Montmorillonite adsorbs creatinine and accelerates creatinine excretion from the intestine

Short-term cold stress can reduce the abundance of antibiotic resistance genes in the cecum and feces in a pig model

Comprehensive studies on the effects of cold stress on antibiotic resistance genes (ARGs) in the intestines and feces remain scarce. In this study, pigs were selected as the animal model and divided into a normal temperature group and a 48-h short-term cold stress group. The ARG profiles in fecal, cecal content and cecal mucosa samples were analyzed. The results showed that the normalized abundance of ARGs in the cecal mucosa samples in the cold stress group was significantly higher than that in the normal temperature group, while the normalized ARG abundances in the fecal and cecal content samples were significantly lower than those in the normal temperature group (P < 0.05). The bacterial community composition (especially Firmicutes) was the major driver impacting the ARG profile and accounted for 32.2% of the variation in the ARG profile, followed by metabolites (especially creatinine and oxypurinol) and mobile genetic elements (MGEs) (especially plasmids and insertion elements). And it was found that creatinine and oxypurinol can reduce the abundance of ARGs and Firmicutes in the in vitro experiment. The results indicate that short-term cold stress can reduce the abundance of ARGs in the cecum and feces of pigs, providing reference data for environmental safety.

Microbial Interaction with Clay Minerals and Its Environmental and Biotechnological Implications

Clay minerals are very common in nature and highly reactive minerals which are typical products of the weathering of the most abundant silicate minerals on the planet. Over recent decades there has been growing appreciation that the prime involvement of clay minerals in the geochemical cycling of elements and pedosphere genesis should take into account the biogeochemical activity of microorganisms. Microbial intimate interaction with clay minerals, that has taken place on Earth’s surface in a geological time-scale, represents a complex co-evolving system which is challenging to comprehend because of fragmented information and requires coordinated efforts from both clay scientists and microbiologists. This review covers some important aspects of the interactions of clay minerals with microorganisms at the different levels of complexity, starting from organic molecules, individual and aggregated microbial cells, fungal and bacterial symbioses with photosynthetic organisms, pedosphere, up to environmental and biotechnological implications. The review attempts to systematize our current general understanding of the processes of biogeochemical transformation of clay minerals by microorganisms. This paper also highlights some microbiological and biotechnological perspectives of the practical application of clay minerals–microbes interactions not only in microbial bioremediation and biodegradation of pollutants but also in areas related to agronomy and human and animal health.

A urine-fuelled soil-based bioregenerative life support system for long-term and long-distance manned space missions

A soil-based cropping unit fuelled with human urine for long-term manned space missions was investigated with the aim to analyze whether a closed-loop nutrient cycle from human liquid wastes was achievable. Its ecohydrology and biogeochemistry were analysed in microgravity with the use of an advanced computational tool. Urine from the crew was used to supply primary (N, P, and K) and secondary (S, Ca and Mg) nutrients to wheat and soybean plants in the controlled cropping unit. Breakdown of urine compounds into primary and secondary nutrients as well as byproduct gases, adsorbed, and uptake fractions were tracked over a period of 20 years. Results suggested that human urine could satisfy the demand of at least 3 to 4 out of 6 nutrients with an offset in pH and salinity tolerable by plants. It was therefore inferred that a urine-fuelled life support system can introduce a number of advantages including: (1) recycling of liquids wastes and production of food; (2) forgiveness of neglect as compared to engineered electro-mechanical systems that may fail under unexpected or unplanned conditions; and (3) reduction of supply and waste loads during space missions.

Montmorillonite adsorbs uric acid and increases the excretion of uric acid from the intestinal tract in mice

Objectives

The aim was to evaluate the adsorbing effect of montmorillonite on uric acid, promoting diffusion of uric acid from blood to intestine, preventing absorption of uric acid in intestine and reducing uric acid level in serum.

Methods

The adsorbing effect of montmorillonite on uric acid was observed in vitro. The intestine and blood vessel of rats were circularly perfused with intestinal perfusate and vascular perfusate, respectively. A model of hyperuricaemia in mice was prepared by intraperitoneal injection of hypoxanthine and potassium oteracil. The concentration of uric acid was determined by the method of urate oxidase and peroxide enzyme.

Key findings

The results showed that different concentrations of montmorillonite could adsorb uric acid in a concentration-dependent manner. The adsorbing effect was fast. The adsorptive rate was high in acid solution and was low in alkaline solution. When blood vessels were circularly perfused by vascular perfusate containing uric acid, the concentration of uric acid in vascular perfusate was decreased and the concentration of uric acid in intestinal perfusate was increased, suggesting that uric acid in blood vessels diffused into the intestine. When the intestine was perfused with intestinal perfusate containing uric acid, the uric acid concentration in vascular perfusate was increased, but the uric acid concentration of intestinal perfusate was decreased, suggesting that uric acid was absorbed in the intestine. The uric acid concentrations of intestinal perfusate and vascular perfusate in montmorillonite 0.5 and 1.0 g/kg groups were lower than the control group. Concentrations of uric acid in serum and urine in the montmorillonite 1 and 2 g/kg groups were lower compared with mice in the hyperuricaemic group.

Conclusions

The results suggested that montmorillonite adsorbed uric acid and promoted diffusion of uric acid from blood vessels to intestine, prevented absorption of uric acid in intestine and decreased uric acid level in serum.