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Development and Evaluation of an Online CO2 Evolution Test and a Multicomponent Biodegradation Test System. Uwe Strotmann, 2004.Well-established biodegradation tests use biogenously evolved carbon dioxide (CO2) as an analytical parameter to determine the ultimate biodegradability of substances . A newly developed analytical technique based on the continuous online measurement of conductivity showed its suitability over other techniques . It could be demonstrated that the method met all criteria of established biodegradation tests, gave continuous biodegradation curves, and was more reliable than other tests . In parallel experiments, only small variations in the biodegradation pattern occurred . When comparing the new online CO2 method with existing CO2 evolution tests, growth rates and lag periods were similar and only the final degree of biodegradation of aniline was slightly lower . A further test development was the unification and parallel measurement of all three important summary parameters for biodegradation—i.e., CO2 evolution, determination of the biochemical oxygen demand (BOD), and removal of dissolved organic carbon (DOC)—in a multicomponent biodegradation test system (MCBTS) . The practicability of this test method was demonstrated with aniline . This test system had advantages for poorly water-soluble and highly volatile compounds and allowed the determination of the carbon fraction integrated into biomass (heterotrophic yield) . The integrated online measurements of CO2 and BOD systems produced continuous degradation curves, which better met the stringent criteria of ready biodegradability (60% biodegradation in a 10-day window) . Furthermore the data could be used to calculate maximal growth rates for the modeling of biodegradation processes . 2-n-Pentyl-4-Quinolinol Produced by a Marine Alteromonas sp . and Its Potential Ecological and Biogeochemical Roles. Richard A. Long, 2003.Bacterium-bacterium interactions occur at intimate spatial scales on the order of micrometers, but our knowledge of interactions at this level is rudimentary . Antagonism is a potential interaction in such microenvironments . To study the ecological role of antibiosis, we developed a model system involving an antibiotic-producing isolate (SWAT5) derived from a marine particle and its dominant antibiotic product, 2-n-pentyl-4-quinolinol (PQ) . This system was used to address questions about the significance of this antibiotic for microbial ecology and carbon cycling on particles . We characterized the chemical and inhibitory properties of PQ in relation to the mechanisms used by particle-associated bacteria in interacting with particles and with other attached bacteria . PQ was produced by SWAT5 only on surfaces . When SWAT5 was grown in polysaccharide matrices, PQ diffused within the matrices but not into the surrounding seawater . SWAT5 might thus be able to generate a localized zone of high antibiotic concentration on particles suspended or sinking through seawater . Target bacterial respiration was most sensitive to PQ (75 nM), while inhibition of DNA synthesis, protein synthesis, and bacterial motility required higher (micromolar) PQ levels . The presence of PQ altered the composition of the bacterial community that colonized and developed in a model particle system . PQ also inhibited Synechococcus and phytoplankton growth . Our results suggest that antibiosis may significantly influence community composition and activities of attached bacterial and thus regulate the biogeochemical fate of particulate organic matter in the ocean .
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