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Query: UMLS:C0271276 (Hudson)
 1,066 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nitrate, sulfate, and carbonate were used as electron acceptors to examine the anaerobic biodegradability of chlorinated aromatic compounds in estuarine and freshwater sediments. The respective denitrifying, sulfidogenic, and methanogenic enrichment cultures were established on each of the monochlorinated phenol and monochlorinated benzoic acid isomers, using sediment from the upper (freshwater) and lower (estuarine) Hudson River and the East River (estuarine) as source materials. Utilization of each chlorophenol and chlorobenzoate isomer was observed under at least one reducing condition; however, no single reducing condition permitted the metabolism of all six compounds tested. The anaerobic biodegradation of the chlorophenols and chlorobenzoates depended on the electron acceptor available and on the position of the chlorine substituent. In general, similar activities were observed under the different reducing conditions in both the freshwater and estuarine sediments. Under denitrifying conditions, degradation of 3- and 4-chlorobenzoate was accompanied by nitrate loss corresponding reasonably to the stoichiometric values expected for complete oxidation of the chlorobenzoate to CO2. Under sulfidogenic conditions, 3- and 4-chlorobenzoate, but not 2-chlorobenzoate, and all three monochlorophenol isomers were utilized, while under methanogenic conditions all compounds except 4-chlorobenzoate were metabolized. Given that the pattern of activity appears different for these chlorinated compounds under each reducing condition, their biodegradability appears to be more a function of the presence of competent microbial populations than one of inherent molecular structure.
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PMID:Influence of alternative electron acceptors on the anaerobic biodegradability of chlorinated phenols and benzoic acids. 847 90

A sparse geological record combined with physics and molecular phylogeny constrains the environmental conditions on the early Earth. The Earth began hot after the moon-forming impact and cooled to the point where liquid water was present in approximately 10 million years. Subsequently, a few asteroid impacts may have briefly heated surface environments, leaving only thermophile survivors in kilometer-deep rocks. A warm 500 K, 100 bar CO(2) greenhouse persisted until subducted oceanic crust sequestered CO(2) into the mantle. It is not known whether the Earth's surface lingered in a approximately 70 degrees C thermophile environment well into the Archaean or cooled to clement or freezing conditions in the Hadean. Recently discovered approximately 4.3 Ga rocks near Hudson Bay may have formed during the warm greenhouse. Alkalic rocks in India indicate carbonate subduction by 4.26 Ga. The presence of 3.8 Ga black shales in Greenland indicates that S-based photosynthesis had evolved in the oceans and likely Fe-based photosynthesis and efficient chemical weathering on land. Overall, mantle derived rocks, especially kimberlites and similar CO(2)-rich magmas, preserve evidence of subducted upper oceanic crust, ancient surface environments, and biosignatures of photosynthesis.
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PMID:The Hadean-Archaean environment. 2051 34