Complete Genome and Calcium Carbonate Precipitation of Alkaliphilic Bacillus sp. AK13 for Self-Healing Concrete

pH-Controlled DNA Switching Circuits with Multi-State Responsiveness for Logic Computation and Control

Dynamic control of DNA circuit functionality is essential for constructing chemical reaction networks (CRNs) that implement complex functions. The triplex has been utilized for dynamically regulating the diverse functionalities of DNA circuits due to its distinctive pH responsiveness. However, it is challenging for triplexes to independently regulate the functionality of DNA circuits, as various triplexes were often required for DNA circuits to function in complex environments, which adds complexity to the design and control of dynamic circuits. Here, we proposed a pH-controlled multi-state DNA switching circuit construction strategy to realize dynamic regulation among three states through conformational transitions of the triplex. In addition, by leveraging the regulatory role of multi-state DNA switching circuits on the toehold-mediated strand displacement reaction, we constructed switchable DNA circuits for logic computation and control of hybridization chain reaction (HCR). We confirmed that the designed DNA switching circuits exhibited multi-state responsiveness, allowing for different logical operations at varying pH levels and programmable control of the diverse reaction pathways in the HCR. Our strategy offers a convenient approach for the intelligent response and dynamic regulation of large-scale CRNs and DNA nanostructure self-assembly. It promises applications in biosensing, disease detection and drug delivery.

Bacteria-powered self-healing concrete: Breakthroughs, challenges, and future prospects

In a world where concrete structures face constant degradation from environmental forces, a revolutionary solution has emerged: bio-self-healing concrete. This innovation involves embedding dormant bacteria within the concrete mix, poised to spring into action when cracks form. As moisture seeps into the cracks, these bacterial agents are activated, consuming nutrients and converting them into calcium carbonate, a natural substance that fills and repairs the fractures, restoring the material's integrity. This fascinating process represents a cutting-edge approach to maintaining concrete infrastructure, turning once-vulnerable materials into self-sustaining systems capable of healing themselves. The ongoing research into bio-self-healing concrete is focused on selecting bacterial strains that can withstand the extreme conditions within concrete, including its highly alkaline environment. The bacteria must also form resilient spores, remaining viable until they are needed for repair. Additionally, the study explores various challenges associated with this technology, such as the cost of production, the bacteria's long-term viability, and their potential environmental impact. Advancements in genetic engineering and smart technology are being explored to enhance these bacterial strains, making them more efficient and robust in their role as microscopic repair agents. This review delves into the potential of bio-self-healing concrete to revolutionize how we approach infrastructure maintenance, offering a glimpse into a future where concrete structures not only endure but actively repair themselves, extending their lifespan and reducing the need for costly repairs.

ONE-SENTENCE SUMMARY

Bio-self-healing concrete utilizes bacteria that activate upon crack formation to repair structures by producing calcium carbonate, offering a sustainable solution to prolong the lifespan of concrete infrastructure.

More than a contaminant: How zinc promotes carbonate-mineralizing bacteria metabolism and adaptation by reshaping precipitation conditions

Although microbial-induced carbonate precipitation (MICP) technology is both environmentally friendly and cost-effective, its efficiency is constrained by challenges such as low bacterial activity and heavy metal stress. This study explored the enhancement of mineralization efficiency by incorporating zinc (Zn) into the cultivation system of carbonate-mineralized bacteria. All Zn salts at a concentration of 30 μmol/L significantly enhanced the density and heavy metal resistance of bacterial cells, while also promoting CO2 hydration efficiency. The activities of urease and carbonic anhydrase (CA) were significantly elevated after treatment with 30 μmol/L ZnCl2 and Zn(C3H5O3)2 (ZnL) compared to the control. The results from qRT-PCR and ELISA confirmed that ZnL exhibited a stable biological effect on CA gene expression. Through the analysis of surface chemistry of cells and the subcellular distribution pattern of cadmium (Cd), it was observed that Zn supplementation maintained the cell surface stability and strengthened the cellular barrier against Cd uptake. SEM, FTIR and XRD results further confirmed that Zn supplementation significantly increased the complexity of the mineral morphology, resulting in a more stable crystal structure of CdCO3. This study offers additional theoretical and technical backing, opening a new avenue for the practical application of MICP technology in heavy metal remediation.

Zoo animal manure as an overlooked reservoir of antibiotic resistance genes and multidrug-resistant bacteria

Animal fecal samples collected in the summer and winter from 11 herbivorous animals, including sable antelope (SA), long-tailed goral (LTG), and common eland (CE), at a public zoo were examined for the presence of antibiotic resistance genes (ARGs). Seven antibiotics, including meropenem and azithromycin, were used to isolate culturable multidrug-resistant (MDR) strains. The manures from three animals (SA, LTG, and CE) contained 10⁴-fold higher culturable MDR bacteria, including Chryseobacterium, Sphingobacterium, and Stenotrophomonas species, while fewer MDR bacteria were isolated from manure from water buffalo, rhinoceros, and elephant against all tested antibiotics. Three MDR bacteria-rich samples along with composite samples were further analyzed using nanopore-based technology. ARGs including lnu(C), tet(Q), and mef(A) were common and often associated with transposons in all tested samples, suggesting that transposons carrying ARGs may play an important role for the dissemination of ARGs in our tested animals. Although several copies of ARGs such as aph(3')-IIc, bla_L1, bla_IND-3, and tet(42) were found in the sequenced genomes of the nine MDR bacteria, the numbers and types of ARGs appeared to be less than expected in zoo animal manure, suggesting that MDR bacteria in the gut of the tested animals had intrinsic resistant phenotypes in the absence of ARGs.

Evaluation of Cyclic Healing Potential of Bacteria-Based Self-Healing Cementitious Composites

At present, little evidence exists regarding the capability of bacteria-based self-healing (BBSH) cementitious materials to successfully re-heal previously healed cracks. This paper investigates the repeatability of the self-healing of BBSH mortars when the initially healed crack is reopened at a later age (20 months) and the potential of encapsulated bacterial spores to heal a new crack generated at 22 months after casting. The results show that BBSH cement mortar cracks that were successfully healed at an early age were not able to successfully re-heal when cracks were reformed in the same location 20 months later, even when exposed to favourable conditions (i.e., high humidity, temperature, calcium source, and nutrients) to promote their re-healing. Therefore, it is likely that not enough bacterial spores were available within the initially healed crack to successfully start a new self-healing cycle. However, when entirely new cracks were intentionally generated at a different position in 22-month-old mortars, these new cracks were able to achieve an average healing ratio and water tightness of 93.3% and 90.8%, respectively, thus demonstrating that the encapsulated bacterial spores remained viable inside the cementitious matrix. The results reported in this paper provide important insights into the appropriate design of practical self-healing concrete and, for the first time, show limitations of the ability of BBSH concrete to re-heal.

The influence of long-term Zn and Cu contamination in Spolic Technosols on water-soluble organic matter and soil biological activity

Potentially toxic elements (PTE) pollution has a pronounced negative effect on the soil and its components. The characteristics of soil organic matter and the activity of soil enzymes can serve as sensitive indicators of the degree of changes occurring in the soil. This study aims to assess the effect of long-term severe soil contamination with Zn and Cu on water-soluble organic matter (WSOM) and the associated changes in the biochemical activity of microorganisms. The total content of Zn and Cu in the studied soils varies greatly: Zn from 118 to 65,311 mg/kg, Cu from 52 to 437 mg/kg. The content of WSOM was determined using cold and hot extraction. It was revealed that the WSOM, extracted with cold water is a sensitive indicator reflecting the nature of the interaction of Zn and Cu with it. With an increase in the Cu and Zn content, the amount of WSOM extracted with cold water increases due to rise in the complex-bound metal compounds associated with it. The content of complex-bound compounds Zn in Spolic Technosols reaches 50% of the total metal content. It is shown that one of the biogeochemical mechanisms of microorganisms' adaptation to metal contamination is clearly manifested by the increase in the content of WSOM. The precipitation of metal carbonates develops in the soil which reduces the mobility and toxicity of PTE. Due to this mechanism, a decrease in the activity of dehydrogenases and urease was not prominent in all studied soils, despite the very high level of pollution and the transformation of organic matter. The study of the relationship of PTE with the most easily transformed part of WSOM and the activity of soil enzymes is of great importance for an objective assessment of possible environmental risks.

Agricultural by-products and oyster shell as alternative nutrient sources for microbial sealing of early age cracks in mortar

Bio-concrete using bacterially produced calcium carbonate can repair microcracks but is still relatively expensive due to the addition of bacteria, nutrients, and calcium sources. Agricultural by-products and oyster shells were used to produce economical bio-concrete. Sesame meal was the optimal agricultural by-product for low-cost spore production of the alkaliphilic Bacillus miscanthi strain AK13. Transcriptomic dataset was utilized to compare the gene expressions of AK13 strain under neutral and alkaline conditions, which suggested that NaCl and riboflavin could be chosen as growth-promoting factors at alkaline pH. The optimal levels of sesame meal, NaCl, and riboflavin were induced with the central composite design to create an economical medium, in which AK13 strain formed more spores with less price than in commercial sporulation medium. Calcium nitrate obtained from nitric acid treatment of oyster shell powder increased the initial compressive strength of cement mortar. Non-ureolytic calcium carbonate precipitation by AK13 using oyster shell-derived calcium ions was verified by energy-dispersive X-ray spectroscopy and X-ray diffraction analysis. Stereomicroscope and field emission scanning electron microscopy confirmed that oyster shell-derived calcium ions, along with soybean meal-solution, increased the bacterial survival and calcium carbonate precipitation inside mortar cracks. These data suggest the possibility of commercializing bacterial self-healing concrete with economical substitutes for culture medium, growth nutrient, and calcium sources.