed to investigate the effects of Baohe pill decoction (BPD) on microbial, lactase activity, and lactase-producing bacteria in the intestinal mucosa of mice with diarrhea induced by high-fat and high-protein diet (HFHPD).

Methods

Thirty male Kunming (KM) mice were randomly divided into normal (NM), model (MD), and BPD groups. Diarrhea models were manufactured using HFHPD combined with a gavage of vegetable oil. At the end of modeling, the BPD group was given BPD (6.63 g·kg^-1d^-1) intervention twice daily for 3 d. The NM and MD groups were given equal amounts of sterile water. Subsequently, the intestinal mucosa of the mice was collected, one portion was used for microbial and lactase activity measurement, and the other portion was used for its lactase-producing bacterial characteristics by high-throughput sequencing technology.

Results

Our results showed that microbial and lactase activity of intestinal mucosa decreased significantly following diarrhea in mice (P_microbial < 0.05, P_lactase < 0.001). After BPD intervention, microbial and lactase activity increased significantly (P < 0.01). The number of operational taxonomic units (OTUs), richness, and diversity index of lactase-producing bacteria increased in the BPD group compared to the MD group (P > 0.05), and the community structure were significant differences (P < 0.01). Compared to other groups, Saccharopolyspora, Rhizobium, Cedecea, and Escherichia were enriched in the BPD group. Notably, the relative abundance of the dominant lactase-producing genus Bifidobacterium decreased after BPD intervention.

Discussion

The mechanism of BPD in relieving diarrhea induced by HFHPD is closely related to the promotion of lactase activity in the intestinal mucosa, which may be achieved by regulating the structure of lactase-producing bacteria.

Development of an Azoreductase-based Reporter System with Synthetic Fluorogenic Substrates

Enzyme/substrate pairs, such as β-galactosidase with chromogenic x-gal substrate, are widely used as reporters to monitor biological events, but there is still a requirement for new reporter systems, which may be orthogonal to existing systems. Here, we focused on azoreductase (AzoR). We designed and synthesized a library of azo-rhodamine derivatives as candidate fluorogenic substrates. These derivatives were nonfluorescent, probably due to ultrafast conformational change around the N═N bond after photoexcitation. We found that AzoR-mediated reduction of the azo bond of derivatives bearing an electron-donating group on the azobenzene moiety was followed by nonenzymatic cleavage to afford highly fluorescent 2-methyl-rhodamine green (2-Me RG), which was well retained in cells. We show that the AzoR/compound 9 reporter system can detect azoreductase-expressing live cells at the single cell level.

Recent developments of biological reporter technology for detecting gene expression

Reporter gene assay is an invaluable tool for both biomedical and pharmaceutical researches to monitor cellular events associated with gene expression, regulation and signal transduction. On the basis of the alternations in reporter gene activities mediated by attaching response elements to these reporter genes, one sensitive, reliable and convenient assay can be provided to efficiently report the activation of particular messenger cascades and their effects on gene expression and regulations inside cells or living subjects. In this review, we introduce the current status of several commonly used reporter genes such as chloramphenicol acetyltransferase (CAT), alkaline phosphatase (AP), β-galactosidase (β-gal), luciferases, green fluorescent protein (GFP), and β-lactamase. Their applications in monitoring gene expression and regulations in vitro and in vivo will be summarized. With the development of advanced technology in gene expression and optical imaging modalities, reporter genes will become increasingly important in real-time detection of the gene expression at the single-cell level. This synergy will make it possible to understand the molecular basis of diseases, track the effectiveness of pharmaceuticals, monitor the response to therapies and evaluate the development process of new drugs.

High-level expression of Lactobacillus beta-galactosidases in Lactococcus lactis using the food-grade, nisin-controlled expression system NICE

In this work the overlapping genes (lacL and lacM) encoding heterodimeric beta-galactosidases from Lactobacillus reuteri , Lb. acidophilus , Lb. sakei , and Lb. plantarum were cloned into two different nisin-controlled expression (NICE) vectors and expressed using Lactococcus lactis NZ9000 and NZ3900 as hosts. The lacL gene, encoding the large subunit of the beta-galactosidases, was fused translationally downstream of the nisin-inducible promoter nisA. Chloramphenicol was employed as selection marker for the standard system using L. lactis NZ9000, whereas lactose utilization based on the complementation of the lacF gene was used as a dominant selection marker for the food-grade system employing L. lactis NZ3900. Comparison of the standard and the food-grade expression system, differing only in their selection markers, gave considerable differences in volumetric beta-galactosidase activity, ranging from 1.17 to 14 kU/L of fermentation broth, depending on both the origin of the lacLM genes and the selection marker used. The occurrence of codons less frequently used by L. lactis especially at the beginning of the lacL gene could be an explanation for the significant differences between the expression levels of lacLM from different origins, while plasmid stability might cause the difference obtained when employing the different selection markers.