Comparison of calcium carbonate production by bacterial isolates from recycled aggregates.

The new technology of microbially induced calcium carbonate precipitation (MICP) has been applied in construction materials as a strategy to enhance their properties. In pursuit of solutions that are more localized and tailored to the study's target, this work focused on isolating and selecting bacteria capable of producing CaCO3 for posterior application in concrete aggregates. First, eleven bacterial isolates were obtained from aggregates and identified as genera Bacillus, Lysinibacillus, Exiguobacterium, and Micrococcus. Then, the strains were compared based on the quantity and nature of calcium carbonate they produced using thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy with energy dispersive spectroscopy. Bacillus sp. dominated the cultured isolates and, along with Lysinibacillus sp., exhibited the highest CaCO3 conversion (up to 80%). On the other hand, Exiguobacterium and Micrococcus genera showed the poor ability to MICP (21.3 and 20.3%, respectively). Calcite and vaterite were the dominant carbonate polymorphs, with varying proportions. Concrete aggregates have proven to be a source of microorganisms capable of producing stable calcium carbonates with a high conversion rate. This indicates the feasibility of using microorganisms derived from local sources for application in construction materials as a sustainable way to enhance their characteristics.

Extremophilic taxa predominate in a microbial community of photovoltaic panels in a tropical region.

Photovoltaic panels can be colonized by a highly diverse microbial diversity, despite life-threatening conditions. Although they are distributed worldwide, the microorganisms living on their surfaces have never been profiled in tropical regions using 16S rRNA high-throughput sequencing and PICRUst metagenome prediction of functional content. In this work, we investigated photovoltaic panels from two cities in southeast Brazil, Sorocaba and Itatiba, using these bioinformatics approach. Results showed that, despite significant differences in microbial diversity (p < 0.001), the taxonomic profile was very similar for both photovoltaic panels, dominated mainly by Proteobacteria, Bacteroidota and lower amounts of Cyanobacteria phyla. A predominance of Hymenobacter and Methylobacterium-Methylorubrum was observed at the genus level. We identified a microbial common core composed of Hymenobacter, Deinococcus, Sphingomonas, Methylobacterium-Methylorubrum, Craurococcus-Caldovatus, Massilia, Noviherbaspirillum and 1174-901-12 sharing genera. Predicted metabolisms focused on specific genes associated to radiation and desiccation resistance and pigments, were detected in members of the common core and among the most abundant genera. Our results suggested that taxonomic and functional profiles investigated were consistent with the harsh environment that photovoltaic panels represent. Moreover, the presence of stress genes in the predicted functional content was a preliminary evidence that microbes living there are a possibly source of metabolites with biotechnological interest.

Isolation and Potential Biocementation of Calcite Precipitation Inducing Bacteria from Colombian Buildings.

Microbiological induced calcium carbonate or calcite precipitation (MICP) has become a highly researched issue due to its multiple applications in the construction industry, being a promising alternative with a great biotechnological importance. In this work, potential calcite precipitation inducing bacteria were isolated from mortar and concrete samples of different buildings at the National University of Colombia. Eighteen crystal-precipitating strains were recovered in Urea-CaCl2 solid medium. The 16S rRNA gene sequencing identified isolates as Arthrobacter, Psychrobacillus and Rhodococcus genera. It is reported, for the first time, the calcite precipitation by P. psycrodurans and R. qingshengii. Optical microscopy and Scanning Electron Microscopy showed crystals with irregular and spherical shapes, and beige and white colours. Furthermore, crystals formation appeared to be strain-specific. X-Ray diffraction analysis confirmed crystals composition as CaCO3. Biocementation tests showed that MICP treatments of mortar cubes using P. psycrodurans caused an increase in their compressive strength compared to control samples. The positive action of a native MICP strain in mortar blocks biomineralization is shown, which is of great interest and potential for the construction industry.

Epilithic and endolithic microorganisms and deterioration on stone church facades subject to urban pollution in a sub-tropical climate.

Weathering of two church facades in Rio de Janeiro was caused substantially by salts, mainly halite and gypsum, detected by SEM and chemical analyses, which cause physical stresses by deposition within the rock. Biofilm populations, determined by SEM and as operational taxonomic units (OTUs), degraded stone by penetration, solubilization and redeposition of minerals on their surfaces. Endolithic cyanobacteria were associated with gypsum deposits. Microbiomes were typical for high-stress environments, high salt, intense insolation, low water and low nutrients (eg halophilic Rubrobacter, Salinicola, Sterigmatomyces). The main colonizers on the church most affected by traffic (Nossa Senhora da Candelária - CA) were Actinobacteria; Gammaproteobacteria (chiefly Pseudomonas) were predominant on the site situated in a leafy square (São Francisco de Paula - SF). Major Gammaproteobacteria on CA were halophilic Halomonas and Rhodobacteriaceae. Fungal OTUs on both churches were principally dimorphic, yeast-like basidiomycetes. Many OTUs of thermophilic microorganisms (eg the Thermomicrobia class, Chloroflexi) were present. This is the first use of next generation sequencing (NGS) to study microbial biofilm interactions with metamorphic and granite buildings in an intensely urban, sub-tropical climate.

Molecular Tools for Monitoring the Ecological Sustainability of a Stone Bio-Consolidation Treatment at the Royal Chapel, Granada.

BACKGROUND: Biomineralization processes have recently been applied in situ to protect and consolidate decayed ornamental stone of the Royal Chapel in Granada (Spain). While this promising method has demonstrated its efficacy regarding strengthening of the stone, little is known about its ecological sustainability. METHODOLOGY/PRINCIPAL FINDINGS: Here, we report molecular monitoring of the stone-autochthonous microbiota before and at 5, 12 and 30 months after the bio-consolidation treatment (medium/long-term monitoring), employing the well-known molecular strategy of DGGE analyses. Before the bio-consolidation treatment, the bacterial diversity showed the exclusive dominance of Actinobacteria (100%), which decreased in the community (44.2%) after 5 months, and Gamma-proteobacteria (30.24%) and Chloroflexi (25.56%) appeared. After 12 months, Gamma-proteobacteria vanished from the community and Cyanobacteria (22.1%) appeared and remained dominant after thirty months, when the microbiota consisted of Actinobacteria (42.2%) and Cyanobacteria (57.8%) only. Fungal diversity showed that the Ascomycota phylum was dominant before treatment (100%), while, after five months, Basidiomycota (6.38%) appeared on the stone, and vanished again after twelve months. Thirty months after the treatment, the fungal population started to stabilize and Ascomycota dominated on the stone (83.33%) once again. Members of green algae (Chlorophyta, Viridiplantae) appeared on the stone at 5, 12 and 30 months after the treatment and accounted for 4.25%, 84.77% and 16.77%, respectively. CONCLUSIONS: The results clearly show that, although a temporary shift in the bacterial and fungal diversity was observed during the first five months, most probably promoted by the application of the bio-consolidation treatment, the microbiota tends to regain its initial stability in a few months. Thus, the treatment does not seem to have any negative side effects on the stone-autochthonous microbiota over that time. The molecular strategy employed here is suggested as an efficient monitoring tool to assess the impact on the stone-autochthonous microbiota of the application of biomineralization processes as a restoration/conservation procedure.

Investigations of biodeterioration by fungi in historic wooden churches of Chiloé, Chile.

The use of wood in construction has had a long history and Chile has a rich cultural heritage of using native woods for building churches and other important structures. In 2000, UNESCO designated a number of the historic churches of Chiloé, built entirely of native woods, as World Heritage Sites. These unique churches were built in the late 1700 s and throughout the 1800 s, and because of their age and exposure to the environment, they have been found to have serious deterioration problems. Efforts are underway to better understand these decay processes and to carryout conservation efforts for the long-term preservation of these important structures. This study characterized the types of degradation taking place and identified the wood decay fungi obtained from eight historic churches in Chiloé, seven of them designated as UNESCO World Heritage sites. Micromorphological observations identified white, brown and soft rot in the structural woods and isolations provided pure cultures of fungi that were identified by sequencing of the internal transcribed region of rDNA. Twenty-nine Basidiomycota and 18 Ascomycota were found. These diverse groups of fungi represent several genera and species not previously reported from Chile and demonstrates a varied microflora is causing decay in these historic buildings.

Microbiologically induced deterioration of concrete: a review

Microbiologically induced deterioration (MID) causes corrosion of concrete by producing acids (including organic and inorganic acids) that degrade concrete components and thus compromise the integrity of sewer pipelines and other structures, creating significant problems worldwide. Understanding of the fundamental corrosion process and the causal agents will help us develop an appropriate strategy to minimize the costs in repairs. This review presents how microorganisms induce the deterioration of concrete, including the organisms involved and their colonization and succession on concrete, the microbial deterioration mechanism, the approaches of studying MID and safeguards against concrete biodeterioration. In addition, the uninvestigated research area of MID is also proposed.

Microbiologically induced deterioration of concrete--a review.

Microbiologically induced deterioration (MID) causes corrosion of concrete by producing acids (including organic and inorganic acids) that degrade concrete components and thus compromise the integrity of sewer pipelines and other structures, creating significant problems worldwide. Understanding of the fundamental corrosion process and the causal agents will help us develop an appropriate strategy to minimize the costs in repairs. This review presents how microorganisms induce the deterioration of concrete, including the organisms involved and their colonization and succession on concrete, the microbial deterioration mechanism, the approaches of studying MID and safeguards against concrete biodeterioration. In addition, the uninvestigated research area of MID is also proposed.

Molecular analysis of microbial diversity in corrosion samples from energy transmission towers.

Microbial diversity in corrosion samples from energy transmission towers was investigated using molecular methods. Ribosomal DNA fragments were used to assemble gene libraries. Sequence analysis indicated 10 bacterial genera within the phyla Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. In the two libraries generated from corroded screw-derived samples, the genus Acinetobacter was the most abundant. Acinetobacter and Clostridium spp. dominated, with similar percentages, in the libraries derived from corrosion scrapings. Fungal clones were affiliated with 14 genera belonging to the phyla Ascomycota and Basidiomycota; of these, Capnobotryella and Fellomyces were the most abundant fungi observed. Several of the microorganisms had not previously been associated with biofilms and corrosion, reinforcing the need to use molecular techniques to achieve a more comprehensive assessment of microbial diversity in environmental samples.

Biocide-containing varnish for the protection of sandstone: comparison of formulations and laboratory test methods.

Two formulations of acrylic varnish, with and without either of two dry film biocides--one a mixture of isothiazolinones and benzimidazole derivatives, and the other a carbamate--were tested in vitro for their activity against mixtures of filamentous fungi and cyanobacteria found on sandstone buildings. Growth on filter-paper squares coated with the varnishes was assessed semi-quantitatively by naked eye, quantitatively by image analysis and chemically by measurement of ergosterol and chlorophyll a. The lower solvent content (higher resin) varnish was more inhibitory to cyanobacteria than the higher varnish content, whilst the opposite was true for the fungal inoculum. The carbamate biocide was effective against cyanobacteria, unlike the isothiazolinone mixture, but the latter produced more inhibition of fungal growth. The three assay methods produced generally similar results, although visual observation was obviously the most imprecise. There was an anomaly in the ergosterol measurements, which was considered to be caused by the varying ergosterol content and unequal inhibition of the three fungal genera used in the inoculum. Fusarium sp. was shown to contain higher levels of this membrane component than Cladosporium sp. and Penicillium sp. For this reason, the most appropriate method overall, giving reliable quantitative results, was deemed to be the image analysis.

Dengue, related to rubble and building construction in Brazil.

The fast-growing formation of solid waste, resulting from demographic density, presents itself as one of the most pressing problems to be addressed by governments of large cities all over the world. In Rio de Janeiro, 60% of solid waste stems from the construction industry. Although envisaged by under current municipal legislation, no application of policy regarding systematic recycling of this kind of waste exists in fact. Both sanitation experts and epidemiologists highlight that the deficient sanitary system contributes to the growth of endemic breeding sites, which may reach epidemic proportions. In Brazil, over the recent years, there has been an increase of Dengue Fever cases followed by deaths. In the first half of 2008, the State of Rio de Janeiro was plagued by an intense Dengue epidemic. The city of Rio de Janeiro alone accounted for 48.7% of the cases, in absolute values. By drawing upon an analytical method based on the interrelation between health and sanitation, the outcomes herein indicate that the city of Rio de Janeiro bears a direct relation between Dengue incidence rates and rubble formation from construction - measured by the total area built. Thus, there is a strong urge to implement recycling systems out of construction rubble as a sanitation measure in order to promote Dengue incidence reduction.

The importance of biofilms in microbial deterioration of constructional materials

Constructional materials, such as concrete, stone, wood, plastic, painted surfaces and metal, are colonized by bacteria, algae and fungi, which form biofilms on the surfaces acceleranting deteriotion of the structure. The mechanisms of such deterioration, the major microbial genera involved some and of factors which can affect the degree of colonization and attack are discussed. The major factor determining microbial growth on constructional materials is moisture and the importance of correct design of structures to avoid the ingress of water is pointed out.