Pelodictyon phaeoclathratifovme sp. nov., a new brown-colored member of the Chlorobiaceae forming net-like colonies

A new strain of the green sulfur bacteria was isolated from the monimolimnion of Buchensee (near Radolfzell, Lake Constance region, FRG). Single cells were rod-shaped, nonmotile and contained gas vacuoles. Typical net-like colonies were formed by ternary fission of the cells. As photosynthetic pigments bacteriochlorophylls a, e, isorenieratene and -isorenieratene were present. Sulfide, sulfur and thiosulfate were used as electron donors during anaerobic phototrophic growth. Besides carbon dioxide, acetate and propionate could serve as carbon sources under mixotrophic conditions in the light. Like all other members of the green sulfur bacteria, the new bacterium is strictly anaerobic and obligately phototrophic. The possession of gas vacuoles and the formation of net-like colonies and the guanine plus cytosine content of the DNA (47.9 mol% G+C) are typical characteristics of the genus Pelodictyon. Because of its photosynthetic pigments which differ from those of Pelodictyon clathratiforme, strain BU 1 represents a new species, P. Phaeoclathratiforme sp. nov

Continuous chemotrophic growth and respiration of Chromatiaceae species at low oxygen concentrations

Endogenous and maximum respiration rates of nine purple sulfur bacterial strains were determined. Endogenous rates were below 10 nmol O2 · (mg protein · min)-1 for sulfur-free cells and 15–35 nmol O2 · (mg protein · min)-1 for cells containg intracellular sulfur globules. With sulfide as electron-donating substrate respiration rates were considerably higher than with thiosulfate. Maximum respiration rates of Thiocystis violacea 2711 and Thiorhodovibrio winogradskyi SSP1 (254.8 and 264.2 nmol O2 · (mg protein · min)-1, respectively) are similar to those of aerobic bacteria. Biphasic respiration curves were obtained for sulfur-free cells of Thiocystis violacea 2711 and Chromatium vinosum 2811. In Thiocystis violacea the rapid and incomplete oxidation of thiosulfate was five times faster than the oxidation of stored sulfur. A high affinity of the respiratoty system for oxygen (K m =0.3–0.9 M O2, V max=260 nmol O2 · (mg protein · min)-1 with sulfide as substrate, K m =0.6–2.4 M O2, V max=14–40 nmol O2 · (mg protein · min)-1 with thiosulfate as substrate), for sulfide (K m =0.47 M, V max=650 nmol H2S · (mg protein × min)-1, and for thiosulfate (K m =5–6 M, V max =24–72 nmol S2O 3 2- · (mg protein · min)-1 was obtained for different strains. Respiration of Thiocystis violacea was inhibited by very low concentrations of NaCN (K i =1.7 M) while CO concentrations of up to 300 M were not inhibitory. The capacity for chemotrophic growth of six species was studied in continuous culture at oxygen concentrations of 11 to 67 M. Thiocystis violacea 2711, Amoebobacter roseus 6611, Thiocapsa roseopersicina 6311 and Thiorhodovibrio winogradskyi SSP1 were able to grow chemotrophically with thiosulfate/acetate or sulfide/acetate. Chromatium vinosum 2811 and Amoebobacter purpureus ML1 failed to grow under these conditions. During shift from phototrophic to chemotrophic conditions intracellular sulfur and carbohydrate accumulated transiently inside the cells. During chemotrophic growth bacteriochlorophyll a was below the detection limit

Gas vesicle formation and buoyancy regulation in Pelodictyon phaeoclathratiforme (Green sulfur bacteria)

Gas vesicle formation and buoyancy regulation in Pelodictyon phaeoclathratiforme strain BU1 (Green sulfur bacteria) was investigated under various laboratory conditions. Cells formed gas vesicles exclusively at light intensities below 5 mol · m-2 · s-1 in the stationary phase. No effect of incubation temperature or nutrient limitation was observed. Gas space of gas vesicles occupied always less than 1.2% of the total cell volume. A maximum cell turgor pressure of 330 kPa was determined which is comparable to values determined for cyanobacterial species. Since a pressure of at least 485 kPa was required to collapse the weakest gas vesicles in Pelodictyon phaeoclathratiforme, short-term regulation of cell density by the turgor pressure mechanism can be excluded. Instead, regulation of the cell density is accomplished by the cease of gas vacuole production and accumulation of carbohydrate at high light intensity. The carbohydrate content of exponentially growing cells increased with light intensity, reaching a maximum of 35% of dry cell mass above 10 mol · m-2 · s-1. Density of the cells increased concomitantly. At maximum density, protein and carbohydrate together accounted for 62% of the total cell ballast. Cells harvested in the stationary phase had a significantly lower carbohydrate content (8–12% of the dry cell mass) and cell density (1010–1014 kg · m-3 with gas vesicles collapsed) which in this case was independent of light intensity. Due to the presence of gas vesicles in these cultures, the density of cells reached a minimum value of 998.5 kg · m-3 at 0.5 mol · m-2 · s-1. The cell volume during the stationary phase was three times higher than during exponential growth, leading to considerable changes in the buoyancy of Pelodictyon phaeoclathratiforme. Microscopic observations indicate that extracellular slime layers may contribute to these variations of cell volume

Influence of vitamin B12 and light on the formation of chlorosomes in green- and brown-colored Chlorobium species

The specific Bchl a and c content of the vitamin B12-dependent Chlorobium limicola strain 1230 decreased strongly under vitamin B12 limitation. In comparison to a regularly grown culture (20 g vitamin B12/l) the specific Bchl c content of a B12-limited culture was reduced to 20% and the specific Bchl a content to 42%. By ultrathin sections it could be clearly demonstrated that B12-deficient cells contained no chlorosomes. After the addition of vitamin B12 to a deficient culture, chlorosomes were formed and the Bchl a and c content increased again to the level of regularly grown cells. The brown-colored Chlorobium phaeobacteroides strain 2430 (type strain) and the extremely low-light-adapted strain MN1 were compared with respect to the influence of light on the formation of chlorosomes and the Bchl e and carotenoid content. By ultrathin sections it could be demonstrated that strain MN1 produced two-fold larger chlorosomes. Chlorosome dimensions of strain MN1 decreased with increasing light intensities. The number of chlorosomes per cell in both strains did not change with different light intensities. Strain MN1 formed twice as much Bchl e as the type strain when grown at 30 or below 1 mol · m-2 · s-1. Under comparable light conditions strain MN1 formed 14–57% more carotenoids than the type strain. Low light intensities aaused the carotenoid content to increase by 25% in strain 2430 in comparison to high light intensity

Developing A Flexible Materials Testing Curriculum For Future Engineers

Engineering students as future maker of things will face the challenge of keeping pace with rapidly evolving technologies and staying up-to-date with the latest innovations in their field. To cope with these demands a flexible course concept is developed for an undergraduate Materials Science lab course: Materials Testing at HTW Berlin based on a blended learning teaching concept implementing inverted classroom lecture scenarios. High quality micro modules are defined that may individually be combined or restructured and therefore offer sufficient flexibility to match the individual scientific background of the lecturer, the course learning outcome, main study subject or actual need based on recent developments. The Moodle course offers different teaching materials, such as micro-lectures, guided questionnaires, lecture and lightboard videos, H5P-activities, etc. Lecturers will find detailed information on the course concept but independently decide on the main aspect of their individual teaching and are therefore granted time for various activating methods in class. With providing well-arranged individual work packages the pressure especially for lecturers from industry - who are teaching on their full time jobs - is relieved and they have more time to interact with students involving them in future common engineering challenges

A new purple sulfur bacterium from saline littoral sediments, Thiorhodotvibrio winogradskyi gen. nov. and sp. nov.

Two strains of a new purple sulfur bacterium were isolated in pure culture from the littoral sediment of a saline lake (Mahoney Lake, Canada) and a marine microbial mat from the North Sea island of Mellum, respectively. Single cells were vibrioid-to spirilloid-shaped and motile by means of single polar flagella. Intracellular photosynthetic membranes were of the vesicular type. As photosynthetic pigments, bacteriochlorophyll a and the carotenoids lycopene, rhodopin, anhydrorhodovibrin, rhodovibrin and spirilloxanthin were present. Hydrogen sulfide and elemental sulfur were used under anoxic conditions for phototrophic growth. In addition one strain (06511) used thiosulfate. Carbon dioxide, acetate and pyruvate were utilized by both strains as carbon sources. Depending on the strain propionate, succinate, fumarate, malate, tartrate, malonate, glycerol or peptone may additionally serve as carbon sources in the light. Optimum growth rates were obtained at pH 7.2, 33 °C, 50 mol m-2 s-1 intensity of daylight fluorescent tubes and a salinity of 2.2–3.2% NaCl. During growth on sulfide, up to ten small sulfur globules were formed inside the cells. The strains grew microaerophilic in the dark and exhibited high specific respiration rates. No vitamins were required for growth. The DNA base composition was 61.0–62.4 mol% G+C. The newly isolated bacterium belongs to the family chromatiaceae and is described as a member of a new genus and species, Thiorhodovibrio winogradskyi gen. nov. and sp. nov. with the type strain SSP1, DSM No. 6702

Successfully planning and implementing peer-to-peer lecture films – “Making it work”

[EN] Since summer 2015 lecture videos are implemented in “inverted classroom” teaching scenarios to teach material science to first year students studying mechanical and automotive engineering at HTW Berlin. Lecture videos so far cover subjects such as material testing, corrosion, composites, defects in crystals, hardening mechanisms and materials families. These videos were initially inspired by students. Each semester a set of lecture videos is conducted during a one term semester project supervised by lecturers and film experts (peer-to-peer approach). The peer-to-peer approach is an important aspect because students` needs and their perspective on teaching material is directly included in the videos. Recordings of lectures were also successfully implemented teaching general phase diagrams and the iron-carbon-phase diagram. Both, lecture films and recordings of lectures were used to study themes after class, prepare for classes (inverted classroom scenarios) and the final exam. Students are familiar with videos as learning source, enjoyed to work independently and not only according to contact hours and were generally more active and better prepared during class resulting in better grades. The teaching method “inverted classroom” and class results directly relate to the quality of the video material. Practice examples introduce the teaching method and evaluation of both, videos and teaching method.http://ocs.editorial.upv.es/index.php/HEAD/HEAD18Pfennig, A. (2018). Successfully planning and implementing peer-to-peer lecture films – “Making it work”. Editorial Universitat Politècnica de València. 37-44. https://doi.org/10.4995/HEAD18.2018.7503OCS374

How flipped classroom teaching methods in first year studying succeed

[EN] Flipping the classroom is a method to let students study the science on their own and then take time to discuss their questions and do extended hands-on lectures or exercises in class – or in the case of the covid-19 pandemic during plenary online sessions. First year mechanical engineering students use different teaching materials (mainly lecture videos, lightboard videos and micro-module lectures) to study from a distance and comprehend the principle underlying science in theory. Then the online plenary lectures offer the opportunity to apply their knowledge and transfer different scientific aspects of the course to get the bigger picture. Exercises, worked solutions, self-assessed tests and peer-instruction during present time help students to check on their learning progress. However, the self-study periods and (online) plenary sessions need to be guided carefully. To meet the course learning outcome and overcome the diversity of a first year class various practical leads have to be fulfilled to turn flipped classroom teaching into success.Pfennig, A. (2021). How flipped classroom teaching methods in first year studying succeed. En 7th International Conference on Higher Education Advances (HEAd'21). Editorial Universitat Politècnica de València. 1211-1218. https://doi.org/10.4995/HEAd21.2021.12792OCS1211121