A preliminary study of improving the MICP effects via the extractions from seashell nacre

In microbially induced calcium carbonate precipitation (MICP) process, it is the precipitated CaCO3 that cements loose sand particles together to improve their mechanical properties. Seashell nacre composed of CaCO3 is a natural product, which is worth researching for its great hardness, strength, and toughness. However, there is no study connecting this natural nacre mineralization with MICP. Therefore, a precedent herein is established to modify the MICP process via the water-soluble matrix (WSM) extracted from nacre, where WSM contributes to the great mechanical properties of nacre. Correspondingly, this study examines the effects of WSM with different concentrations on urease activity and strength as well as microstructure of bio-cemented sand samples. The experimental results show that a small number of WSM (50mg/L) can improve the average strength of bio-cemented sand samples 1.5 times. This is because 50mg/L WSM can significantly improve the urease activity of bacteria meanwhile increasing the Ca2+ utilization rate. Thus, more CaCO3 crystals are precipitated, and the higher UCS of bio-cemented sand samples is achieved. Moreover, the XRD results indicate that the precipitated CaCO3 is almost calcite, and only a little aragonite is detected when the concentration of WSM increases to 100mg/L. Additionally, the SEM images demonstrate that WSM involvement can affect the shapes and sizes of CaCO3 crystals. Overall, this work is an unprecedented exploration imitating nacre that hopefully paves way for future studies.

Influence of Soil Fertility Management on Nitrogen Mineralization, Urease Activity and Maize Yield

For studying the effect of soil fertility management practices on N mineralization, urease activity and maize yield, replicated field trials were established in 2015 at Misamfu and Msekera agricultural research stations (ARS) representing two geo-climatic regions of Zambia. The soil at Msekera ARS is a sandy clay loam (SCL) from a Paleustult, while that at Misamfu is a loamy sand (LS) from a Kandiustult. The field trials had three categories of treatments namely legumes, traditional and conventional. The legumes group consisted of researcher-recommended legume-cereal intercrop systems of maize with Cajanus cajan, Crotalaria juncea and Tephrosia vogelii in combination with compound D (10% N, 20% P2O5, 10% K2O) and urea (46% N) at the recommended rate (200 kg ha-1) and half of the recommended rate (100 kg ha-1). Composted cattle manure and Fundikila, a special plant biomass management technique, were the inputs under the traditional category. The conventional category consisted of a treatment to which only chemical fertilizer was applied. Urease activity was determined in surface soil samples (0-20 cm) collected from the field trials after 3 years. For N mineralization, a laboratory incubation study was conducted over 13 weeks. For the laboratory incubation, an additional treatment to which no input was applied was included as control. Application of organic inputs significantly increased the potentially mineralizable N (No) by 127% to 256% on the LS and by 51% to 131% on the SCL in comparison to the control. Similarly, the cumulative N mineralized (Ncum) was twice or thrice higher where organic inputs had been applied in comparison to the control. The No followed the order traditional > legumes > conventional > control, while the mineralization rate constant (k) followed the order legumes > conventional > traditional > control on both soils. The rate of N mineralization was significantly higher on the LS than the SCL. Higher rates of chemical fertilizer resulted in high Ncum and higher maize yield. Maize yield was significantly and positively correlated to Ncum, but inversely correlated to the amount of applied N that was mineralized (%Nmin). Urease activity was stimulated by application of organic inputs and suppressed by higher rates of chemical fertilizers. The type of organic inputs; the rate of chemical fertilizers; and soil texture are factors influencing N mineralization and maize yield. Urease activity was largely influenced by the rate of chemical fertilizer, but not the type of organic inputs or soil texture.

Activity- and Enrichment-Based Metaproteomics Insights into Active Urease from the Rumen Microbiota of Cattle

Regulation of microbial urease activity plays a crucial role in improving the utilization efficiency of urea and reducing nitrogen emissions to the environment for ruminant animals. Dealing with the diversity of microbial urease and identifying highly active urease as the target is the key for future regulation. However, the identification of active urease in the rumen is currently limited due to large numbers of uncultured microorganisms. In the present study, we describe an activity- and enrichment-based metaproteomic analysis as an approach for the discovery of highly active urease from the rumen microbiota of cattle. We conducted an optimization method of protein extraction and purification to obtain higher urease activity protein. Cryomilling was the best choice among the six applied protein extraction methods (ultrasonication, bead beating, cryomilling, high-pressure press, freeze-thawing, and protein extraction kit) for obtaining protein with high urease activity. The extracted protein by cryomilling was further enriched through gel filtration chromatography to obtain the fraction with the highest urease activity. Then, by using SDS-PAGE, the gel band including urease was excised and analyzed using LC-MS/MS, searching against a metagenome-derived protein database. Finally, we identified six microbial active ureases from 2225 rumen proteins, and the identified ureases were homologous to those of Fibrobacter and Treponema. Moreover, by comparing the 3D protein structures of the identified ureases and known ureases, we found that the residues in the β-turn of flap regions were nonconserved, which might be crucial in influencing the flexibility of flap regions and urease activity. In conclusion, the active urease from rumen microbes was identified by the approach of activity- and enrichment-based metaproteomics, which provides the target for designing a novel efficient urease inhibitor to regulate rumen microbial urease activity.

Effect of Different Agricultural Farming Practices on Microbial Biomass and Enzyme Activities of Celery Growing Field Soil

Soil quality is directly affected by alterations in its microbiological, biological, biochemical, physical, and chemical aspects. The microbiological activities of soil can affect soil fertility and plant growth because it can speed up the cycling of nutrients, enzymes, and hormones that are needed by plants for proper growth and development. The use of different agricultural management practices can influence microbial biomass and enzyme activities by altering soil microclimate, soil microorganism habitat, and nutrient cycling. Based on this, the present work planned to evaluate the impact of conventional, low-input, and organic farming systems in a vegetable field growing celery on microbial biomass and different soil enzyme activities. The present study showed a comparison of the effect of different practices on biological soil quality indicators during two sampling times, i.e., one month after colonization and one month before harvesting. It was observed that the soil microbial biomass in the organic farming system was significantly higher than that found in conventional and low-input practices. Under an organic farming system, the soil microbial biomass in December was significantly higher than that in October. The soil microbial biomass carbon in the 0–20 cm soil layer showed higher variation compared to that in the 20–40 cm layer for all the three of the farming management practices that were used in the study. Additionally, the soil total carbon and total organic carbon were recorded as being higher in the December samples than they were in the October samples. Under all the three of the management practices that were applied, the soil catalase activity was higher in the October samples than it was in the December soil samples that were collected the from 20–40 cm soil layer compared to those that were taken from the 0–20 cm layer. The application of organic fertilizer (chicken and cowmanure compost) resulted inincreases in the soil urease and in the protease activity. The protease activity of the soil samples that were extracted from the 0–20 cm and 20–40 cm soil layers in October was higher in the samples that were taken from farms using conventional practices than it was in the samples that were taken from farms using organic and low-input practices, while the samples that were collected during December from both of the soil layers showed higher protease activity when organic methods had been used. No significant variation in the soil urease activity was observed between the two soil layer samples. Urease activity was the highest when organic management practices were being used, followed by the low-input and the conventional modes. For the conventional and low-input practices, the soil urease activity showed an obvious trend of change that was related to thetime of sampling, i.e., activity in December was significantly higher than activity in October. The novelty of this study was to determine the microbial biomass carbon and enzymatic activity in a six-field crop rotation (tomato, cucumber, celery, fennel, cauliflower, and eggplant) using three management practices: low-input, conventional, and organic systems. The present study showed that the long-term application of organic fertilizers plays a large role in maintaining excellent microbial and enzyme activitythat result in improved soil quality.

Highly Stable Potentiometric (Bio)Sensor for Urea and Urease Activity Determination

There is growing interest for bioanalytical tools that might be designed for a specific user, primarily for research purposes. In this perspective, a new, highly stable potentiometric sensor based on glassy carbon/polyazulene/NH4+-selective membrane was developed and utilized for urease activity determination. Urease–urea interaction studies were carried out and the Michaelis–Menten constant was established for this enzymatic reaction. Biofunctionalization of the ammonium ion-selective sensor with urease lead to urea biosensor with remarkably good potential stability (drift coefficient ~0.9 mV/h) and short response time (t95% = 36 s). The prepared biosensor showed the Nernstian response (S = 52.4 ± 0.7 mV/dec) in the urea concentration range from 0.01 to 20 mM, stable for the experimental time of 60 days. In addition, some insights into electrical properties of the ion-to-electron transducing layer resulting from impedance spectroscopy measurements are presented. Based on the RCQ equivalent circuits comparison, it can be drawn that the polyazulene (PAz) layer shows the least capacitive behavior, which might result in good time stability of the sensor in respect to response as well as potential E0. Both the polyazulene-based solid-contact ion selective electrodes and urea biosensors were successfully used in trial studies for determination of ammonium ion and urea in human saliva samples. The accuracy of ammonium ion and urea levels determination by potentiometric method was confirmed by two reference spectrophotometric methods.

Domestic Birds as Source of Cryptococcus deuterogattii (AFLP6/VGII): Potential Risk for Cryptococcosis

Cryptococcosis is an infection caused by encapsulated basidiomycetous yeasts belonging to the Cryptococcus neoformans/Cryptococcus gattii species complexes. It is acquired through inhalation of infectious propagules, often resulting in meningitis and meningoencephalitis. The ecological niche of these agents is a wide variety of trees species, as well as pigeon, parrot and passerine excreta. The objective of this study was to isolate Cryptococcus yeasts from excreta of commercially traded parrots and passerines. The 237 samples were collected between October 2018 and April 2019 and processed using conventional methodologies. Nineteen colonies with a dark brown phenotype, caused by phenol oxidase activity, were isolated, suggesting the presence of pathogenic Cryptococcus yeasts. All isolates tested positive for urease activity. URA5-RFLP fingerprinting identified 14 isolates (68.4%) as C. neoformans (genotype AFLP1/VNI) and 5 (26.3%) as C. deuterogattii (genotype AFLP6/VGII). Multi-locus sequence typing was applied to investigate the relatedness of the C. deuterogattii isolates with those collected globally, showing that those originating from bird-excreta were genetically indistinguishable from some clinical isolates collected during the past two decades.