RESUMO
Akinetes are resistant cells which have the ability to persist in sediment for several decades. We have investigated the temporal distribution of akinetes of two species, Dolichospermum macrosporum and Dolichospermum flos-aquae, in a sediment core sampled in Lake Aydat (France), which covers 220 years. The upper part, from 1907 to 2016, the number of akinetes fluctuated but stayed at high concentrations, especially for D. macrosporum in surface sediment (with the maximal value close to 6.105 akinetes g DW-1 of sediment), suggesting a recurrence of blooms of this species which was probably closely related to anthropic eutrophication since the 1960s. Before 1907, the abundance of akinetes of both species was very low, suggesting only a modest presence of these cyanobacteria. In addition, the percentage of intact akinetes was different for each species, suggesting different ecological processes in the water column. This percentage also decreased with depth, revealing a reduction in germination potential over time. In addition, biosynthetic genes of anatoxin-a (anaC) and microcystin (mcyA) were detected. First results show a high occurrence of mcyA all down the core. In contrast, anaC gene was mostly detected in the surface sediment (since the 1980s), revealing a potentially more recent occurrence of this cyanotoxin in Lake Aydat which may be associated with the recurrence of blooms of D. macrosporum and thus with anthropic activities.
Assuntos
Cianobactérias/genética , Genes Bacterianos , Sedimentos Geológicos/microbiologia , Lagos/microbiologia , Toxinas Bacterianas/genética , Toxinas Bacterianas/história , Toxinas de Cianobactérias , Monitoramento Ambiental , Eutrofização , História do Século XVIII , História do Século XIX , História do Século XX , História do Século XXI , Microcistinas/genética , Microcistinas/história , Tropanos/história , Poluição da ÁguaRESUMO
The 1917 total synthesis of tropinone by Sir Robert Robinson represents a landmark achievement in organic synthesis. Decades ahead of its time in terms of its retrosynthetic logic and biomimetic approach, the elegant combination of these two elements in this synthesis continues to serve as an inspiration for the development of new and efficient strategies for complex molecule synthesis.
Assuntos
Técnicas de Química Sintética/história , Tropanos/síntese química , Tropanos/história , Produtos Biológicos/síntese química , Produtos Biológicos/química , Produtos Biológicos/história , História do Século XIX , História do Século XX , Estrutura Molecular , Tropanos/químicaRESUMO
Poisoning of livestock by toxic cyanobacteria was first reported in the 19th century, and throughout the 20th century cyanobacteria-related poisonings of livestock and wildlife in all continents have been described. Some mass mortality events involving unrelated fauna in prehistoric times have also been attributed to cyanotoxin poisoning; if correct, this serves as a reminder that toxic cyanobacteria blooms predate anthropogenic manipulation of the environment, though there is probably general agreement that human intervention has led to increases in the frequency and extent of cyanobacteria blooms. Many of the early reports of cyanobacteria poisoning were anecdotal and circumstantial, albeit with good descriptions of the appearance and behaviour of cyanobacteria blooms that preceded or coincided with illness and death in exposed animals. Early necropsy findings of hepatotoxicity were subsequently confirmed by experimental investigations. More recent reports supplement clinical and post-mortem findings with investigative chemistry techniques to identify cyanotoxins in stomach contents and tissue fluids.
