Intensive monitoring of the strongly variable BL Lac S5 0716+714

The BL Lac object S5 0716+714 was monitored during a multifrequency campaign in 1996. Preliminary analysis of the optical, ROSAT and RXTE data are presented. Strong variability on short time scales was observed. The data suggest an interpretation within a multi-component model.Comment: To appear in The Active X-ray Sky: Results from BeppoSAX and Rossi-XTE, Rome, Italy, 21-24 October, 1997. Eds.: L. Scarsi, Bradt, P. Giommi and F. Fiore. PS-file avialable at http://www.lsw.uni-heidelberg.de/projects/extragalactic/bl_lac.htm

Observations Concerning the Effects of Ruminal Evacuation on Intake and Ruminal Recovery of Dry Matter

The effect of repeated total ruminal evacuations on feed intake and animal behavior and rate of ruminal recovery expressed as percentage of feed bunk dry matter disappearance were observed in an observation trial with six Angus crossbred steers. Evacuation stimulated meal size and daily intake in comparison to that of a previous feeding. Feed intake decreased with consecutive evacuations. Two evacuation cycles at a 2-day interval may be the practical Limit to frequency of evacuations without a 1 to 2-week recovery period. Rate of recovery of dry matter from the rumen over a 4-hour period was extremely variable and not correlated with feed intake during the same period

Comparative genomics and mutagenesis analyses of choline metabolism in the marine Roseobacter clade

Choline is ubiquitous in marine eukaryotes and appears to be widely distributed in surface marine waters; however, its metabolism by marine bacteria is poorly understood. Here, using comparative genomics and molecular genetic approaches, we reveal that the capacity for choline catabolism is widespread in marine heterotrophs of the marine Roseobacter clade (MRC). Using the model bacterium Ruegeria pomeroyi, we confirm that the betA, betB and betC genes, encoding choline dehydrogenase, betaine aldehyde dehydrogenase and choline sulfatase, respectively, are involved in choline metabolism. The betT gene, encoding an organic solute transporter, was essential for the rapid uptake of choline but not glycine betaine (GBT). Growth of choline and GBT as a sole carbon source resulted in the re-mineralization of these nitrogen-rich compounds into ammonium. Oxidation of the methyl groups from choline requires formyltetrahydrofolate synthetase encoded by fhs in R.pomeroyi, deletion of which resulted in incomplete degradation of GBT. We demonstrate that this was due to an imbalance in the supply of reducing equivalents required for choline catabolism, which can be alleviated by the addition of formate. Together, our results demonstrate that choline metabolism is ubiquitous in the MRC and reveal the role of Fhs in methyl group oxidation in R.pomeroyi

Some characteristics of cytochrome f in the cyanobacterium Phormidium laminosum: its sequence and charge properties in the reaction with plastocyanin

AbstractPart of the petCA operon was cloned and the sequence of the cytochrome f gene from the moderately thermophilic cyanobacterium Phormidium laminosum determined. A partial sequence of the petC gene encoding the Rieske iron-sulphur protein was also obtained. The cytochrome f gene encodes a mature protein of 385 residues and a leader sequence of 45 residues. The mature protein contains several acidic or neutral residues corresponding to basic residues in the turnip protein. Some of the latter are thought to be important for the interaction with plastocyanin via its ‘eastern’ face. Many of the corresponding residues on the eastern face of P. laminosum plastocyanin are either basic or neutral instead of acidic. These comparisons suggested that the local charges on P. laminosum cytochrome f that are important for its interaction with the homologous plastocyanin may be negative rather than positive. The importance of acidic groups was confirmed by measuring the rates of reduction of horse heart cytochrome c and P. laminosum and spinach plastocyanins by the cytochrome bf complex isolated from P. laminosum. P. laminosum plastocyanin gave the highest rates, which decreased at high ionic strength, confirming the importance of positive local charges on this protein. When extrapolated to infinite ionic strength the rates observed with the two kinds of plastocyanin were similar, but cytochrome c became unreactive. An optimum was observed in the ionic strength response with P. laminosum plastocyanin

Complexity of diatom response to Lateglacial and Holocene climate and environmental change in ancient, deep, and oligotrophic Lake Ohrid (Macedonia/Albania)

Lake Ohrid (Macedonia/Albania) is a rare example of a deep, ancient Mediterranean lake and is a key site for palaeoclimate research in the northeastern Mediterranean region. This study conducts the first high-resolution diatom analysis during the Lateglacial and Holocene in Lake Ohrid. It demonstrates a complex diatom response to temperature change, with a direct response to temperature-induced productivity and an indirect response to temperature-related stratification/mixing regime and epilimnetic nutrient availability. During the Lateglacial (ca. 12 300–11 800 cal yr BP), the low-diversity dominance of hypolimnetic Cyclotella fottii indicates low temperature-dependent lake productivity. During the earliest Holocene (ca. 11 800–10 600 cal yr BP), although the slight increase in small, epilimnetic C. minuscula suggests climate warming and enhanced thermal stratification, diatom concentration remains very low as during the Lateglacial, indicating that temperature increase was muted. The early Holocene (ca. 10 600–8200 cal yr BP) marked a sustained increase in epilimnetic taxa, with mesotrophic C. ocellata indicating high temperature-induced lake productivity between ca. 10 600–10 200 cal yr BP and between ca. 9500–8200 cal yr BP, and with C. minuscula in response to low nutrient availability in the epilimnion between ca. 10 200–9500 cal yr BP. During the mid Holocene (ca. 8200–2600 cal yr BP), when sedimentological and geochemical proxies provide evidence for high temperature, anomalously low C. ocellata abundance is probably a response to epilimnetic nutrient limitation, almost mimicking the Lateglacial flora apart from mesotrophic Stephanodiscus transylvanicus indicative of high temperature-induced productivity in the hypolimnion. During the late Holocene (ca. 2600–0 cal yr BP), high abundance and fluctuating composition of epilimnetic taxa is largely a response to enhanced anthropogenic nutrient input. In this deep, oligotrophic lake, this study demonstrates the strong influence of lake physical and chemical processes in mediating the complex response of diatoms to climate change with particular respect to temperature

Complexity of diatom response to Lateglacial and Holocene climate and environmental change in ancient, deep and oligotrophic Lake Ohrid (Macedonia and Albania)

Lake Ohrid (Macedonia and Albania) is a rare example of a deep, ancient Mediterranean lake and is a key site for palaeoclimate research in the northeastern Mediterranean region. This study conducts the analysis of diatoms as a proxy for Lateglacial and Holocene climate and environmental change in Lake Ohrid at a higher resolution than in previous studies. While Lake Ohrid has the potential to be sensitive to water temperature change, the data demonstrate a highly complex diatom response, probably comprising a direct response to temperature-induced lake productivity in some phases and an indirect response to temperature-related lake stratification or mixing and epilimnetic nutrient availability in others. The data also demonstrate the possible influence of physical limnological (e.g. the influence of wind stress on stratification or mixing) and chemical processes (e.g. the influence of catchment dynamics on nutrient input) in mediating the complex response of diatoms. During the Lateglacial (ca. 12 300–11 800 cal yr BP), the low-diversity dominance of hypolimnetic Cyclotella fottii indicates low lake productivity, linked to low water temperature. Although the subsequent slight increase in small, epilimnetic C. minuscula during the earliest Holocene (ca. 11 800–10 600 cal yr BP) suggests climate warming and enhanced stratification, diatom concentration remains as low as during the Lateglacial, suggesting that water temperature increase was muted across this major transition. The early Holocene (ca. 10 600–8200 cal yr BP) is characterised by a sustained increase in epilimnetic taxa, with mesotrophic C. ocellata indicating high water-temperature-induced productivity between ca. 10 600–10 200 cal yr BP and between ca. 9500–8200 cal yr BP and with C. minuscula in response to low nutrient availability in the epilimnion between ca. 10 200–9500 cal yr BP. During the middle Holocene (ca. 8200–2600 cal yr BP), when sedimentological and geochemical proxies provide evidence for maximum Holocene water temperature, anomalously low C. ocellata abundance is probably a response to epilimnetic nutrient limitation, almost mimicking the Lateglacial flora apart from the occurrence of mesotrophic Stephanodiscus transylvanicus in the hypolimnion. During the late Holocene (ca. 2600 cal yr BP–present), high abundance and fluctuating composition of epilimnetic taxa are probably a response more to enhanced anthropogenic nutrient input, particularly nitrogen enrichment, than to climate. Overall, the data indicate that previous assumptions concerning the linearity of diatom response in this deep, ancient lake are invalid, and multi-proxy analysis is essential to improve understanding of palaeolimnological dynamics in future research on the long, Quaternary sequence

Light-addressable Potentiometric Sensors and Light–addressable Electrodes as a Combined Sensor-and-manipulator Microsystem with High Flexibility

AbstractThis work describes the novel combination of the light-addressable electrode (LAE) and the light-addressable potentiometric sensor (LAPS) into a microsystem set-up. Both the LAE as well as the LAPS shares the principle of addressing the active spot by means of a light beam. This enables both systems to manipulate resp. to detect an analyte with a high spatial resolution. Hence, combining both principles into a single set-up enables the active stimulation e.g., by means of electrolysis and a simultaneous observation e.g., the response of an entrapped biological cell by detection of extracellular pH changes. The work will describe the principles of both technologies and the necessary steps to integrate them into a single set-up. Furthermore, examples of application and operation of such systems will be presented