Specific Consumption Rate Research Articles

Quantitative Analysis of the High Temperature-induced Glycolytic Flux Increase in Saccharomyces cerevisiae Reveals Dominant Metabolic Regulation

A major challenge in systems biology lies in the integration of processes occurring at different levels, such as transcription, translation, and metabolism, to understand the functioning of a living cell in its environment. We studied the high temperature-induced glycolytic flux increase in Saccharomyces cerevisiae and investigated the regulatory mechanisms underlying this increase. We used glucose-limited chemostat cultures to separate regulatory effects of temperature from effects on growth rate. Growth at increased temperature (38 degrees C versus 30 degrees C) resulted in a strongly increased glycolytic flux, accompanied by a switch from respiration to a partially fermentative metabolism. We observed an increased flux through all enzymes, ranging from 5- to 10-fold. We quantified the contributions of direct temperature effects on enzyme activities, the gene expression cascade and shifts in the metabolic network, to the increased flux through each enzyme. To do this we adapted flux regulation analysis. We show that the direct effect of temperature on enzyme kinetics can be included as a separate term. Together with hierarchical regulation and metabolic regulation, this term explains the total flux change between two steady states. Surprisingly, the effect of the cultivation temperature on enzyme catalytic capacity, both directly through the Arrhenius effect and indirectly through adapted gene expression, is only a moderate contribution to the increased glycolytic flux for most enzymes. The changes in flux are therefore largely caused by changes in the interaction of the enzymes with substrates, products, and effectors.

Genotyping by Amplified Fragment Length Polymorphism and malate metabolism performances of indigenous Oenococcus oeni strains isolated from Primitivo wine

The Amplified Fragment Length Polymorphism (AFLP) technique was applied for the first time to investigate the genotyping of Oenococcus oeni, the most important species involved in malolactic fermentation (MLF) in wine. A total of 87 out of 220 lactic acid bacteria, isolates from “Primitivo” wine (Apulia, Italy) undergoing MLF, identified as O. oeni by species-specific PCR and 16S rRNA sequence analysis, were studied by AFLP analysis. Four main clusters were distinguished and three of them showed intraspecific homology higher than 60%. A total of 28 strains, representative of AFLP clusters, were tested for malate metabolism in order to gain information on their malolactic performances. Significant differences were observed among strains for malic acid consumed, biomass produced and specific malic acid consumption rate. These findings indicated that AFLP technique is reliable for typing O. oeni strains and that, together with metabolism studies it may be used to individuate possible candidates as industrial malolactic starters.

Kinetic measurement of biological oxidation of ferrous iron at low ferric to ferrous ratios in a controlled potential batch reactor

Traditionally, the kinetics of microbial ferrous iron oxidation have been studied in continuous or in batch culture. Both methods have drawbacks: in continuous culture experiments have to be repeated at a number of dilution rates to cover the entire spectrum of ferrous to ferric ratios, which is time-consuming. Furthermore, experiments at very low ferric-to-ferrous ratios require high dilution rates which are close to or exceed those at which wash-out occurs. In batch experiments, on the other hand, the prevalent ferric to ferrous ratio rapidly changes due to substrate depletion while the microbial population continually grows, making determination of specific momentary rates difficult. The present paper describes initial work with a novel device, the Redostat™, which allows careful electrochemical control of ferric to ferrous ratio in a batch reactor. A culture of Leptospirillum ferriphilum was grown at 35 °C and 5 g dm − 3 total iron by maintaining the ferric to ferrous ratio at 0.17, 0.51 and 1.65 (corresponding to redox potentials of 419, 452 and 482 mV vs. Ag/AgCl), respectively. The correlation of data obtained from off-gas and current measurements was excellent, and fitted Monod kinetics with ferric inhibition. A hitherto unobserved effect indicates the onset of ferric iron inhibition at the low redox potentials employed here. It was also noted that the biomass concentration has an effect on the biomass specific ferrous iron consumption rate and the biomass yield on ferrous iron.

Effects of different glycerol feeding strategies on S-adenosyl- l-methionine biosynthesis by P GAP-driven Pichia pastoris overexpressing methionine adenosyltransferase

Methionine adenosyltransferase (MAT) was overexpressed within Pichia pastoris employing the promoter of glyceraldehyde-3-phosphate dehydrogenase gene (P GAP), to biosynthesize S-adenosyl- l-methionine (SAM). Effects of five glycerol feeding tactics on MAT activity were first investigated. Strategies A–C were based on limited feeding correlated with dissolved oxygen (DO) at 50.0%, 25.0% and 0.0%, respectively. For strategies D and E, unlimited supplementation was executed by pulsed feeding mode. Gradual decline (2–0%) (w:v) of the residual glycerol level was shown between any two pulses in strategy D, while a nearly stable content (2%) throughout fed-batch cultivation with strategy E. With shifting strategies A–E in alphabetical order, gradual improvements of MAT activities were achieved, with the maximum of 9.05 U g −1 dried biomass for strategy E, since the specific glycerol consumption rate ( F G) ascended due to the elevated specific oxygen uptake rate ( q O 2 ). The success was ascribed to the enhancement of oxygen transfer rate (OTR), because 2% glycerol improved oxygen saturation content in broth ( C*) and volumetric oxygen transfer coefficient ( k L a). Strategy E also led to the highest values of ATP and biomass besides MAT. Consequently, the highest SAM yield and volumetric level were obtained at 0.058 g g −1 and 9.26 g l −1, respectively.

Effect of loading rate on TOC consumption efficiency in a sulfate reducing process: sulfide effect in batch culture

AbstractBACKGROUND: The sulfate reducing process (SRP) was analyzed in order to identify factors that diminish the effectiveness of the SRP during wastewater treatment. The effect of different sulfate loading rates (SLR, 290 to 981 mg SO4‐S L−1d−1) and lactate at a stoichiometric C/S ratio of 0.75 on SRP was studied in an upflow anaerobic sludge blanket (UASB) reactor. The effect of sulfide concentration (0 to 200 mg sulfide‐S L−1) on SRP in batch culture was evaluated.RESULTS: When the SLR was increased, the total organic carbon (TOC) and sulfate consumption efficiencies decreased from 93% ± 3 to 66% ± 2 and 60% ± 5 to 45% ± 4, respectively. Acetate and propionate were accumulated. Microbial analysis showed the presence of microorganisms related with the SRP, fermentation and methanogenesis. In batch culture, when lactate and sulfate were present, SRP and fermentation were observed. When sulfide was added only SRP was observed. At concentrations higher than 150 mg sulfide‐S L−1 the efficiencies, yields and specific consumption rates (q) decreased.CONCLUSION: Based on the sulfide‐S/volatile suspended solid ratio, it was found that the decrease in efficiency and accumulation of acetate and propionate in the UASB reactor was not related to sulfide inhibition but to the q of acetate and propionate, which were up to 11 times lower than lactate. Copyright © 2008 Society of Chemical Industry

Production of the exopolysacchzrides by Streptococcus thermophilus: Effect of growth conditions on fermentation kinetics and intrinsic viscosity

Production of exopolysacharides (EPS) by a commercial Streptococcus thermophilus strain was evaluated at different growth conditions [temperature (32–45 °C), carbon source and initial nitrogen (N) content]. Lactose from deproteinized whey and sucrose allowed to obtain EPS yields higher than 1200 mg/mM of the consumed carbon source. Intrinsic viscosity of the EPS was significantly reduced by ionic strength indicating a polyelectrolyte behavior. Growth conditions used for the production of the EPS had a significant effect ( p < 0.05) on the intrinsic viscosity. This was attributed to the effect of growth conditions on the molecular properties of the EPS [stiffness and molecular weight (MW)]. High MW EPS were produced when the bacteria grew at a high specific growth rate; however MW of the EPS and specific growth rate were not linearly associated. In the lactose fermentations carried out at different temperatures specific EPS synthesis rate was positive and linearly associated with the specific lactose consumption rate ( R 2 = 0.967) and specific galactose production rate ( R 2 = 0.967). Critical coil overlap parameter, [ η] C⁎, for the EPS produced in the lactose fermentations carried out at 43 and 45 °C was determined to be approximately 7.6, and their critical overlap concentrations ( C⁎) were 0.45 and 0.87 g/dL, respectively.

Kinetics of batch microbial degradation of phenols by indigenous Pseudomonas fluorescence

The potential of various organisms to metabolize organic compounds has been observed to be a potentially effective means in disposing of hazardous and toxic wastes. Phenols and their compounds have long been recognized as one of the most recalcitrant and persistent organic chemicals in the environment. The bioremediation potential of an indigenous Pseudomonas fluorescence was studied in batch culture using synthetic phenol in water in the concentration range of (100–500) mg/L as a model limiting substrate. The effect of initial phenol concentration on the degradation process was investigated. Phenol was completely degraded at different cultivation times for the different initial phenol concentrations. Increasing the initial phenol concentration from 100 mg/L to 500 mg/L increased the lag phase from 0 to 66 h and correspondingly prolonged the degradation process from 84 h to 354 h. There was decrease in biodegradation rate as initial phenol concentration increased. Fitting data into Monod kinetic model showed the inhibition effect of phenol The kinetic parameters have been estimated up to initial phenol concentration of 500 mg/ L. The rsmax decreased and Ks increased with higher concentration of phenol. The rsmaxhas been found to be a strong function of initial phenol concentration. The culture followed substrate inhibition kinetics and the specific phenol consumption rates were fitted to Haldane, Yano and Koga, Aiba et al., Teissier and Webb models. Between the five inhibition models, the Haldane model was found to give the best fit. Therefore, the biokinetic constants estimated using these models showed good potential of the Pseudomonas fluorescence and the possibility of using it in bioremediation of phenol waste effluents.

Significance of acetogenic H2 consumption in dark fermentation and effectiveness of pH

Two identical thermophilic H(2) fermenters (R1 and R2) were operated at different pH levels between 4.7 and 5.7. In R1, several unexpected and severe drops in H(2) yield inversely proportional to increase in acetate production were experienced at pH 5.5 and 5.7. In contrast, R2 operated at pH 5 and 4.7 performed more stable H(2) production mainly through butyrate fermentation. Although the H(2) partial pressure (>50 kPa) was far above the favorable values, acetate was produced as well as butyrate in all pH levels tested. To determine whether some portion of the acetate is produced through another pathway such as autotrophic synthesis via H(2) dependent reduction of CO(2) or not, batch dissolved H(2) consumption rate tests were performed at pH 5.0, 5.5 and 6. The specific H(2) consumption rate was 488(+/-49) micromol/gVSS.hr at pH 6 and slightly higher than at pH 5 and 5.5. The results of continuous and batch experiments revealed that acetogenic H(2) consumption is more favorable at pH levels above 5.5 and is one of the reasons of instabilities in dark fermentative H(2) production.

Inhibition Kinetics of Phenol Degradation by Pseudomonas aeruginosa from Continuous Culture and Washout Data

ABSTRACT Steady states of a continuous culture with an inhibitory substrate were used to estimate kinetic parameters under substrate limitation (chemostat operation). Pure cultures of an indigenous Pseudomonas aeruginosa were grown in continuous culture on phenol, the sole source of carbon and energy, at dilution rates of 0.010 to 0.20 h− 1. Using different dilution rates, several steady states were investigated and the specific phenol consumption rates were calculated. In addition, phenol degradation was investigated by increasing the dilution rate above the critical dilution rate (washout cultivation). The results showed that the specific phenol consumption rate increased with increased dilution rate at steady state and that the degradation by Pseudomonas aeruginosa can be described by simple substrate inhibition kinetics under substrate limitation but cannot be described by simple substrate inhibition kinetics under washout cultivation. Fitting of the steady-state data from continuous cultivation to various inhibition models resulted in the best fit for the Yano and Koga kinetic inhibition model. The r s max value of 0.278 mg/mg/h obtained from the Yano and Koga equation was comparable to the experimentally calculated r s max value of 0.283 mg/mg/h obtained under washout cultivation.

The effect of pharmaceuticals on the kinetics of methanogenesis and acetogenesis

In this study, the widely used anaerobic digestion model (ADM1) was used in order to simulate the inhibition of three pharmaceuticals, propranolol hydrochloride, ofloxacin and diclofenac sodium, on two groups of microorganisms, acetogens and acetoclastic methanogens, the most sensitive microorganisms groups involved in the anaerobic digestion process. The specific maximum consumption rate and saturation constant of acetate and propionate degraders were estimated through fitting the model to experimental data taken from continuous and batch experiments. A modified non-competitive inhibition function was used, and the inhibition constants were estimated using data from Batch experiments conducted at various concentrations of pharmaceuticals using enriched cultures with propionate and acetate degraders. It was found that propranolol hydrochloride was the most inhibitory pharmaceutical to both microorganisms groups.

Transcription of hexose transporters of Saccharomyces cerevisiae is affected by change in oxygen provision

BackgroundThe gene family of hexose transporters in Saccharomyces cerevisiae consists of 20 members; 18 genes encoding transporters (HXT1-HXT17, GAL2) and two genes encoding sensors (SNF3, RGT2). The effect of oxygen provision on the expression of these genes was studied in glucose-limited chemostat cultivations (D = 0.10 h-1, pH 5, 30°C). Transcript levels were measured from cells grown in five steady state oxygen levels (0, 0.5, 1, 2.8 and 20.9% O2), and from cells under conditions in which oxygen was introduced to anaerobic cultures or removed from cultures receiving oxygen.ResultsThe expression pattern of the HXT gene family was distinct in cells grown under aerobic, hypoxic and anaerobic conditions. The transcription of HXT2, HXT4 and HXT5 was low when the oxygen concentration in the cultures was low, both under steady state and non-steady state conditions, whereas the expression of HXT6, HXT13 and HXT15/16 was higher in hypoxic than in fully aerobic or anaerobic conditions. None of the HXT genes showed higher transcript levels in strictly anaerobic conditions. Expression of HXT9, HXT14 and GAL2 was not detected under the culture conditions studied.ConclusionWhen oxygen becomes limiting in a glucose-limited chemostat cultivation, the glucose uptake rate per cell increases. However, the expression of none of the hexose transporter encoding genes was increased in anaerobic conditions. It thus seems that the decrease in the moderately low affinity uptake and consequently the relative increase of high affinity uptake may itself allow the higher specific glucose consumption rate to occur in anaerobic compared to aerobic conditions.

Effect of prolonged hypoxia on food consumption, respiration, growth and reproduction in marine scavenging gastropod Nassarius festivus

The effects of prolonged exposure to reduced oxygen levels (3.0 and 1.5 mg O 2 l −1) on marine scavenging gastropods Nassarius festivus were studied for 8 weeks. The percentages of individuals engaged in feeding and amount of food consumed were reduced as oxygen level decreased; absorption efficiency, however, did not vary significantly with oxygen level. Oxygen consumption rates and specific oxygen consumption rates were lower at reduced oxygen levels. Reproduction occurred at all oxygen levels with less egg capsules being produced at lower oxygen levels. Egg size and number of eggs per capsule, however, were not significantly affected by oxygen level. The increase in shell length was 12%, 6% and 5% at 6.0 mg O 2 l −1 (normoxia), 3.0 mg O 2 l −1 and 1.5 mg O 2 l −1, respectively. At the end of the experiment, the amount of energy allocated to growth and reproduction decreased at reduced oxygen levels with values obtained at 3.0 mg O 2 l −1 and 1.5 mg O 2 l −1 being 48% and 70% lower than those at 6.0 mg O 2 l −1. At all oxygen levels, most of the accumulated energy was allocated to shell growth and reproduction, and the amount allocated to somatic growth was relatively insignificant. The reduction in energy allocated to reproduction was greater than that to shell growth as the oxygen level was reduced, indicating a strategic energy allocation of marine scavengers under stressful conditions to enhance survival.

Growth, condition, diet, and consumption rates of northern pike in three Arizona reservoirs

Northern pike (Esox lucius L.) introductions are controversial in the western United States due to suspected impacts they might have on established sport fisheries and potential illegal introductions. Three Arizona reservoirs, Parker Canyon Lake, Upper Lake Mary and Long Lake were sampled to examine the diet, consumption dynamics, and growth of northern pike. Northern pike diets varied by season and reservoir. In Parker Canyon Lake, diets were dominated by rainbow trout in winter and spring and bluegill and green sunfish in the fall. In Long Lake the northern pike ate crayfish in spring and early summer and switched to young of the year common carp in summer and fall. Black crappie, golden shiners, and crayfish were the major prey in Upper Lake Mary during spring, but they switched to stocked rainbow trout in the fall. Northern pike growth was in the high range of growth reported throughout the United States. Estimated northern pike specific consumption rate (scr) of rainbow trout (g/g/d × 10−6) was greatest in Upper Lake Mary (scr = 329.1 ± 23.7 g/g/d × 10−6) where stocked fingerling (<120 mm total length [TL]) rainbow trout were most vulnerable to these predators, compared to larger (>280 mm TL) rainbow trout stocked in Long Lake (scr = 1.4 ± 0.1 g/g/d × 10−6) and Parker Canyon Lake (scr = 287.2 ± 15.1 g/g/d × 10−6) where catchable-sized rainbow trout were stocked. Managers should consider the cost-benefits of stocking fish >200 mm TL in lakes containing northern pike.

Contribution of Citrate Metabolism to the Growth of Lactococcus lactis CRL264 at Low pH

Lactococcus lactis subsp. lactis biovar diacetylactis CRL264 is a natural strain isolated from cheese (F. Sesma, D. Gardiol, A. P. de Ruiz Holgado, and D. de Mendoza, Appl. Environ. Microbiol. 56:2099-2103, 1990). The effect of citrate on the growth parameters at a very acidic pH value was studied with this strain and with derivatives whose citrate uptake capacity was genetically manipulated. The culture pH was maintained at 4.5 to prevent alkalinization of the medium, a well-known effect of citrate metabolism. In the presence of citrate, the maximum specific growth rate and the specific glucose consumption rate were stimulated. Moreover, a more efficient energy metabolism was revealed by analysis of the biomass yields relative to glucose consumption or ATP production. Thus, it was shown that the beneficial effect of citrate on growth under acid stress conditions is not primarily due to the concomitant alkalinization of the medium but stems from less expenditure of ATP, derived from glucose catabolism, to achieve pH homeostasis. After citrate depletion, a deleterious effect on the final biomass was apparent due to organic acid accumulation, particularly acetic acid. On the other hand, citrate metabolism endowed cells with extra ability to counteract lactic and acetic acid toxicity. In vivo 13C nuclear magnetic resonance provided strong evidence for the operation of a citrate/lactate exchanger. Interestingly, the greater capacity for citrate transport correlated positively with the final biomass and growth rates of the citrate-utilizing strains. We propose that increasing the citrate transport capacity of CRL264 could be a useful strategy to improve further the ability of this strain to cope with strongly acidic conditions.

A kriging interpolation strategy for the optimization of Acidithiobacillus ferrooxidans biomass production using fed-batch bioreactors

In this work, a procedure for the optimization of Acidithiobacillus ferrooxidans biomass production in fed-batch reactors using a model based on optimal spatial interpolation of experimental data is proposed. The approach is useful in those cases where specific growth and substrate consumption rates are unknown. Based on interpolation, the optimal values of biomass and substrate concentrations set points are obtained at the minimum of 2-dimensional cost function. In the fed-batch reactor biomass and substrate concentrations are controlled at their set points by changing the input flow and its concentration. We propose a minimum variance control strategy which improves the classical proportional plus integral control. Since the interpolation is optimal, the proposed linear control strategy allows obtaining a tight minimized upper bound of the variance error in the controlled variables.

Effect of pH and inoculum size on pentachlorophenol degradation by &lt;i&gt;Pseudomonas sp.&lt;/i&gt;

Pentachlorophenol (PCP) is a toxic compound which is used as a fungicide, bactericide, herbicide and chemical intermediate. Because of its toxicity, there is a need to decontaminate the PCP-laden soils and bioremediation is a very useful alternative to conventional clean-up methods. The success of this depends on finding strains able to degrade PCP in a changeable environment. The aim of this work was to study the influence of pH of the medium and the effect of inoculum size on pentachlorophenol degradation by Pseudomonas sp. A study of PCP degradation kinetics was performed to assess such effects. PCP was degraded rapidly at pH values from 6.3 to 8, but the maximum rate of PCP degradation by Pseudomonas sp. was at pH 6.3. In contrast, the PCP degradation kinetics at pH 5.5 were significantly lower, although PCP was totally depleted. These results show the broad range of pHs for PCP degradation for this strain. PCP was degraded at every inoculum size tested and PCP degradation increased with the increasing inoculum size, but cultures inoculated with the lowest inoculum showed the highest specific consumption rate. This reveals a lower consumption of PCP per CFU at a high population density. These results are useful to understand the physiological and biochemical properties of Pseudomonas sp. before its optimum use in environmental application and these data will assist in choosing the right PCP-degrader for a changeable environment. Water SA Vol 32(1)pp:93-98

Effects of anionic surfactant and salinity on the bioenergetics of juveniles of Centropomus parallelus (Poey)

The acute and sublethal chronic effects of sodium dodecyl sulphate (SDS) on the survival, metabolism, and growth of juveniles of Centropomus parallelus were investigated at three different salinities. Results of 96 h LC50 test showed that juveniles of C. parallelus were very sensitive to SDS in comparison to other species investigated. For each group of exposure to nominal concentrations of SDS (0.10 and 0.25 mg/L) and the control group (0.0 mg/L), at the different salinities (5, 20, and 30) there were significant differences in the specific growth rate, oxygen consumption, and ammonia excretion rates, O:N atomic ratio at the different exposure periods (15 and 30 days). There were also interactions between factors for the parameters investigated. The present results show a pronounced effect of SDS, mainly at the highest concentration and salinity, as well as after a long time of exposure.

KINETICS OF PHENOL AND BENZOATE BIODEGRADATION IN STATIC CULTIVATION SYSTEM BY Burkholderia cepacia G4.

Kinetics of phenol and benzoate degradation by Burkholderia cepacia G4 in classical batch mode of static culture were investigated over a wide range of initial substrate concentrations applied as single substrates. Due to better adaptation to changing conditions, faster degradation of both phenol and benzoate was observed when higher concentrations were used. The results show decrease of the biomass yield coefficient, YX/S, from 0.83 to 0.31 g g-1 when the initial phenol concentration was increased from 0.54 to 0.73 g L-1, supporting the well known inhibitory effect of phenol. On the other hand, linear increasing of the yield coefficient was observed with increasing benzoate concentration. During all experiments, maximum specific substrate consumption rates, rSmax, were reached to 0.27 g g-1h-1 for phenol and to 0.40 g g-1h-1 when benzoate was the sole source of carbon in the bioreactor. In the present study, minor inhibitory effect of benzoate was observed during their investigated concentration range. To explain their degradation modelling, experimental data of both phenol and benzoate biodegradation were fitted using various kinetic models. The results demonstrated that the Yano and Koga equation gave the best fit, compared with the other models. It means that biodegradation of phenol and benzoate can be described by the same kinetic model. Based on the kinetic data, all experiments were not sensitive to change in the saturation constant, KS; therefore, KS-value was fixed at 0.042 and 0.068 g L-1 for phenol and benzoate, respectively. After that, rSmax and the inhibition constant, Ki, parameters were re-fitted in all experiments. In general, the kinetic parameters of both phenol and benzoate degradation were influenced by the initial substrate and bacterial cell mass concentrations, in addition to adaptation with changing in the culture conditions.

Sugar utilization patterns and respiro-fermentative metabolism in the baker's yeast Torulaspora delbrueckii

The highly osmo- and cryotolerant yeast species Torulaspora delbrueckii is an important case study among the non-Saccharomyces yeast species. The strain T. delbrueckii PYCC 5321, isolated from traditional corn and rye bread dough in northern Portugal, is considered particularly interesting for the baking industry. This paper reports the sugar utilization patterns of this strain, using media with glucose, maltose and sucrose, alone or in mixtures. Kinetics of growth, biomass and ethanol yields, fermentation and respiration rates, hydrolase activities and sugar uptake rates were used to infer the potential applied relevance of this yeast in comparison to a conventional baker's strain of Saccharomyces cerevisiae. The results showed that both maltase and maltose transport in T. delbrueckii were subject to glucose repression and maltose induction, whereas invertase was subject to glucose control but not dependent on sucrose induction. A comparative analysis of specific sugar consumption rates and transport capacities suggests that the transport step limits both glucose and maltose metabolism. Specific rates of CO(2) production and O(2) consumption showed a significantly higher contribution of respiration to the overall metabolism in T. delbrueckii than in S. cerevisiae. This was reflected in the biomass yields from batch cultures and could represent an asset for the large-scale production of the former species. This work contributes to a better understanding of the physiology of a non-conventional yeast species, with a view to the full exploitation of T. delbrueckii by the baking industry.

A combined approach to understand trophic interactions between Cercopagis pengoi (Cladocera: Onychopoda) and mysids in the Gulf of Finland

We use molecular markers, feeding experiments, and stable isotopes to understand trophic interactions between native mysids, Mysis mixta and Mysis relicta, and a recent invader to the Baltic Sea, the cladoceran Cercopagis pengoi. In feeding experiments, both mysid species ingested C. pengoi at a maximum of 16 prey mysid‐1 d‐1 and a specific consumption rate of 0.15 d‐1, similar to rates reported for predation on other prey species. The frequency of predation on C. pengoi assayed by molecular diet analysis of field‐collected mysids varied between 5% and 43% depending on mysid size and species. Surprisingly, it was consistently higher in juveniles than in adults and in M. mixta than in M. relicta. The results of stable isotope analysis corroborate those of feeding experiments and molecular analysis and indicate a higher contribution of C. pengoi to the nutrition of juveniles and M. mixta. These ontogenetic and interspecific differences in mysid predation on C. pengoi are likely to reflect differences related to their different migratory behavior. Thus, despite its low relative abundance, C. pengoi is readily consumed by mysids; this may impact lower food web interactions and the nutrition of mysids in the invaded ecosystems.