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At least 253 records · Page 14Linked to original sources
PubMed2006

Amino acid starvation induces the SNAT2 neutral amino acid transporter by a mechanism that involves eukaryotic initiation factor 2alpha phosphorylation and cap-independent translation.

Nutritional stress caused by amino acid starvation involves a coordinated cellular response that includes the global decrease of protein synthesis and the increased production of cell defense proteins. Part of this response is the induction of transport system A for neutral amino acids that leads to the recovery of cell volume and amino acid levels once extracellular amino acid availability is restored. Hypertonic stress also increases system A activity as a mechanism to promote a rapid recovery of cell volume. Both a starvation-dependent and a hypertonic increase of system A transport activity are due to the induction of SNAT2, the ubiquitous member of SLC38 family. The molecular mechanisms underlying SNAT2 induction were investigated in tissue culture cells. We show that the increase in system A transport activity and SNAT2 mRNA levels upon amino acid starvation were blunted in cells with a mutant eIF2alpha that cannot be phosphorylated. In contrast, the induction of system A activity and SNAT2 mRNA levels by hypertonic stress were independent of eIF2alpha phosphorylation. The translational control of the SNAT2 mRNA during amino acid starvation was also investigated. It is shown that the 5'-untranslated region contains an internal ribosome entry site that is constitutively active in amino acid-fed and -deficient cells and in a cell-free system. We also show that amino acid starvation caused a 2.5-fold increase in mRNA and protein expression from a reporter construct containing both the SNAT2 intronic amino acid response element and the SNAT2-untranslated region. We conclude that the adaptive response of system A activity to amino acid starvation requires eukaryotic initiation factor 2alpha phosphorylation, increased gene transcription, and internal ribosome entry site-mediated translation. In contrast, the response to hypertonic stress does not involve eukaryotic initiation factor 2alpha phosphorylation, suggesting that SNAT2 expression can be modulated by specific signaling pathways in response to different stresses.

5' Untranslated Regions↗
PubMed2006

Root plasma membrane H+-ATPase is involved in the adaptation of soybean to phosphorus starvation.

The plasma membrane H+-ATPase plays an important role in the plant response to nutrient and environmental stresses. However, the involvement of plant root plasma membrane H+-ATPase in adaptation to phosphate (P) starvation is not yet fully elucidated. In this study, experiments were performed with soybean roots in low-P nutrient solution (10 microM). Treatment with fusicoccin, an activator of the plasma membrane H+-ATPase, increased P uptake by 35%, while vanadate, an inhibitor of plasma membrane H+-ATPase, severely suppressed it. These results suggested that P uptake might be regulated via the modulation of the activity of plasma membrane H+-ATPase under P starvation. The relationship between P uptake and the activity of plasma membrane H+-ATPase was examined further by using plasma membrane H+-ATPase transgenic Arabidopsis thaliana under low-P conditions. Transgenic plants absorbed more P compared with wild-type Arabidopsis. Results from real-time RT-PCR, western-blotting and immunolocalization analysis indicated that the increase in activity of the plasma membrane H+-ATPase by P starvation was caused by its transcriptional and translational regulation. A higher expression was observed at the translational level than at the transcriptional level. P starvation could induce a transient increase of endogenous indole-3-acetic acid (IAA) in soybean roots. The exogenous application of IAA stimulated the activity of plasma membrane H+-ATPase and P uptake, while naphthylphthalamic acid (NPA), an IAA transport inhibitor, blocked IAA effects. Taken together, these results suggested an involvement of root plasma membrane H+-ATPase in the adaptation of soybean to P starvation. IAA might be involved in signal transduction of P starvation by activating the plasma membrane H+-ATPase in soybean roots.

Adaptation, Physiological↗
PubMed2002

Genes for a nuclease and a protease are involved in the drastic decrease in cellular RNA amount in fission yeast cells during nitrogen starvation.

Cellular RNA in Schizosaccharomyces pombe cells drastically decreases in amount during nitrogen starvation. Previously, we found and purified a soluble RNA-degrading enzyme whose activity drastically increased in the cells of S. pombe undergoing nitrogen starvation. The enzyme was a nuclease encoded by pnu1(+). In this study, the increase in the RNA-degrading activity and the decrease in cellular RNA level are examined in a null-mutant of pnu1(+) (pnu1Delta). During nitrogen starvation, wild-type cells show an apparent increase in RNA-degrading activity, whereas the pnu1Delta cells do not. The wild-type cells show a drastic decrease in cellular RNA amount, whereas the pnu1Delta cells show only a slight decrease. These results suggest that Pnu1 nuclease is implicated in the decrease in cellular RNA amount during nitrogen starvation, probably via the RNA-degrading activity. The increase in the RNA-degrading activity is independent of both the Wis1 stress-activated MAP kinase cascade and Tor1 signaling pathway, but it is strongly dependent on isp6(+), a gene for a possible protease, whose expression is induced during nitrogen starvation. A disruption mutant for isp6(+) (isp6Delta) is deficient in both the increase in the RNA-degrading activity and the drastic decrease in the cellular RNA amount during nitrogen starvation, which suggests that isp6(+) is involved in the RNA degradation via regulating the RNA-degrading activity of Pnu1.

Endopeptidases↗
PubMed2000

Synthesis of phosphatidylserine in carrot cells cultured under carbon-source starvation.

When carrot suspension cells were cultured on medium containing no carbon source (starvation), the levels of phosphatidylserine (PS) increased transiently 3-4 d after the initiation of starvation while levels of most other phospholipid (PL) species decreased. We previously reported that fatty acids of these PLs served as an alternative carbon source during starvation. The present study showed that cells possess two different biosynthetic pathways involving phosphatidylcholine (PC)/phosphatidylethanolamine (PE) exchange enzymes and PS synthase to synthesize PS. These activities peaked similarly 4 d after the initiation of starvation and coincided with the peak of PS level. The synthesis of serine was also significantly activated during starvation. The activity of phosphoserine aminotransferase (PSAT) which is involved in serine synthesis increased with a time course similar to that of the increase in the PS level. These observations suggest that the increase in PS level plays an important role in membranes which are degraded during starvation.

CDPdiacylglycerol-Serine O-Phosphatidyltransferase↗
PubMed1979

Selective advantage of a Spirillum sp. in a carbon-limited environment. Accumulation of poly-beta-hydroxybutyric acid and its role in starvation.

A freshwater Spirillum sp., which apparently belongs to a niche of low nutritional status (Matin & Veldkamp, 1978), accumulated poly-beta-hydroxybutyric acid (PHB) during lactate-limited growth in continuous culture. The PHB content varied in a complex manner with the dilution rate (D), but was greatest at the lowest D value examined: about 18% (w/w) at D = 0.025 h-1. It is not known what mechanism accounted for PHB accumulation during carbon-limited growth. The resistance of cultures of Spirillum sp. to starvation after growth at various D values was compared with that of a Pseudomonas sp. which appears to belong to relatively richer environments (Matin & Veldkamp, 1978) and does not accumulate PHB. In Spirillum sp., resistance correlated directly with the PHB content of the culture subjected to starvation, whereas in Pseudomonas sp. it increased with RNA content. Further, after growth at D = 0.03 to 0.05 h-1, the Spirillum sp. was much more resistant to starvation than was the Pseudomonas sp. Since the microflora of oligotrophic environments are probably often subjected to starvation conditions, PHB accumulation by Spirillum sp. during growth in such environments may assist survival. PHB in Spirillum sp. was rapidly degraded during starvation but it had no sparing effect on RNA degradation. It is not known how PHB enhanced resistance to starvation.

Hydroxybutyrates↗
PubMed1993

Effect of previous growth conditions on the starvation-survival of Escherichia coli in seawater.

The starvation-survival of Escherichia coli in seawater was assessed by plate and epifluorescence counts, 3H-label decrease, cellular DNA concentrations, and metabolic activities. These assays were performed on two types of populations, adapted and non-adapted to seawater. The number of viable cells in the adapted population remained constant throughout starvation-survival in sterile seawater. In contrast, a significant decrease in the ability of the non-adapted E. coli to form colonies on plates following starvation-survival in sterile seawater was observed. However, this drop in viable counts was not mirrored by the epifluorescence counts and 3H-label, which did not show major changes for either population during the experiments, indicating maintenance of the number of cells. In addition, a significant increase in and subsequent maintenance of DNA content and thymidine incorporation was observed for both populations during starvation-survival in sterile seawater. The changes in cell-attached exoproteolytic activity and electron transport system activity showed that adapted and non-adapted E. coli cells maintain their metabolic potential. Cell-free exoproteolytic activity was drastically reduced in both populations. Adapted cells showed higher electron transport system activity and thymidine incorporation than non-adapted cells at the onset of starvation-survival. The effect of previous adaptation on E. coli starvation-survival, as assessed by plate counts and 3H-label decrease, was also observed in raw seawater. It seems from these data that the biological potential of E. coli cells suspended in sterile seawater has not been switched off or impaired seriously.

Acridine Orange↗
PubMed1995

Starvation stress modulates the expression of the Aspergillus nidulans brlA regulatory gene.

Expression of the Aspergillus nidulans brlA gene plays a fundamental role in the switch from vegetative growth to asexual reproduction. Using a media-shifting protocol to induce submerged sporulation and brlA-lacZ as an expression marker, it was shown that carbon and nitrogen starvation stress induced brlA transcription to different degrees. Glucose starvation induced briA rapidly to high levels and resulted in spore formation on reduced conidiophores, whereas nitrogen starvation induced brlA gradually to lower levels and sporulation occurred to a lesser extent but from more complex conidiophores. beta-Galactosidase activity paralleled brlA alpha and brlA beta mRNA. No clear qualitative differences between the two brlA transcripts were found in these starvation conditions, suggesting that the different patterns of sporulation could be explained by quantitative expression differences. Since brlA mRNA did not accumulate in the presence of a high glucose concentration, we investigated the role of other carbon sources on brlA expression. Non-repressing carbon sources such as glycerol, acetate and arabinose were as effective as glucose in preventing brlA mRNA accumulation, suggesting that the glucose effects on brlA expression could be explained as a response to nutrient starvation, rather than by carbon catabolite repression. Despite similar low levels of brlA transcripts being detected during growth in glucose or non-repressing carbon sources, conidiophores were formed only in medium containing glycerol, acetate or arabinose. When mycelia were not shifted to starvation conditions, sporulation was not observed in standard minimal medium even after glucose was exhausted, unless the medium was buffered.(ABSTRACT TRUNCATED AT 250 WORDS)

Aspergillus nidulans↗
PubMed2004

Effects of mutations in the rpoS gene on cell viability and global gene expression under nitrogen starvation in Escherichia coli.

Escherichia coli bearing an rpoS amber or disrupted mutation exhibited a significant decrease in the number of colony-forming units (c.f.u.) when exposed to nitrogen starvation, which was not observed in cells bearing a functional rpoS allele. The decrease in the number of c.f.u. that was observed about 25 h after initiation of nitrogen starvation was prevented by the addition of nitrogen within 3 h but not by the addition of nitrogen at more than 7 h after the initiation of nitrogen starvation, suggesting that a process leading to a decline in c.f.u. starts within this period. DNA microarray analysis of the rpoS mutant showed that a large number of genes including many functionally undefined genes were affected by nitrogen starvation. The expression levels of sigma(S) and sigma(H) regulon genes encoding acid-resistant proteins (hdeA, hdeB, gadA and gadB), DNA-binding protein (dps), chaperones (dnaK, ibpA, ibpB, dnaJ and htpG), chaperonins (mopB and mopA) and energy-metabolism-related proteins (hyaABCDF and gapA), and those of other genes encoding nucleotide-metabolism-related proteins (deoC and deoB), cell-division protein (ftsL), outer-membrane lipoprotein (slp) and DNA-binding protein (stpA) were significantly decreased by 10 h nitrogen starvation. The genes encoding transport/binding proteins (nac, amtB, argT, artJ, potF and hisJ) and amino acid-metabolism-related proteins (glnA, trpB, argG, asnB, argC, gdhA, cstC, ntrB, asd and lysC) were significantly up-regulated under the same condition, some of which are known Ntr genes expressed under nitrogen limitation. On the basis of these results, possible causes of the decrease in the number of c.f.u. under nitrogen starvation are discussed.

Bacterial Proteins↗
PubMed2006

Large-scale analysis of mRNA translation states during sucrose starvation in arabidopsis cells identifies cell proliferation and chromatin structure as targets of translational control.

Sucrose starvation of Arabidopsis (Arabidopsis thaliana) cell culture was used to identify translationally regulated genes by DNA microarray analysis. Cells were starved by subculture without sucrose, and total and polysomal RNA was extracted between 6 and 48 h. Probes were derived from both RNA populations and used to screen oligonucleotide microarrays. Out of 25,607 screened genes, 224 were found to be differentially accumulated in polysomal RNA following starvation and 21 were found to be invariant in polysomal RNA while their total RNA abundance was modified. Most of the mRNA appears to be translationally repressed (183/245 genes), which is consistent with a general decrease in metabolic activities during starvation. The parallel transcriptional analysis identifies 268 regulated genes. Comparison of transcriptional and translational gene lists highlights the importance of translational regulation (mostly repression) affecting genes involved in cell cycle and cell growth, these being overrepresented in translationally regulated genes, providing a molecular framework for the arrest of cell proliferation following starvation. Starvation-induced translational control also affects chromatin regulation genes, such as the HD1 histone deacetylase, and the level of histone H4 acetylation was found to increase during starvation. This suggests that regulation of the global nuclear transcriptional activity might be linked to cytoplasmic translational regulations.

Arabidopsis↗
PubMed2000

Enhancement of Na(+) uptake currents, time-dependent inward-rectifying K(+) channel currents, and K(+) channel transcripts by K(+) starvation in wheat root cells.

Excessive low-affinity Na(+) uptake is toxic to the growth of glycophytic plants. Recently, several reports have suggested that the interaction between K(+) and Na(+) uptake might represent a key factor in determining the Na(+) tolerance of plants. We investigated the effects of K(+) starvation on Na(+) and K(+) uptake mechanisms in the plasma membrane of wheat (Triticum aestivum L.) root cortex cells using the patch-clamp technique. Unexpectedly, K(+) starvation of wheat seedlings was found to enhance the magnitude and frequency of occurrence of time-dependent inward-rectifying K(+) channel currents (I(K)(+)(in)). We examined whether the transcription of a wheat root K(+)(in) channel gene is induced by K(+) starvation. A cDNA coding for a wheat root K(+) channel homolog, TaAKT1 (accession no. AF207745), was isolated. TaAKT1 mRNA levels were up-regulated in roots in response to withdrawal of K(+) from the growth medium. Furthermore, K(+) starvation caused an enhancement of instantaneous Na(+) currents (I(Na)(+)). Electrophysiological analyses suggested that I(K)(+)(in) and I(Na)(+) are not mediated by the same transport protein based on: (a) different activation curves, (b) different time dependencies, (c) different sensitivities to external Ca(2+), and (d) different cation selectivities. These data implicate a role for I(Na)(+) in Na(+) uptake and stress during K(+) starvation, and indicate that K(+)(in) channels may contribute to K(+)-starvation-induced K(+) uptake in wheat roots.

Amino Acid Sequence↗
PubMed2000

Multiple signaling pathways in gene expression during sugar starvation. Pharmacological analysis of din gene expression in suspension-cultured cells of Arabidopsis.

We have identified many dark-inducible (din) genes that are expressed in Arabidopsis leaves kept in the dark. In the present study we addressed the question of how plant cells sense the depletion of sugars, and how sugar starvation triggers din gene expression in suspension-cultured cells of Arabidopsis. Depletion of sucrose in the medium triggered marked accumulation of din transcripts. Suppression of din gene expression by 2-deoxy-Glc, and a non-suppressive effect exerted by 3-O-methyl-Glc, suggested that sugar-repressible expression of din genes is mediated through the phosphorylation of hexose by hexokinase, as exemplified in the repression of photosynthetic genes by sugars. We have further shown that the signaling triggered by sugar starvation involves protein phosphorylation and dephosphorylation events, and have provided the first evidence that multiple pathways of protein dephosphorylation exist in sugar starvation-induced gene expression. An inhibitor of serine/threonine protein kinase, K-252a, inhibited din gene expression in sugar-depleted cells. Okadaic acid, which may preferentially inhibit type 2A protein phosphatases over type 1, enhanced the transcript levels of all din genes, except din6 and din10, under sugar starvation. Conversely, a more potent inhibitor of type 1 and 2A protein phosphatases, calyculin A, increased transcripts from din2 and din9, but decreased those from other din genes, in sugar-depleted cells. On the other hand, calyculin A, but not okadaic acid, completely inhibited the gene expression of chlorophyll a/b-binding protein under sugar starvation. These results indicate that multiple signaling pathways, mediated by different types of protein phosphatases, regulate gene expression during sugar starvation.

Arabidopsis↗
PubMed1991

Study of glucose starvation in excised maize root tips.

Excised maize (Zea mays) root tips were used to follow the effects of a prolonged glucose starvation. Respiration rate began to decrease immediately after excision, reaching 30 to 40% of its initial value after 20 hours, and then declined more slowly until death of the tissues, which occurred after 200 hours of starvation. During the whole process, respiration could be uncoupled by 2,4-dinitrophenol and the energy charge remained high. These results suggest that in excised maize root tips, respiration rate is essentially limited by the rate of biosyntheses (ATP-utilizing processes) rather than mitochondrial number. During starvation the sugar content sharply decreased for the first 20 hours and reached zero at 120 hours. Following root excision, proteins and lipids were continuously degraded and were virtually the only substrates for respiration and biosyntheses after 20 hours of starvation. Over the first 90 hours of starvation, enzymic activities related to sugar metabolic pathways and the Krebs cycle decreased to 20% or less of their initial activity. Starvation was reversible only for the first 80 to 90 hours. Between 80 and 100 hours, there was a sharp fall in intracellular osmolarity and a 25% loss in the dry weight. The irreversibility may be due, as in senescence, to a change in membrane selective permeability.

Journal Article↗
PubMed2004

Kigamicin D, a novel anticancer agent based on a new anti-austerity strategy targeting cancer cells' tolerance to nutrient starvation.

Both tolerance to nutrient starvation and angiogenesis are essential for cancer progression because of the insufficient supply of nutrients to tumor tissue. Since chronic nutrient starvation seldom occurs in normal tissue, cancer's tolerance to nutrient starvation should provide a novel target for cancer therapy. In this study, we propose an anti-austerity strategy to exploit the ability of agents to eliminate cancer cells' tolerance to nutrient starvation. We established a simple screening method for agents that inhibit cancer cell viability preferentially during nutrient starvation, using PANC-1 cell line cultured in nutrient-rich and nutrient-deprived media. After screening over 2000 culture media of actinomycetes, we identified a new compound, kigamicin D (C(48)H(59)NO(19)), which shows preferential cytotoxicity to cancer cells under nutrient-deprived conditions, but hardly any cytotoxicity under nutrient-rich conditions. Both subcutaneous and oral administration of kigamicin D strongly suppressed the tumor growth of several tested pancreatic cancer cell lines in nude mice. Moreover, kigamicin D was observed to block the activation of Akt induced by nutrient starvation. Therefore, our results suggest that kigamicin D be a candidate for implementing our novel concept, anti-austerity, which may serve as a new strategy for cancer therapy.

Animals↗
PubMed1995

The influence of intracellular polyglucose and prior growth rate on the survival of Fusobacterium nucleatum under starvation conditions.

Grown in a chemically defined medium containing glucose at a dilution rate of D = 0.065 h-1, Fusobacterium nucleatum D212B-2 produced large amounts of intracellular polyglucose. Aliquots of this culture were starved by anaerobic incubation at 37 degrees C and at various times, assayed for intracellular polyglucose content and viability. This protocol was repeated using cells grown under the same conditions in a chemically defined medium, a medium lacking carbohydrate and in which the organism produced no intracellular polyglucose. Both cultures had 50% survival time values of about 1.5 h and were not eliminated even after 32 h of starvation. It was, therefore concluded that starvation-survival is not influenced by intracellular polyglucose. Starvation-survival was also determined for cells grown in a chemically defined medium at D = 0.048 h-1 and D = 0.12 h-1. The faster-grown cells had a 50% survival time of 3.8 h but were completely eliminated after 8-16 h of starvation. In contrast, slower-grown cells had a 50% survival time of 1.5 h but were not completely eliminated after 32 h of starvation. This illustrates the importance of cell history and technique standardization in comparing the starvation-survival of different organisms.

Adaptation, Physiological↗
PubMed2006

Evidence for ORC-dependent repression of budding yeast genes induced by starvation and other stresses.

The highly conserved origin recognition complex (ORC) is required for repressing genes in the silent mating type loci of budding yeast. Here we report that at a non-permissive temperature, the temperature-sensitive orc2-1 mutation induces the expression of more than 500 genes, the majority of which are also induced during starvation of wild-type cells. Many genes induced by starvation or by the orc2-1 mutation are also induced by inactivation of proteins required for chromatin-mediated repression of transcription. Genes induced by the orc2-1 mutation, starvation, or inactivation of repressor proteins, map near ORC-binding loci significantly more frequently compared to all genes. Genes repressed by starvation map near ORC-binding sites less frequently compared to all genes, which suggests they have been evolutionarily excluded from regions of repressive chromatin near ORC-binding sites. Deletion of sequences containing ORC-binding sites near the DAL2 and DAL4 genes in the DAL gene cluster, which are induced by either the orc2-1 mutation or by starvation, constitutively activates these genes and abolishes their activation by the orc2-1 mutation. Our findings suggest a role for ORC in the repression of a large number of budding yeast genes induced by starvation or other aspects of a deleterious environment.

Apoptosis↗
PubMed2000

Influence of growth rate and starvation on fluorescent in situ hybridization of Rhodopseudomonas palustris.

In situ hybridization with a fluorescently labeled 16S rRNA-targeted probe was examined using Rhodopseudomonas palustris as a model organism, which had been grown at different rates and under different conditions of growth and starvation. The specific growth rate did not affect the percentage of hybridized cells in aerobically grown R. palustris cultures. However, significant changes in the percentage of hybridized cells occurred during extended periods of starvation. These changes were observed both in batch cultures grown and starved aerobically in the dark, and in cultures grown phototrophically and starved anaerobically in the dark. Aerobic growth in batch culture and subsequent starvation resulted in a complete lack of detectable hybridization after 20 days of starvation. In contrast, even after 30 days of starvation, 50% of all cells were still detectable in cultures grown aerobically at growth rates <0.06 h(-1) and then starved aerobically in the dark. The same was true for phototrophically grown cells that were starved anaerobically in the light. During starvation there was a clear, though non-linear, positive correlation between the percentage of hybridized cells and the RNA content. In contrast, no direct correlation was observed between the number of hybridized cells in a culture and the viability of this culture. Thus, in habitats with growing, non-growing, and starving bacteria, data on quantitative detection of populations based on 16S rRNA-targeted probing should be used with extreme caution as the detectability of the individual cells is strongly influenced by their physiological history and current physiological state.

Journal Article↗
PubMed1976

Starvation effects on Escherichia coli and aquatic bacterial responses to nutrient addition and secondary warming stresses.

A gram-negative polar flagellated rod, isolated from a Colorado mountain stream and considered to be an Aeromonas sp., a mixed aquatic microbial population, and a culture of Escherichia coli were starved to determine their responses to the short-term presence of nutrients and mild warming stress (49.5 C for 2 min) in relation to starvation time. At the beginning of the starvation period, the Aeromonas isolate was extremely sensitive to the secondary warming stress. This response was markedly diminished after a 3-week starvation period. The mixed aquatic microbial population showed a similar trend in becoming less sensitive to stress with increased starvation. E coli under similar conditions, became more sensitive to the secondary stress after exposure to glucose. Respiration measurements after glucose additions also indicated that E. coli responded in a different manner to starvation stress and glucose presence than the Aeromonas isolate. The increased sensitivity of E. coli to secondary stress and short-term nutrient availability after starvation may contribute to the exclusion of this organism from aquatic environments.

Aeromonas↗
PubMed1990

Exoprotease Activity of Two Marine Bacteria during Starvation.

Exoprotease activity during 120 h of total energy and nutrient starvation was examined in two marine bacteria, Vibrio sp. strain S14 and Pseudomonas sp. strain S9. The activity was determined by spectrophotometric measurement of the rate of release of soluble color from an insoluble azure dye derivative of hide powder (hide powder azure). Starved cells of both strains (5 h for S14, and 4 or 24 h for S9) showed greater extracellular proteolytic activity than at the onset of starvation. The exoprotease activity of cells starved for longer periods of time then decreased, but was found to be present at significant levels throughout the starvation period studied (120 h). The accumulation of exoprotease activity in the bulk phase during starvation indicated that both strains constitutively excreted extracellular proteases. As deduced from experiments with chloramphenicol, de novo protein synthesis during starvation was required for the production and/or release of the exoproteases into the surrounding environment. The degradation of hide powder azure allowed an immediate increase in respiration rate, also by long-term-starved cells. This suggests that metabolic systems are primed to respond to the availability of substrates, allowing the cells to recover rapidly. The regulation of exoprotease activity was also studied and found to be different in the two strains. Casamino Acids repressed exoprotease activity in Pseudomonas sp. strain S9, whereas a mechanism similar to catabolite repression was found for Vibrio sp. strain S14 in that glucose repressed activity and cyclic AMP reversed this effect. The exoproteases appeared to be metalloproteinases because the addition of EDTA to cell-free starvation supernatants from both strains significantly inhibited the activity of the proteases.

Journal Article↗