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Unique genome evolution in an intracellular N2-fixing symbiont of a rhopalodiacean diatom

100%

Nakayama T. , Inagaki Y.

nr 4

Cyanobacteria, the major photosynthetic prokaryotic lineage, are also known as a major nitrogen fixer in nature. N2-fixing cyanobacteria are frequently found in symbioses with various types of eukaryotes and supply fixed nitrogen compounds to their eukaryotic hosts, which congenitally lack N2-fixing abilities. Diatom species belonging to the family Rhopalodiaceae also possess cyanobacterial symbionts called spheroid bodies. Unlike other cyanobacterial N2-fixing symbionts, the spheroid bodies reside in the cytoplasm of the diatoms and are inseparable from their hosts. Recently, the first spheroid body genome from a rhopalodiacean diatom has been completely sequenced. Overall features of the genome sequence showed significant reductive genome evolution resulting in a diminution of metabolic capacity. Notably, despite its cyanobacterial origin, the spheroid body was shown to be truly incapable of photosynthesis implying that the symbiont energetically depends on the host diatom. The comparative genome analysis between the spheroid body and another N2-fixing symbiotic cyanobacterial group corresponding to the UCYN-A phylotypes – both were derived from cyanobacteria closely related to genus Cyanothece – revealed that the two symbionts are on similar, but explicitly distinct tracks of reductive evolution. Intimate symbiotic relationships linked by nitrogen fixation as seen in rhopalodiacean diatoms may help us better understand the evolution and mechanisms of bacterium-eukaryote endosymbioses.

A Prescriptive Exercise Program for Health Maintenance

80%

Yamashita A. , Kawakami M. , Inagaki Y. , Ohkubo T.

International Journal of Occupational Safety and Ergonomics

2001

tom Vol. 7, No. 2

195--209

The aim of this study was to design a prescriptive exercise program for people of various age and fitness basing on the popular in Japan Radio Physical Fitness Exercise, a program based on an experimental approach. The evaluation indices used in the experiment were heart rate (HR), oxygen consumption, and electrical activity of the rectus femoris, latissimus dorsi, and trapezius muscles, which measured during various motion elements of the program performed at various rate. The results of this study enable to calculate equations for predicting HR during exercise from relative metabolic rate (RMR). The data on HR, RMR, and myoelectric potential presented in this study may be a basis for designing individual exercise programs for elderly people.