Metabolism of Sarcina lutea

Survival of a psychrophilic marine Vibrio under long-term nutrient starvation

Ant-300, a psychrophilic marine vibrio isolated from the surface water of the Antarctic convergence, was starved for periods of more than 1 year. During the first week of starvation, cell numbers increased from 100 to 800% of the initial number of cells. Fifty percent of the starved cells remained viable for 6 to 7 weeks while a portion of the population remained viable for more than 1 year. During the first 2 days of starvation, the endogenous respiration of the cells decreased over 80%. After 7 days, respiration had been reduced to 0.0071% total carbon respired per hour and remained constant thereafter. After 6 weeks of starvation, 46% of the cellular deoxyribonucleic acid had been degraded. Observation of the cellular deoxyribonucleic acid with Feulgen staining before starvation showed 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 number of nuclear bodies per cell and the increase in cell numbers upon starvation. Our data suggest that Ant-300 is capable of surviving long periods of time with little or no nutrients and is therefore well adapted for the sparse nutrient conditions of the colder portions of the open ocean.

STUDIES ON THE ENDOGENOUS METABOLISM OF ESCHERICHIA COLI

1. The endogenous metabolism of Escherichia coli has been studied by examining changes in cellular composition and of the suspending fluid during starvation of washed suspensions of the organism, in water or in phosphate buffer, at 37 degrees under aerobic and anaerobic conditions. 2. When E. coli is grown in glucose-ammonium salts media the cells contain glycogen, which is utilized rapidly during subsequent starvation of the cells. 3. Ammonia is released by starved cells only after a lag period, which corresponds to the time taken for the cellular glycogen to be almost completely utilized. 4. If cells are grown under conditions that permit incorporation of (14)C into protein but not into glycogen and are then starved, release of (14)CO(2) commences immediately and continues at a linear rate throughout the period of glycogen utilization; it is concluded that the presence of glycogen in the cell prevents the net degradation of nitrogenous materials but does not suppress protein turnover. 5. RNA is degraded by the cells immediately they are starved, ribose is oxidized and ultraviolet-absorbing materials are released to the suspending medium. 6. There is no significant utilization of lipid during the starvation of glucose-grown E. coli. 7. There is no loss of viability during the initial 12hr. period of starvation under either aerobic or anaerobic conditions, but thereafter the cells die more rapidly under conditions of anaerobiosis. 8. These results are discussed in relation to the known patterns of endogenous metabolism and survival of other bacteria.

NITROGENOUS SUBSTRATES OF ENDOGENOUS RESPIRATION IN PSEUDOMONAS AERUGINOSA

Gronlund, Audrey F. (University of British Columbia, Vancouver, Canada) and J. J. R. Campbell. Nitrogenous substrates of endogenous respiration in Pseudomonas aeruginosa. J. Bacteriol. 86:58-66. 1963.-The nature of the nitrogenous reserves of Pseudomonas aeruginosa that are oxidized during endogenous respiration was studied by following the changes in the chemical constituents and in the distribution of radioactivity of starving cells that had been grown on C(14)-labeled substrates. The total protein and nucleic acid of Warburg vessel contents decreased during starvation. Deoxyribonucleic acid increased slightly, whereas ribonucleic acid (RNA) decreased. C(14)O(2) was evolved from endogenously respiring cells specifically labeled in the nucleic acid fraction and from cells specifically labeled in the protein fraction. Chemical fractionation of C(14)-labeled cells showed a decrease in hot trichloroacetic acid-soluble and -insoluble compounds, indicating that the C(14)O(2) arose from the degradation of RNA and protein and not free pool compounds. A decrease in ribosomal RNA and protein was evident from physical fractionations of starved, labeled cells. An enzyme responsible for the initiation of ribosomal degradation was found to be associated with the ribosome fraction. It was concluded that oxidation of the ribonucleo-protein during endogenous respiration may be a general phenomenon in microorganisms.

Studies on the endogenous metabolism and senescence of starved Sarcina lutea

1. When washed suspensions of Sarcina lutea are starved aerobically in phosphate buffer at the growth temperature of 37 degrees , the rate of endogenous oxygen consumption decreases to very low values after 10hr., although many of the cells survive for 40hr. If starvation is prolonged further, the bacteria die at a rate of approximately 1.5% of the initial viable population per hour. 2. Oxidation of intracellular free amino acids accounts for most of the observed endogenous oxygen uptake but RNA is also utilized and a portion of the component bases and pentose is degraded and presumably oxidized. Ammonia appears in the supernatant and some pentose and ultraviolet-absorbing nucleotide are released from the cells. DNA, protein and polysaccharide are not measurably degraded. 3. Survival can be correlated with the ability of aerobically starved bacteria to oxidize exogenous l-glutamate and glucose. When starved under nitrogen for 40hr. cells continue to oxidize their endogenous reserves at undiminished rates when transferred to aerobic conditions; on prolonging anaerobic starvation the rate of oxidation declines during the period of most rapid loss of viability. 4. In the presence of Mg(2+), RNA degradation during aerobic starvation is almost completely suppressed without affecting the period for which the bacteria survive. 5. Cells grown in peptone supplemented with glucose accumulate reserves of polysaccharide which are metabolized in aerobic starvation, together with free amino acids. Ammonia is evolved and RNA is degraded to a greater extent than in peptone-grown suspensions. Bacteria rich in polysaccharide survive less well than those which are deficient in the polymer; the reason for this phenomenon has yet to be established. 6. In peptone medium, endogenous oxygen uptake and the concentration of intracellular free amino acids decline as growth progresses and they continue to decrease when the organism is held in stationary phase. Under the conditions used, the endogenous Q(o2) and free amino acid pool of cells grown in peptone with 2% (w/v) glucose did not decline so markedly and the bacteria contained large amounts of polysaccharide at all stages of growth.