Thiocapsa litoralis, sp. nov., a new purple sulfur bacterium from microbial mats of the White Sea

A new phototrophic purple sulfur bacterium, isolated from benthic microbial mats from the White Sea littoral zone, is described. Individual cells were spherical, non-motile and lacked gas vesicles. In pure cultures cells appeared in regular platelet-like arrangements of four, eight or sixteen cells. Cell division occurred inside a common envelope, surrounded by a thick capsule. Internal photosynthetic membranes were of the vesicular type. The colour of cell suspensions was pink to rose-red. Bacteriochlorophyll a and carotenoids of the spirilloxanthin series were found as photosynthetic pigments. Under anoxic conditions in the light, photolithoautotrophic growth occurred with sulfide, thiosulfate, sulfite and elemental sulfur as electron donors. Sulfur globules were stored as an intermediary oxidation product and were visible microscopically inside the cells. In the presence of sulfide and bicarbonate, photomixotrophic growth occurred with a number of organic substrates. Sulfate could serve as sole assimilatory source of sulfur. Chemolithoautotrophic growth in the dark was possible with sulfide and thiosulfate as electron donors. Optimum growth occurred in the presence of 1% NaCl, at pH 6.5 and at 30 degrees C. The DNA base composition of the type strain, BM5T, was 64.0 mol% G+C. According to 16S rDNA sequence information and DNA-DNA hybridization, the new isolate clearly belongs to the genus Thiocapsa, but is sufficiently different from other recognized Thiocapsa species to be described as a new species of this genus for which the name Thiocapsa litoralis sp. nov. is proposed. The type strain is BM5T (= ATCC 700894)

Differences between male and female university students in sleepiness, weekday sleep loss, and weekend sleep duration

Introduction: Women and men experience sleep differently and the difference in intrinsic desire for sleep might underlie some of the observed male-female differences. The objective of this cross-sectional questionnaire study of university students was to determine male-female differences in self-reported sleepiness and sleep-wake patterns. Methods: Five questionnaires were completed by 1650 students at four Russian universities. Results: Compared to male students, female students reported a lower subjective sleep quality score, had a higher morning sleepability score and lower nighttime and daytime wakeability scores. They more often reported excessive daytime sleepiness and expected to be sleepier at any time of the day with the largest male-female difference around the times of sleep onset and offset. On free days, they reported a longer sleep duration and an earlier sleep onset. Free-weekday difference was larger for sleep duration and smaller for sleep onset. Such male-female differences showed similarity to the differences observed in university and high school students from different countries around the globe. There was no significant male-female difference in weekly averaged sleep duration, weekday sleep duration, hours slept, midpoint of sleep on free days, free-weekday difference in sleep offset, social jetlag, and morningness-eveningness score. Therefore, when studies rely on these self-reports, the most salient male-female differences might not be immediately evident. Conclusions: It seems that the intrinsic desire for longer sleep duration might contribute to a higher susceptibility of female students to weekday sleep loss. Among these students, negative effects of reduced sleep duration might be more common and more detrimental. © 2021 The Foundation for Professionals in Services for Adolescent

Single-Item Chronotyping (SIC), a method to self-assess diurnal types by using 6 simple charts

Research on individual differences in the fields of chronobiology and chronopsychology mostly focuses on two – morning and evening – chronotypes. However, recent developments in these fields pointed at a possibility to extend chronotypology beyond just two chronotypes. We examined this possibility by implementing the Single-Item Chronotyping (SIC) as a method for self-identification of chronotype among six simple chart options illustrating the daily change in alertness level. Of 2283 survey participants, 2176 (95%) chose one of these options. Only 13% vs. 24% chose morning vs. evening type (a fall vs. a rise of alertness from morning to evening), while the majority of participants chose four other types (with a peak vs. a dip of alertness in the afternoon and with permanently high vs. low alertness levels throughout the day, 15% vs. 18% and 9% vs. 16%, respectively). The same 6 patterns of diurnal variation in sleepiness were yielded by principal component analysis of sleepiness curves. Six chronotypes were also validated against the assessments of sleep timing, excessive daytime sleepiness, and abilities to wake or sleep on demand at different times of the day. We concluded that the study results supported the feasibility of classification with the 6 options provided by the SIC. © 2020 Elsevier Lt