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Nonreductive biomineralization is a cost-effective method to remediate uranium (U) contaminated wastes. In this work, we explored the immobilization mechanism of U(VI) induced by Bacillus thuringiensis 016. Enzymes denaturation and functional groups shielding experiments revealed that the biosorption of uranium by B. thuringiensis 016 was a nonenzymatic process in which phosphate, amino, and carboxyl groups played a major role. Fe3+ and CO32− had a strong ability to inhibit uranium biosorption. The biomineralization of uranium by B. thuringiensis 016 was a synergistic effect of enzymes and cell metabolism. In addition, K+, Na+, and Mg2+ slightly promoted the ability of bacteria to mineralize U(VI). Besides, when the initial uranium concentration was 100 mg/L, the reaction of B. thuringiensis 016 with uranium was a rapid process consisting of extracellular biosorption and intracellular biomineralization. When the initial uranium concentration exceeded 200 mg/L, B. thuringiensis 016 can only adsorb uranium. Furthermore, by tracking the concentration of soluble U(VI) in the cells, it was confirmed that the amorphous compounds, formed on the cell surface, were an insoluble form when entering the cells. Our findings provide a further understanding of the mechanisms of uranium immobilization, which would be useful for the application of B. thuringiensis 016 in uranium pollution treatment.

Outbreaks of fish bacterial diseases have become quite frequent with the intensification of practices in aquaculture. Vaccination has become an increasingly important prevention strategy against infectious agents in farmed fishes. However, only a few licensed fish bacterial vaccines are commercially available worldwide, and the majority of them are conventional inactivated vaccines. The use of bacterial ghosts (BGs) as novel candidate vaccines has attracted increasing attention from researchers. BGs are nonliving empty cell envelopes mainly derived from gram-negative bacteria. Pores in gram-negative bacteria are formed most commonly through the strictly controlled expression of bacteriophage PhiX174 lysis gene E, whereas pores in gram-positive bacteria can be formed through minimally inhibitory gentle chemical protocols. In biological protocols, the temperature-sensitive λ system has been widely used for quick and efficient lysis without the need for any addition of chemical inducers. To produce BGs with enhanced safety, the incorporation of the staphylococcal nuclease A gene, holin-endolysin system, or antimicrobial peptide genes into gene E-mediated lysis cassettes has been applied to improve lysis efficiency. The ghosts of a few fish pathogenic bacteria, such as Edwardsiella spp., Aeromonas spp., Vibrio spp., and Streptococcus spp., have been successfully developed by gene E-mediated lysis, which maintain the original cell morphology but eliminate genetic contents. Although the lysis efficiency of these BGs does not reach 100%, the lyophilized BGs were free of any living cells. These lyophilized BGs not only have high biological safety for fish, but also can induce stronger humoral, cellular and mucosal immune responses compared to conventional inactivated vaccines. Moreover, BGs are easy to produce in large quantities by fermentation without laborious purification procedures and easy to administer through oral or immersion immunization. Therefore, BGs are good fish vaccine candidates and can be engineered to display heterologous antigens or deliver DNA for use as multivalent vaccines against fish pathogen infection. Yet, completely inactivation was not achieved by the gene E-mediated lysis procedure, how to improve the lysis efficiency of BGs is an important problem for BG production. It is believed that the BG system will play an increasingly important role in the prevention and control of fish diseases with further research and continuous biotechnological development.

Rural housing abandonment (RHA) is happening on a large scale in China and accumulatively leads to the phenomenon of village hollowing. This paper conducts a microscopic analysis on the influencing factors of individual decision making in the process of RHA through an empirical study on Pi County in southwest China. Our multi-level logistic regression shows that RHA is mainly influenced by the pulling forces of urban economy and the deteriorated physical condition of rural houses. We discuss that how these factors exert their influence is further linked with the institutional barriers in China that impede the free movement of residents and properties between urban and rural systems, which distorts individual choices towards RHA. Therefore, we suggest policies that promote the equalization of rural and urban residents and recognize the need for the free transfer of rural land and property, as well as the need to develop tools that effectively predict the emergence of RHA.

Bacterial diseases are a threat to food security. Most bacterial pathogens inject effector proteins inside plant cells, using a type-III secretion system, to suppress plant immunity. However, whether and how effector proteins co-opt plant metabolism to produce nutrients that support extensive bacterial replication is not understood. In this work, we found that Ralstonia solanacearum, the causal agent of bacterial wilt disease, secretes an effector protein, named RipI, which interacts with host glutamate decarboxylases (GADs) inside plant cells. GADs catalyse the biosynthesis of GABA, and are activated by calmodulin. RipI promotes the interaction of GADs with calmodulin, enhancing the production of GABA. Unlike other pathogens, Ralstonia is able to replicate efficiently using GABA as a nutrient, and requires both RipI and plant GABA to achieve a successful infection. This reveals a pathogenic strategy to hijack plant metabolism for the biosynthesis of nutrients to support microbial growth during plant colonization.

Effector proteins delivered inside plant cells are powerful weapons for bacterial pathogens, but this exposes the pathogen to potential recognition by the plant immune system. Therefore, the effector repertoire of a given pathogen must be balanced for a successful infection. Ralstonia solanacearum is an aggressive pathogen with a large repertoire of secreted effectors. One of these effectors, RipE1, is conserved in most R. solanacearum strains sequenced to date. In this work, we found that RipE1 triggers immunity in N. benthamiana, which requires the immune regulator SGT1, but not EDS1 or NRCs. Interestingly, RipE1-triggered immunity induces the accumulation of salicylic acid (SA) and the overexpression of several genes encoding phenylalanine-ammonia lyases (PALs), suggesting that the unconventional PAL-mediated pathway is responsible for the observed SA biosynthesis. Surprisingly, RipE1 recognition also induces the expression of jasmonic acid (JA)-responsive genes and JA biosynthesis, suggesting that both SA and JA may act cooperatively in response to RipE1. Finally, we found that RipE1 expression leads to the accumulation of glutathione in plant cells, which precedes the activation of immune responses. R. solanacearum encodes another effector, RipAY, which is known to inhibit immune responses by degrading cellular glutathione. Accordingly, we show that RipAY inhibits RipE1-triggered immune responses. This work shows a strategy employed by R. solanacearum to counteract the perception of its effector proteins by the plant immune system.

The increase of vegetable planting area lead to the large amounts of VPW (vegetable processing wastes). Effects of V% (VPW proportion) and I% (inoculum proportion) on water free anaerobic co-digestion of VPW with CS (cattle slurry) for methane production was investigated. The results showed that the total methane production was increased from 141.2 L/kg VS (volatile solids) to 186.8 L/kg VS with V% increasing from 17% to 35%. When V%, I% and TS% (total solids content) were 35%, 40% and 7.9%, respectively, the maximal methane production of 186.8 L/kg VS was obtained. However, the optimal conditions were 35% of V% and 30% of I%, the methane production was 170.8 L/kg VS, the maximal methane production was only 9.4% higher than that of the optimal conditions, the TS% of the optimal condition was 8.6% and higher than that of the maximal methane production, the reductions of TS% and VS% for this condition were 29.5% and 49.2%, respectively, and the T 80 for this condition was 42.9% shorter than that of the maximal methane production. The results indicate VPW can be co-digested with CS without water addition.

Regenerated silk fibroin (SF) materials are increasingly used for tissue engineering applications. In order to explore the feasibility of a novel biomimetic silk fibroin tubular scaffold (SFTS) crosslinked by poly(ethylene glycol) diglycidyl ether (PEG-DE), biocompatibility with cells was evaluated. The novel biomimetic design of the SFTS consisted of three distinct layers: a regenerated SF intima, a silk braided media and a regenerated SF adventitia. The SFTS exhibited even silk fibroin penetration throughout the braid, forming a porous layered tube with superior mechanical, permeable and cell adhesion properties that are beneficial to vascular regeneration. Cytotoxicity and cell compatibility were tested on L929 cells and human umbilical vein endothelial cells (EA.hy926). DNA content analysis, scanning electron and confocal microscopies and MTT assay showed no inhibitory effects on DNA replication. Cell morphology, viability and proliferation were good for L929 cells, and satisfactory for EA.hy926 cells. Furthermore, the suture retention strength of the SFTS was about 23 N and the Young's modulus was 0.2–0.3 MPa. Collectively, these data demonstrate that PEG-DE crosslinked SFTS possesses the appropriate cytocompatibility and mechanical properties for use as vascular scaffolds as an alternative to vascular autografts.