Microbially mediated anaerobic oxidation of methane (AOM) moderates the input of methane, an important greenhouse gas, to the atmosphere by consuming methane produced in various marine, terrestrial, and subsurface environments. AOM coupled to sulfate reduction has been most extensively studied because of the abundance of sulfate in marine systems, but electron acceptors otherthan sulfate are more energetically favorable. Phylogenetic trees based on 16S rRNA gene clone libraries derived from microbial communities where AOM occurs show evidence of diverse, methanotrophic archaea (ANME) closely associated with sulfate-reducing bacteria, but these organisms have not yet been isolated as pure cultures. Several biochemical pathways for AOM have been proposed, including reverse methanogenesis, acetogenesis, and methylogenesis, and both culture-dependent and independent techniques have provided some clues to howthese communities function. Still, questions remain regarding the diversity, physiology, and metabolic restrictions of AOM-related organisms.
Silicification of organisms in silica-depositing environments can impact both their ecology and their presence in the fossil record. Although microbes have been silicified under laboratory and environmental conditions, viruses have not. Bacteriophage T4 was successfully silicified under laboratory conditions that closely simulated those found in silica-depositing hot springs. Virus morphology was maintained, and a clear elemental signature of phosphorus was detected by energy-dispersive X-ray spectrophotometry (EDS).
c Long-distance host-independent virus dispersal is poorly understood, especially for viruses found in isolated ecosystems. To demonstrate a possible dispersal mechanism, we show that bacteriophage T4, archaeal virus Sulfolobus spindle-shaped virus Kamchatka, and vaccinia virus are reversibly inactivated by mineralization in silica under conditions similar to volcanic hot springs. In contrast, bacteriophage PRD1 is not silicified. Moreover, silicification provides viruses with remarkable desiccation resistance, which could allow extensive aerial dispersal.T he mechanisms and extent of virus dispersal are often unclear. Given the importance of viruses in maintaining microbial diversity and recycling nutrients on a global scale (1) and causing disease (2), understanding virus distribution is essential. However, it is not clear whether virus species are cosmopolitan (3) or display regional endemism (4-8). Interestingly, local hot spring virus dispersal can result from aerosolization by fumaroles (8), indicating at least one possible host-independent dispersal mechanism.Stratospheric winds are capable of carrying bacteria and fungi from the Sahara Desert as far as the Caribbean Sea (9, 10). However, a critically limiting factor for wind-borne virus spread is the ability of the virus to resist drying; most viruses are highly sensitive to desiccation (for examples, see references 11 to 13). However, if viruses could be reversibly coated in a protective coat in addition to their capsid, they could potentially spread very widely. Silica coating is a particularly attractive possibility, since in hot spring environments, viruses can be coated with silica (14, 15). However, the effect of silicification on virus infectivity was not known. Therefore, we tested both enveloped and unenveloped viruses for their susceptibility and response to silicification. Viruses tested included bacteriophage T4 (16), bacteriophage PRD1 (17), the archaeal virus Sulfolobus spindle-shaped virus Kamchatka (SSV-K) (18), and vaccinia virus (VACV) (19).Bacteriophage T4, PRD1, SSV-K, and VACV were propagated in host cell cultures using Escherichia coli B, Salmonella enterica serovar Typhimurium LT2, Sulfolobus solfataricus strain G⍜, and murine BSC-1 cells, respectively. After growth, cell debris was removed. The resulting viruses were mixed with freshly prepared pH 7.0 to 7.1 sodium metasilicate solution in either 10 mM sodium bicarbonate-5 mM magnesium chloride for bacteriophage T4, PRD1, and SSV-K or Dulbecco's phosphate-buffered saline for VACV to final silica concentrations of 0, 5, and 10 mM (0, 300, and 600 ppm). Solutions were placed in dialysis tubing in a reservoir of the same buffer and silica concentration. The bathing solution was replaced daily. Samples were withdrawn immediately and on days 1, 3, 8, and 10. The virus titer was determined in triplicate by plaque assay. On day 10, aliquots were diluted 1:10 with a 0-ppm silica solution. Plaque assays were performed with these diluted samples on days 12, 14, 16, and 20. On day 10, aliquo...
ABSTRACT. Many autism advocacy groups use the data collected by the US Department of Education (USDE) to show a rapidly increasing prevalence of autism. Closer examination of these data to follow each birth-year cohort reveals anomalies within the USDE data on autism. The USDE data show not only a rise in overall autism prevalence with time but also a significant and nearly linear rise in autism prevalence within a birth-year cohort as it ages, with significant numbers of new cases as late as 17 years of age. In addition, an unexpected reduction in the rise of autism prevalence occurs in most cohorts at 12 years of age, the age when most children would be entering middle school. These anomalies point to internal problems in the USDE data that make them unsuitable for tracking autism prevalence. Pediatrics 2005;116:e120-e124. URL: www. pediatrics.org/cgi
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