1. Using light microscopy, you examine the soil samples and the “goo” from the degraded polyurethane. Will this approach allow you to observe all microorganisms present in the samples? Why or why not? What are the limitations of this approach?
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Effect of Fe0 quantity on the efficiency of integrated microbial-Fe0 treatment processes; Fernandez-Sanchez JM et al.; Batch experiments were conducted with different reaction systems to investigate how the treatment efficiency of integrated microbial-Fe0 processes is affected by the amount of Fe0 added . Abiotic experiments with hexavalent chromium and carbon tetrachloride mixtures corroborated that different pollutants could compete for reactive sites on the iron surface, which would hinder specific degradation rates when the available Fe0 surface area is relatively small . . In such cases, reductive precipitation of chromium could occlude reactive sites and significantly inhibit removal efficiency . Microbial participation in the cleanup process was also influenced by the amount of Fe0 added . Increasing the Fe0 dose (and thus the available surface area) had a stimulatory effect possibly due to a higher production of cathodic H2, which can be used as electron donor for reductive biotransformation of many pollutants . However, high Fe0 doses had an inhibitory effect due to a corrosion-induced increase in pH beyond the optimum range of the bacteria . This suggest that there may be a system-specific, optimum quantity of Fe0 that satisfies availability requirements to preclude contaminant competition for reactive sites and biological requirements for H2 production while minimizing inhibitory increases in pH . Results also confirmed extensive RDX mineralization in bioaugmented (but not in abiotic) Fe0 systems, and support the notion that permeable reactive iron barriers performance might be enhanced by the participation of some microorganisms.
Development of immunoglobulin A in infancy and childhood; Weemaes C et al.; Serum and salivary concentrations of immunoglobulin A1 (IgA1) and IgA2 were studied in 105 Icelandic children aged 0-12 years . Serum concentrations of both IgA1 and IgA2 increased slightly (P < 0.001) during childhood . The salivary IgA1/IgA2 ratio tended to decrease during the same period; this trend is less apparent when omitting the youngest children . The salivary IgA1 and IgA2 output could be high, even in children with low levels of serum IgA . Only polymeric IgA was found in whole saliva . Interestingly, in serum, most IgA1 and IgA2 were polymeric during infancy . The proportion of polymeric IgA decreased, when the concentration of IgA increased . The polymeric form of IgA might provide the infant with better protection against invading microorganisms by activation of the innate immune mechanisms.
Effect of Mycobacterium vaccae on atopic dermatitis in children of different ages; Arkwright PD et al.; BACKGROUND: Exposure to environmental microorganisms is associated with variations in the prevalence and severity of atopic diseases . We have previously shown that administration of a Mycobacterium vaccae suspension significantly reduced the severity of atopic dermatitis (AD) in children aged 5-18 years . OBJECTIVES: This study aimed to extend these observations to younger children . METHODS: Fifty-six children aged 2-6 years with moderate to severe AD were enrolled in a randomized, double-blind, placebo-controlled trial and given one intradermal injection of either killed M . vaccae suspension or buffer solution (placebo) . Skin surface area affected and dermatitis severity score were assessed before and 1, 3 and 6 months after treatment . RESULTS: Although a 38-54% reduction in surface area affected by dermatitis was noted at all time points after M . vaccae administration (P = 0.005), this improvement was not significantly different from that observed in the placebo group . Meta-analysis of this and our previous cohort (97 children aged 2-18 years) showed that M . vaccae was associated with a significant improvement in clinical severity at all ages, whereas within the placebo group, younger but not older children showed a similar improvement . CONCLUSIONS: Despite a reduction in clinical severity associated with M . vaccae at all ages, no benefit could be found after administering M . vaccae to children with AD aged 2-6 years when compared with placebo . M . vaccae may offer greater benefit in children over 5 years old, whose AD appears less likely to regress spontaneously.