Utilization of phosphonic acid compounds by marine bacteria of the genera Phaeobacter, Ruegeria, and Thalassospira (α-Proteobacteria).

Phosphonic acid (phosphonate) that possesses a carbon-phosphours bond is a chemically stable form of organic phosphorus. Various phosphonic acids are widely distributed in oceanic waters; in particular, methylphosphonic acid (namely methylphosphonate) is believed to be responsible for global methane production. To discuss the microbial degradation of phosphonic acids, we investigated the utilization of phosphonic acid compounds by cultures of marine bacteria, Phaeobacter sp., Ruegeria sp. (Rhodobacterales), and Thalassospira sp. (Rhodospirillales). These bacterial cultures were able to grow on methylphosphonic acid as well as on the tested alkyl-, carboxy-, aminoalkyl-, and hydroxyalkyl-phosphonic acid compounds. Cell yields and growth rates of Ruegeria and Thalassospira cultures grown on methyl-, ethyl-, propyl-, and butyl-phosphonic acid compounds tended to decrease with increasing alkyl chain length. In contrast, Phaeobacter sp. grew well on such alkyl-phosphonic acids. Our results suggest that these marine bacteria, which exhibit varied utilization, are involved in microbial degradation of various phosphonic acid compounds.

Exposure assessment of metal intakes from drinking water relative to those from total diet in Japan.

Daily intakes of 17 metals (boron, aluminium, chromium, manganese, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium, antimony, lead, uranium, magnesium, calcium, and iron) via drinking water and total diet were investigated in six cities in Japan. The daily metal intakes were estimated and compared with tolerable daily intake (TDI) values proposed by the WHO or Joint FAO/WHO Expert Committee on Food Additives for toxic metals and with recommended dietary allowances (RDAs) or adequate intake (AI) values proposed for essential metals by the Japanese Ministry of Health, Labour and Welfare. Among the 13 toxic metals, mean dietary intakes of 10 (except arsenic, selenium, and molybdenum) were less than 50% of TDI, suggesting that for these 10 metals the allocation of intake to drinking water in establishing guidelines or standards could possibly be increased from the normal allocation of 10-20% of TDI. For the 13 toxic metals, the contribution of drinking water to TDI was 2% or less in all six cities. Mean dietary intakes of the essential elements magnesium, calcium, and iron were less than the RDA or AI values. Drinking water did not contribute much to essential metal intake, accounting for less than 10% of RDA or AI.