Abstract
The present study demonstrated formation of Ca and P rich nanoglobules by a mixed natural halophilic population enriched from hypersaline lake sediments in laboratory culture experiments. Nanoglobules consisting of complex mixture of Ca, P, O, and C with minor amount of Mg occurred in the external envelop of bacterial cell in the first week of incubation at various Mg+2/Ca+2 ratios and salinity at 30 °C. Unlike the control experiments (e.g., non-viable cells and without cells), later aggregation and transformation of nanoglobules caused the precipitation of calcium and/or magnesium carbonates in variable amount depending on the Mg+2/Ca+2 ratios of the medium after 37 days of incubation. By showing the nucleation of carbonates on bacterial nanoglobules closely associated with the cell surfaces of mixed natural population this study emphasis that formation of nanoglobules may not be specific to a microbial strain or to activity of a particular microbial group. Formation of carbonate nanoglobules under various conditions (e.g., Mg+2/Ca+2 ratios, salinity) with the same halophilic culture suggest that the although metabolic activity of bacteria have an influence on formation of nanoglobules the mineralogy of nanoglobules may be controlled by the physicochemical conditions of the precipitation solution and the rate of mineral precipitation.
Highlights
Tracing microbial activity in the geologic records primarily rely on our knowledge obtained from the recent laboratory experiments and field observations in geologically diverse environments.The finding evidence for existence of microorganism in the geologic record, for carbonate, stimulate researches to develop new proxies for identifying microbial fingerprints as well as their role in carbonate precipitation under various geochemical conditions
A shorter time periods were required for a pH rise from 7.2 to 9.2 in the low salinity experiments
The highest pH value was obtained from M6 medium with 80 g/L salinity and Mg+2 /Ca+2 ratio of 7.2 at the end of 37-day incubation
Summary
Tracing microbial activity in the geologic records primarily rely on our knowledge obtained from the recent laboratory experiments and field observations in geologically diverse environments. The finding evidence for existence of microorganism in the geologic record, for carbonate, stimulate researches to develop new proxies for identifying microbial fingerprints as well as their role in carbonate precipitation under various geochemical conditions. It is widely accepted that formation of carbonates in marine (e.g., foraminiferal calcite, and corals) and fresh water environments (e.g., surface fresh water deposits, and tufas) is influenced by microbial activity. Numerous laboratory experiments and field studies have been carried out to elucidate the role of microorganism in precipitation of carbonate minerals [5,6,7,11,12,13]. Geochemical cycles of P and Ca exert significant control on carbonate precipitation processes in organic rich environments
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
