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61.
Bio-deposition of a calcium carbonate layer on degraded limestone by Bacillus species 总被引:4,自引:0,他引:4
Dick J De Windt W De Graef B Saveyn H Van der Meeren P De Belie N Verstraete W 《Biodegradation》2006,17(4):357-367
To obtain a restoring and protective calcite layer on degraded limestone, five different strains of the Bacillus sphaericus group and one strain of Bacillus lentus were tested for their ureolytic driven calcium carbonate precipitation. Although all the Bacillus strains were capable of depositing calcium carbonate, differences occurred in the amount of precipitated calcium carbonate on agar plate colonies. Seven parameters involved in the process were examined: calcite deposition on limestone cubes, pH increase, urea degrading capacity, extracellular polymeric substances (EPS)-production, biofilm formation, ζ-potential and deposition of dense crystal layers. The strain selection for optimal deposition of a dense CaCO3 layer on limestone, was based on decrease in water absorption rate by treated limestone. Not all of the bacterial strains were effective in the restoration of deteriorated Euville limestone. The best calcite precipitating strains were characterised by high ureolytic efficiency, homogeneous calcite deposition on limestone cubes and a very negative ζ-potential. 相似文献
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This study investigated the feasibility of a slow-release inoculation approach as a bioaugmentation strategy for the degradation of lindane (gamma-hexachlorocyclohexane [gamma-HCH]). Slow-release inoculation of Sphingomonas sp. gamma 1-7 was established in both liquid and soil slurry microcosms using open-ended silicone tubes in which the bacteria are encapsulated in a protective nutrient-rich matrix. The capacity of the encapsulated cells to degrade lindane under aerobic conditions was evaluated in comparison with inoculation of free-living cells. Encapsulation of cells in tubes caused the removal of lindane by adsorption to the silicone tubes but also ensured prolonged biodegradation activity. Lindane degradation persisted 2.2 and 1.4 times longer for liquid and soil slurry microcosms, respectively, than that for inoculation with free cells. While inoculation of free-living cells led to a loss in lindane-degrading activity in limited time intervals, encapsulation in tubes allowed for a more stable actively degrading community. The loss in degrading activity was linked to the loss of the linA gene, encoding gamma-HCH dehydrochlorinase (LinA), which is involved in the initial steps of the lindane degradation pathway. This work shows that a slow-release inoculation approach using a catabolic strain encapsulated in open-ended tubes is a promising bioaugmentation tool for contaminated sites, as it can enhance pollutant removal and can prolong the degrading activity in comparison with traditional inoculation strategies. 相似文献
64.
Cultivation of Denitrifying Bacteria: Optimization of Isolation Conditions and Diversity Study 总被引:4,自引:1,他引:3
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Kim Heylen Bram Vanparys Lieven Wittebolle Willy Verstraete Nico Boon Paul De Vos 《Applied microbiology》2006,72(4):2637-2643
An evolutionary algorithm was applied to study the complex interactions between medium parameters and their effects on the isolation of denitrifying bacteria, both in number and in diversity. Growth media with a pH of 7 and a nitrogen concentration of 3 mM, supplemented with 1 ml of vitamin solution but not with sodium chloride or riboflavin, were the most successful for the isolation of denitrifiers from activated sludge. The use of ethanol or succinate as a carbon source and a molar C/N ratio of 2.5, 20, or 25 were also favorable. After testing of 60 different medium parameter combinations and comparison with each other as well as with the standard medium Trypticase soy agar supplemented with nitrate, three growth media were highly suitable for the cultivation of denitrifying bacteria. All evaluated isolation conditions were used to study the cultivable denitrifier diversity of activated sludge from a municipal wastewater treatment plant. One hundred ninety-nine denitrifiers were isolated, the majority of which belonged to the Betaproteobacteria (50.4%) and the Alphaproteobacteria (36.8%). Representatives of Gammaproteobacteria (5.6%), Epsilonproteobacteria (2%), and Firmicutes (4%) and one isolate of the Bacteroidetes were also found. This study revealed a much more diverse denitrifying community than that previously described in cultivation-dependent research on activated sludge. 相似文献
65.
Diatomaceous earth as a protective vehicle for bacteria applied for self-healing concrete 总被引:1,自引:0,他引:1
Wang JY Belie ND Verstraete W 《Journal of industrial microbiology & biotechnology》2012,39(4):567-577
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. 相似文献
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Patrick LJM Zeeuwen Jos Boekhorst Ellen H van den Bogaard Heleen D de Koning Peter MC van de Kerkhof Delphine M Saulnier Iris I van Swam Sacha AFT van Hijum Michiel Kleerebezem Joost Schalkwijk Harro M Timmerman 《Genome biology》2012,13(11):R101
Background
Recent advances in sequencing technologies have enabled metagenomic analyses of many human body sites. Several studies have catalogued the composition of bacterial communities of the surface of human skin, mostly under static conditions in healthy volunteers. Skin injury will disturb the cutaneous homeostasis of the host tissue and its commensal microbiota, but the dynamics of this process have not been studied before. Here we analyzed the microbiota of the surface layer and the deeper layers of the stratum corneum of normal skin, and we investigated the dynamics of recolonization of skin microbiota following skin barrier disruption by tape stripping as a model of superficial injury.Results
We observed gender differences in microbiota composition and showed that bacteria are not uniformly distributed in the stratum corneum. Phylogenetic distance analysis was employed to follow microbiota development during recolonization of injured skin. Surprisingly, the developing neo-microbiome at day 14 was more similar to that of the deeper stratum corneum layers than to the initial surface microbiome. In addition, we also observed variation in the host response towards superficial injury as assessed by the induction of antimicrobial protein expression in epidermal keratinocytes.Conclusions
We suggest that the microbiome of the deeper layers, rather than that of the superficial skin layer, may be regarded as the host indigenous microbiome. Characterization of the skin microbiome under dynamic conditions, and the ensuing response of the microbial community and host tissue, will shed further light on the complex interaction between resident bacteria and epidermis. 相似文献69.
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