Versatile cyanobacteria control the timing and extent of sulfide production in a Proterozoic analog microbial mat

Cyanobacterial mats were hotspots of biogeochemical cycling during the Precambrian. However, mechanisms that controlled O₂ release by these ecosystems are poorly understood. In an analog to Proterozoic coastal ecosystems, the Frasassi sulfidic springs mats, we studied the regulation of oxygenic and sulfide-driven anoxygenic photosynthesis (OP and AP) in versatile cyanobacteria, and interactions with sulfur reducing bacteria (SRB). Using microsensors and stable isotope probing we found that dissolved organic carbon (DOC) released by OP fuels sulfide production, likely by a specialized SRB population. Increased sulfide fluxes were only stimulated after the cyanobacteria switched from AP to OP. O₂ production triggered migration of large sulfur-oxidizing bacteria from the surface to underneath the cyanobacterial layer. The resultant sulfide shield tempered AP and allowed OP to occur for a longer duration over a diel cycle. The lack of cyanobacterial DOC supply to SRB during AP therefore maximized O₂ export. This mechanism is unique to benthic ecosystems because transitions between metabolisms occur on the same time scale as solute transport to functionally distinct layers, with the rearrangement of the system by migration of microorganisms exaggerating the effect. Overall, cyanobacterial versatility disrupts the synergistic relationship between sulfide production and AP, and thus enhances diel O₂ production.Subject terms: Microbial ecology, Biogeochemistry, Water microbiology     

A new Middle Devonian gasterocomid crinoid from central Turkey and revision of the Gasterocomidae

A juvenile cup, disarticulated arm plates, and columnals of the crinoid Arachnocrinus sarizensis n. sp. are described from the Eastern Taurus Mountains of central Turkey. This is the first Paleozoic crinoid based on a cup and arm plates reported from Turkey. Suggested revision of the Gasterocomidae includes transfer of Arachnocrinus and Ancyrocrinus to the family and rejection of Kopficrinus from the family. The stratigraphic range of Arachnocrinus is extended upward into the Middle Devonian from the Early Devonian. The Devonian of Turkey is of special interest because it includes Laurasian and Gondwanan components on different tectonic blocks. The paleogeographic range of Arachnocrinus is extended from the North American plate onto the Anatolian block, which would have been located on the southern edge of the Paleotethys Sea in the Middle Devonian in a shelf basin off the northern coast of Gondwana at approximately 42° south latitude.     

45,XO Turner's syndrome,Wilm's tumor and imperforate anus

Summary An eleven-year-old girl with 45,XO Turner's syndrome, Wilms' tumor and imperforate anus is presented. The family history revealed that a sib of the patient also had imperforate anus. A review of the literature showed that the occurrence of Wilm's tumor in patients with Turner's syndrome has not been recorded previously, although it is known that anomalous differentiation of the kidneys is relatively common in this condition.

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Zusammenfassung Ein elfjähriges Mädchen mit 45,XO-Turner-Syndrom, Wilms-Tumor und Atresia ani wird beschrieben. Ein Geschwister hatte ebenfalls eine Atresia ani gezeigt. Wie eine Durchsicht der Literatur ergab, was das Vorkommen des Wilms-Tumors beim Turner-Syndrom vorher neimals beschrieben worden, obwohl bekannt ist, daß Nierenfehlbildungen bei diesem Syndrom relativ häufig sind.