A pure culture of the luminous bacterium Vibrio fischeri is maintained in the light-emitting organ of the sepiolid squid Euprymna scolopes. When the juvenile squid emerges from its egg it is symbiont-free and, because bioluminescence is part of an anti-predatory behavior, therefore must obtain a bacterial inoculum from the surrounding environment. We document here the kinetics of the process by which newly hatched juvenile squids become infected by symbiosis-competent V. fischeri. When placed in seawater containing as few as 240 colony-forming-units (CFU) per ml, the juvenile became detectably bioluminescent within a few hours. Colonization of the nascent light organ was initiated with as few as 1 to 10 bacteria, which rapidly began to grow at an exponential rate until they reached a population size of approximately 10(5) cells by 12 h after the initial infection. Subsequently, the number of bacteria in the established symbiosis was maintained essentially constant by a combination of both a > 20-fold reduction in bacterial growth rate, and an expulsion of excess bacteria into the surrounding seawater. While V. fischeri cells are normally flagellated and motile, these bacteria did not elaborate these appendages once the symbiosis was established; however, they quickly began to synthesize flagella when they were removed from the light organ environment. Thus, two important biological characteristics, growth rate and flagellation, were modulated during establishment of the association, perhaps as part of a coordinated series of symbiotic responses.

SummaryIn a previous study we observed favorable effects of egg white on serum lipids in rats and mice. The present study was designed to elucidate these effects in 24 female university students with moderate hypercholesterolemia. About 30% of total protein was supplied with egg white, tofu or cheese. The experiment was conducted for a complete menstruation cycle of each subject. Lipid intake was about 30% of total energy intake. The energy intake of each subject was constant throughout the experiment. Body weight was measured every morning. Daily activity was measured by a pedometer. Blood was withdrawn after an overnight fast on the first, 15th and last days and serum lipids were measured. Body weight and daily activity were maintained in all the groups throughout the experiment. The egg white group showed a similar decrease in the total cholesterol (Total-C) concentration but a greater increase of high-density lipoprotein cholesterol (HDL-C) concentration as compared to the tofu group and a greater decrease in Total-C and low-density lipoprotein cholesterol (LDL-C) concentrations and a greater increase in the HDL-C concentration as compared to the cheese group (p<0.05). The results indicate the favorable effects of egg white in the control of hypercholesterolemia.

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