Periodic synthesis of phospholipids during the Caulobacter crescentus cell cycle.

Net phospholipid synthesis is discontinuous during the Caulobacter crescentus cell cycle with synthesis restricted to two discrete periods. The first period of net phospholipid synthesis begins in the swarmer cell shortly after cell division and ends at about the time when DNA replication initiates. The second period of phospholipid synthesis begins at a time when DNA replication is about two-thirds complete and ends at about the same time that DNA replication terminates. Thus, considerable DNA replication, growth, and differentiation (stalk growth) occur in the absence of net phospholipid synthesis. In fact, when net phospholipid synthesis was inhibited by the antibiotic cerulenin through the entire cell cycle, both the initiation and the elongation phases of DNA synthesis occurred normally. An analysis of the kinetics of incorporation of radioactive phosphate into macromolecules showed that the periodicity of phospholipid synthesis could not have been detected by pulse-labeling techniques, and only an analysis of cells prelabeled to equilibrium allowed detection of the periodicity. Equilibrium-labeled cells also allowed determination of the absolute amount of phosphorus-containing macromolecules in newborn swarmer cells. These cells contain about as much DNA as one Escherichia coli chromosome and about four times as much RNA as DNA. The amount of phosphorus in phospholipids is about one-seventh of that in DNA, or about 3% of the total macromolecular phosphorus.     

Rates of accumulation of glycosidase activities during growth and differentiation of Dictyostelium discoideum.

1. The rates of accumulation (enzyme units/h per 10(8) cells) of a number of glycosidase activities were studied in Dictyostelium discoideum cells during the growth and differentiation phases of this organism's life cycle. 2. The rates of accumulation of the enzymes beta-N-acetylglucosaminidase, alpha-glucosidase and beta-galactosidase remain unchanged during the growth and early differentiation phases. 3. The considerable changes in specific activity of the enzymes which occur in the early differentiation phase are due to the massive loss of total cellular protein which occurs at this time. 4. Significant alterations can occur in the rates of accumulation of alpha-mannosidase during both the growth and differentiation phases, and since, on the onset of differentiation, beta-glucosidase activity is excreted and degraded, the rate of accumulation of this enzyme differs in the growth and differentiation phases. 5. The characteristic rates of accumulation of all these glycosidases change markedly with changes in the growth conditions of the myxamoebae, and thus these rates of synthesis must be regulated independently; however, addition of cyclic AMP to the growth medium has no effect on them.     

Lipid variation of the green alga Fritschiella tuberosa during growth in axenic batch culture

The lipid and pigment pattern of the chaetophoralean green alga Fritschiella tuberosa was studied during different growth periods. Four phases in axenic batch culture are observed. The first phase commences at the end of logarithmic growth and results in a decrease of phosphatidyl inositol and hexadecatetraenoic acid.The second phase coincides with the end of linear growth and is characterized by a decrease in glycolipids, phospholipids and α-linolenic acid, and an increase of linoleic and oleic acid. The third phase starts with the beginning of the stationary phase. During this time glycolipids, phospholipids, and α-linolenic acid decrease and oleic acid, linoleic acid and triacylglycerol increase. The fourth phase begins about one week after the onset of the stationary growth phase. A marked accumulation of triacylglycerol took place, secondary carotenoids were detectable and the long filamentous cells of Fritschiella changed into slightly rotund short cells.     

Protein degradation and protease activity during the late cycle of Blastocladiella emersonii

Analysis of protein degradation during the life cycle of Blastocladiella emersonii showed that (i) protein degradation is especially high during two phases of differentiation (sporulation, 12%/h and germination, 5%/h) in contrast with a much smaller degradation rate in the other phases (growth and zoospores, less than 1%/hr); (ii) protein degradation during germination in growth medium, as well as most of the germination process, is quantitatively unaffected by cycloheximide; (iii) a caseinolytic protease (pH optimum 5.5, apparent molecular weight 55,000 to 60,000) is present in extracts of zoospores and germinating cells; (iv) this protease activity is very low (perhaps absent) in extracts of late growth phase cells, but reappears during induced sporulation; (v) a different class of caseinolytic protease activity (pH optima 7 and 10; apparent molecular weight 25,000 to 30,000) is found in cellular extracts of late growth phase and early phases of sporulation; (vi) the latter class of enzyme activity is released into the medium during later phases of sporulation and is replaced in the cells by the former class. Speculations as to the roles of protein degradation in cell differentiation are discussed.     

Alterations in the composition of membrane glycero-and sphingolipids in the course of <Emphasis Type="Italic">Flammulina velutipes</Emphasis> surface culture development

Qualitative and quantitative characteristics of the alterations in the lipid composition of the membrane of the basidial fungus Flammulina velutipes in the course of surface culture development were investigated. Modifications of the lipid composition were shown to be timed to specific ontogeny stages, such as changes in the growth rate of the colonies, the appearance of differentiated vegetative cells, and the formation of generative structures. A slowdown of growth correlated with an alteration in the ratio of major classes of phospholipids, namely, with a decrease of phosphatidylcholine relative content and an increase in phosphatidylethanolamines. The differentiation of vegetative cells of the mycelium proceeded along with modifications of molecular composition of glycoceramides. In the course of the first week of growth, the surface culture of F. velutipes produced monohexosylceramides with epoxidized methyl sphingadienine as a sphingoid base. Later on, along with culture growth and specialization of mycelium cells, molecular species with methyl sphingadienine, common for basidiomycetes, start to prevail among the fungal glycoceramides. The formation of fruit bodies is accompanied by enrichment of molecules of phospholipids, mainly, the phosphatidylcholines, with unsaturated fatty acids.     

Phospholipids are synthesized in the G2/M phase of the cell cycle

Very little is known about the metabolism of phospholipids in the G2 and M phases of the cell cycle, but limited studies have led to the postulation that phospholipid synthesis ceases during this period. To investigate whether phospholipids are synthesized in the G2/M phase of the cell cycle, protocols were developed to produce synchronized MCF-7 cell populations with greater than 80% of the cells in G1/S or G2/M phases that moved in synchrony following removal of the blocking agent. Analysis of the activities of key phosphatidylcholine and phosphatidylethanolamine biosynthetic enzymes in subcellular fractions obtained from MCF-7 cells at different cell cycle phases revealed that there was robust activity of key enzymes in the fractions prepared from MCF-7 cells in G2/M phase. Radiolabeled choline and ethanolamine were rapidly incorporated into cells maintained at G2/M phase with nocodazole, and the rates of incorporation were similar to those obtained in cells allowed to progress into the G1 phase. Furthermore, radiolabeled glycerol was incorporated into phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine and phosphatidic acid in MCF-7 cells maintained at G2/M phase with nocodazole. Similar results were obtained in CHO cells. These results demonstrate that glycerophospholipid synthesis is very active in the G2/M phase of these cells. Therefore, the postulated cessation of phospholipid synthesis in G2/M phases is not applicable to all cell types.     

Fatty-acid composition of lipids and physicochemical characteristics of membrane fractions and the membrane of endoplasmic reticulum of thymus and Pliss' lymphosarcoma

The paper is concerned with composition of neutral lipids and phospholipids, the regularity of lipid bilayer and structural reorganization of plasma membranes, and membranes of smooth and rough cell reticulum of thymus and Pliss lymphosarcoma are studied at linear and stationary growth phase. No qualitative differences are found in the fatty-acid composition of lipid membranes in normal and tumour cells. In plasma membranes of phospholipids and in membranes of smooth reticulum of tumour cells the unsaturated lipid component increases in the process of growth, the cholesterin/phospholipids ratio decreases, fluidity of the lipid bilayer diminishes and structural heterogeneity of these membranes rises while in membranes of rough reticulum the saturation of lipids increases, but the cholesterin/phospholipids ratio does not change. The temperatures of structural reorganization also does not change, which evidences for a less structural lability of membranes of rough reticulum as compared with other membranes.     

Differentiation of the adult Leydig cell population in the postnatal testis

Five main cell types are present in the Leydig cell lineage, namely the mesenchymal precursor cells, progenitor cells, newly formed adult Leydig cells, immature Leydig cells, and mature Leydig cells. Peritubular mesenchymal cells are the precursors to Leydig cells at the onset of Leydig cell differentiation in the prepubertal rat as well as in the adult rat during repopulation of the testis interstitium after ethane dimethane sulfonate (EDS) treatment. Leydig cell differentiation cannot be viewed as a simple process with two distinct phases as previously reported, simply because precursor cell differentiation and Leydig cell mitosis occur concurrently. During development, mesenchymal and Leydig cell numbers increase linearly with an approximate ratio of 1:2, respectively. The onset of precursor cell differentiation into progenitor cells is independent of LH; however, LH is essential for the later stages in the Leydig cell lineage to induce cell proliferation, hypertrophy, and establish the full organelle complement required for the steroidogenic function. Testosterone and estrogen are inhibitory to the onset of precursor cell differentiation, and these hormones produced by the mature Leydig cells may be of importance to inhibit further differentiation of precursor cells to Leydig cells in the adult testis to maintain a constant number of Leydig cells. Once the progenitor cells are formed, androgens are essential for the progenitor cells to differentiate into mature adult Leydig cells. Although early studies have suggested that FSH is required for the differentiation of Leydig cells, more recent studies have shown that FSH is not required in this process. Anti-Müllerian hormone has been suggested as a negative regulator in Leydig cell differentiation, and this concept needs to be further explored to confirm its validity. Insulin-like growth factor I (IGF-I) induces proliferation of immature Leydig cells and is associated with the promotion of the maturation of the immature Leydig cells into mature adult Leydig cells. Transforming growth factor alpha (TGFalpha) is a mitogen for mesenchymal precursor cells. Moreover, both TGFalpha and TGFbeta (to a lesser extent than TGFalpha) stimulate mitosis in Leydig cells in the presence of LH (or hCG). Platelet-derived growth factor-A is an essential factor for the differentiation of adult Leydig cells; however, details of its participation are still not known. Some cytokines secreted by the testicular macrophages are mitogenic to Leydig cells. Moreover, retarded or absence of Leydig cell development has been observed in experimental models with impaired macrophage function. Thyroid hormone is critical to trigger the onset of mesenchymal precursor cell differentiation into Leydig progenitor cells, proliferation of mesenchymal precursors, acceleration of the differentiation of mesenchymal cells into Leydig cell progenitors, and enhance the proliferation of newly formed Leydig cells in the neonatal and EDS-treated adult rat testes.     

Oxidized low-density lipoprotein promotes mature dendritic cell transition from differentiating monocyte

Proinflammatory oxidized phospholipids are generated during oxidative modification of low-density lipoproteins (LDL). The production of these proinflammatory oxidized phospholipids is controlled by secreted enzymes that circulate as proteins complexed with LDL and high-density lipoprotein. During the acute phase response to tissue injury, profound changes occur in lipoprotein enzymatic composition that alter their anti-inflammatory function. Monocytes may encounter oxidized phospholipids in vivo during their differentiation to macrophages or dendritic cells (DC). In this study we show that the presence of oxidized LDL (oxLDL) at the first day of monocyte differentiation to DC in vitro yielded phenotypically atypical cells with some functional characteristics of mature DC. Addition of oxLDL during the late stage of monocyte differentiation gave rise directly to phenotypically mature DC with reduced uptake capacity, secreting IL-12 but not IL-10, and supporting both syngeneic and allogeneic T cell stimulation. In contrast to known mediators of DC activation, oxLDL did not trigger maturation of immature DC. An intriguing possibility is that a burst of oxidized phospholipids is an endogenous activation signal for the immune system, which is tightly controlled by lipoproteins during the acute phase response.     

Morphological and functional differentiation in epithelial cultures obtained from human skin explants

The present study was undertaken to characterize primary epithelial cultures obtained from human skin explants as experimental systems for studies of the differentiation process. When human skin explants were incubated at 34-35 degrees C, fibroblastic growth was strongly inhibited, whereas the epithelial growth proceeded unchanged. The lateral growth of the epithelial cells could be divided into two phases - a migratory and a proliferative one. Only cultures incubated at 35 degrees C or below completed the morphological differentiation process before sloughing, whereas no qualitative difference in protein synthesis was observed between cultures incubated at temperatures from 33-37 degrees C. Cultured epidermal cells were labelled with 3H-thymidine and analysed by flow cytometry and cell sorting. Cells sorted from the S- and G2-phase populations were further analysed by autoradiography and a considerable heterogeneity as to the nuclear labelling was disclosed. A large fraction of S-phase cells were found to be totally unlabelled. The grain count distributions revealed similar cell cycle subpopulations as have been shown to occur in vivo. The relationship of these subpopulations to the differentiation process is discussed.     

Relation of Cellular Phospholipid Composition to Oligodendroglial Differentiation in C-6 Glial Cells

The relation of the polar head group composition of cellular phospholipids to a biochemical expression of oligodendroglial differentiation was studied in cultured C-6 glial cells. Induction of the oligodendroglial enzyme, 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP), was determined after alteration of the polar head group composition of phospholipids by exposure of the cells to choline analogues, especially N,N'-dimethylethanolamine. To accomplish the phospholipid alteration, cells were grown in the presence of the analogue in medium free of exogenous lipid, i.e., first for 24 h in 10% delipidated serum and then for 48 h in serum-free medium. The 48-h exposure to serum-free medium resulted in untreated C-6 cells in a several fold increase in CNP activity, but in cells treated with 2.5 mM N,N'-dimethylethanolamine, total inhibition of this induction was observed. A graded, concentration-dependent inhibitory effect of the analogue on the induction of CNP was defined. The effect of the analogue was relatively specific, e.g., the activity of another plasma membrane enzyme of C-6 cells, (Na+ + K+)-activated ATPase, was not affected. Morever, there was no evidence of a toxic effect of the analogue; thus, total protein synthesis and cell growth were not altered, and the induction of CNP in serum-free medium recurred after removal of the analogue. N,N'-Dimethylethanolamine was shown to be incorporated into cellular phospholipids, primarily at the expense of phosphatidylcholine. The data define an important role for the polar head group composition of membrane phospholipids in oligodendroglial differentiation in this model system.     

Thermotropic behavior of lipids and the morphology of Yersinia pseudotuberculosis cells with a high content of lysophosphatidylethanolamine

The content of lysophosphatidylethanolamine (LPE) in Y. pseudotuberculosis cells was found to increase during their growth at 8 degrees C under stationary conditions (without stirring the medium) and at 37 degrees C when the medium contained glucose. The maximum level of LPE (up to 45% of the total phospholipids) was observed in cells grown at 8 degrees C under stationary conditions. Such cells showed an enhanced growth rate, a reduced yield of biomass, an altered cell morphology, and an increased cell area. The cells contained unsaturated fatty acids, phosphatidylethanolamine (PE), and total phospholipids in small amounts, whereas neutral lipids and diphosphatidylglycerol were abundant. In addition, the cells contained an amount of methylated PE and phospholipids of unknown structure. Irrespective of whether the temperature for growth was low or high, the LPE-rich cells showed a high value (32-36 degrees C) of the maximum temperature of thermal transition of lipids (Tmax). This finding is indicative of a densification of the membrane lipid matrix of the LPE-rich cells. The suggestion is made that LPE is accumulated in glucose-fermenting bacterial cells in response to stress caused by oxygen deficiency and low pH values of the growth medium. The possible relationship between LPE accumulation and the virulence of Y. pseudotuberculosis cells grown at low temperatures is discussed.     

Coupling of proadipocyte growth arrest and differentiation. I. Induction by heparinized medium containing human plasma

The differentiation of proadipocytes in vitro typically required prolonged culture of cells as a high density in high concentrations of serum and added hormones. With such culture conditions it is difficult to design experiments to determine the mechanisms that control the differentiation process. We now describe the rapid and parasynchronous growth arrest and differentiation of low density murine proadipocytes in heparinized medium containing only human plasma. When low density cells are cultured under these conditions, growth arrest at a distinct state in the G1 phase of the cell cycle occurs within 2 d and the differentiation of 80-100% of the cell population occurs within 4 d thereafter. The factors in human plasma which promote growth arrest and differentiation are heat labile and can be separated by barium adsorption. In the following paper we have used these methods to show that there are five separate phases which regulate the coupling of proadipocyte growth arrest and differentiation. The data reported in this paper establish that: (a) high cell density and extensive cell-to- cell contact are not required for adipocyte differentiation, (b) prolonged culture is not required for adipocyte differentiation, and (c) high concentrations of serum and/or added hormones are not required for adipocyte differentiation.     

Retinoic acid binds to the C2-domain of protein kinase C(alpha)

Protein kinase C(alpha) (PKC(alpha)) is a key enzyme regulating the physiology of cells and their growth, differentiation, and apoptosis. PKC activity is known to be modulated by all-trans retinoic acid (atRA), although neither the action mechanism nor even the possible binding to PKCs has been established. Crystals of the C2-domain of PKC(alpha), a regulatory module in the protein that binds Ca(2+) and acidic phospholipids, have now been obtained by cocrystallization with atRA. The crystal structure, refined at 2.0 A resolution, shows that RA binds to the C2-domain in two locations coincident with the two binding sites previously reported for acidic phospholipids. The first binding site corresponds to the Ca(2+)-binding pocket, where Ca(2+) ions mediate the interactions of atRA with the protein, as they do with acidic phospholipids. The second binding site corresponds to the conserved lysine-rich cluster localized in beta-strands three and four. These observations are strongly supported by [(3)H]-atRA-binding experiments combined with site-directed mutagenesis. Wild-type C2-domain binds 2 mol of atRA per mol of protein, while the rate reduces to one in the case of C2-domain variants, in which mutations affect either Ca(2+) coordination or the integrity of the lysine-rich cluster site. Competition between atRA and acidic phospholipids to bind to PKC is a possible mechanism for modulating PKC(alpha) activity.     

Elevated cyclin E levels, inactive retinoblastoma protein, and suppression of the p27(KIP1) inhibitor characterize early development of promyeloid cells into macrophages.

Cyclin-dependent kinase inhibitors such as p27(KIP1) have recently been shown to lead to cellular differentiation by causing cell cycle arrest, but it is unknown whether similar events occur in differentiating promyeloid cells. Hematopoietic progenitor cells undergo lineage-restricted differentiation, which is accompanied by expression of distinct maturation markers. Here we show that the classical growth factor insulin-like growth factor I (IGF-I) potently promotes vitamin D(3)-induced macrophage differentiation of promyeloid cells, as assessed by measurement of a coordinate increase in expression of the integrin alpha subunit CD11b, the CD14 lipopolysaccharide receptor, and the macrophage-specific esterase, alpha-naphthyl acetate esterase, as early as 24 h following initiation of terminal differentiation. Addition of IGF-I to cells undergoing vitamin D(3)-induced differentiation also leads to an early increase in expression of cyclin E, phosphorylation of the retinoblastoma tumor suppressor protein, and a doubling of the cell number. Early expression of CD11b (24 h) is simultaneously accompanied by inhibition in the expression of p27(KIP1). Cell cycle analysis with propidium iodide revealed that CD11b expression at 24 h following initiation of differentiation occurs at all phases of the cell cycle instead of only those cells arrested in G(0)/G(1). Similarly, development of a novel double-labeling intra- and extracellular flow-cytometric technique demonstrated that single cells expressing the mature leukocyte differentiation antigen CD11b can also incorporate the thymidine analog bromodeoxyuridine. Likewise, expression of the intracellular DNA polymerase delta cofactor/proliferating-cell nuclear antigen at 24 h is also simultaneously expressed with the surface marker CD11b, indicating that these cells continue to proliferate early in their differentiation program. Finally, at 24 h following induction of differentiation, IGF-I promoted a fourfold increase in the uptake of [(3)H]thymidine by purified populations of CD11b-expressing cells. Taken together, these data demonstrate that the initial steps associated with terminal macrophage differentiation occur concomitantly with progression through the cell cycle and that these very early differentiation events do not require the accumulation of p27(KIP1).     

Ageing-related changes in Mycoplasma canadense membranes.

Fluidity and composition of cell membranes during progression of Mycoplasma canadense cultures grown in a serum-free medium was assessed. The fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene at 25 degrees C of intact cells and liposomes in the exponential and stationary phases of growth was compared. A decrease in fluidity and an increase in the ratio of saturated to unsaturated fatty acids was detected in cell membranes on aging. Nevertheless, membrane density remained unaltered although the molar ratio of cholesterol to phospholipids decreased. It is proposed that the increase in lipid order is primarily due to the increase in the ratio of saturated to unsaturated membrane fatty acids, being the diminished molar ratio of cholesterol to phospholipids involved in the reduced unsaturated fatty acid uptake.     

Ageing-related changes in Mycoplasma canadense membranes

Fluidity and composition of cell membranes during progression of Mycoplasma canadense cultures grown in a serum-free medium was assessed. The fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene at 25°C of intact cells and liposomes in the exponential and stationary phases of growth was compared. A decrease in fluidity and an increase in the ratio of saturated to unsaturated fatty acids was detected in cell membranes on ageing. Nevertheless, membrane density remained unaltered although the molar ratio of cholesterol to phospholipids decreased. It is proposed that the increase in lipid order is primarily due to the increase in the ratio of saturated to unsaturated membrane fatty acids, being the diminished molar ratio of cholesterol to phospholipids involved in the reduced unsaturated fatty acid uptake.     

The effect of growth temperature on the thermotropic behavior of the membranes of a thermophilic Bacillus. Composition-structure-function relationships

The following study was carried out with the aim of widening our understanding of the thermoadaptive mechanisms of the membrane of thermophiles, using Bacillus stearothermophilus var. nondiastaticus as test-organism. The phospholipids and their acyl chain composition of this Bacillus studied in relation to the physical properties of its membrane from bacteria grown at various temperatures. Phospholipids account for 68-75 weight% of the total lipid in cells grown at 45, 55 or 65 degrees C. Phosphatidylglycerol and diphosphatidylglycerol constitute up to 90% of the total phospholipids; no amino phospholipids were found. Increasing the growth temperatures from 45 degrees to 65 degrees C caused an approximately 4-fold decrease in the proportion of the branched-chain fatty acids and a 2-fold increase in the amount of the saturated acyl chains. The reduced proportion of the branched fatty acids was mainly due to a decrease in their anteiso forms. Unsaturated fatty acids were not produced by cells grown at 65 degrees C. In accordance with the fatty acid composition, the molecular packing of phospholipids in monolayers was more expanded with phospholipids from 45 degrees C grown cells as compared with cultures grown at 55 degrees C. The thermotropic gel to liquid-crystalline phase transition of the membrane lipids was monitored by differential scanning calorimetry and fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene. With increase of the growth temperature the phase transition was progressively shifted to higher but narrower range of temperatures. Completion of the lipid melting occurred always at temperatures below those employed for growth. A constructed phase diagram enabled to relate the growth temperature, the fatty acid composition and the lipid apparent microviscosity at temperatures not used in the present study for growth of the thermophile. The minimum temperature for growth and the upper boundary temperature of the least saturated lipid crystallization were extrapolated in this manner; they correspond to the experimentally determined minimal growth temperature. The apparent microviscosity, a measure of membrane order, decreased gradually and conspicuously as the growth temperature was elevated. The delimiting apparent microviscosity values, at the maximal (65 degrees C) and minimal (41 degrees C) growth temperatures were 0.8 and 1.8 poise, respectively. This lack of rigorous homeostatic control of the bulk lipid viscosity prompted reevaluation of the physiological significance of 'homeoviscous adaptation' in Bacillus stearothermophilus.     

Causes and correlations in cambium phenology: towards an integrated framework of xylogenesis

Although habitually considered as a whole, xylogenesis is a complex process of division and maturation of a pool of cells where the relationship between the phenological phases generating such a growth pattern remains essentially unknown. This study investigated the causal relationships in cambium phenology of black spruce [Picea mariana (Mill.) BSP] monitored for 8 years on four sites of the boreal forest of Quebec, Canada. The dependency links connecting the timing of xylem cell differentiation and cell production were defined and the resulting causal model was analysed with d-sep tests and generalized mixed models with repeated measurements, and tested with Fisher's C statistics to determine whether and how causality propagates through the measured variables. The higher correlations were observed between the dates of emergence of the first developing cells and between the ending of the differentiation phases, while the number of cells was significantly correlated with all phenological phases. The model with eight dependency links was statistically valid for explaining the causes and correlations between the dynamics of cambium phenology. Causal modelling suggested that the phenological phases involved in xylogenesis are closely interconnected by complex relationships of cause and effect, with the onset of cell differentiation being the main factor directly or indirectly triggering all successive phases of xylem maturation.     

Effect of Growth Temperature on the Lipid Composition of Cyanidium caldarium: II. Glycolipid and Phospholipid Components

Cyanidium caldarium was grown at 20 and 55 C and harvested during exponential growth phase. Lipids were extracted and separated by silicic acid column and thin layer chromatography. The major glycolipids were identified as mono- and digalactosyl diglyceride and sulfolipid. Major phospholipids were identified as phosphatidyl choline and phosphatidyl ethanolamine. The cells grown at 20 C contained significantly larger quantities of these glycolipids and phospholipids than cells grown at 55 C.