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Fibrillar and fimbriate strains of Streptococcus salivarius were compared for their ability to adhere to buccal epithelial cells and saliva-coated hydroxyapatite beads, and for their ability to coaggregate with Veillonella strains. The fibrillar Lancefield group K strains adhered statistically significantly better to both buccal epithelial cells and saliva-coated hydroxyapatite beads than the fimbriate strains, which lacked the Lancefield group K antigen. After 1 h the fibrillar strains coaggregated statistically significantly better than the fimbriate strains with V. parvula strain V1, but after 24 h, coaggregation both of fibrillar and of fimbriate strains reached approximately 90%. Freshly isolated Veillonella strains all coaggregated with the S. salivarius strains, but the percentage coaggregation varied considerably after 1 h depending on the Veillonella strain. Coaggregation was independent of the presence of Ca2+. S. salivarius strain HB-V5, a mutant of strain HB that had lost the Veillonella-binding protein, coaggregated weakly with V. parvula strain V1, but coaggregated very well with other wild-type veillonellae, suggesting the presence of an alternative mechanism for Veillonella-binding for strain HB. Fibrillar strains were, therefore, more adhesive to oral surfaces and coaggregated with veillonellae after 1 h better than the fimbriate S. salivarius strains. Both fibrillar and fimbriate strains were highly hydrophobic in the hexadecane-buffer partition assay.

Significant substratum damage can occur when plasticized PVC (pPVC) is colonized by microorganisms. We investigated microbial colonization of pPVC in an in situ, longitudinal study. Pieces of pPVC containing the plasticizers dioctyl phthalate and dioctyl adipate (DOA) were exposed to the atmosphere for up to 2 years. Fungal and bacterial populations were quantified, and colonizing fungi were identified by rRNA gene sequencing and morphological characteristics. Aureobasidium pullulans was the principal colonizing fungus, establishing itself on the pPVC between 25 and 40 weeks of exposure. A group of yeasts and yeast-like fungi, including Rhodotorula aurantiaca and Kluyveromyces spp., established themselves on the pPVC much later (after 80 weeks of exposure). Numerically, these organisms dominated A. pullulans after 95 weeks, with a mean viable count ؎ standard error of 1,000 ؎ 200 yeast CFU cm ؊2 , compared to 390 ؎ 50 A. pullulans CFU cm ؊2 . No bacterial colonization was observed. We also used in vitro tests to characterize the deteriogenic properties of fungi isolated from the pPVC. All strains of A. pullulans tested could grow with the intact pPVC formulation as the sole source of carbon, degrade the plasticizer DOA, produce extracellular esterase, and cause weight loss of the substratum during growth in vitro. In contrast, several yeast isolates could not grow on pPVC or degrade DOA. These results suggest that microbial succession may occur during the colonization of pPVC and that A. pullulans is critical to the establishment of a microbial community on pPVC.Plasticized PVC (pPVC) is highly susceptible to microbial attack in many different environmental situations. The problem was first identified in U.S. government reports of the deterioration of military equipment (8, 44), and subsequent reports described defacement and deterioration of commercial pPVC products (20,50). Biodeterioration of pPVC is now known to occur in a wide range of industrial, commercial, and structural applications (18,19,22).The susceptibility of pPVC results from the presence of plasticizers, commonly organic acid esters such as dioctyl phthalate (DOP) and dioctyl adipate (DOA), added to modify physical or mechanical properties of the polymer. Both bacteria (6,7,14) and fungi (5, 36) can degrade ester-based plasticizers. Loss of plasticizers from pPVC due to microbial degradation results in brittleness, shrinkage, and ultimately failure of the pPVC in its intended application.Microbial deterioration of pPVC has been studied extensively in vitro. Many studies have examined the resistance of pPVC formulations incorporating biocides to colonization by test organisms (38,39,46). Other research has determined biodegradability by measuring changes in the physical properties of pPVC, such as changes in tensile strength (49), mass (9), or electrical properties (42) during biodegradation. Several international standard test methods for microbiological susceptibility of plastics have been established (1, 2, 26).Colonization processes occurring...

Soil fungal communities involved in the biodegradation of polyester polyurethane (PU) were investigated. PU coupons were buried in two sandy loam soils with different levels of organic carbon: one was acidic (pH 5.5), and the other was more neutral (pH 6.7). After 5 months of burial, the fungal communities on the surface of the PU were compared with the native soil communities using culture-based and molecular techniques. Putative PU-degrading fungi were common in both soils, as <45% of the fungal colonies cleared the colloidal PU dispersion Impranil on solid medium. Denaturing gradient gel electrophoresis showed that fungal communities on the PU were less diverse than in the soil, and only a few species in the PU communities were detectable in the soil, indicating that only a small subset of the soil fungal communities colonized the PU. Soil type influenced the composition of the PU fungal communities. Geomyces pannorum and a Phoma sp. were the dominant species recovered by culturing from the PU buried in the acidic and neutral soils, respectively. Both fungi degraded Impranil and represented >80% of cultivable colonies from each plastic. However, PU was highly susceptible to degradation in both soils, losing up to 95% of its tensile strength. Therefore, different fungi are associated with PU degradation in different soils but the physical process is independent of soil type.The worldwide production of synthetic polymers continues to rise, resulting in an increased environmental burden through the generation of plastic waste. More than 140 million tonnes of plastic was produced worldwide in 2001 (34), and the proportion of household plastic waste in the average American home increased from 3 to 5% of total waste in 1969 (15) to more than 30% in 1995 (21) and continues to rise. Many plastics are both physically and chemically robust and cause waste management problems (10). However, several families of plastics undergo biodegradation in the environment, and an understanding of how this degradation occurs may aid in the development of strategies to exploit these processes for waste management purposes.Microorganisms are responsible for the majority of plastic degradation (6), and abiotic factors such as photodegradation or hydrolysis play a very minor role (18,42). Plastics vulnerable to biodegradation include the polyhydroxyalkanoates, polycaprolactone, polylactic acid, polyvinyl chloride (31, 32), and polyester polyurethane (PU). PU is used in a variety of industrial applications, including insulating foams, fibers, and synthetic leather and rubber goods. The presence of ester and urethane linkages in the backbone of PUs makes them susceptible to hydrolysis by enzymes secreted by microorganisms, releasing breakdown products which may act as a carbon source and lead to a weakening of the tensile strength (1,13,22,26,27).Both PU-degrading fungi (5,6,12,32) and bacteria (1, 20, 23) have been isolated from PU, indicating that there are potential reservoirs of PU-degrading organisms widespread in the environment. It...