Graduate Thesis Or Dissertation
 

Effects of long-term nutrient starvation on a marine psychrophilic vibrio

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  • Ant-300, a psychrophilic marine vibrio, was starved for periods in excess of one year. Cells starved at a high initial cell density increased in numbers from 100 to 800% of the initial number of cells during the first week. Fifty percent of the population remained viable for six weeks while a portion of the population remained viable for more than one year. Cells starved at a low initial cell density increased in numbers over 400 fold during the first week and after 70 weeks of starvation over 15 times the original number of cells were still viable. Observation of cellular DNA with Feulgen staining prior to starvation showed that the average number of nuclear bodies per cell varied from 1.44 to 4.02 depending on the age of the culture. A linear relationship was found between the average number of nuclear bodies per cell and the increase in numbers upon starvation. The data indicate that DNA replication is not necessary for the increase in cell numbers and suggest that the cells divide by fragmentation under starvation conditions. Concomitant with the increase in cell numbers was a decrease in cell size and a change in shape from a rod to a coccus. After three weeks of starvation, 50% of the viable cells were able to pass through a 0.4 μm Nuclepore filter. Electron microscopy of thin sections of the small cells revealed normal cell structure except for an enlarged periplasmic space. When inoculated into a fresh medium, small starved cells grew without a significant lag and regained "normal" size and shape within 48 h. During the first two days of starvation, the endogenous respiration of the cells decreased over 80%; after six weeks of starvation cellular DNA and protein had been reduced 46 and 43%, respectively. Additions of nutrients to starving cell populations showed that phosphate or nitrate had little effect while glucose caused a highly accelerated cell death. The addition of glucose and nitrate or glutamate to starving cell suspensions resulted in recovery and growth of the cells with no detectable loss in viability. Cells starved in seawater or a starvation menstruum amended with small amounts of amino acids showed a slight increase in cell numbers but was otherwise characteristic of complete starvation.
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file details NovitskyJamesA1977.pdf 2017-08-23 Pubblico Scaricare