Starvation Period Research Articles

Winter condition, physiology, and growth potential of juvenile Antarctic krill

In recent years, substantial efforts have been made to understand the implications of climate change on Antarctic krill, Euphausia superba, because of their pivotal role in the Southern Ocean food web and in biogeochemical cycling. Winter is one of the least studied seasons in Antarctica and we have limited understanding about the strategies Antarctic krill use to survive the winter. In particular, data on the winter physiology and condition of juvenile Antarctic krill are severely lacking. From May to September (the austral autumn-winter) of 2019, we maintained juvenile Antarctic krill in large (1,330 L) aquarium tanks at Palmer Station, Antarctica and, at monthly time intervals, measured their physiology and condition. Each tank served as a “food environment scenario”, representing possible food environments the krill may encounter during winter along the Western Antarctic Peninsula. We found that, unlike adults, juvenile krill maintain relatively high respiration rates through the winter and respond positively to increased food concentrations by increasing their ingestion rates. Unlike larval krill, juveniles use lipid stores accumulated during the summer and autumn to sustain themselves through periods of starvation in the winter. We used our empirically derived measurements of physiology and condition to estimate the energy budget and growth potential of juvenile krill during the winter. We found that, given their comparatively high respiration rates, small juvenile krill (20 mg dry weight) would need to encounter food at concentrations of ~ 0.15 mg C L-1 daily to avoid loss of body carbon. Without sufficient lipid reserves, this value increases to ~ 0.54 mg C L-1, daily. The health of juvenile krill in the wintertime is dependent on their ability to accumulate lipid stores in the summer and autumn and to find sufficient food during the winter. Changes in food availability to Antarctic krill throughout the year may become problematic to juvenile krill in the future. Understanding the variability in the winter energy budget of juvenile Antarctic krill will allow us to improve population models that make assumptions on seasonal growth patterns.

Bicistronic vector-based procedure to measure correlative expression and bacteriostatic activity of recombinant neutrophil gelatinase-associated lipocalin

Neutrophil gelatinase-associated lipocalin (NGAL) is a component of the human innate immune system that exerts bacteriostatic effects. Recent research suggests that NGAL is also a promising biomarker for tubular damage and aids in the early diagnosis of acute kidney injury. Therefore, the development of a method to efficiently produce recombinant NGAL has considerable clinical value. This study aimed to analyze the correlation between fluorescence reporter (enhanced green fluorescent protein, EGFP) intensity and NGAL levels, mediated by a bicistronic expression system based on internal ribosome entry sites (IRESs). During the 14-day culture period, EGFP intensity was positively correlated with NGAL concentrations. The purified protein also exerted bacteriostatic effects, interfering with bacterial iron uptake machinery during periods of iron starvation. The purified NGAL was also applied to generate a standard curve that could be used for enzyme-linked immunosorbent assay of samples containing unknown NGAL quantities. In conclusion, we successfully developed a procedure using EGFP and IRES-based vector to predict NGAL production levels and optimize protein harvest time. Our approach is also a simple and effective method for evaluating bioactivity.

Resource allocation strategies for survival and reproduction by an invasive pest in response to intermittent fasting.

Intermittent fasting (IF) is a type of dietary restriction that involves fasting periods in intervals, which has been used as a strategy to improve health and extend longevity. Regular fasting is common during the process of biological invasions in nature. Yet, it is not clear how invasive animals adjust their resource allocations to survival and reproduction when periodical starvation occurs. Here, we used Tetranychus ludeni, a haplodiploid spider mite and an important invasive pest of horticultural crops around the world, to investigate the effects of IF on its life history strategies. We show that IF increased the longevity in females but not in males probably because of differences in resource storage, metabolic rate, and mating cost between sexes. In response to IF, females traded off fecundity and egg size but not the number of daughters for longevity gain, suggesting that T. ludeni females can adjust their life history strategies for population survival and growth during invasion process. Eggs produced by fasted females realized the same hatch rate and resultant young had the same survival rate as those by unfasted ones. In addition, IF had transgenerational maternal effects which prolonged offspring development period. We suggest that the longer immature developmental period can increase the body size of resulting adults, compensating egg size loss for offspring fitness. Our findings provide insight into resource allocations as responses to fasting, knowledge of which can be used for evaluation of pest invasions and for management of animal survival and reproduction by dietary regulations.

“There and back again” - Ultrastructural changes in the gills of Bathymodiolus vent-mussels during symbiont loss: Back to a regular filter-feeding epidermis

Deep-sea mussels Bathymodiolus azoricus, from Azorean hydrothermal vents, house two types of symbionts in their fleshy gills: methane-oxidizing (MOX) and sulfide-oxidizing (SOX) Gamma-proteobacteria. As soon as the mussels are collected, their symbionts are deprived from their environmental nutrient flux, and cannot rely on their usual metabolism. Recent studies have shown that the gill cells undergo high rates of apoptosis, as well as regionalized cell proliferation. This study follows the fate of the symbionts and of the hosting bacteriocytes at the ultrastructural level, during an extended starvation period. Just upon collection, we evidenced an apico-basal journey of the symbionts in the bacteriocytes, starting with (1) apical single symbiont endocytosis, (2) symbiont division, (3) symbiont storage, (4) and symbiont digestion within lysosomes, above the basal lamina. After 4-9 days starvation, endocytosis occurred with (5) empty blebbing, (6) the lysosomes increased in size, and the bacteriocytes lost their apical membrane, resulting in (7) a baso-apical return of the symbiont-containing lysosomes outside the gills, while the nucleus showed condensed chromatin, characteristic of apoptosis/necroptosis (8). Between the bacteriocytes, narrow intercalary cells appear to divide (9). Our hypothesis is that intercalary cells are stem cells that replace lost bacteriocytes. After 61 days there was no symbiont left, and the epidermis resembled those of the non-symbiotic filter-feeding mussel Mytilus edulis.

How delousing affects the short-term growth of Atlantic salmon (Salmo salar)

Infestations with salmon lice and subsequent salmon lice management is one of the most challenging and costly aspects of marine salmonid aquaculture. Both the handling and treatment, specifically non-medicinal treatment, against salmon lice cause stress and physical injuries to the host, the Atlantic salmon (Salmo salar). This in turn leads to reduced appetite and increased mortality. In this study, we have estimated the short-term growth loss of Atlantic salmon related to treatments (thermal, mechanical, hydrogen peroxide bath, freshwater bath and combination medicinal baths) for removal of salmon lice. To achieve this, we have obtained daily production data at cage-level from 2014 to 2019 from three large Norwegian aquaculture companies. We have used the registered feed-amount, number of fish and seawater temperature at cage level to calculate the thermal growth coefficient (TGC) of 635 fish-groups the week before a pre-treatment starvation period and the week after 2530 different treatments to estimate the reduction in TGC. We modelled this outcome using a mixed effect linear regression model, with treatment method as the main fixed effect of interest and fish weight, seawater temperature, smolt-age and year-class included as fixed effects. Results showed a period of suboptimal feeding and growth after all treatment methods, where non-medicinal treatment methods had a significantly larger negative effect on growth compared to medicinal treatments. The results also showed that timing of treatment played a role in the outcome of a treatment. The short-term biomass-loss in one cage following one non-medicinal treatment was estimated to 31,200 kg (average cage containing 150,000 fish weighing 3 kg, and seawater temperature of 10 °C). Thus, there could exist a potential for increased production in the Atlantic salmon aquaculture industry by reducing the number of delousing operations.

Nitrification upon Nitrogen Starvation and Recovery: Effect of Stress Period, Substrate Concentration and pH on Ammonia Oxidizers’ Performance

Nitrification has been widely applied in wastewater treatment, however gaining more insight into the nitrifiers’ physiology and stress response is necessary for the optimization of nutrient removal and design of advanced processes. Since nitrification initiates with ammonia oxidation performed by ammonia-oxidizing bacteria (AOB), the purpose of this study was to investigate the effects of short-term ammonia starvation on nitrogen uptake and transformation efficiency, as well as the performance of starved nitrifiers under various initial substrate concentrations and pH values. Ammonium deprivation for 3 days resulted in fast ammonium/ammonia accumulation upon nitrogen availability, with a maximum uptake rate of 3.87 mmol gprotein−1 min−1. Furthermore, a delay in the production of nitrate was observed with increasing starvation periods, resulting in slower recovery and lower nitrification rate compared to non-starved cells. The maximum accumulation capacity observed was 8.51% (w/w) independently of the external nitrogen concentration, at a range of 250–750 mg N L−1, while pH significantly affected ammonia oxidizers’ response, with alkaline values enhancing nitrogen uptake. In total, ammonia accumulation after short-term starvation might serve as an important strategy that helps AOB restore their activity, while concurrently it could be applied in wastewater treatment for effective nitrogen removal and subsequent biomass utilization.

Fill‐and‐Spill, Tilt‐and‐Repeat (FaSTaR) cycles: Stratigraphic evolution above a dynamic submarine stepped slope

AbstractThe classic fill‐and‐spill model is widely applied to interpret topographic controls on depositional architecture and facies distributions in slope successions with complicated topography. However, this model implies a constant topographic configuration over the lifespan of a turbidite system. In contrast, the impact on patterns of erosion and deposition above dynamic slopes whose topographic configuration varies spatially over time remains poorly investigated. Here, using high‐resolution 3D seismic reflection data and more than 100 wells from a 40 km long stepped slope system (Campos Basin, offshore Brazil), we document the evolution of a sand‐prone turbidite system active during the Oligocene–Miocene transition. This turbidite system was influenced by vertical and lateral deformation, and we propose a new stratigraphic model to explain the resultant depositional architecture. Two depocentres were identified as steps, with channels on the proximal step, and channel–lobe complexes on the distal step, bounded by sediment bypass‐dominated ramps. Lateral stepping of channels on the proximal step, and oblique stacking of the down‐dip lobe complexes, each cut by through‐going channels, indicate multiple fill‐and‐spill cycles. A persistent north‐east‐ward stepping and thickening on the steps are interpreted to reflect lateral tilting of the seafloor driven by salt tectonics. The dynamic substrate prevented the establishment of a single long‐lived conduit across the proximal step, as recorded in systems with fixed topographic configurations. The filling of through‐going channels with mud at the end of each cycle suggests waxing‐to‐waning sediment supply cycles and periods of sand starvation when the lateral tilting dominated and drove avulsion of the feeder channels towards topographic lows. This study demonstrates that subtle dynamic slope deformation punctuated by discrete sediment supply cycles results in complex stratigraphic patterns with multiple phases, and multiple entry and exit points. Repeated cycles of fill‐and‐spill, tilt‐and‐repeat are likely to be present in other stepped slope systems.

Feeding and lipophagy: it takes guts to deliver.

Refeeding after a period of starvation is known to suppress autophagy in the liver. Surprising new work by Seok et al (2022) shows that refeeding activates lipophagy in the intestine, which may help fats in our diet to be efficiently processed after a meal.

Carbohydrates complement high-protein diets to maximize the growth of an actively hunting predator.

In nature, food is often variable in composition and availability. As a consequence, predators may need to seek non‐prey food sources. Some predators are known to feed on nectar when food is limited. Nectar and other carbohydrate resources could also be beneficial when prey are more abundant if it helps predators balance protein‐biased diets. We tested if an actively hunting predator, the jumping spider, Phidippus audax, benefited from liquid carbohydrates when prey were not limited. We also tested if the benefit of carbohydrates varied with the nutrient content of prey (i.e., from protein to lipid biased). Spiders were reared on one of six live prey, Drosophila melanogaster, treatments that ranged from high protein to high lipid. Half of the spiders were given access to a 20% sucrose solution. After 2 months, we measured spider mass, cephalothorax width, instar duration, percent body fat, survival, and estimated number of prey eaten. Spiders reared on high‐protein diets with carbohydrates were larger and heavier than spiders on other treatments. Access to carbohydrates also increased percent body fat and survival across prey treatments. Our results suggest that carbohydrates may be a valuable component of spider diets, especially when prey have high protein and low lipid content as is commonly observed in prey in the field. Our results highlight the importance of diet balancing for predators, and that liquid carbohydrates can be an important nutrient to supplement a diet of prey rather than just being an energy supplement during periods of starvation.

Air starvation of proton exchange membrane fuel cells and its beneficial effects on performance

Air starvation occurring in a proton exchange membrane fuel cell will result in voltage drop and even a slightly reversal. However, a short period of air starvation may have a beneficial effect on the cell. In this paper, single cells are used to simulate the air starvation of a single cell in the stack and the related phenomena are studied. The experimental results show that when the starvation occurs in a single cell, the larger the output current, the more negative the voltage, the more obvious the hydrogen pumping; When the starvation occurs in the whole stack, the current and voltage of the cell and the amount of hydrogen pumping are only related to the hydrogen concentration on both sides of the cell. Subsequent research on single starved cell found that after a short period of 100 s of starvation, the cell's performance has improved, with an average increase of 22.3%@1500 mA/cm2, and ECSA of the catalyst increased slightly. The characterization of the catalyst before and after the air starvation found that the catalyst was not destroyed, indicating that the short-term air starvation will not damage the cell, but will improve the performance of it.

Exploring the impacts of different fasting and refeeding regimes on Nile tilapia (Oreochromis niloticus L.): growth performance, histopathological study, and expression levels of some muscle growth-related genes

The current study investigated how different fasting and refeeding regimes would impact Nile tilapia growth performance, histopathological examination, and gene expression of myostatin, myogenin, GH, IGF-1, and NPYa. Nile tilapia fish (n = 120) were randomly allocated into four groups, including the control group fed on a basal diet for 6 weeks (F6), group A starved for 1 week and then refed for 5 weeks (S1F5), group B starved for 2 weeks and then refed for 4 weeks (S2F4), while group C starved for 4 weeks and then refed for 2 weeks (S4F2). Fasting provoked a decrease in body weight coincided with more extended starvation periods. Also, it induced muscle and liver histological alterations; the severity was correlated with the length of fasting periods. Gene expression levels of GH, MSTN, MYOG, and NPYa were significantly increased, while IGF1 was markedly depressed in fasted fish compared to the control group. Interestingly, refeeding after well-planned short fasting period (S1F5) modulated the histopathological alterations. To some extent, these changes were restored after refeeding. Restored IGF-I and opposing fasting expression profiles of the genes mentioned above thus recovered weights almost like the control group and achieved satisfactory growth compensation. Conversely, refeeding following more extended fasting periods failed to restore body weight. In conclusion, refeeding after fasting can induce a compensatory response. Still, the restoration capacity is dependent on the length of fasting and refeeding periods through exhibiting differential morphological structure and expressions pattern for muscle and growth-related genes.Graphical abstract

A Qualitative Systematic Review of Risk Factors for Refeeding Syndrome

ObjectivesRefeeding syndrome (RFS) is characterized by potentially fatal electrolyte shifts after resumption of feeding following a period of prolonged starvation. The lack of a standardized definition has made the study of RFS difficult. Early identification of patients at risk of RFS may prevent life-threatening complications and improve outcomes. However, the sensitivity of reported risk factors depends on the definition used, and many have never been validated. This study was designed to identify risks for RFS that have been identified in prior studies. It is preparatory for a larger analysis to better identify sensitive and specific risk factors for RFS.MethodsThis is a qualitative systematic review of observational studies following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies reporting the incidence of RFS were included. Risk factors were extracted whether identified in review or as a measured exposure. Risk factors were considered distinct if they were not described similarly (e.g., BMI, admit BMI, nadir BMI, BMI < 16, BMI < 18.5 were each treated as distinct).ResultsRisk factors were reviewed or studied in 43 of 49 studies that met inclusion criteria. A total of 129 distinct risk factor definitions were extracted. Of these, only 29 used definitions similar enough to other studies to be considered the same by the reviewers (range 2 to 8 studies per risk factor; median 3 studies). NICE guidelines were mentioned in 3 studies. No other published guidelines were found.ConclusionsCreating a risk profile for patients may help tailor interventions to prevent RFS. There was a large heterogeneous number of risk factors and numerous discrepancies in description of risk factors among the studies. The low incidence of inclusion of poor intake (i.e., less than 100%) in the identified studies was of interest. Next steps will include prospective validation of identified risks, as well as AI analyses to identify and validate other risk factors and biomarkers, with the goal to develop sensitive and specific risk assessments, and effective preventive and treatment protocols.Funding SourcesNone.

Insights into the denitrifying phosphorus removal decay processes by profiling of the response mechanism of denitrifying phosphate-accumulating organisms to starvation stress

Starvation conditions were inevitably encountered by biological wastewater treatment systems. Four anaerobic starvation periods (5, 10, 16 and 20 days) were conducted to investigate the response mechanism of denitrifying phosphate-accumulating organisms (DPAOs) in order to dissect denitrifying phosphorus removal (DPR) decay processes. The denitrifying phosphorus removal performance suffered with the decay rate of 0.162 ± 0.022 d−1 during 20-day starved duration. Metabolic activity decay was responsible 93.20 ± 0.11% for the damaged DPR performance, while biomass decay contributed to 6.79 ± 0.68%. The genus Dechloromonas affiliated to DPAOs exerted stronger survival adaptability to starvation with the abundance increasing from 1.98% to 3.15%, depended upon the endogenous consumption of intracellular polymers. In view of PHA-driven DPR mechanism of DPAOs, the metabolic activity was restricted by the depletion of available PHA. These results revealed the poorer stability but preponderant recovery of DPR system encountering with starvation.

Monitoring the Starvation-Survival Response of Edwardsiella piscicida and E. tarda in Freshwater Microcosms, at Various Temperatures.

Edwardsiella piscicida is an important fish pathogen responsible for economic losses in global aquaculture, and E. tarda is also a human zoonotic pathogen. In this study, the survival of E. piscicida and E. tarda strains kept in filtered and sterilized lake water microcosms was investigated during a 20-week period at 7 °C, 15 °C and 25 °C, as well as its pathogenicity retention during a starvation period. E. tarda V43.2 stayed culturable for 6 weeks at 7 °C, 9 weeks at 25 °C and 12 weeks at 15 °C. Both E. piscicida strains (V12.1 and V57.2) stayed culturable even longer, for at least 12 weeks at 7 °C, 15 °C and 25 °C under the same starvation conditions. After Edwardsiella cells entered into the VBNC state, some became shorter and ”rounded up,” but others aggregated and retained a short rod shape. Aggregates of Edwardsiella cells were common throughout the VBNC period, and a well-formed biofilm was observed for all tested strains at the end of the experiment. The growth capacity of VBNC cells was restored by cultivating microcosm water samples in LB broth at 28 °C. Resuscitated E. piscicida cells were as virulent for the European eel as the controls. Natural waters can be a reservoir for Edwardsiella, and its underestimation in environmental samples poses a risk to public health and aquaculture.

Sedimentologic and stratigraphic criteria to distinguish between basin‐floor and slope mudstones: Implications for the delivery of mud to deep‐water environments

AbstractDeep‐water mudstones overlying basin‐floor and slope sandstone‐prone deposits are often interpreted as hemipelagic drapes deposited during sand starvation periods. However, mud transport and depositional processes, and resulting facies and architecture of mudstones in deep‐water environments, remain poorly understood. This study documents the sedimentology and stratigraphy of basin‐floor and slope mudstones intercalated with sandstone‐prone deposits of the Laingsburg depocentre (Karoo Basin, South Africa). Sedimentologic and stratigraphic criteria are presented here to distinguish between slope and basin‐floor mudstones, which provide a tool to refine palaeogeographical reconstructions of other deep‐water successions. Several mudstone units were mapped at outcrop for 2500 km2 and investigated using macroscopic and microscopic core descriptions from two research boreholes. Basin‐floor mudstones exhibit a repeated and predictable alternation of bedsets dominated by low‐density turbidites, and massive packages dominated by debrites, with evidence of turbulent‐to‐laminar flow transformations. Slope mudstones exhibit a similar facies assemblage, but the proportion of low‐density turbidites is higher, and no repeated or predictable facies organisation is recognised. The well‐ordered and predictable facies organisation of basin‐floor mudstones suggest local point sources from active slope conduits, responsible for deposition of compensationally stacked muddy lobes. The lack of predictable facies organisation in slope mudstones suggests deposition took place in a more variable range of sub‐environments (i.e. ponded accommodation, minor gully/channel‐fills, levees). However, regional mapping of three mudstone units evidence basinward tapering and similar thicknesses across depositional strike. This geometry is consistent with the distal part of basin margin clinothems, and suggests laterally extensive mud delivery across the shelf edge combined with along‐margin transport processes. Therefore, the sedimentology and geometry of mudstones suggests that mud can be delivered to deep‐water dominantly by sediment gravity flows through point source and distributed regionally, during periods of up‐dip sand storage. These findings challenge the common attribution of deep‐water mudstones to periods of basin‐floor sediment starvation.

Impact and Persistence of Serratia marcescens in Tenebrio molitor Larvae and Feed under Optimal and Stressed Mass Rearing Conditions.

Simple SummaryA few insects are actually considered for mass production as an alternative protein source for animal feed, notably in the fish and poultry sector. Industrial insect rearing, aims at producing high quality insects, following secure sanitary conditions. As for other livestock’s optimal rearing conditions should avoid stress and pathogens. In this study we investigated how abiotic stresses (sieving, starvation and density) and the presence of the bacteria, Serratia marcescens, an opportunistic human and insect pathogen, affect the growth and survival of the yellow mealworm, Tenebrio molitor. We also set up tests to determine if this bacterium could survive in the rearing system by analysing over time its persistence in the feed, in the insect and in the feces. Our result indicate that the studied Serratia strain is not very virulent to the yellow mealworm, that it can persist in the rearing system and can be detected easily by using a selective growth medium. The stress factors showed no impact from sieving but positive importance was found from high larval density while starvation should be avoided. Serratia could be considered as a potential marker, in the assessment of infectious pressure in a rearing system, and should be monitored for sanitary risk issues as well.Industrial insect mass rearing aims to produce quality insects under safe sanitary conditions which can be compromised by pathogens and abiotic stressors. Therefore, knowledge on pathogen persistence, virulence and means of detection is of importance. This study focuses on the opportunistic pathogen Serratia marcescens (Sm) as a possible candidate to reveal sanitary issues in Tenebrio molitor (Tm) breeding. A screening test was performed to assess the impact of abiotic stressors (starvation, density and sieving) in presence and absence of Sm. Two Sm detection methods were conducted, and the kinetics of Sm persistence were investigated. Our results show that (i) the presence of Sm had a low but significant effect on Tm mortality, (ii) a short temporary starvation period had a negative impact on larval growth, (iii) the detection of Sm by q-PCR was sensitive but less convenient than a specific Sm growth media, (iv) the kinetics of persistence showed that Sm declined but survived for nine days in the feed and in the feces for three weeks. Both the relatively low virulence and the persistence in the environment suggest that Sm could be used as an indicator for the sanitary status of mealworm production.

Molecular detection of blood meal source up to three months since the last meal: Experimental starvation resistance in triatomines

The identification of Blood Meal Source (BMS) in hematophagous vectors contributes to a better understanding of the ecology of hemoparasite transmission. Those insects can endure long periods without feeding, waiting for a favorable setting. Although this represents an important behavior observed in those groups, such as triatomines, little is known about how time can affect BMS detection, especially considering extended periods. To comprehend to which extent this behavioral phenomenon can impact molecular detection, we submitted two groups of Rhodnius robustus to increasing periods of starvation under experimental conditions. It was possible to recover the BMS until the 12th week of the starvation process. Nymphs were more resistant to prolonged periods of starvation (up to more than 189 days) than adults (maximum of 137 days), with no significant difference between their weights after being fed. The study brought new insights to the understanding of Trypanosoma cruzi transmission by R. robustus in the nature, with a temporal perspective.

Med13 Plays a Dual Role in Promoting P‐Body Assembly

In response to stress, cells rapidly adjust gene expression, translation, and protein levels to mitigate damage and initiate repair pathways. The Cdk8 Kinase Module (CKM) is a highly conserved, detachable unit of the Mediator complex that plays a vital role in regulating transcription and communicating stress signals from the nucleus to other organelles. Previously, our laboratory has shown that the scaffold protein within the CKM, Med13, is exported from the nucleus and degraded via a selective autophagy pathway following nitrogen starvation. In periods of starvation, cells attenuate translation and biosynthetic pathways to reserve nutrient pools. To rapidly adapt to starvation, cytosolic ribonucleoprotein (RNP) granules such as processing bodies (P‐bodies) tightly regulate mRNA accessibility and translation. Here we show that Med13 plays a dual role in promoting P‐body assembly. In physiological conditions, Med13 functions as a positive transcriptional regulator of P‐body formation as the deletion of MED13 significantly decreases the quantity of P‐bodies. In addition, during stress Med13 co‐localizes with the P‐body marker, Edc3, suggesting that Med13 may also play a scaffolding role within these membrane‐less organelles. Taken together, these data demonstrate the duality of Med13 as a transcriptional regulator of P‐bodies in unstressed conditions and a scaffolding component during stress. The nutrient sensing kinase, Ksp1, plays an important role in mediating P‐body localization of Med13 and other mRNA binding proteins following nitrogen starvation. These data demonstrate a novel cytosolic role for Med13 and expand the known proteome of P‐bodies.

Coping with starvation: Cysteine keeps mTORC1 suppressed to ensure survival

Jouandin etal. (2022) show that lysosomal-derived cysteine serves as a signal to promote the tricarboxylic acid (TCA) cycle and suppress TORC1 signaling for Drosophila to endure starvation periods.

Distinct Survival, Growth Lag, and rRNA Degradation Kinetics during Long-Term Starvation for Carbon or Phosphate.

ABSTRACTThe stationary phase is the general term for the state a bacterial culture reaches when no further increase in cell mass occurs due to exhaustion of nutrients in the growth medium. Depending on the type of nutrient that is first depleted, the metabolic state of the stationary phase cells may vary greatly, and the subsistence strategies that best support cell survival may differ. As ribosomes play a central role in bacterial growth and energy expenditure, ribosome preservation is a key element of such strategies. To investigate the degree of ribosome preservation during long-term starvation, we compared the dynamics of rRNA levels of carbon-starved and phosphorus-starved Escherichia coli cultures for up to 28 days. The starved cultures’ contents of full-length 16S and 23S rRNA decreased as the starvation proceeded in both cases, and phosphorus starvation resulted in much more rapid rRNA degradation than carbon starvation. Bacterial survival and regrowth kinetics were also quantified. Upon replenishment of the nutrient in question, carbon-starved cells resumed growth faster than cells starved for phosphate for the equivalent amount of time, and for both conditions, the lag time increased with the starvation time. While these results are in accordance with the hypothesis that cells with a larger ribosome pool recover more readily upon replenishment of nutrients, we also observed that the lag time kept increasing with increasing starvation time, also when the amount of rRNA per viable cell remained constant, highlighting that lag time is not a simple function of ribosome content under long-term starvation conditions.IMPORTANCE The exponential growth of bacterial populations is punctuated by long or short periods of starvation lasting from the point of nutrient exhaustion until nutrients are replenished. To understand the consequences of long-term starvation for Escherichia coli cells, we performed month-long carbon and phosphorus starvation experiments and measured three key phenotypes of the cultures, namely, the survival of the cells, the time needed for them to resume growth after nutrient replenishment, and the levels of intact rRNA preserved in the cultures. The starved cultures’ concentration of rRNA dropped with starvation time, as did cell survival, while the lag time needed for regrowth increased. While all three phenotypes were more severely affected during starvation for phosphorus than for carbon, our results demonstrate that neither survival nor lag time is correlated with ribosome content in a straightforward manner.