Effect of calcifying bacteria on permeation properties of concrete structures

Microbially enhanced calcite precipitation on concrete or mortar has become an important area of research regarding construction materials. This study examined the effect of calcite precipitation induced by Sporosarcina pasteurii (Bp M-3) on parameters affecting the durability of concrete or mortar. An inexpensive industrial waste, corn steep liquor (CSL), from starch industry was used as nutrient source for the growth of bacteria and calcite production, and the results obtained with CSL were compared with those of the standard commercial medium. Bacterial deposition of a layer of calcite on the surface of the specimens resulted in substantial decrease of water uptake, permeability, and chloride penetration compared with control specimens without bacteria. The results obtained with CSL medium were comparable to those obtained with standard medium, indicating the economization of the biocalcification process. The results suggest that calcifying bacteria play an important role in enhancing the durability of concrete structures

Lactose mother liquor as an alternative nutrient source for microbial concrete production by Sporosarcina pasteurii

Microbiologically induced calcite precipitation by the bacterium Sporosarcina pasteurii (NCIM 2477) using the industrial effluent of the dairy industry, lactose mother liquor (LML) as growth medium was demonstrated for the first time in this study. The urease activity and the calcite precipitation by the bacterium was tested in LML and compared with the standard media like nutrient media and yeast extract media. Calcite constituted 24.0% of the total weight of the sand samples plugged by S. pasteurii and urease production was found to be 353 U/ml in LML medium. The compressive strength of cement mortar was increased by S. pasteurii in all the media used compared to control. No significant difference in the growth, urease production and compressive strength of mortar among the media suggesting LML as an alternative source for standard media. This study demonstrates that microbial calcite acts as a sealing agent for filling the gaps or cracks and fissures in constructed facilities and natural formations alike

Strain improvement of Sporosarcina pasteurii for enhanced urease and calcite production

Phenotypic mutants of Sporosarcina pasteurii (previously known as Bacillus pasteurii) (MTCC 1761) were developed by UV irradiation to test their ability to enhance urease activity and calcite production. Among the mutants, Bp M-3 was found to be more efficient compared to other mutants and wild-type strain. It produced the highest urease activity and calcite production compared to other isolates. The production of extracellular polymeric substances and biofilm was also higher in this mutant than other isolates. Microbial sand plugging results showed the highest calcite precipitation by Bp M-3 mutant. Scanning electron micrography, energy-dispersive X-ray and X-ray diffraction analyses evidenced the direct involvement of bacteria in CaCO 3 precipitation. This study suggests that calcite production by the mutant through biomineralization processes is highly effective and may provide a useful strategy as a sealing agent for filling the gaps or cracks and fissures in any construction structures

2,3,7,8-Tetrachlorodibenzo-p-dioxin regulates Bovine Herpesvirus type 1 induced apoptosis by modulating Bcl-2 family members

Exposure to environmental contaminants, like 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), leads to an increased susceptibility to infectious agents. Infection of bovine cells (MDBK) with Bovine Herpesvirus 1 (BHV-1) anticipates virus-induced apoptosis, suggesting an involvement of TCDD in virus infection. Herein we analyzed the effects of TCDD on apoptotic pathway in MDBK cells infected with BHV-1. After 12 h of infection, TCDD induced a significant increase in apoptotic cells. TCDD caused a dose-dependent up-regulation and anticipated activation of caspases 3, 8 and 9, with respect to unexposed groups. TCDD anticipated cleavage of PARP, compared to controls. Furthermore TCDD increased Bax and Bid levels, and decreased Bcl-2 and Bcl-XL levels. Such events took place earlier in exposed than unexposed cells. These results showed that TCDD influences BHV-1 induced apoptosis through members of Bcl-2 family and up-regulating activation of caspases

Technology Insight: magnetic navigation in coronary interventions

Magnetic navigation is rapidly emerging as a useful technology in the field of interventional cardiology. Precise control of the direction of a guide wire or a device in three-dimensional space offers a means to access vessels and areas of the heart that are often challenging to access with conventional methods. In this comprehensive Review, we detail the development of magnetic navigation technology and how this tool has been adapted for use during percutaneous coronary intervention. We aim to provide an up-to-date analysis of what is currently possible with this technology and an insight into what the future holds, particularly with respect to chronic occluded arteries and cell transplantation