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Microbial-induced carbonate precipitation technology allows concrete to detect and diagnose cracks autonomously. However, the concrete’s compact structure and alkaline environment necessitate the adoption of a proper carrier material to safeguard microorganisms. In this study, various bacterial strains, including Bacillus subtilis, Bacillus sphaericus, and Bacillus megaterium, were immobilized in lightweight expanded clay aggregates (LECA) to investigate their effect on the self-healing performance, mechanical strength, and freeze–thaw durability. Self-healing concrete specimens were prepared using immobilized LECA, directly added bacterial spores, polyvinyl acetate (PVA) fibers, and air-entraining admixture (AEA). The pre-cracked prisms were monitored for 224 days to assess self-healing efficiency through ultrasonic pulse velocity (UPV) and surface crack analysis methods. A compressive strength restoration test was conducted by pre-loading the cube specimens with 60% of the failure load and re-testing them after 28 days for strength regain. Additionally, X-ray diffraction and scanning electron microscopy (SEM) were conducted to analyze the precipitate material. The findings revealed that self-healing efficiency improved with the biomineralization activity over the healing period demonstrated by the bacterial strains. Compression and flexural strengths decreased for the bacterial specimens attributed to porous LECA. However, restoration in compression strength and freeze–thaw durability significantly improved for the bacterial mixes compared to control and reference mixes. XRD and SEM analyses confirmed the formation of calcite as a self-healing precipitate. Overall, results indicated the superior performance of Bacillus megaterium followed by Bacillus sphaericus and Bacillus subtilis. The findings of the current study provide important insights for the construction industry, showcasing the potential of bacteria to mitigate the degradation of concrete structures and advocating for a sustainable solution that reduces reliance on manual repairs, especially in inaccessible areas of the structures.

We observed instances of cannibalism (intraspecific predation) among intra-instar larvae of Culex pipiens Linnaeus, 1758 while performing a bioassay of Lysinibacillus sphaericus (formerly named Bacillus sphaericus) larvicide, when the larvae were exposed to the larvicide for 48 h in the absence of food. Larvae without symptoms of poisoning attacked and devoured those visibly affected. Cannibalism was more prevalent in 1 -2 instar larvae than in 3 -4 instar. This phenomenon should be taken into account when interpreting the results of larvicide bioassays, especially when the exposure lasts over 24 h. The necessity of creating optimal conditions for organisms tested is emphasised.

Because it is often logistically impossible to monitor all catch basins within an operational area, local mosquito control programs will preemptively treat catch basins with larvicides each season. However, these larvicides can, ostensibly, be considered water quality pollutants. To experimentally reduce the use of larvicides toward improving water quality, 30 basins within a small 0.7-km super( 2) residential area were monitored weekly for the presence of larvae and pupae for 14 wk in the summer of 2013. Once a basin was found to reach a threshold of 12 mosquitoes per dip sample, it received a FourStar registered Briquet (a 180-day briquet formulation of 6% Bacillus sphaericus and 1% B. thuringiensis israelensis). Each week a FourStar-treated basin surpassed this threshold, it was treated with an application of CocoBear(TM) oil (10% mineral oil). By the end of trials, all but one basin received a briquet and 13 required at least 4 treatments of CocoBear, suggesting that preemptive treatment is appropriate for the study area.

Elicitation of induced systemic resistance (ISR) by plant-associated bacteria was initially demonstrated using Pseudomonas spp. and other gram-negative bacteria. Several reviews have summarized various aspects of the large volume of literature on Pseudomonas spp. as elicitors of ISR. Fewer published accounts of ISR by Bacillus spp. are available, and we review this literature for the first time. Published results are summarized showing that specific strains of the species B. amyloliquefaciens, B. subtilis, B. pasteurii, B. cereus, B. pumilus, B. mycoides, and B. sphaericus elicit significant reductions in the incidence or severity of various diseases on a diversity of hosts. Elicitation of ISR by these strains has been demonstrated in greenhouse or field trials on tomato, bell pepper, muskmelon, watermelon, sugar beet, tobacco, Arabidopsis sp., cucumber, loblolly pine, and two tropical crops (long cayenne pepper and green kuang futsoi). Protection resulting from ISR elicited by Bacillus spp. has been reported against leaf-spotting fungal and bacterial pathogens, systemic viruses, a crown-rotting fungal pathogen, root-knot nematodes, and a stem-blight fungal pathogen as well as damping-off, blue mold, and late blight diseases. Reductions in populations of three insect vectors have also been noted in the field: striped and spotted cucumber beetles that transmit cucurbit wilt disease and the silver leaf whitefly that transmits Tomato mottle virus. In most cases, Bacillus spp. that elicit ISR also elicit plant growth promotion. Studies on mechanisms indicate that elicitation of ISR by Bacillus spp. is associated with ultrastructural changes in plants during pathogen attack and with cytochemical alterations. Investigations into the signal transduction pathways of elicited plants suggest that Bacillus spp. activate some of the same pathways as Pseudomonas spp. and some additional pathways. For example, ISR elicited by several strains of Bacillus spp. is independent of salicylic acid but dependent on jasmonic acid, ethylene, and the regulatory gene NPR1—results that are in agreement with the model for ISR elicited by Pseudomonas spp. However, in other cases, ISR elicited by Bacillus spp. is dependent on salicylic acid and independent of jasmonic acid and NPR1. In addition, while ISR by Pseudomonas spp. does not lead to accumulation of the defense gene PR1 in plants, in some cases, ISR by Bacillus spp. does. Based on the strains and results summarized in this review, two products for commercial agriculture have been developed, one aimed mainly at plant growth promotion for transplanted vegetables and one, which has received registration from the U.S. Environmental Protection Agency, for disease protection on soybean.

Microbially induced calcium carbonate precipitation is an emerging process for the production of self-healing concrete. This study was aimed to investigate the effects and optimum conditions on calcium carbonate biosynthesis. Bacillus licheniformis , Bacillus sphaericus , yeast extract, urea, calcium chloride and aeration were found to be the most significant factors affecting the biomineralization of calcium carbonate. It was noticed that the morphology of microbial calcium carbonate was mainly affected by the genera of bacteria (cell surface properties), the viscosity of the media and the type of electron acceptors (Ca 2+ ). The maximum calcium carbonate concentration of 33.78 g/L was achieved at the optimum conditions This value is the highest concentration reported in the literature.

Concrete cracks must be repaired promptly in order to prevent structural damage and to prolong the structural life of the building (or other such construction). Biological self-healing concrete is a recent alternative technology involving the biochemical reaction of microbial induced calcium carbonate precipitation (MICP). This study determined the most appropriate technique to encapsulate spores of Bacillus sphaericus LMG 22257 with sodium alginate so as to protect the bacterial spores during the concrete mixing and hardening period. Three techniques (extrusion, spray drying and freeze drying) to encapsulate the bacterial spores with sodium alginate were evaluated. The freeze-drying process provided the highest bacterial spore survival rate (100%), while the extruded and spray-dried processes had a lower spore survival rate of 93.8% and 79.9%, respectively. To investigate the viability of microencapsulated spores after being mixed with mortar, the decomposed urea analysis was conducted. The results revealed that the freeze-dried spores also showed the highest level of urea decomposition (metabolic activity assay used as a surrogate marker of spore germination and vegetative cell viability). Thus, the self-healing performance of concrete mixed with freeze-dried spores was evaluated. The results showed that the crack healing ratio observed from the mortar specimens with freeze-dried microencapsulated spores were significantly higher than those without bacteria. This study revealed that freeze drying has a high potential as a microencapsulation technique for application to self-healing concrete technology.

The suitability of using a spore-forming ureolytic strain, Bacillus sphaericus , was evaluated for self-healing of concrete cracks. The main focus was on alkaline tolerance, calcium tolerance, oxygen dependence, and low-temperature adaptability. Experimental results show that B. sphaericus had a good tolerance. It can grow and germinate in a broad range of alkaline pH. The optimal pH range is 7 ∼ 9. High alkaline conditions (pH 10 ∼ 11) slow down but not stop the growth and germination. Oxygen was strictly needed during bacterial growth and germination, but not an essential factor during bacterial urea decomposition. B. sphaericus also had a good Ca tolerance, especially at a high bacterial concentration of 10 8  cells/mL; no significant influence was observed on bacterial ureolytic activity of the presence of 0.9M Ca 2+ . Furthermore, at a low temperature (10 °C), bacterial spores germinated and revived ureolytic activity with some retardation. However, this retardation can be counteracted by using a higher bacterial concentration and by supplementing yeast extract. It can be concluded that B. sphaericus is a suitable bacterium for application in bacteria-based self-healing concrete.

Abstract Crack repair is crucial since cracks are the main cause for the decreased service life of concrete structures. An original and promising way to repair cracks is to pre-incorporate healing agents inside the concrete matrix to heal cracks the moment they appear. Thus, the concrete obtains self-healing properties. The goal of our research is to apply bacterially precipitated CaCO3 to heal cracks in concrete since the microbial calcium carbonate is more compatible with the concrete matrix and more environmentally friendly relative to the normally used polymeric materials. Diatomaceous earth (DE) was used in this study to protect bacteria from the high-pH environment of concrete. The experimental results showed that DE had a very good protective effect for bacteria. DE immobilized bacteria had much higher ureolytic activity (12–17 g/l urea was decomposed within 3 days) than that of un-immobilized bacteria (less than 1 g/l urea was decomposed within the same time span) in cement slurry. The optimal concentration of DE for immobilization was 60% (w/v, weight of DE/volume of bacterial suspension). Self-healing in cracked specimens was visualized under light microscopy. The images showed that cracks with a width ranging from 0.15 to 0.17 mm in the specimens containing DE immobilized bacteria were completely filled by the precipitation. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to characterize the precipitation around the crack wall, which was confirmed to be calcium carbonate. The result from a capillary water absorption test showed that the specimens with DE immobilized bacteria had the lowest water absorption (30% of the reference ones), which indicated that the precipitation inside the cracks increased the water penetration resistance of the cracked specimens.

Several trials and reviews have outlined the potential role of larviciding for malaria control in sub-Saharan Africa (SSA) to supplement the core indoor insecticide-based interventions. It has been argued that widespread use of long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) interventions in many parts of Africa result in many new areas with low and focal malaria transmission that can be targeted with larvicides. As some countries in SSA are making good progress in malaria control, larval source management, particularly with bacterial larvicides, could be included in the list of viable options to maintain the gains achieved while paving the way to malaria elimination. We conducted a review of published literature that investigated the application of bacterial larvicides, Bacillus thuringiensis var. israelensis ( Bti ) and/or Bacillus sphaericus ( Bs ) for malaria vector control in SSA. Data for the review were identified through PubMed, the extensive files of the authors and reference lists of relevant articles retrieved. A total of 56 relevant studies were identified and included in the review. The findings indicated that, at low application rates, bacterial larvicide products based on Bti and/or Bs were effective in controlling malaria vectors. The larvicide interventions were found to be feasible, accepted by the general community, safe to the non-target organisms and the costs compared fairly well with those of other vector control measures practiced in SSA. Our review suggests that larviciding should gain more ground as a tool for integrated malaria vector control due to the decline in malaria which creates more appropriate conditions for the intervention and to the recognition of limitations of insecticide-based vector control tools. The advancement of new technology for mapping landscapes and environments could moreover facilitate identification and targeting of the numerous larval habitats preferred by the African malaria vectors. To build sustainable anti-larval measures in SSA, there is a great need to build capacity in relevant specialties and develop organizational structures for governance and management of larval source management programmes.

Effective larviciding for malaria control requires detailed studies of larvicide efficacies, aquatic habitat characteristics, and life history traits of target vectors. Mosquitoes with brief larval phases present narrower timeframes for biolarvicidal effects than mosquitoes with extended periods. We evaluated two biolarvicides, VectoBac ( Bacillus thuringiensis israelensis ( Bti )) and VectoMax ( Bti and Bacillus sphaericus ) against Anopheles funestus and Anopheles arabiensis in shaded and unshaded habitats; and explored how larval development might influence retreatment intervals. These tests were done in semi-natural habitats using field-collected larvae, with untreated habitats as controls. Additionally, larval development was assessed in semi-natural and natural habitats in rural Tanzania, by sampling daily and recording larval developmental stages. Both biolarvicides reduced larval densities of both species by >98% within 72 h. Efficacy lasted one week in sun-exposed habitats but remained >50% for two weeks in shaded habitats. An. funestus spent up to two weeks before pupating (13.2(10.4–16.0) days in semi-natural; 10.0(6.6–13.5) in natural habitats), while An. arabiensis required slightly over one week (8.2 (5.8–10.6) days in semi-natural; 8.3 (5.0–11.6) in natural habitats). The findings suggest that weekly larviciding, which is essential for An. arabiensis might be more effective for An. funestus whose prolonged aquatic growth allows for repeated exposures. Additionally, the longer residual effect of biolarvicides in shaded habitats indicates they may require less frequent treatments compared to sun-exposed areas.