Evidence is accumulating to challenge the paradigm that biogenic methanogenesis, considered a strictly anaerobic process, is exclusive to archaea. We demonstrate that cyanobacteria living in marine, freshwater, and terrestrial environments produce methane at substantial rates under light, dark, oxic, and anoxic conditions, linking methane production with light-driven primary productivity in a globally relevant and ancient group of photoautotrophs. Methane production, attributed to cyanobacteria using stable isotope labeling techniques, was enhanced during oxygenic photosynthesis. We suggest that the formation of methane by cyanobacteria contributes to methane accumulation in oxygen-saturated marine and limnic surface waters. In these environments, frequent cyanobacterial blooms are predicted to further increase because of global warming potentially having a direct positive feedback on climate change. We conclude that this newly identified source contributes to the current natural methane budget and most likely has been producing methane since cyanobacteria first evolved on Earth.
The thermal springs of Zerka Ma'in, with waters emerging at temperatures up to 63 degrees C, have been of interest to biologists already from the beginning of the 19th century. These waters, springing out from below ground and flowing into the hypersaline Dead Sea, form an isolated environment from a biogeographic point of view. We have investigated the molecular diversity of the cyanobacteria in the springs. The diversity discovered was large, defining operational taxonomic units (OTUs) by a cutoff of 97% similarity; 10 major OTUs were found, including an as yet unidentified cluster of cyanobacteria. The various patterns of similarities of our sequences to others obtained from different thermal environments worldwide led us to rethink the common theories in biogeography. Based on the data obtained, we suggest that there is no constant geographical separation of microorganisms; however, local speciation does occur at a rate dictated mainly by local community dynamics and the rate of entrance of new organisms into the ecosystem.
The difficulty of completely eliminating micro-organism contaminating water used for dental treatment and the resulting biofilm suggest that flushing of DUWL can be a first solution in reducing L. pneumophila counts, while the incorporation of a disinfection method is highly recommended. Water heating and softening should be considered in practicing dentistry as factors that may aid in L. pneumophila proliferation inside the DUWL.
86.7% of the dental units were contaminated with P. aeruginosa, the conservative dentistry units had the highest amount of contamination. Flushing the DUW for 2 min significantly reduced the counts of P. aeruginosa.
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