Background Melanin pigments are ubiquitous in nature. Melanized microorganisms are often the dominating species in certain extreme environments, such as soils contaminated with radionuclides, suggesting that the presence of melanin is beneficial in their life cycle. We hypothesized that ionizing radiation could change the electronic properties of melanin and might enhance the growth of melanized microorganisms. Methodology/principal findings Ionizing irradiation changed the electron spin resonance (ESR) signal of melanin, consistent with changes in electronic structure. Irradiated melanin manifested a 4-fold increase in its capacity to reduce NADH relative to non-irradiated melanin. HPLC analysis of melanin from fungi grown on different substrates revealed chemical complexity, dependence of melanin composition on the growth substrate and possible influence of melanin composition on its interaction with ionizing radiation. XTT/MTT assays showed increased metabolic activity of melanized C. neoformans cells relative to non-melanized cells, and exposure to ionizing radiation enhanced the electron-transfer properties of melanin in melanized cells. Melanized Wangiella dermatitidis and Cryptococcus neoformans cells exposed to ionizing radiation approximately 500 times higher than background grew significantly faster as indicated by higher CFUs, more dry weight biomass and 3-fold greater incorporation of (14)C-acetate than non-irradiated melanized cells or irradiated albino mutants. In addition, radiation enhanced the growth of melanized Cladosporium sphaerospermum cells under limited nutrients conditions. Conclusions/significance Exposure of melanin to ionizing radiation, and possibly other forms of electromagnetic radiation, changes its electronic properties. Melanized fungal cells manifested increased growth relative to non-melanized cells after exposure to ionizing radiation, raising intriguing questions about a potential role for melanin in energy capture and utilization.

/pdf/ionizing-radiation-changes-the-electronic-properties-of-19iiwcwyli.pdf

Ionizing Radiation Changes the Electronic Properties of Melanin and Enhances the Growth of Melanized Fungi

One of the most important carbon cycle perturbations following the end-Permian mass extinction event straddles the Smithian-Spathian boundary (SSB) (Olenekian, Early Triassic). This anomaly is characterized by a prominent positive carbon isotope excursion known from Tethyan marine rocks. Its global signifi cance is established here by a new high paleolatitude record (Spitsbergen). Paleontological evidence, such as Boreal palynological data (Barents Sea, Norway) and global patterns of ammonoid distribution, indicates a synchronous major change in terrestrial and marine ecosystems near the SSB. The reestablishment of highly diverse plant ecosystems, including the rise of woody gymnosperms and decline of the formerly dominating lycopods, is interpreted as an effect of a major climate change. This hypothesis is supported by modeling of ammonoid paleobiogeography, the distribution patterns of which are interpreted as a proxy for sea surface temperatures (SST). The latest Smithian thus appears to have been a time of a warm and equable climate as expressed by an almost fl at pole to equator SST gradient. In contrast, the steep Spathian SST gradient suggests latitudinally differentiated climatic conditions. We propose that this drastic climate change and the global carbon cycle perturbation were triggered by a massive end-Smithian CO2 injection. The SSB event could therefore represent one of the causes for stepwise and delayed recovery of marine and terrestrial biotas in the wake of the end-Permian biotic crisis.

Smithian-Spathian boundary event: Evidence for global climatic change in the wake of the end-Permian biotic crisis

Biotic cycles in the early Silurian correlate broadly with postulated sea-level changes, but are better explained by a model that involves episodic changes in oceanic state. Primo episodes were characterized by cool high-latitude climates, cold oceanic bottom waters, and high nutrient supply which supported abundant and diverse planktonic communities. Secundo episodes were characterized by warmer high-latitude climates, salinity-dense oceanic bottom waters, low diversity planktonic communities, and carbonate formation in shallow waters. Extinction events occurred between primo and secundo episodes, with stepwise extinctions of taxa reflecting fluctuating conditions during the transition period. The pattern of turnover shown by conodont faunas, together with sedimentological information and data from other fossil groups, permit the identification of two cycles in the Llandovery to earliest Wenlock interval. The episodes and events within these cycles are named: the Spirodden Secundo episode, the Jong Primo episode, the Sandvika event, the Malmoykalven Secundo episode, the Snipklint Primo episode, and the Ireviken event.

Early Silurian oceanic episodes and events

Records of abnormal gymnosperm pollen morphotypes from coeval localities in Russia and NW China provide independent and unique evidence of deteriorating atmospheric conditions at the close of the Permian. Although at similar palaeolatitude, the Vologda region of European Russia and the Junggar Basin of Xinjiang Province, China, were thousands of kilometres apart and on different tectonic plates. The co-occurrence of the megaspore Otynisporites eotriassicus Fuglewicz 1977, and its restricted distribution elsewhere in marine sections with either Late Permian ammonoids or the basal Triassic conodont marker Hindeodus parvus , confirms the age range, and correlation of the Russian and NW Chinese sections. In three Chinese sections, rapid changes in carbon isotopic (δ 13 C org ) composition of between 4 and 10‰ occur over the intervals showing abnormal pollen. These patterns reflect bioclastic facies contributions responding to local environmental changes. They are nevertheless coincident with global perturbations in the atmosphere, caused by extensive volcanic activity around the Permian–Triassic boundary.

Abnormal pollen grains: an outcome of deteriorating atmospheric conditions around the Permian–Triassic boundary

Biotic and sedimentological cycles in the late Silurian are closely similar to those recognized in the early Silurian. They are explained here by alternations between primo and secundo conditions, the former being characterized by cold dense oceanic bottom waters and high nutrient supply, and the latter by salinity-dense bottom waters and diminished nutrient supply. The lithological pattern, together with the turnover of conodont faunas and of other fossil groups, permits the identification of a sequence of episodes and events in the Ludlow following the Klinte Secundo Episode, which developed in the latest Wenlock: The Sproge Primo Episode, the Linde Event, the Etelhem Secundo Episode, the Havdhem Primo Episode, the Lau Event, the Hoburgen Secundo Episode and the Klev Secundo–Primo Event, continuing into the earliest Přidoli. Testing of this model against others that invoke a primary sea-level control is marred by the current imprecisions of biostratigraphical correlation.

Ludlow (late Silurian) oceanic episodes and events

Palynology of the Permian and Triassic of the Tesero and Bulla sections (Western Dolomites, Italy) and consideration about the enigmatic species Reduviasporonites chalastus

Selected Tertiary Angiosperm Pollens from India and Their Relationship with African Tertiary Pollens

Reworking of Devonian, Carboniferous and Permian palynomorphs into the Lower Triassic of western Canada, Yukon, the Canadian Arctic Archipelago and Alaska has been documented by a number of workers. The phenomenon occurs in other northern circumpolar localities, such as East Greenland and the Barents Sea, and was probably widespread. Examples are given from western and eastern Europe, Russia, the Middle East, Pakistan, China, Brazil and Australia. The abundance and diversity of reworked palynomorphs from a number of stratigraphic units of different ages into the Lower Triassic is an important palynostratigraphic phenomenon of chronostratigraphic value. It may be the result of a major regional regression in the late Permian, followed by a widespread marine transgression in the Early Triassic, or it may be due to tectonic activity resulting in eustatic sea-level rise. Whatever the mechanism, the advancing transgression resulted in erosion of exposed Devonian, Carboniferous and Permian rocks, but by...

https://bioone.org/journals/Palynology/volume-28/issue-1/28.1.75/REWORKED-MIOSPORES-IN-THE-UPPER-PALEOZOIC-AND-LOWER-TRIASSIC-OF/10.2113/28.1.75.pdf

Reworked miospores in the upper paleozoic and lower triassic of the northern circum-polar area and selected localities

Silurian paulinitid polychaetes from Gotland; fossils and strata, no.25

(40-41) Proposals to Amend Provisions regarding Typification of the Names of Fossil Plants

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