Associations between fungal species and water-damaged building materials

Fungal growth in damp or water-damaged buildings worldwide is an increasing problem, which has adverse effects on both the occupants and the buildings. Air sampling alone in moldy buildings does not reveal the full diversity of fungal species growing on building materials. One aim of this study was to estimate the qualitative and quantitative diversity of fungi growing on damp or water-damaged building materials. Another was to determine if associations exist between the most commonly found fungal species and different types of materials. More than 5,300 surface samples were taken by means of V8 contact plates from materials with visible fungal growth. Fungal identifications and information on building material components were analyzed using multivariate statistic methods to determine associations between fungi and material components. The results confirmed that Penicillium chrysogenum and Aspergillus versicolor are the most common fungal species in water-damaged buildings. The results also showed Chaetomium spp., Acremonium spp., and Ulocladium spp. to be very common on damp building materials. Analyses show that associated mycobiotas exist on different building materials. Associations were found between (i) Acremonium spp., Penicillium chrysogenum, Stachybotrys spp., Ulocladium spp., and gypsum and wallpaper, (ii) Arthrinium phaeospermum, Aureobasidium pullulans, Cladosporium herbarum, Trichoderma spp., yeasts, and different types of wood and plywood, and (iii) Aspergillus fumigatus, Aspergillus melleus, Aspergillus niger, Aspergillus ochraceus, Chaetomium spp., Mucor racemosus, Mucor spinosus, and concrete and other floor-related materials. These results can be used to develop new and resistant building materials and relevant allergen extracts and to help focus research on relevant mycotoxins, microbial volatile organic compounds (MVOCs), and microparticles released into the indoor environment.     

Diversity of streptomycetes in water-damaged building materials based on 16S rDNA sequences

AIMS: The diversity of streptomycetes in two different types of water-damaged building materials was investigated. METHODS AND RESULTS: Direct PCR amplification of 16S rDNA from DNA isolated from building materials, cloning of the fragments and sequence analysis were used. In the phylogenetic analysis of the variable gamma region of the PCR amplification products, the sequences affiliated with five groups. CONCLUSIONS: Several different sequences were found in both materials, suggesting the presence of several species. Also, previously unknown sequences were detected, although all the sequences clustered together with sequences of known species. SIGNIFICANCE AND IMPACT OF THE STUDY: Streptomycetes are known as indicators for moisture and mould damage in buildings and potential health risk, but their diversity in indoor environments is still unknown.     

Mycobacteria and fungi in moisture-damaged building materials

In contrast to the growth of fungi, the growth of mycobacteria in moisture-damaged building materials has rarely been studied. Environmental mycobacteria were isolated from 23% of samples of moisture-damaged materials (n = 88). The occurrence of mycobacteria increased with increasing concentrations of fungi. Mycobacteria may contribute to indoor exposure and associated adverse health effects.     

Negative chemotaxis in cellular slime molds.

This study confirms the suggestion of earlier workers that the vegetative amoebae of Dictyostelium repel each other while those of Polysphondylium violaceum do not. When Dictyostelium amoebae were placed in drops on thin and thick agar, the cells moved out faster on the thin agar, presumably because the repellent was more concentrated. This did not occur with Polysphondylium amoebae. Also, if 2 drops of cells were placed side by side, or a single drop was placed near an edge, in Dictyostelium there were fewer cells emerging between the drops (or near an edge) than on the far side. Polysphondylium showed no such difference. However, Polysphondylium amoebae were repelled by Dictyostelium cells (but not vice versa) when drops of each were placed beside one another. Finally, if Dictyostelium discoideum cells were placed in drops over thick and thin agar, but separated from the agar by a dialysis membrane, the cells again spread farther on the thin agar, indicating that the repellent is a dialyzable molecule.     

Altruism, cheating, and anticheater adaptations in cellular slime molds

Cellular slime molds (CSMs) possess a remarkable life cycle that encompasses an extreme act of altruism. CSM cells live as individual amoebae until starved, then aggregate and ultimately transform themselves into a multicellular fruiting body. This fruiting body consists of stalk cells (altruists that eventually die) and spores (the beneficiaries of this sacrifice). Altruistic systems such as this are vulnerable to cheaters, which are individuals unrelated to the altruists that obtain the benefits provided by them without reciprocating. Here, we investigate two forces that can maintain CSM altruism despite cheating: kin selection and anticheater adaptations. First, we present new kinship-based models based on CSM developmental biology to evaluate the efficacy of kin selection. These models show that stalk-making genotypes can still be maintained when aggregations are initiated by multiple "founder" spores, provided that spores of stalkless fruiting bodies have low rates of dispersal and dispersal success is a concave function of stalk height. Second, we review proposals that several features of CSM development, such as the chemical suppression of the redifferentiation of prestalk cells into prespores, act as anticheater adaptations.     

Applications of biopolymers and other biotechnological products in building materials

Bio admixtures are functional molecules used in building products to optimize material properties. They include natural or modified biopolymers, biotechnological and biodegradable products. Concrete and dry-mix mortars (e.g. wall plasters or tile adhesives) represent two major applications for bio admixtures. Examples of bio products used in concrete are lignosulfonate, sodium gluconate, pine root extract, protein hydrolysates and Welan gum; and in dry-mix mortar methyl hydroxypropyl cellulose, hydroxypropyl starch, guar gum, tartaric acid, casein, succinoglycan and Xanthan gum. In a number of applications, bio admixtures compete well with synthetic admixtures. Sometimes, they are indispensable in the formulation of certain building products. Their market share is expected to increase because of technological advances, particularly in the field of microbial biopolymers, and because of the growing trend to use naturally based or biodegradable products in building materials.     

A trimeric building block model for Cry toxins in vitro ion channel formation

The crystal (Cry) insecticidal toxins, or δ-endotoxins, are lethal to a wide variety of insect larvae, and are therefore very important in insect control. Toxicity has been explained by formation of transmembrane oligomeric pores or ion channels and, more recently, by the ability of the monomeric toxin to subvert cellular signaling pathways. The structure, topology, and precise role of the putative pore in toxicity are not known. However, in vitro biophysical studies suggest that helices α4 and α5 in domain I insert into the lipid bilayer as an α-helical hairpin. Mutagenesis studies have assigned an important role to α5 in maintaining oligomerization, and to α4 in channel formation. To detect the possible homo-oligomerizing tendencies of these two helices, we have used the evolutionary conservation data contained in sixteen Cry homologs in order to filter non-native interactions found during a global conformational search. No conserved homo-oligomer was found for α4, but a right handed trimeric α5 model was present in the simulations of all Cry sequences. We propose a model for Cry toxin oligomerization based on sequence analysis and available mutagenesis data.     

A trimeric building block model for Cry toxins in vitro ion channel formation

The crystal (Cry) insecticidal toxins, or delta-endotoxins, are lethal to a wide variety of insect larvae, and are therefore very important in insect control. Toxicity has been explained by formation of transmembrane oligomeric pores or ion channels and, more recently, by the ability of the monomeric toxin to subvert cellular signaling pathways. The structure, topology, and precise role of the putative pore in toxicity are not known. However, in vitro biophysical studies suggest that helices alpha4 and alpha5 in domain I insert into the lipid bilayer as an alpha-helical hairpin. Mutagenesis studies have assigned an important role to alpha5 in maintaining oligomerization, and to alpha4 in channel formation. To detect the possible homo-oligomerizing tendencies of these two helices, we have used the evolutionary conservation data contained in sixteen Cry homologs in order to filter non-native interactions found during a global conformational search. No conserved homo-oligomer was found for alpha4, but a right handed trimeric alpha5 model was present in the simulations of all Cry sequences. We propose a model for Cry toxin oligomerization based on sequence analysis and available mutagenesis data.     

Occurrence and moisture requirements of microbial growth in building materials

Microbial growth was studied in six damp buildings. Mesophilic fungi, especially Penicillium spp., yeasts, and species of Cladosporium and Aspergillus, occurred most abundantly on building constructions. Thermophilic fungi and mesophilic actinomycetes were occasionally found. A toxigenic fungus, Stachybotrys sp., was also detected on cellulose-based materials. In a cytotoxicity test, 23% of samples were positive. Spore counts varied considerably on materials, but no correlation between counts and the substrate or its water activity (a_w) was observed. In experiments a rapid increase in CO₂ production and spore propagule count was observed in all materials incubated at a relative humidity (RH) (RH=0·01^*water activity) of 96–98°. Some differences were noted between materials in CO₂ evolved, but not in propagule counts.     

Pathogens, toxins, and lipid rafts

Summary The plasma membrane is not a uniform two-dimensional space but includes various types of specialized regions containing specific lipids and proteins. These include clathrin-coated pits and caveolae. The existence of other cholesterol- and glycosphingolipid-rich microdomains has also been proposed. The aim of this review is to illustrate that these latter domains, also called lipid rafts, may be the preferential interaction sites between a variety of toxins, bacteria, and viruses and the target cell. These pathogens and toxins have hijacked components that are preferentially found in rafts, such as glycosylphosphatidylinositol-anchored proteins, sphingomyelin, and cholesterol. These molecules not only allow binding of the pathogen or toxin to the proper target cell but also appear to potentiate the toxic action. We briefly review the structure and proposed functions of cholesterol- and glycosphingolipid-rich microdomains and then describe the toxins and pathogens that interact with them. When possible the advantage conferred by the interaction with microdomains will be discussed.Abbreviation GPI glycosylphosphatidylinositol