P. O. Akinwole is a senior researcher at the University of Alabama, USA
Dissolved organic carbon (DOC) is the largest organic carbon pool in lotic systems. Current paradigms describing terrestrial DOC in streams depict DOC as both an important carbon and energy source for microorganisms and containing large amounts of chemical and biological refractory humic substances. To better evaluate the reliance of stream microorganisms on terrestrial DOC, we produced 13C-labeled DOC by leaching composted 13C-labelled tulip poplar leaves and twigs in soil columns for 3 months and then leaching the soil with water. This process yields 13C-labeled DOC with size and liability fractions approximating stream water DOC. To determine the microbial groups actively using stream water DOC we incubated streambed sediments in recirculating mesocosm chambers amended with 13C-labeled DOC and examined 13C incorporation into microbial phospholipid fatty acids. Prokaryotes comprised 61% of the mesocosm microbial community and consisted of aerobic, facultative anaerobic and anaerobic bacteria while microeukaryotes comprised the remaining 39%. Comparison by principal component analysis of the microbial communities in stream sediments and stream sediments incubated with or without 13C-labeled humic DOC showed our mesocosm-based experimental design was sufficiently robust to investigate the use of 13DOC by sediment microbial communities. After 48 hours of incubation, phospholipid fatty acids i15:0, 16:0, 16:1w9, 18:1w9c, 18:1w7c (aerobic/facultative anaerobic bacterial biomarkers) and 20:4w6, 20:5w3 (microeukaryotic biomarkers) showed increased abundance of 13C. This suggests that the hetero organotrophic bacteria actively utilized the 13DOC and that microeukaryotic predators consumed those bacteria. These findings indicate that DOC, although generally considered refractory and poorly utilized by microbiota, substantially contributes to the energy and carbon flow in aquatic ecosystems.
Sahar Essa works at the Department of Microbiology, Faculty of Medicine at the Kuwait University
Introduction: Hepatitis C virus (HCV) is a life threatening human pathogen. Chronicity of the disease leads to cirrhosis, hepatocellular carcinoma and end-stage liver disease. Clearance of the virus is characterized by a vigorous, persistent T-cell response. Standard treatment involves a combination of pegylated interferon-α (PEG-IFN) and ribavirin, Mechanisms for the observed synergistic effects of the two drugs are still not well understood, but in addition to direct antiviral mechanisms, immunomodulatory effects of both drugs seem to be important with a possible shift from Th2 to Th1 cytokine profiles in successfully treated patients.\r\n\r\nMethod: This study will determine Th1 and Th2 cytokine responses to infection with the major HCV genotypes, before, during and after treatment with PEG-IFN and ribavirin. The proliferative response of peripheral blood mononuclear cells to mitogen will be assessed by measuring uptake of radioactive thymidine and the production of Th1 type and Th2 type cytokines by ELISA.\r\n\r\nResults: We have inducted a total of 36 patients (27 responders and 9 non-responders). There were a significant increase in the levels of Th1 type cytokines IFN, IL-17A and IL-17F between responders and non-responders. IL-4 and IL-6 anti-inflammatory Th2 cytokines is produced at significantly higher levels in non-responders. The ratios involving IFN and IL-4 showed interesting differences. At baseline measurement, IFN/IL-4 and IFN/IL-10 ratios were 18 and 10 fold higher in responders. Likewise, at the end of the treatment, IFN/IL-4, IFN/IL-6 and IFN/IL-10 ratios were 90, 80 and 50 fold respectively higher in responders as compared to non-responders.\r\n\r\nConclusion: Our data suggests that, Th1 biased reactivity and poor Th2 response state appears to be associated with drug effectiveness. In other words, we suggest that the host cytokine profile can either dampen or aid the immune viral response to recent and future drug therapy.\r\n