Mild Starvation Research Articles

Cold atmospheric pressure plasma treatment combined with starvation increases autophagy and apoptosis in melanoma invitro and in vivo.

Despite advances in therapy, malignant melanoma remains a fatal disease. Among several emerging approaches to combat cancer, cold atmospheric pressure plasma (CAP) has shown promising results as a novel antitumor agent in preclinical models so far. The technology mainly relies on the emittance of various reactive oxygen and nitrogen species (ROS/RNS) that are tumor-toxic at high concentrations. Moreover, malignant melanoma has a metabolic dimension that can be targeted by mild starvation. To this end, we investigated the combined effect of starvation and CAP treatment on melanoma in vitro and in vivo. In vitro, starvation+CAP led to cell morphology changes, decreased metabolic activity and increased lipid peroxidation accompanied by apoptosis and DNA fragmentation in murine B16 melanoma cells but not murine non-malignant L929 fibroblasts. This was paralleled by increased apoptosis (Bax, Bcl-2 and Caspase-3) and autophagy (Lc3 and Atg5)-related gene expression. In vivo, starvation reduced tumor burden. Combination with CAP treatment augmented this effect significantly, albeit there was no difference of combination treatment to CAP exposure alone. Interestingly, there was an overall greater increase of Lc3 and Atg5 in the tumor tissue compared to CAP exposure alone, while starvation-induced autophagy-related gene expression was similar to in the combination group. These data collectively suggest that CAP-derived ROS/RNS treatment and autophagy-induction augment antitumor effects in malignant melanoma in vitro and in vivo.

Ubiquitin-proteasome-mediated cyclin C degradation promotes cell survival following nitrogen starvation.

Environmental stress elicits well-orchestrated programs that either restore cellular homeostasis or induce cell death depending on the insult. Nutrient starvation triggers the autophagic pathway that requires the induction of several Autophagy (ATG) genes. Cyclin C–cyclin-dependent kinase (Cdk8) is a component of the RNA polymerase II Mediator complex that predominantly represses the transcription of stress-responsive genes in yeast. To relieve this repression following oxidative stress, cyclin C translocates to the mitochondria where it induces organelle fragmentation and promotes cell death prior to its destruction by the ubiquitin–proteasome system (UPS). Here we report that cyclin C-Cdk8, together with the Ume6-Rpd3 histone deacetylase complex, represses the essential autophagy gene ATG8. Similar to oxidative stress, cyclin C is destroyed by the UPS following nitrogen starvation. Removing this repression is important as deleting CNC1 allows enhanced cell growth under mild starvation. However, unlike oxidative stress, cyclin C is destroyed prior to its cytoplasmic translocation. This is important as targeting cyclin C to the mitochondria induces both mitochondrial fragmentation and cell death following nitrogen starvation. These results indicate that cyclin C destruction pathways are fine tuned depending on the stress and that its terminal subcellular address influences the decision between initiating cell death or cell survival pathways.

CRF-like receptor SEB-3 in sex-common interneurons potentiates stress handling and reproductive drive in C. elegans.

Environmental conditions can modulate innate behaviours. Although male Caenorhabditis elegans copulation can be perturbed in the presence of stress, the mechanisms underlying its decision to sustain copulation are unclear. Here we describe a mating interference assay, which quantifies the persistence of male C. elegans copulation in noxious blue light. We show that between copulations, the male escapes from blue light illumination at intensities over 370 μW mm−2. This response is attenuated in mutants with constitutive activation of the corticotropin-releasing factor receptor family homologue SEB-3. We show that activation of this receptor causes sex-common glutamatergic lumbar ganglion interneurons (LUA) to potentiate downstream male-specific reproduction circuits, allowing copulatory behaviours to partially override the light-induced escape responses in the male. SEB-3 activation in LUA also potentiates copulation during mild starvation. We suggest that SEB-3 activation allows C. elegans to acclimate to the environment and thus continue to execute innate behaviours even under non-optimal conditions.

Mild Nutrient Starvation Triggers the Development of a Small-Cell Survival Morphotype in Mycobacteria.

Mycobacteria, generally believed to be non-sporulating, are well known to survive shock starvation in saline for extended periods of time in a non-replicating state without any apparent morphological changes. Here, we uncover that mycobacteria can undergo cellular differentiation by exposing Mycobacterium smegmatis to mild starvation conditions. Traces of various carbon sources in saline triggered the development of a novel small resting cell (SMRC) morphotype. Development of SMRCs could also be observed for other mycobacteria, suggesting evolutionary conservation of this differentiation pathway. Fluorescence microscopic analyses showed that development of SMRCs progresses via septated, multi-nucleoided cell intermediates, which divide to generate mono-nucleoided SMRCs. Intriguingly, saline shock-starved large resting cells (LARCs), which did not show cell size or surface changes when observed by scanning electron microscopy, remodeled their internal structure to septated, multi-nucleoided cells, similar to the intermediates seen during differentiation to SMRCs. Our results suggest that mycobacteria harbor a starvation-induced differentiation program in which at first septated, multi-nucleoided cells are generated. Under zero-nutrient conditions bacteria terminate development at this stage as LARCs. In the presence of traces of a carbon source, these multi-nucleoided cells continue differentiation into mono-nucleoided SMRCs. Both SMRCs and LARCs exhibited extreme antibiotic tolerance. SMRCs showed increased long-term starvation survival, which was associated with the presence of lipid inclusion bodies.

Mild Glucose Starvation Induces KDM2A-Mediated H3K36me2 Demethylation through AMPK To Reduce rRNA Transcription and Cell Proliferation.

Environmental conditions control rRNA transcription. Previously, we found that serum and glucose deprivation induces KDM2A-mediated H3K36me2 demethylation in the rRNA gene (rDNA) promoter and reduces rRNA transcription in the human breast cancer cell line MCF-7. However, the molecular mechanism and biological significance are still unclear. In the present study, we found that glucose starvation alone induced the KDM2A-dependent reduction of rRNA transcription. The treatment of cells with 2-deoxy-d-glucose, an inhibitor of glycolysis, reduced rRNA transcription and H3K36me2 in the rDNA promoter, both of which were completely dependent on KDM2A in low concentrations of 2-deoxy-d-glucose, that is, mild starvation conditions. The mild starvation induced these KDM2A activities through AMP-activated kinase (AMPK) but did not affect another AMPK effector of rRNA transcription, TIF-IA. In the triple-negative breast cancer cell line MDA-MB-231, the mild starvation also reduced rRNA transcription in a KDM2A-dependent manner. We detected KDM2A in breast cancer tissues irrespective of their estrogen receptor, progesterone receptor, and HER2 status, including triple-negative cancer tissues. In both MCF-7 and MDA-MB-231 cells, mild starvation reduced cell proliferation, and KDM2A knockdown suppressed the reduction of cell proliferation. These results suggest that under mild glucose starvation AMPK induces KDM2A-dependent reduction of rRNA transcription to control cell proliferation.

GAAC pathway limits autophagy to a light snack

![Figure][1] Cells lacking ATF4 (right) contain more autophagosomes (green) than control cells (left) after 12 hours of mild starvation. Chen et al. reveal how cells coordinate their response to starvation so that they don’t degrade their components unnecessarily. Cells respond to

SIRT2 knockdown increases basal autophagy and prevents postslippage death by abnormally prolonging the mitotic arrest that is induced by microtubule inhibitors

Mitotic catastrophe, a form of cell death that occurs during mitosis and after mitotic slippage to a tetraploid state, plays important roles in the efficacy of cancer cell killing by microtubule inhibitors (MTIs). Prolonged mitotic arrest by the spindle assembly checkpoint is a well-known requirement for mitotic catastrophe, and thus for conferring sensitivity to MTIs. We previously reported that turning off spindle assembly checkpoint activation after a defined period of time is another requirement for efficient postslippage death from a tetraploid state, and we identified SIRT2, a member of the sirtuin protein family, as a regulator of this process. Here, we investigated whether SIRT2 regulates basal autophagy and whether, in that case, autophagy regulation by SIRT2 is required for postslippage death, by analogy with previous insights into SIRT1 functions in autophagy. We show, by combined knockdown of autophagy genes and SIRT2, that SIRT2 serves this function at least partially by suppressing basal autophagy levels. Notably, increased autophagy induced by rapamycin and mild starvation caused mitotic arrest for an abnormally long period of time in the presence of MTIs, and this was followed by delayed postslippage death, which was also observed in cells with SIRT2 knockdown. These results underscore a causal association among increased autophagy levels, mitotic arrest for an abnormally long period of time after exposure to MTIs, and resistance to MTIs. Although autophagy acts as a tumor suppressor mechanism, this study highlights its negative aspects, as increased autophagy may cause mitotic catastrophe malfunction. Thus, SIRT2 offers a novel target for tumor therapy.

A Case of Nondiabetic Ketoacidosis in Third Term Twin Pregnancy

We report on a case of nondiabetic ketoacidosis due to mild starvation in a third term twin pregnancy. The aim was to present a case report and review of the literature in nondiabetic ketoacidosis in pregnancy, including precipitating factors and underlying pathophysiology. The case report includes collation of earlier data and literature review. The patient was admitted to the obstetrics ward of a large general hospital and, after cesarean section, was transferred to the intensive care unit. We present the case of a 26-yr-old obese patient with a 35-wk twin pregnancy. We provided appropriate management with fluid infusion after cesarean delivery. The patient and her two daughters survived, and no disabilities were foreseen. Alcohol, methanol, and lactic acid levels were normal. No signs of renal disease or diabetes were present. Pathological examination revealed no abnormalities of the placentae. Toxicological tests revealed a salicylate level of less than 5 mg/liter, an acetaminophen level of less than 1 mg/liter, and an acetone level of 300 mg/liter (reference, 5-20 mg/liter). We present a case of third term twin pregnancy with high anion gap metabolic acidosis due to (mild) starvation. Starvation, obesity, third term twin pregnancy, and perhaps a gastroenteritis were the ultimate provoking factors. In the light of the erroneous suspicion of sepsis and initial fluid therapy lacking glucose, one wonders whether, under a different fluid regime, cesarean section could have been avoided. Severe ketoacidosis in the pregnant woman is associated with impaired neurodevelopment. It therefore demands early recognition and immediate intervention.

Relationship between learning ability and starvation status in taste aversion learning of a pond snail

Event Abstract Back to Event Relationship between learning ability and starvation status in taste aversion learning of a pond snail Etsuro Ito1*, Koichi Mita1, Dai Hatakeyama1, Ryuichi Okada1, Mika Morikawa1, Yuki Sakamoto1, Miki Yamagishi1 and Akiko Okuta2 1 Tokushima Bunri University, Kagawa School of Pharmaceutical Science, Japan 2 Kyoto University, Graduate School of Science, Japan The pond snail Lymnaea stagnalis acquires taste aversion learning and maintains it as a long-term memory (LTM) referred to as conditioned taste aversion. In the present study, we examined the relationship among learning ability, starvation period and hemolymph glucose concentration in taste aversion learning. One-day mild starvation improves the learning score and keeps good LTM, but 5-day heavy starvation failed the snails to learn the taste aversion. During this 5-day starvation period, the hemolymph glucose concentration appeared to decrease. On the other hand, when we injected glucose into the abdominal cavity or fed sucrose to 1-day mild starved snails for a short period, the snails showed worse scores than the case of no injection or ingestion. Further, when mammalian insulin was injected into snails with a complete bellyful of food, the hemolymph glucose concentration decreased and the learning score and LTM were improved. The number of insulin-like receptors in the Lymnaea brain was not changed by taste aversion learning. These results showed that learning ability depends on the starvation period and the hemolymph glucose concentration and that learning ability can be controlled by direct manipulation of hemolymph glucose concentration or injection of insulin in taste aversion learning of Lymnaea. Keywords: Lymnaea, conditioned taste aversion, Glucose, Insulin, Starvation Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster (but consider for Participant Symposium) Topic: Learning, Memory and Behavioral Plasticity Citation: Ito E, Mita K, Hatakeyama D, Okada R, Morikawa M, Sakamoto Y, Yamagishi M and Okuta A (2012). Relationship between learning ability and starvation status in taste aversion learning of a pond snail. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00088 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 18 Apr 2012; Published Online: 07 Jul 2012. * Correspondence: Prof. Etsuro Ito, Tokushima Bunri University, Kagawa School of Pharmaceutical Science, Sanuki, 769-2193, Japan, eito@waseda.jp Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Etsuro Ito Koichi Mita Dai Hatakeyama Ryuichi Okada Mika Morikawa Yuki Sakamoto Miki Yamagishi Akiko Okuta Google Etsuro Ito Koichi Mita Dai Hatakeyama Ryuichi Okada Mika Morikawa Yuki Sakamoto Miki Yamagishi Akiko Okuta Google Scholar Etsuro Ito Koichi Mita Dai Hatakeyama Ryuichi Okada Mika Morikawa Yuki Sakamoto Miki Yamagishi Akiko Okuta PubMed Etsuro Ito Koichi Mita Dai Hatakeyama Ryuichi Okada Mika Morikawa Yuki Sakamoto Miki Yamagishi Akiko Okuta Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Sex-different hepatic glycogen content and glucose output in rats

BackgroundGenes involved in hepatic metabolism have a sex-different expression in rodents. To test whether male and female rat livers differ regarding lipid and carbohydrate metabolism, whole-genome transcript profiles were generated and these were complemented by measurements of hepatic lipid and glycogen content, fatty acid (FA) oxidation rates and hepatic glucose output (HGO). The latter was determined in perfusates from in situ perfusion of male and female rat livers. These perfusates were also analysed using nuclear magnetic resonance (NMR) spectroscopy to identify putative sex-differences in other liver-derived metabolites. Effects of insulin were monitored by analysis of Akt-phosphorylation, gene expression and HGO after s.c. insulin injections.ResultsOut of approximately 3 500 gene products being detected in liver, 11% were significantly higher in females, and 11% were higher in males. Many transcripts for the production of triglycerides (TG), cholesterol and VLDL particles were female-predominant, whereas genes for FA oxidation, gluconeogenesis and glycogen synthesis were male-predominant. Sex-differences in mRNA levels related to metabolism were more pronounced during mild starvation (12 h fasting), as compared to the postabsorptive state (4 h fasting). No sex-differences were observed regarding hepatic TG content, FA oxidation rates or blood levels of ketone bodies or glucose. However, males had higher hepatic glycogen content and higher HGO, as well as higher ratios of insulin to glucagon levels. Based on NMR spectroscopy, liver-derived lactate was also higher in males. HGO was inhibited by insulin in parallel with increased phosphorylation of Akt, without any sex-differences in insulin sensitivity. However, the degree of Thr172-phosphorylated AMP kinase (AMPK) was higher in females, indicating a higher degree of AMPK-dependent actions.ConclusionsTaken together, males had higher ratios of insulin to glucagon levels, higher levels of glycogen, lower degree of AMPK phosphorylation, higher expression of gluconeogenic genes and higher hepatic glucose output. Possibly these sex-differences reflect a higher ability for the healthy male rat liver to respond to increased energy demands.

ADAPTATION TO DESICCATION FAILS TO GENERATE PRE- AND POSTMATING ISOLATION IN REPLICATEDROSOPHILA MELANOGASTERLABORATORY POPULATIONS

Many laboratory speciation experiments have raised allopatric populations in different environments to determine whether reproductive isolation evolves as a byproduct of adaptation (a form of ecological speciation). Few, however, have addressed the evolution of both pre- and postmating isolation or investigated the conditions affecting the process. We present results of an evolution experiment in which 12 lines of Drosophila melanogaster were derived from a common population and then independently evolved for more than 57 generations under alternative selection treatments. Six "desiccation" populations had access to food and water removed during a period of their adult lives generating strong desiccation selection, and six "starvation" populations had access to food but not water removed for the same period, generating a mild starvation stress. Substantial divergence of cuticular hydrocarbons occurred between the desiccation and starvation populations, key traits that have been implicated in sexual isolation in Drosophila. Despite this divergence, there was no detectable premating isolation between desiccation and starvation populations and postmating isolation was asymmetrical: the fitness of F1 hybrids was reduced in the desiccation but not the starvation environment. This asymmetry was likely caused by the absence of divergent selection: adaptation to desiccation appears to have come at no cost to performance in the starvation environment. Novel environments are thought to promote the evolution of reproductive isolation. Understanding the conditions that favor or hamper this remains a key challenge for speciation research.

Sex-different and growth hormone-regulated expression of microRNA in rat liver

BackgroundMicroRNAs (miRNAs) are short non-coding RNAs playing an important role in post-transcriptional regulation of gene expression. We have previously shown that hepatic transcript profiles are different between males and females; that some of these differences are under the regulation of growth hormone (GH); and that mild starvation diminishes some of the differences. In this study, we tested if hepatic miRNAs are regulated in a similar manner.ResultsUsing microarrays, miRNA screening was performed to identify sex-dependent miRNAs in rat liver. Out of 324 unique probes on the array, 254 were expressed in the liver and eight (3% of 254) of those were found to be different between the sexes. Among the eight putative sex-different miRNAs, only one female-predominant miRNA (miR-29b) was confirmed using quantitative real-time PCR. Furthermore, 1 week of continuous GH-treatment in male rats reduced the levels of miR-451 and miR-29b, whereas mild starvation (12 hours) raised the levels of miR-451, miR-122a and miR-29b in both sexes. The biggest effects were obtained on miR-29b with GH-treatment.ConclusionWe conclude that hepatic miRNA levels depend on the hormonal and nutritional status of the animal and show that miR-29b is a female-predominant and GH-regulated miRNA in rat liver.

Hormonal and nutritional regulation of alternative CD36 transcripts in rat liver – a role for growth hormone in alternative exon usage

BackgroundCD36 is a multiligand receptor involved in various metabolic pathways, including cellular uptake of long-chain fatty acids. Defect function or expression of CD36 can result in dyslipidemia or insulin resistance. We have previously shown that CD36 expression is female-predominant in rat liver. In the present study, hormonal and nutritional regulation of hepatic CD36 expression was examined in male and female rats. Since alternative transcription start sites have been described in murine and human Cd36, we investigated whether alternative CD36 transcripts are differentially regulated in rat liver during these conditions.ResultsSequence information of the rat Cd36 5'-UTR was extended, showing that the gene structure of Cd36 in rat is similar to that previously described in mouse with at least two alternative first exons. The rat Cd36 exon 1a promoter was sequenced and found to be highly similar to murine and human Cd36. We show that alternative first exon usage is involved in the female-predominant expression of CD36 in rat liver and during certain hormonal states that induce CD36 mRNA abundance. Estrogen treatment or continuous infusion of growth hormone (GH) in male rats induced CD36 expression preferentially through the exon 1a promoter. Old age was associated with increased CD36 expression in male rats, albeit without any preferential first exon usage. Intermittent GH treatment in old male rats reversed this effect. Mild starvation (12 hours without food) reduced CD36 expression in female liver, whereas its expression was increased in skeletal muscle.ConclusionThe results obtained in this study confirm and extend our previous observation that GH is an important regulator of hepatic CD36, and depending on the mode of treatment (continuous or intermittent) the gene might be either induced or repressed. We suggest that the effects of continuous GH secretion in females (which is stimulatory) and intermittent GH secretion in males (which is inhibitory) explains the sex-different expression of this gene. Furthermore, a female-specific repression of hepatic CD36 in response to food deprivation was found, which was in contrast to a stimulatory effect in skeletal muscle. This demonstrates a tissue-specific regulation of Cd36.

The Candida albicans cell wall-associated glyceraldehyde-3-phosphate dehydrogenase activity increases in response to starvation and temperature upshift.

We have determined the effect of environmental factors (mild thermal upshift and starvation) on the Candida albicans cell wall-associated glyceraldehyde-3-phosphate dehydrogenase (cwGAPDH) activity. Temperature upshift (from 28 to 37 degrees C) and/ or starvation (at 28 or 37 degrees C in water) of exponentially growing yeast cells caused an increase in cwGAPDH activity (3 to 5-, and 7 to 8-fold, respectively). This increase in activity did not correlate with an increase in the amount of cwGAPDH protein present, as determined by flow cytometry, immunoelectron microscopy and Western-blotting. These results indicate that thermal upshift and starvation cause an activation of the cwGAPDH in C. albicans cells.

Phototaxis in Chlamydodon mnemosyne: Determination of the illuminance-response curve and the action spectrum

The cyrtophorid ciliate Chlamydodon mnemosyne shows accurate orientation with respect to the direction of light. Positive phototaxis occurs during mild starvation, while the cells are negatively phototactic in the well-fed state. Beside the determination of the illuminance-response curve for white light, we have measured the action spectrum of phototaxis in this ciliate by means of an automatic cell-tracking system. Phototactic reactions occur at illuminances from 100 lx to 100 klx, with an optimum at 10 klx. The action spectrum has one main peak centred at 470 nm, and two secondary ones at 450 and 390 nm. Responses also occur at other wavelengths in the blue and near-UV range of the spectrum, while no significant phototactic reactions are measured between 500 and 710 nm. Results confirm the view that bluelight photoreceptor molecules, e.g., flavins or flavin-like pigments, are responsible for light perception in C. mnemosyne and trigger phototactic orientation.

Effects of repeated cycles of starvation and refeeding on lungs of growing rats.

Adult male rats were subjected to four cycles of mild starvation (2 wk) and refeeding (1 wk) and were compared with a fed group. Starvation was induced by giving rats one-third of their measured daily food consumption. During each starvation cycle, rats lost approximately 20% of their body weight. Despite catch-up growth and overall weight gain, starved rats had lower final body weight than fed rats. Lung dry weight and lung volumes were also reduced in the starved group. The mechanical properties of air- and saline-filled lungs did not change significantly with repeated cycles of starvation. Mean linear intercept was similar in the two groups, but alveolar surface area was reduced in the starved rats. Total content of crude connective tissue and concentration per lung dry weight of hydroxyproline and crude connective tissue were reduced in starved rats. We conclude that lung growth is retarded in growing rats subjected to repeated cycles of mild starvation and refeeding, as manifested by smaller lung volume and reduced alveolar surface area. Because alveolar size is unchanged, a reduced number of alveoli is most likely responsible for decreased lung volumes.

Inhomogeneity of liver glycogen synthesis upon refeeding after starvation

Normal hepatic glycogen levels are in the range 300-400 pmol/g of tissue wet weight [ 11. Starvation for periods longer than 12 h severely depletes the hepatic glycogen store, as it is rapidly mobilized to provide glucose for extrahepatic tissue metabolism [ 11. Typical levels remaining after mild starvation of 24-48 h are reported as being less than 40 pmol/g of tissue wet weight for the rat and other mammals [ l] . Upon refceding after a period of starvation, there is rapid repletion of the hepatic glycogen store and the long-held belief, based upon experiments performed by Hers [2], was that most glucose absorbed from a carbohydrate load is taken up into the liver and directly converted into glycogen. However, a number of recent reports have suggested that hepatic glycogen synthesis does not proceed via this route under physiological conditions; rather it has been shown that the synthesis is via the so-called indirect route, whereby glucose is metabolized to the level of 3-carbon intermediates before glycogen synthesis (see reviews in [3-71). It has long been known that liver glycogen exists over a vast size range (see 18, Y]), and a study from this laboratory [ 101 showed that post-starvation rabbit liver glycogen repletion is a metabolically inhomogeneous process, with material of large size being synthesized preferentially. This study, along with those from other groups [ 1 1, 121, was performed without accurate knowledge of the values of diffusion coefficients of the glycogen fractions and so accurate molecular mass profiles could not be calculated. Diffusion coefficients have since been measured for glycogen fractions from rat liver ( [ 131, see also [ X I ) and accurate molecular mass profiles described. Since accurate molecular mass data are now available for liver glycogen, it was decided t o reinvestigate the

Morphological Drift Accompanying Nascent Population Differentiation in the Ciliate Euplotes vannus

ABSTRACTA rare phenomenon can occur in ciliated protists of the genus Euplotes, which can undergo genetic recombination by the normal outbreeding process of conjugation following mild starvation. Occasionally, the dominant mutation for the autogamy trait arises. Individuals possessing the trait show obligate self‐fertilization upon mild starvation. This yields, after normal asexual division, a population of individuals that are reproductively isolated from the parental outbreeding strain. A morphometric analysis of sympatric autogamous and non‐autogamous populations of Euplotes vannus from Somalia demonstrates that there has been morphological drift in gross body proportions in the autogamous populations. However, the positional patterns of the locomotory organelles on the ventral surface remain unchanged. The changes in body proportions in the autogamous populations are relevant to the mechanics of the conjugation process, which involves fusion of the oral regions of paired cells belonging to complementary mating types.

Correlation between histidine operon expression and guanosine 5'-diphosphate-3'-diphosphate levels during amino acid downshift in stringent and relaxed strains of Salmonella typhimurium

We have analyzed the correlation of attenuator-independent expression of the Salmonella typhimurium histidine operon in vivo with levels of the "alarmone" guanosine 5'-diphosphate 3'-diphosphate. Amino acid downshift caused by serine hydroxamate addition increased his expression in a relA+ strain and decreased his expression in a relA mutant, whereas levels of guanosine 5'-diphosphate-3'-diphosphate varied in parallel with the changes in his expression in the two strains. In several experiments, overall variations in his expression ranged from 20- to 60-fold after downshift. The mild downshift allowed growth of the cultures to continue at near-preshift rates. Serine hydroxamate addition was also used to analyze the effect of amino acid downshift on induced expression of wild-type and mutant lac promoters. There was a 12-fold difference in lac expression when a relA+-relA1 pair was subjected to mild starvation but only a 3-fold difference when the strains carried the lacZpL8UV5 promoter mutation. These results suggest that guanosine 5'-diphosphate-3'-diphosphate stimulates gene expression in vivo at the level of transcription initiation.

Survival and activity of Klebsiella pneumoniae at super-optimal temperatures

The effect of temperature on a population of Klebsiella pneumoniae was examined together with the imposition of mild starvation conditions at temperatures of 35°, 41°, 49°, 55° and 60 °C. Results for changes in biomass, protein and metabolic activity are presented in terms of gross population changes and show that these parameters decline with increasing temperature. Increases in the amount of dissolved organic carbon, together with a decrease in the number of cells present with increasing temperature, suggest that death and lysis processes are occurring. Regrowth in the bioreactor occurred after returning the temperature to 35 °C and starting a flow of carbon and other nutrients. This was probably due to reinoculation from head space wall growth drainage rather than reversion of heat-stressed microbes. The consequences of this for thermophilic sludge treatment processes are discussed. The concept of endogenous metabolism is questioned with respect to it being a realistic description of the survival process.