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PubMed2002

Fed-batch cultivation of baker's yeast followed by nitrogen or carbon starvation: effects on fermentative capacity and content of trehalose and glycogen.

An industrial strain of Saccharomyces cerevisiae (DGI 342) was cultivated in fed-batch cultivations at a specific growth rate of 0.2 h(-1). The yeast was then exposed to carbon or nitrogen starvation for up to 8 h, to study the effect of starvation on fermentative capacity and content of protein, trehalose and glycogen. Nitrogen starvation triggered the accumulation of trehalose and glycogen. After 8 h of starvation, the content of trehalose and glycogen was increased 4-fold and 2-fold, respectively. Carbon starvation resulted in a partial conversion of glycogen into trehalose. The trehalose content increased from 45 to 64 mg (g dry-weight)(-1), whereas the glycogen content in the same period was reduced from 55 to 5 mg (g dry-weight)(-1). Glycogen was consumed faster than trehalose during storage of the starved yeast for 1 month. Nitrogen starvation resulted in a decrease in the protein content of the yeast cells, and the fermentative capacity per gram dry-weight decreased by 40%. The protein content in the carbon-starved yeast increased as a result of starvation due to the fact that the content of glycogen was reduced. The fermentative capacity per gram dry-weight was, however, unaltered.

Biomass↗

PubMed1999

The effects of exopolymers on cell morphology and culturability of Leuconostoc mesenteroides during starvation.

Biofilm formation by bacterial cells can be used to modify the subsurface permeability for the purpose of microbial enhanced oil recovery, bio-barrier formation, and in situ bioremediation. Once injected into the subsurface, the bacteria undergo starvation due to a decrease in nutrient supply and diffusion limitations in biofilms. To help understand the starvation response of bacteria in biofilms, the relationship between exopolymer formation and cell culturability was examined in a batch culture. The average cell diameter was observed to decrease from 0.8 micron to 0.35 micron 3 days after starvation began. Cell chain fragmentation was also observed during starvation. Cells that underwent starvation in the presence of insoluble exopolymers showed a slower rate of decrease in cell diameter and in cell chain length than cells without insoluble exopolymers. The rate of decrease in the average cell diameter and cell chain length were determined using a first order decay model. Cells starved in the presence of exopolymers showed greater culturability than cells starved without exopolymers. After 200 days starvation, 2.5 x 10(-3)% cells were culturable, but no increase in cell number was observed. During starvation, the exopolymer concentration remained constant, an indication that the exopolymer was not consumed by the starving bacteria as an alternative carbon or energy source.

Biofilms↗

PubMed2006

Developmental and age-specific effects of selection on divergent virgin life span on fat content and starvation resistance in Drosophila melanogaster.

Investigations into the genetic basis of longevity variation have shown life span to be positively correlated with starvation resistance and negatively with female fecundity, both of which rely on lipid content. To assess the firmness of this relation, we assayed correlated responses in age-specific relative fat content (RFC) and starvation resistance in lines successfully selected for divergent virgin life span. We have previously demonstrated that genetic differentiation in female fecundity between our selection lines had disappeared during relaxation of selection. Therefore, we also expected genetic differences in lipid content and starvation resistance to have disappeared. However, RFC and starvation resistance were still significantly lower in short-lived flies than in control flies. Surprisingly, also in long-lived flies RFC and starvation resistance were mostly, but not invariably, found to be significantly lower than in control flies. These results indicate that the genetic correlation of RFC and starvation resistance with reproduction has broken down. Furthermore, the relationship between life span and starvation resistance appears to be more complex than previously anticipated. Also, we could demonstrate that differences in RFC were not brought about by differences in lipid accumulation during adult life, but were already present at eclosion. These findings suggest that pre-adult developmental pathways already impact on the rate of ageing of the adult fly.

Animals↗

PubMed1997

Differential expression of TPS11, a phosphate starvation-induced gene in tomato.

Plants respond to phosphate (Pi) deficiency through adaptive mechanisms involving several morphological, biochemical and molecular changes. In this study, we have characterized the structure and expression of a tomato (Lycopersicon esculentum L.) phosphate starvation-induced gene (TPSI1). A 3.5 kb genomic fragment containing the 474 bp TPSI1 transcript was isolated. The TPSI1 transcript contains an open reading frame of 174 nucleotides encoding a 58 amino acid polypeptide. TPSI1 is an intron-less gene and only one copy could be detected in the tomato genome. The promoter region of TPSI1 contains several conserved sequences found in phosphate starvation induced genes of yeast. The TPSI1 transcripts are rapidly induced in roots and leaves during Pi starvation. A significant increase in the TPSI1 mRNA was observed in cell cultures and roots after 3 and 12 h of Pi starvation, respectively. Induction of the TPSI1 gene appears to be a response specific to Pi starvation since it is not affected by starvation of other nutrients (nitrogen, potassium and iron). The amount of TPSI1 transcript decreased rapidly when Pi-starved tomato plants were resupplied with Pi. These results suggest that TPSI1 gene expression may be a part of the early Pi starvation response mechanism in plants.

Adaptation, Physiological↗

PubMed2000

Influence of cytokinins on the expression of phosphate starvation responsive genes in Arabidopsis.

The increase in the ratio of root growth to shoot growth that occurs in response to phosphate (Pi) deprivation is paralleled by a decrease in cytokinin levels under the same conditions. However, the role of cytokinin in the rescue system for Pi starvation remains largely unknown. We have isolated a gene from Arabidopsis thaliana (AtIPS1) that is induced by Pi starvation, and studied the effect of cytokinin on its expression in response to Pi deprivation. AtIPS1 belongs to the TPSI1/Mt4 family, the members of which are specifically induced by Pi starvation, and the RNAs of which contain only short, non-conserved open reading frames. Pi deprivation induces AtIPS1 expression in all cells of wild-type plants, whereas in the pho1 mutant grown on Pi-rich soils, AtIPS1 expression in the root was delimited by the endodermis. This supports the view that pho1 is impaired in xylem loading of Pi, and that long-distance signals controlling the Pi starvation responses act via negative control. Exogenous cytokinins repress the expression of AtIPS1 and other Pi starvation-responsive genes in response to Pi deprivation. However, cytokinins did not repress the increase in root-hair number and length induced by Pi starvation, a response dependent on local Pi concentration rather than on whole-plant Pi status. Our results raise the possibility that cytokinins may be involved in the negative modulation of long-distance, systemically controlled Pi starvation responses, which are dependent on whole-plant Pi status.

Amino Acid Sequence↗

PubMed2003

Effect of starvation on resuscitation and the surface characteristics of bacteria.

Resuscitation behavior of bacteria after starvation for carbon and nitrogen was investigated. In addition effect of carbon and nitrogen starvation conditions on the surface characteristics and adhesive properties of bacteria were studied. Two pure culture herbicide degrading bacteria were used in the study: Pseudomonas sp. strain A, and Rhodococcus corallinus strain 11. These bacteria are known to degrade cyanuric acid which is a derivative of s-triazine, a common herbicide used widely. Selected bacteria were starved for carbon (glucose) and nitrogen (cyanuric acid) in different bioreactors and their physiological responses to starvation and resuscitation were measured. Different resuscitation responses were observed under different starvation conditions such that long lag phase was, observed for Rhodococcus corallinus strain 11 subjected to cyanuric acid starvation. Slow exponential growth rates were calculated for both microorganisms subjected to cyanuric acid starvation. The surface properties of both microorganisms were investigated using MATH test with two different hydrocarbons (hexadecane and octane). Hexadecane was observed to be the best organic attachment phase for these tests. Surface hydrophobiciy for all the microorganisms stayed unchanged during carbon starvation conditions. Significant decrease in hydrophobicity was observed for both cultures starved for nitrogen. When the hydrophobicity of the cultures decreased, the attachment capabilities of the microorganisms decreased. The decrease in attachment capabilities is a result of highly hydrated extracellular polysaccharides produced in the presence of carbon in the medium. Results of this study can be used as control tools in soil remediation applications.

Bioreactors↗

PubMed1980

Effect of thymidine auxotrophy, thymidine starvation and nalidixic acid inhibition on the properties of DNA labelled by a pulse of [3H]thymidine in Staphylococcus aureus.

The labelling of DNA by pulse/chase experiments in Staphylococcus aureus has been investigated, analysing the products by alkaline sucrose velocity centrifugation. In S. aureus NCTC 8325 a short (60 s) pulse of [3H]thymidine labels both small (10 to 20 S) fragments and DNA that co-sediments with long-term label. In a thymidine-requiring derivative, 8325thy, most pulse label is incorporated into small fragments. In both bacterial strains small fragments can be chased into high molecular weight DNA. Thymidine starvation of 8325thy prior to pulse labelling results in smaller fragments (4 to 10S) being labelled. In a subsequent chase with unlabelled thymidine this label is incorporated into high molecular weight DNA, although more slowly than in the absence of thymidine starvation. The fact that nalidixic acid, an antibiotic which specifically inhibits DNA replication in S. aureus, does not inhibit the [3H]thymidine incorporation immediately after thymidine starvation and that nalidixic acid shows down the increase in size of pulse-labelled fragments through inhibition of DNA synthesis suggests that thymidine starvation results in changes at the replication fork. The possible nature of these changes is discussed. It is proposed that one of the results of thymidine starvation is to cause a long-lived gap between DNA synthesized before starvation and DNA synthesized after starvation.

Centrifugation, Density Gradient↗

PubMed1991

The molecular basis of carbon-starvation-induced general resistance in Escherichia coli.

At the onset of starvation Escherichia coli undergoes a temporally ordered program of starvation gene expression involving 40-80 genes which some four hours later yields cells possessing an enhanced general resistance. Two classes of genes are induced upon carbon starvation: the cst genes, requiring cyclic AMP, and the pex genes, not requiring this nucleotide for induction. The cst genes are not involved in the development of the resistant state and are concerned with escape from starvation, while the pex gene induction appears to be associated with resistance. Many of the latter are induced in response to a variety of starvation conditions. They include heat shock and oxidation resistance genes, and some utilize minor, stationary-phase-specific sigma factors for induction during starvation. The protective role of stress proteins may be due to their ability to rescue misfolded macromolecules. The starvation promoters can be potentially useful for selective expression of desired genes in metabolically sluggish populations, e.g. in high-density industrial fermentations and in situ bioremediation.

Bacterial Proteins↗

PubMed2000

Starvation-induced changes in the cell surface of Azospirillum lipoferum.

Three starvation regimes (a deficient culture medium, a saline buffer solution and distilled water) were evaluated for their possible effect on cell surface characteristics of Azospirillum lipoferum 1842 related to the initial adsorption of the bacterium to surfaces. The bacteria survived for 7 days in all media although they did not multiply. Upon transfer from a rich growth medium (nutrient agar) to starvation conditions, cell surface hydrophobicity dropped sharply but recovered its initial value within 24 to 48 h, except in phosphate-buffered saline, the length of the recovery period depending on the starvation medium. Starvation affected the sugar affinity of the A. lipoferum cell surface mainly towards p-aminophenyl-alpha-D-mannopyranoside, to a lesser extent to glucose, but not to other monosaccharides tested. Starvation changed the concentration of several cell surface proteins but did not induce the synthesis of new ones. The cell surface hydrophobic protein (43 kDa) of A. lipoferum 1842 was unaffected by any starvation treatment for a period of up to 48 h, but later disappeared. These data showed that starvation is not a major factor in inducing changes in the cell surface which lead to the primary phase of attachment of Azospirillum to surfaces.

Journal Article↗

PubMed1984

Starvation-induced effects on bacterial surface characteristics.

Changes in bacterial surface hydrophobicity, charge, and degree of irreversible binding to glass surfaces of seven marine isolates were followed during starvation. The degree of hydrophobicity was measured by hydrophobic interaction chromatography and by two-phase separation in a hexadecane-water system, whereas changes in charge were measured by electrostatic interaction chromatography. All isolates underwent the starvation-induced responses of fragmentation, which is defined as division without growth, and continuous size reduction, which results in populations with increased numbers of smaller cells. The latter process was also responsible for a significant proportion of the total drop in cell volume; this was observed by noting the biovolume (the average cell multiplied by the number of bacteria) of a population after various times of starvation. Four strains exhibited increases in both hydrophobicity and irreversible binding, initiated after different starvation times. The most hydrophilic and most hydrophobic isolates both showed a small increase in the degree of irreversible binding after only 5 h, followed by a small decrease after 22 h. Their hydrophobicity remained constant, however, throughout the entire starvation period. On the other hand, one strain, EF190, increased its hydrophobicity after 5 h of starvation, although the degree of irreversible binding remained constant. Charge effects could not be generally related to the increase in irreversible binding. Scanning electron micrographs showed a large increase in surface roughness throughout the starvation period for all strains that showed marked changes in physicochemical characteristics.

Journal Article↗

PubMed1989

Effect of growth rate and starvation-survival on the viability and stability of a psychrophilic marine bacterium.

Cell populations of the marine bacterium ANT-300, from either batch or continuous culture with dilution rates ranging from D = 0.015 h to D = 0.200 h, were monitored for viability, direct counts, and optical density for 98 days under starvation conditions. Three stages of starvation survival were observed for each of the cell populations. Although direct counts remained at 2 x 10 to 3 x 10 cells ml throughout the starvation period, large fluctuations occurred in cell viability during stage 1 (0 to 14 days) of starvation survival. Stage 2 (14 to 70 days) involved an overall decrease in viability for each of the cell populations; the rate of viability loss was dependent upon the growth rate. Cell viability stabilized at approximately 0.3% of the direct count in stage 3 (70 to 98 days). Long-term starvation corresponded to the prolongation of stage 3 starvation survival. Cell volumes for each of the cell populations decreased with the length of the starvation period. However, the cell volume of starved cells was also dependent more on growth rate than on the length of the time starved. We hypothesize that the cell population with the slowest growth rate is most closely representative of cells found in the oligotrophic marine environment.

Journal Article↗

PubMed1994

Induction of Carbon Starvation-Induced Proteins in Vibrio vulnificus.

By using two-dimensional polyacrylamide gel electrophoresis of pulse-labelled proteins, carbon starvation-induced (Sti) proteins produced by Vibrio vulnificus were identified. At least 34 proteins were induced over a 26-h period of carbon starvation. Although the total rate of protein synthesis over the 26-h starvation period suggests that there is a dramatic decrease in total protein synthesis within the first hour of starvation, at least 23 of the Sti proteins were induced within the first 20 min of carbon depletion. Six temporal classes of proteins could be identified, with class A(ii) encompassing the largest (21 proteins) group. All of the proteins in this group could be characterized by one of two patterns of protein synthesis. The addition of chloramphenicol at sequential times throughout starvation revealed that proteins required for starvation survival are made within the first 4 h of starvation.

Journal Article↗

PubMed1998

Starvation-Induced Changes in Motility, Chemotaxis, and Flagellation of Rhizobium meliloti

The changes in motility, chemotactic responsiveness, and flagellation of Rhizobium meliloti RMB7201, L5-30, and JJ1c10 were analyzed after transfer of the bacteria to buffer with no available C, N, or phosphate. Cells of these three strains remained viable for weeks after transfer to starvation buffer (SB) but lost all motility within just 8 to 72 h after transfer to SB. The rates of motility loss differed by severalfold among the strains. Each strain showed a transient, two- to sixfold increase in chemotactic responsiveness toward glutamine within a few hours after transfer to SB, even though motility dropped substantially during the same period. Strains L5-30 and JJ1c10 also showed increased responsiveness to the nonmetabolizable chemoattractant cycloleucine. Cycloleucine partially restored the motility of starving cells when added after transfer and prevented the loss of motility when included in the SB used for initial suspension of the cells. Thus, interactions between chemoattractants and their receptors appear to affect the regulation of motility in response to starvation independently of nutrient or energy source availability. Electron microscopic observations revealed that R. meliloti cells lost flagella and flagellar integrity during starvation, but not as fast, nor to such a great extent, as the cells lost motility. Even after prolonged starvation, when none of the cells were actively motile, about one-third to one-half of the initially flagellated cells retained some flagella. Inactivation of flagellar motors therefore appears to be a rapid and important response of R. meliloti to starvation conditions. Flagellar-motor inactivation was at least partially reversible by addition of either cycloleucine or glucose. During starvation, some cells appeared to retain normal flagellation, normal motor activity, or both for relatively long periods while other cells rapidly lost flagella, motor activity, or both, indicating that starvation-induced regulation of motility may proceed differently in various cell subpopulations.

Journal Article↗

PubMed1970

Intracellular substrates for endogenous metabolism during long-term starvation of rod and spherical cells of Arthrobacter crystallopoietes.

Cells of Arthrobacter crystallopoietes, harvested during growth as spheres and as rods, were starved by shaking at 30 C in phosphate buffer for 30 days, during which time they maintained 100% viability. Changes in cellular components and the activity of specific enzyme pathways were monitored. A glycogen-like polysaccharide comprised 40% of the dry weight of growing spherical cells and 10% of the dry weight of rod cells. This material was utilized at approximately the same rate, on a percentage basis, during starvation of both cell forms. The rods degraded intracellular protein at approximately twice the rate of the spheres. At the end of 30 days, the rods had degraded 40% and the spheres 20% of their initial content of protein. Ribonucleic acid (RNA) was degraded significantly more rapidly in the rods. After 30 days starvation, 85 and 32% of the initial RNA of rods and spheres, respectively, had been depleted. Magnesium ion followed this same general pattern; the rods lost 65% and the spheres 45% of their initial content during 28 days of starvation. Deoxyribonucleic acid increased by 20% during the first few hours of starvation of both cell forms and then remained constant. The ability of glucose-, succinate-, and 2-hydroxypyridine (2-HP)-grown cells to oxidize glucose remained constant during 14 days of starvation. The ability of succinate-grown cells to oxidize succinate decreased rapidly during the first few hours of starvation to a rate which remained constant for 14 days. Cells adapted to growth on 2-HP completely lost their ability to oxidize this substrate after 3 days starvation.

Ammonia↗

PubMed1973

Effect of thymine starvation on deoxyribonucleic acid repair systems of Escherichia coli K-12.

Thymine starvation of Escherichia coli K-12 results in greatly increased sensitivity to ultraviolet light (UV). Our studies, using isogenic strains carrying rec and uvr mutations, have shown the following. (i) Common to all strains tested is a change from multihit to single-hit kinetics of survival to UV after 60 min of thymine starvation. However, the limiting slope of UV survival curves decreases in the rec(+)uvr(+) strain and changes very little in several rec mutant strains and one uvrB mutant strain. Thus, when either the rec or uvr system is functioning alone, the limiting slopes of the UV survival curves are relatively unaffected by thymine starvation. (ii) Thymine starvation does not significantly inhibit repair processes carried out by either repair system alone; i.e., host cell reactivation of irradiated phage (carried out by the uvr system), excision of thymine dimers (uvr), or X-ray repair (rec). (iii) In a rec(+)uvr(+) strain, repair appears to be a synergistic rather than additive function of the two systems. However, after thymine starvation, repair capacity is reduced to about the sum of the repair capacities of the independent systems. (iv) The kinetics of thymineless death are not changed by rec and uvr mutations. This indicates that the lesions responsible for thymineless death are not repaired by rec or uvr systems. (v) Withholding thymine from thy rec(+)uvr(+) bacteria not undergoing thymineless death has no effect on UV sensitivity. Under these conditions one sees higher than normal UV resistance in the presence or absence of thymine. This is due to increased repair carried out by the uvr system. To explain these results we postulate that thymine starvation does not inhibit either the rec or uvr repair pathway directly. Rather it appears that thymine starvation results in increased UV sensitivity in part by inhibiting a function which normally carries out efficient coordination of rec and uvr pathways.

Cell Survival↗

PubMed1987

Bioenergetic consequences of lactose starvation for continuously cultured Streptococcus cremoris.

Streptococcus cremoris cells that had been grown in a chemostat were starved for lactose. The viability of the culture remained essentially constant in the first hours of starvation and subsequently declined logarithmically. The viability pattern during starvation varied with the previously imposed growth rates. The death rates were 0.029, 0.076, and 0.298 h-1 for cells grown at dilution rates of 0.07, 0.11 and 0.38 h-1, respectively. The proton motive force and the pools of energy-rich phosphorylated intermediates in cells grown at a dilution rate of 0.10 h-1 fell to zero within 2 h of starvation. The culture, however, remained fully viable for at least 20 h, indicating that these energy-rich intermediates are not crucial for survival during long-term lactose starvation. Upon starvation, the intracellular pools of several amino acids depleted with the proton motive force, while large concentration gradients of the amino acids alanine, glycine, aspartate, and glutamate were retained for several hours. A quantitative analysis of the amino acids released indicated that nonspecific protein degradation was not a major cause of the loss in viability. The response of the energy metabolism of starved S. cremoris cells upon refeeding with lactose was monitored. Upon lactose starvation, the glycolytic activity and the rate of proton motive force generation decreased rapidly but the steady-state level of the proton motive force decreased significantly only after several hours. The decreasing steady-state level of the proton motive force and consequently the capacity to accumulate amino acids after the addition of lactose correlated well with the loss of viability. The response of the energy metabolism of starved S. cremoris cells upon refeeding with lactose was monitored. Upon lactose starvation, the glycolytic activity and the rate of proton motive force generation decreased rapidly but the steady-state level of the proton motive force decreased significantly only after several hours. The decreasing steady-state level of the proton motive force and consequently the capacity to accumulate amino acids after the addition of lactose correlated well with the loss of viability. It is concluded that a regulatory loss of glycolytic capacity has pivotal role in the survival of S. cremoris under the conditions used.

Adenosine Triphosphate↗

PubMed1988

Induction of cat-86 by chloramphenicol and amino acid starvation in relaxed mutants of Bacillus subtilis.

The chloramphenicol acetyltransferase gene cat-86 is induced through a mechanism that is a variation of classical attenuation. Induction results from the destabilization of an RNA stem-loop that normally sequesters the cat-86 ribosome-binding site. Destabilization of the stem-loop is due to the stalling of a ribosome in the leader region of cat-86 mRNA at a position that places the A site of the stalled ribosome at leader codon 6. Two events can stall ribosomes at the correct location to induce cat-86 translation: addition of chloramphenicol to cells and starvation of cells for the amino acid specified by leader codon 6. Induction by amino acid starvation is an anomaly because translation of the cat-86 coding sequence requires all 20 amino acids. To explain this apparent contradiction we postulated that amino acid starvation triggers intracellular proteolysis, thereby providing levels of the deprived amino acid sufficient for cat-86 translation. Here we show that a mutation in relA, the structural gene for stringent factor, blocks intracellular proteolysis that is normally triggered by amino acid starvation. The relA mutation also blocks induction of cat-86 by amino acid starvation, but the mutation does not interfere with chloramphenicol induction. Induction by amino acid starvation can be demonstrated in relA mutant cells if the depleted amino acid is restored at very low levels (e.g., 2 micrograms/ml). A mutation in relC, which may be the gene for ribosomal protein L11, blocks induction of cat-86 by either chloramphenicol or amino acid starvation. We believe this effect is due to a structural alteration of the ribosome resulting from the relC mutation and not to the relaxed phenotype of the cells.

Amino Acid Sequence↗

PubMed1988

Starvation-induced cross protection against heat or H2O2 challenge in Escherichia coli.

Glucose- or nitrogen-starved cultures of Escherichia coli exhibited enhanced resistance to heat (57 degrees C) or H2O2 (15 mM) challenge, compared with their exponentially growing counterparts. The degree of resistance increased with the time for which the cells were starved prior to the challenge, with 4 h of starvation providing the maximal protection. Protein synthesis during starvation was essential for these cross protections, since chloramphenicol addition at the onset of starvation prevented the development of thermal or oxidative resistance. Starved cultures also demonstrated stronger thermal and oxidative resistance than did growing cultures adapted to heat, H2O2, or ethanol prior to the heat or H2O2 challenge. Two-dimensional gel electrophoresis of 35S-pulse-labeled proteins showed that subsets of the 30 glucose starvation proteins were also synthesized during heat or H2O2 adaptation; three proteins were common to all three stresses. Most of the common proteins were among the previously identified Pex proteins (J.E. Schultz, G. I. Latter, and A. Matin, J. Bacteriol. 170:3903-3909, 1988), which are independent of cyclic AMP positive control for their induction during starvation. Induction of starvation proteins dependent on cyclic AMP was not important in these cross protections, since a delta cya strain of E. coli K-12 exhibited the same degree of resistance to heat or H2O2 as the wild-type parent did during both growth and starvation.

Autoradiography↗