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Biomedical subjects

L Daneo-Moore

Publications and source records attributed to L Daneo-Moore.

At least 73 records · Page 4Linked to original sources
PubMed1978

Cellular autolytic activity in synchronized populations of Streptococcus faecium.

The autolytic capacity of Streptococcus faecium (S. faecalis ATCC 9790) varied during synchronous cell division. This phenomenon was initially observed in rapidly dividing populations (TD=30 to 33 min) synchronized by a combination of induction and size selection techniques. To minimize the problems inherent in studies of cells containing overlapping chromosome cycles and possible artifacts generated by induction techniques, the autolytic capacities of slowly dividing populations (TD=60 to 110 min) synchronized by selection only were examined. Although the overall level of cellular autolytic capacity was observed to decline with decreasing growth rate, sharp, periodic fluctuations in cellular autolytic capacity were seen during synchronous growth at all growth rates examined. On the basis of similar patterns of cyclic fluctuations in autolytic capacity of cultures synchronized by (i) selection, (ii) amino acid starvation followed by size selection, and (iii) amino acid starvation followed by inhibition of DNA synthesis, a link of such fluctuations with the cell division cycle has been postulated.

Amino Acids↗
PubMed1978

Relationship between cellular autolytic activity, peptidoglycan synthesis, septation, and the cell cycle in synchronized populations of Streptococcus faecium.

Synchronized, slowly growing (TD = 70 to 80 min) cultures were used to study several wall-associated parameters during the cell cycle: rate of peptidoglycan synthesis, septation, and cellular autolytic activity. The rate of peptidoglycan synthesis per cell declined during most of the period of chromosome replication (C), but increased during the latter part of C and into the period between chromosome termination and cell division (D). An increase in cellular septation was correlated with the increased rate of peptidoglycan synthesis. Cellular autolytic capacity increased during the early portion of C, reached a maximum late in C or early in D, and declined during D. Inhibition of DNA synthesis during C prevented the decline in autolytic capacity at the end of the cell cycle, caused a slight reduction in the rate of peptidoglycan synthesis, delayed but did not prevent septation, and prevented the impending cell division by inhibiting cell separation. Inhibition of DNA synthesis during D did not prevent the increase in autolytic capacity during the next C phase, but, once again, prevented the decline at the end of the subsequent cycle. Thus, increased autolytic capacity at the beginning of the cell cycle did not seem to be related to chromosome initiation, whereas decreased autolytic capacity at the end of the cell cycle seemed to be related to chromosome termination. The data presented are consistent with the role of autolytic enzyme activity in the previously proposed model for cell division of S. faecium (G.D. Shockman et al., Ann. N.Y Acad. Sci. 235:161-197, 1974).

Cell Cycle↗
PubMed1978

Approximation of the cell cycle in synchronized populations of Streptococcus faecium.

Slowly growing populations (TD = 70 to 80 min) of Streptococcus faecium (S. faecalis ATCC 9790) were synchronized by selection after sucrose gradient fractionation. The cell cycle was approximated by correlating the patterns of DNA accumulation and cell division. More specifically, the beginning of cell cycle was equated with the beginning of a rapid linear increase in DNA accumulation. The DNA content of the culture approximately doubled during the period of accumulation, which lasted about 51 min. The period of rapid DNA accumulation, was followed by a period of reduced accumulation that lasted about 24 min. During synchronized growth, cell numbers increased rapidly in coordination with the period of rapid DNA accumulation and exhibited a plateau during the period of reduced DNA accumulation. In contrast, RNA and protein appeared to accumulate exponentially throughout the cell cycle at the same rate as culture mass.

Bacterial Proteins↗
PubMed1978

Effects of temperature on the autolytic enzyme system of Streptococcus faecalis.

The cellular autolytic reaction system in Streptococcus faecalis ATCC 9790 was analyzed for relative increases in reaction rates with increasing temperature by determination of Arrhenius activation energies (E). The systems examined were: (i) an isolated wall-enzyme complex in 0.01 M sodium phosphate, pH 6.9; (ii) exponential-phase cells suspended in 0.01 or o.3 M sodium phosphate pH 6.8, or in 0.04 M ammonium acetate, pH 6.8, (iii) growing cultures deprived of glucose or lysine; and (iv) cultures treated in growth media with the nonionic detergent, Triton X-100. For detergent-treated cells, E values were between 23.9 and 27.4 kcal/mol (ca. 100.1 to 174.7 kJ/mol) at concentrations of Triton X-100 between about 0.03 and 0.072 mg/ml. E values dropped sharply to 11.5 to 13.0 kcal/m-l (ca. 48.2 to 54.4 kJ/mol) at Triton X-100 concentrations of 0.12 mg/ml or higher. For the remaining systems, E values ranged from 16 to 20 kcal/mol (ca. 67.0 to 83.7 kJ/mol) (wall lysis, cellular autolysis in 0.01 M sodium phosphate or in 0.04 M ammonium acetate, and autolysis of glucose-starved cells) to 31 to 38 kcal/mol (ca 129.8 to 159.1 kJ/mol) (cellular autolysis in 0.3 M sodium phosphate or autolysis of lysine-starved cells). High concentrations of Triton X-100 appear to lower the E values below the 16 to 20 kcal/mol observed for the autolysis of isolated walls. This effect may be related to disruption by the detergent of a hydrophobic complex regulating cellular autolysis in vivo.

Amidohydrolases↗
PubMed1977

Temperature effects on minimum inhibitory and bactericidal concentrations of cell wall antibiotics in Streptococcus faecalis.

The minimal inhibitory and bactericidal concentrations were determined at 30 and 37 degrees C for several antibiotics affecting cell wall biosynthesis. The test organism, Streptococcus faecalis ATCC 9790, possesses a single autolytic enzyme and does not produce penicillinase. Penicillin, methicillin, and, possibly, bacitracin appeared more effective at 37 than at 30 degrees C. Vancomycin, ristocetin, and phosphonomycin appeared equally effective at both temperatures, and cycloserine appeared consistently more active at 30 than at 37 degrees C.

Anti-Bacterial Agents↗
PubMed1977

Factors regulating cell wall thickening and intracellular iodophilic polysaccharide storage in Streptococcus mutans.

The effects of a series of different antibiotics on the synthesis and accumulation of deoxyribonucleic acid (DNA), ribonucleic acid (RNA), protein, cell wall peptidoglycan (PG), and intracellular iodophilic polysaccharide (IPS) in Streptococcus mutans FA-1 were examined. d-Cycloserine, penicillin G, or vancomycin treatment resulted in rapid inhibitions of PG synthesis and a consequent decrease in the relative amount of lysine found in PG fractions. Decreases in culture turbidity, an indicator of gross cellular lysis, were not observed. Secondary inhibitions of the rates and extent of syntheses of DNA, RNA, and protein were observed. With all three inhibitors of PG synthesis, IPS synthesis continued for varying time intervals but, at most, resulted in only relatively small and transient increases in cellular IPS content. Chloramphenicol inhibited protein synthesis but permitted continued synthesis of RNA and PG. After 6 h, the cells contained 42% of their [(3)H] lysine in the PG fraction compared with 25% in exponential-phase cells, a good indication of thickened cell walls. In the presence of chloramphenicol, cellular IPS content increased about 2.5-fold during the first 45 min and then decreased to a level (13%) at 6 h very similar to that of exponential-phase cells (about 10%). Rifampin inhibition of RNA (and, consequently, also protein) synthesis resulted in accumulation of cellular PG and IPS. After 6 h, IPS accounted for 38% of the cellular dry weight, and the cells contained 43% of their lysine in PG. Thus, rifampin-inhibited cells appear to have both thickened walls and a high IPS content. The correlation between inhibition of RNA synthesis and IPS accumulation was confirmed by exposing cultures to rifampin for 60 min and then removing the drug, thus permitting the cells to regrow. Upon removal of rifampin and resumption of RNA synthesis, cellular IPS content rapidly decreased to the level expected for exponentialphase cells.

Anti-Bacterial Agents↗
PubMed1976

Inhibition of wall autolysis in Streptococcus faecalis by lipoteichoic acid and lipids.

Fully acylated lipoteichoic acid (LTA) isolated from Streptococcus faecalis ATCC9790 (S. faecium) inhibited autolysis of walls from the same organism at concentrations (1.0 to 1.5 nmol of LTA per mg of wall) comparable to those found in intact cells. Partially deacylated LTA isolated from S. faecalis or chemically deacylated LTA failed to inhibit significantly in the same concentration range. Beef heart cardiolipin and commercially obtained dipalmitoyl phosphatidyl glycerol were also found to inhibit wall autolysis in S. faecalis. Chemical deacylation of beef heart cardiolipin also removed the inhibitory activity of this molecule. Lipid fractions isolated from S. faecalis that inhibited wall autolysis were: diphosphatidyl glycerol (cardiolipin), phosphatidyl glycerol, aminoacyl phosphatidyl glycerol, and a neutral lipid fraction. Glycolipids were not found to be effective inhibitors. The possible role of LTA and/or certain lipids as regulators of cellular autolytic activity is discussed.

Acylation↗
PubMed1976

Organization of mesosomes in fixed and unfixed cells.

After the addition of glutaraldehyde (GA) to cells incubated at 3 or 37 degrees C, mesosomes were observed with increasing frequencies in freeze fractures of cells. These increases were related to the kinetics with which GA cross-linked adjacent amino acids. Upon the addition of GA, mesosomes were first observed in the periphery of freeze-fractured cells usually attached to septal membranes. However, the time, while the septal attachment sites were maintained, the "bodies" of the mesosomes were observed to move toward the center of the cytoplasm. This centralization process was much more rapid at 37 than at 3 degrees C. It is hypothesized that upon fixation, or receipt of some physical insult, mesosome precursors found in undisturbed cells undergo a change in state that results in their visibility in freeze fractures.

Aldehydes↗
PubMed1975

Turnover of the cell wall peptidoglycan of Lactobacillus acidophilus. The presence of a fraction immune to turnover.

Exponentially growing cultures of Lactobacillus acidophilus strain 60AM Gasser were previously shown to lose about one-third of their cell wall peptidoglycan per generation via turnover (Boothby, D., Daneo-Moore, L., Higgins, M. L., Coyette, J., and Shockman, G. D. (1973) J. Biol. Chem. 248, 2161-2169). We now show that 20 to 30% of the [3H]lysine initially present in insoluble peptidoglycan fractions was retained after 4 or more generations of continued exponential growth of cultures in the absence of label. Treatment of peptidoglycan fractions, before and after 6 or 8 generations of chase with lysozyme (EC 3.2.1.17), released soluble products containing [3H]lysine which had electrophoretic mobilities identical with the disaccharide-peptide derivatives obtained from the wall peptidoglycan of this species. Because protein is known to contaminate peptidoglycan residues, the double labeled technique was used to show that one-half or less of the label lysine present after 6 or 8 generations of chase could be attributed to protein contamination. This then left a minimum fraction of 10 to 20% of the peptidoglycan that was immune to turnover. The absence of turnover of peptidoglycan labeled during short pulses has now been quantitated to show that pulses shorter than 12% of a generation (6 to 7 min) did not turn over. This turnover-immune fraction is in reasonably good agreement with the immune fraction of 10 to 20% observed after long periods of chase of extensively labeled peptidoglycan.

Amino Acids↗
PubMed1975

Analysis of growth rate in sucrose-supplemented cultures of Streptococcus mutans.

In the presence of sucrose, Streptococcus mutans grows in large glucan-containing aggregates. Because of reports of linear rather than exponential growth of sucrose-grown cultures, the kinetics of growth of sucrose-grown cultures of S. mutans strain OMZ-176 were compared with those of glucose-grown cultures. Culture turbidity measurements indicated that growth of sucrose cultures was slower, did not follow exponential kinetics, and slowed and stopped at lower absorbance values than did glucose-grown cultures. However, measurements of the rates of accumulation of deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and protein using fully equilibrated radioactively labeled precursors of each of these macromolecular species in sucrose and glucose-grown cultures showed that: (i) for glucose cultures the synthesis of each of the three informational molecules occurred at the same exponential rate, which was identical to the rate of turbidity increase; (ii) for sucrose cultures each macromolecular species was synthesized at the same exponential rate and these rates were identical to the rate of increase of turbidity of the glucose-grown culture for periods of up to 7 h. Furthermore, the ratios of DNA to RNA, RNA to protein, and protein to DNA for the sucrose cultures were identical to those for the glucose cultures for up to 10 doublings. From these data it was concluded that in the presence of sucrose S. mutans grows in a balanced fashion at the same exponential rate as it does in glucose. The deviation from an exponential growth model of the absorbance in sucrose cultures was attributed to an optical artifact due to the formation of large glucan-containing aggregates of cells. The addition of dextranase to sucrose cultures resulted in cultures which increased in turbidity at the same exponential rate as glucose-grown cultures, without affecting the rate or extent of macromolecular synthesis.

Carbon Radioisotopes↗
PubMed1975

Evidence for the synthesis of soluble peptidoglycan fragments by protoplasts of Streptococcus faecalis.

Growing protoplasts of Streptococcus faecalis 9790 were found to synthesize and excrete soluble peptidoglycan fragments. The presence of soluble peptidoglycan derivatives in culture supernatants was determined by (i) incorporation of three different radioactively labeled precursors (L-lysine, D-alanine, and acetate) into products which, after hen egg-white lysozyme hydrolysis, had the same KD values on gel filtration as muramidase hydrolysis products of isolated walls; (ii) inhibition of net synthesis of these products by cycloserine and vancomycin; and (iii) identification of disaccharide-peptide monomer using the beta-elimination reaction, gel filtration, and high-voltage paper electrophoresis. Under the conditions of these experiments the presence of newly synthesized, acid-precipitable (macromolecular) peptidoglycan was not detected. The predominance of monomer (70 to 80%) in lysozyme digests of peptidoglycan synthesized by protoplasts was in sharp contrast to digest of walls from intact streptococci which contain mostly peptide cross-linked products. Biosynthesis and release of relatively uncross-linked, soluble peptidoglycan fragments by protoplasts was related to the absence of suitable, preexisting acceptor wall.

Acetates↗
PubMed1974

Factors influencing the frequency of mesosomes observed in fixed and unfixed cells of Streptococcus faecalis.

Mesosomes of Streptococcus faecalis (American Type Culture Collection 9790) were seen about 92% less frequently in freeze fractures of unfixed cells than in freeze fractures and sections of fixed cells. This difference in frequency was not related to any period of unbalanced macromolecular synthesis induced by chemical fixation. All measured synthetic processes (DNA, RNA, and protein synthesis, and glycerol incorporation) were halted with either osmium tetroxide (OS) or glutaraldehyde fixation. That fewer mesosomes were seen in freeze fractures of unfixed cells was probably due to the difficulty of observing cross-fractured mesosomes in this organism in the unfixed state. Unfortunately, mesosomes probably preferentially cross fracture in the unfixed state and therefore are usually only observed, infrequently, in those cases where the freeze fracture follows the surface layer of a mesosomal membrane. However, the addition of glycerol to unfixed cells, especially in the chilled state, greatly increased the frequency of observation of cytoplasmic mesosomes in freeze fractures. It is thought that glycerol, like chemical fixation, increases the number of surface-fractured mesosomes, which in turn increases the frequency of mesosome observation. It was also observed that cellular autolysis occurring during OS fixation seemingly reduced the number of mesosomes observed in thin sections and freeze fractures of OS-fixed cells.

Autolysis↗
PubMed1974

Effect of inhibition of deoxyribonucleic acid and protein synthesis on the direction of cell wall growth in Streptococcus faecalis.

Selective inhibition of protein synthesis in Streptococcus faecalis (ATCC 9790) was accompanied by a rapid and severe inhibition of cell division and a reduction of enlargement of cellular surface area. Continued synthesis of cell wall polymers resulted in rapid thickening of the wall to an extent not seen in exponential-phase populations. Thus, the normal direction of wall growth was changed from a preferential feeding out of new wall surface to that of thickening existing cell surfaces. However, the overall manner in which the wall thickened, from nascent septa toward polar regions, was the same in both exponential-phase and inhibited populations. In contrast, selective inhibition of deoxyribonucleic acid (DNA) synthesis using mitomycin C was accompanied by an increase in cellular surface area and by division of about 80% of the cells in random populations. Little or no wall thickening was observed until the synthesis of macromolecules other than DNA was impaired and further cell division ceased. Concomitant inhibition of both DNA and protein synthesis inhibited cell division but permitted an increase in average cell volume. In such doubly inhibited cells, walls thickened less than in cells inhibited for protein synthesis only. On the basis of the results obtained, a model for cell surface enlargement and cell division is presented. The model proposes that: (i) each wall enlargement site is influenced by an individual chromosome replication cycle; (ii) during chromosome replication peripheral surface enlargement would be favored over thickening (or septation); (iii) a signal associated with chromosome termination would favor thickening (and septation) at the expense of surface enlargement; and (iv) a factor or signal related to protein synthesis would be required for one or more of the near terminal stages of cell division or cell separation, or both.

Azacitidine↗
PubMed1972

Morphokinetic reaction of Streptococcus faecalis (ATCC 9790) cells to the specific inhibition of macromolecular synthesis: nucleoid condensation on the inhibition of protein synthesis.

In glutaraldehyde-prefixed exponential-phase cells of Streptococcus faecalis the nucleoid is "frozen" in a dispersed configuration. Exposure of exponential-phase cells to threonine starvation or to antibiotics inhibiting protein synthesis resulted in progressive condensation of nucleoid fibrils producing an expanding central nucleoid zone or pool. The condensation of the nucleoid was observed to occur at a rate directly proportional to the rate of inhibition of protein synthesis. However, the extent of nucleoid condensation depended on continuing deoxyribonucleic acid synthesis. Significantly less nucleoid condensation occurred when cells were inhibited in deoxyribonucleic acid and protein synthesis than when cells were inhibited in protein synthesis alone. These results suggest a model in which, during nucleoid replication, the chromosome fibrils are normally maintained in a dispersed state by the active agents of transcription-translation, such as ribonucleic acid polymerase molecules and ribosomes.

Anti-Bacterial Agents↗