Chloroform decreases rumen methanogenesis and methanogen populations without altering rumen function in cattle

Anthropogenic CH emissions are widely recognised as a world wide problem due to their global warming potential and because they represent a loss of dietary energy to ruminants. Few recent studies have examined medium or long term effects of methanogen inhibitors on rumen functional parameters and development of resistance to them. The aim of our study was to investigate medium term effects of a potent methanogen inhibitor on methanogen populations using molecular techniques and rumen function. Six rumen fistulated cows were divided into two groups and allocated to control and chloroform treatment and fed at a fixed rate of 8.4kgdry matter (DM)/cow/d. After 7d of acclimatization, treatment cows were dosed daily with 1.5ml of chloroform in 30ml of sunflower oil for 42 d, while control cows only received sunflower oil. Key indicators of rumen function monitored included rumen pH, rumen fill, apparent feed digestibility, apparent rumen digesta retention time, total protozoa numbers, and volatile fatty acid (VFA) and NH concentrations. Methane emissions were monitored using the SF tracer technique, and methanogens using denaturing gradient gel electrophoresis (DGGE) and four clone libraries. Methanogens and acetogens were monitored in a single cow by most probable number culturing methods. Chloroform, a known inhibitor of methanogenesis, resulted in an immediate and dramatic decrease in CH emissions and methanogen numbers, with the effect being most pronounced 1wk after the start of the treatment. Thereafter, CH emissions increased slowly, reaching 62% of pre-treatment levels by d 42. The effect on CH emissions was reflected by a near complete disappearance of DGGE bands associated with methanogens in treated cows. This response was particularly obvious for Methanobrevibacter species. There were no effects of chloroform on apparent rumen digesta retention time, apparent feed digestibility, pH, NH or rumen fill. Total protozoa numbers tended to increase during the study in both groups. Total VFA concentrations did not change with chloroform treatment, but the acetate:propionate ratio during the period of dosing was lower (

Growth phase-dependent expression and degradation of histones in the thermophilic archaeon Thermococcus zilligii

The majority of cells in nature probably exist in a stationary-phase-like state, due to nutrient limitation in most environments. Studies on bacteria and yeast reveal morphological and physiological changes throughout the stationary phase, which lead to an increased ability to survive prolonged nutrient limitation. However, there is little information on archaeal stationary phase responses. We investigated protein- and lipid-level changes in Thermococcus kodakarensis with extended time in the stationary phase. Adaptations to time in stationary phase included increased proportion of membrane lipids with a tetraether backbone, synthesis of proteins that ensure translational fidelity, specific regulation of ABC transporters (upregulation of some, downregulation of others), and upregulation of proteins involved in coenzyme production. Given that the biological mechanism of tetraether synthesis is unknown, we also considered whether any of the protein-level changes in T. kodakarensis might shed light on the production of tetraether lipids across the same period. A putative carbon-nitrogen hydrolase, a TldE (a protease in Escherichia coli) homologue, and a membrane bound hydrogenase complex subunit were candidates for possible involvement in tetraether-related reactions, while upregulation of adenosylcobalamin synthesis proteins might lend support to a possible radical mechanism as a trigger for tetraether synthesis