Changes in morphology and elemental composition of Vibrio splendidus along a gradient from carbon-limited to phosphate-limited growth.

We examined morphology, elemental composition (C, N, P), and orthophosphate-uptake efficiency in the marine heterotrophic bacterium Vibrio splendidus grown in continuous cultures. Eight chemostats were arranged along a gradient of increasing glucose concentrations in the reservoirs, shifting the limiting factor from glucose to phosphate. The content of carbon, nitrogen, and phosphorus was measured in individual cells by x-ray microanalysis using a transmission electron microscope (TEM). Cell volumes (V) were estimated from length and width measurements of unfixed, air-dried cells in TEM. There was a transition from coccoid cells in C-limited cultures toward rod-shaped cells in P-limited cultures. Cells in P-limited cultures with free glucose in the media were significantly larger than cells in glucose-depleted cultures (P < 0.0001). We found functional allometry between cellular C-, N-, and P content (in femtograms) and V (in cubic micrometers) in V. splendidus (C = 224 x V(0.89), N = 52.5 x V(0.80), P = 2 x V(0.65)); i.e., larger bacteria had less elemental C, N, and P per V than smaller cells, and also less P relative to C. Biomass-specific affinity for orthophosphate uptake in large P-limited V. splendidus approached theoretical maxima predicted for uptake limited by molecular diffusion toward the cells. Comparing these theoretical values to respective values for the smaller, coccoid, C-limited V. splendidus indicated, contrary to the traditional view, that large size did not represent a trade-off when competing for the non-C-limiting nutrients.

Disability pensions due to musculo-skeletal disorders among men in heavy occupations. A case-control study.

The relative risk of disability pension due to musculo-skeletal disorders has been studied with regard to occupation and work load. The study population comprised men born 1915 to 1934, living in Stockholm county. 1307 men who received a disability pension during 1979, 1980, 1981 and 1984 due to disorders from the low back, neck/shoulder, hip, and knee were compared with 298 randomly selected men concerning occupation and occupational work load. Disability pensions were more common both in men with medium and high physical work load compared to men with low physical work load. Construction workers and metal workers had a high relative risks of receiving disability pensions because of disorders in all four body regions, and men in many other occupations had disorders in two or three regions. In office workers the risk of disability pension because of musculo-skeletal disorders was low.