11:00 〜 13:00
[BBG01-P04] Diverse phosphorus sources in serpentinized ecosystem
キーワード：蛇紋岩化反応、リン、炭素
Serpentinization is a process whereby water interacts with reduced mantle rock called peridotite to produce a new suite of minerals (e.g., serpentine), a highly alkaline fluid, and hydrogen. The hydrogen and carbon dioxide present in the system are thought to react under the highly reducing and alkaline conditions, leading to the formation of methane and hydrocarbons and the concomitant production of carbon monoxide, formate, formaldehyde and methanol. Given that the reduced compounds delivered from the water-rock reaction can support microbial energy metabolisms, such serpentinization systems have been viewed as potential habitats for early life or the other planetary bodies. Studies of serpentinizing environments to date have shown that these ecosystems host extremely low-abundance microbial communities, which is presumably attributed to the multiple extremes: 1) the highly-alkaline condition of the fluid; 2) the extremely low concentrations of oxidants (electron acceptors); and, 3) the under detectable level of available inorganic carbon and phosphate (below 2 uM).
Phosphorus is an essential element of many biomolecules that control biological functions, including nucleic acids (DNA, RNA), which are responsible for the transmission of genetic information in life, ATP, which is the currency of energy, and phospholipids, which are major components of cell membranes. Although phosphorus is an essential nutrient for life, it is often depleted in many serpentinizing aquifers due to the reaction with divalent cations (e.g. Mg and Ca) . Under this situation, how does life make a living? As for the carbon cases, while bioavailable inorganic carbons (CO2 gas or bicarbonate ion) are also depleted in serpentinizing aquifer at highly alkaline environment, it could be converted to various carbon species in the reductive environment created by the rock-water reactions, as described above. That suggests that the microbes living there uses those carbon speces as the energy and carbon source.
One interesting feature was found in the studies of Serpentinimonas species which are hyperalkaliphilic microorganisms, isolated from serpentinization sites, that fix inorganic carbon using hydrogen as an energy source. Available carbon species for the Serpentinimonas revealed that mineral calcite (CaCO3) is also the major carbon source, which indicate that solid inorganic carbon also can be an important carbon source for those organisms. Here, we investigated the availability of various phosphorus species that could be present in serpentinized water systems using Serpentinomonas and showed that the Serpentinomonas species utilize a wide variety of different phosphorus species. These results indicate that unique life strategies in extreme environments and further suggest that phosphorus reuqired life may exist even in ocean planet where phosphorus cannot be easily detected in the seawater.
Phosphorus is an essential element of many biomolecules that control biological functions, including nucleic acids (DNA, RNA), which are responsible for the transmission of genetic information in life, ATP, which is the currency of energy, and phospholipids, which are major components of cell membranes. Although phosphorus is an essential nutrient for life, it is often depleted in many serpentinizing aquifers due to the reaction with divalent cations (e.g. Mg and Ca) . Under this situation, how does life make a living? As for the carbon cases, while bioavailable inorganic carbons (CO2 gas or bicarbonate ion) are also depleted in serpentinizing aquifer at highly alkaline environment, it could be converted to various carbon species in the reductive environment created by the rock-water reactions, as described above. That suggests that the microbes living there uses those carbon speces as the energy and carbon source.
One interesting feature was found in the studies of Serpentinimonas species which are hyperalkaliphilic microorganisms, isolated from serpentinization sites, that fix inorganic carbon using hydrogen as an energy source. Available carbon species for the Serpentinimonas revealed that mineral calcite (CaCO3) is also the major carbon source, which indicate that solid inorganic carbon also can be an important carbon source for those organisms. Here, we investigated the availability of various phosphorus species that could be present in serpentinized water systems using Serpentinomonas and showed that the Serpentinomonas species utilize a wide variety of different phosphorus species. These results indicate that unique life strategies in extreme environments and further suggest that phosphorus reuqired life may exist even in ocean planet where phosphorus cannot be easily detected in the seawater.