DNA interaction with biologically active divalent metal ions: binding constants calculation

In our previous work we have shown that under the action of Cu²⁺, Mn²⁺ and Ca²⁺ ions DNA is able to transit into a compact state in aqueous solution. In the present work we carried out calculations of binding constants for divalent metal ions interacting with DNA in terms of the macromolecule statistical sum. The formula for calculation of the binding constants and cooperativity parameters was proposed. It was shown that on the “coil state”–“compact (globule) state” transition a single DNA molecule may undergo the first-order phase transition while the transition of the assembly of average DNA chains is of sigmoidal character typical of the cooperative and continuous transition.     

Effects of Basal [Ca]i on Calcium Handling in Ca-Overloaded Rat Cultured Heart Muscle Cells

To elucidate the relationship between intracellular free Ca²⁺ concentration ([Ca²⁺]_i) and Ca²⁺-signalling by the sarcoplasmic reticulum (SR) in Ca²⁺-overloaded heart muscle cells, the direct effects of “basal” [Ca²⁺]_i on calcium waves were investigated by altering the membrane potential. When basal inter-calcium wave (BCW) [Ca²⁺]_i was maintained at a high level, (i) calcium waves showed more gradual and more rapidly suppressed increase in [Ca²⁺]-profile (P < 0.005), and (ii) calcium waves occurred at a significantly higher frequency and velocity (259% and 137%), than when low BCW [Ca²⁺]_i was maintained. Similar investigations on inhibition of the Na⁺-Ca²⁺ exchanger, however, showed that membrane potential did not elicit direct effects on calcium waves. These results showed that the elevation of BCW [Ca²⁺]_i per se directly influences Ca²⁺-signalling in heart muscle cells through non-equilibrated release-restoration Ca²⁺-handling by the SR.     

The effect of infra-red radiation on rectal temperature and respiration rate of unacclimated female new zealand white rabbits

1. 1.|An experiment was carried out to examine the effects of various levels of infra-red (i.r.) radiation on rectal temperature (RT) and respiration rate (RR) in New Zealand While rabbits.

2. 2.|A 4 × 3 × 6 factorial design was employed in which the factors were: four intensities of i.r. radiant heating of 0.0, 1.9, 2.1 and 2.4 MJ/m²/h, three replicates and six rabbits.

3. 3.|rectal temperature differed (P < 0.05) between treatments and were highest at the “high” level of i.r. radiation (1°C higher than for controls). At the “medium” and “low” levels of i.r. heating RTs were respectively 0.3 and 0.2°C higher than in controls.

4. 4.|At different levels of radiation RR were different (P < 0.05), with the highest (422.7 ± 218.1 breaths/min) at 2.4 MJ/m²/h i.r. radiant heating. This RR was almost 2.5 times that in controls, while at the “low” and “medium” i.r. levels RR values were respectively 1.5 and 2 times those of controls.

Anthroyl stearate as a fluorescent probe of chloroplast membranes

1. A reversible light-induced enhancement of the fluorescence of a “hydrophobic fluorophore”, 12-(9-anthroyl)-stearic acid (anthroyl stearate), is observed with chloroplasts supporting phenazine methosulfate, cyclic or 1,1′-ethylene-2,2′-dipyridylium dibromide (Diquat) pseudo-cyclic electron flow; no fluorescence change is observed when methyl viologen or ferricyanide are used as electron acceptors. The stearic acid moiety of anthroyl stearate is important for its localization and fluorescence response in the thylakoid membrane, since structural analogs of anthroyl stearate lacking this group do not show the same response.

2. This effect is decreased under phosphorylating conditions (presence of ADP, P_i, Mg²⁺), and completely inhibited by the uncoupler of phosphorylation NH₄Cl (5–10 mM), as well as the ionophores nigericin and gramicidin-D (both at 5 · 10⁻⁸ M). The MgCl₂ concentration dependence of the anthroyl stearate enhancement effect is identical to that previously observed for cyclic photophosphorylation, as well as for the formation of a “high energy intermediate”. The anthroyl stearate fluorescence enhancement is inhibited by increasing concentrations of ionophores in parallel with the decrease in ATP synthesis, but is essentially unaffected by specific inhibitors (Dio-9 and phlorizin) of photophosphorylation; thus, it appears that anthroyl stearate monitors a component of the “high energy state” of the thylakoid membrane rather than a terminal phosphorylation step.

3. The light-induced anthroyl stearate fluorescence enhancement is suggested to monitor a proton gradient in the energized chloroplast because (a) similar enhancement can be produced by sudden injection of hydrogen ions in a solution of anthroyl stearate; (b) when the proton gradient is dissipated by gramicidin or nigericin light-induced anthroyl stearate fluorescence is eliminated; (c) when the proton gradient is dissipated by tetraphenylboron, light-induced anthroyl stearate fluorescence decreases, and (d) light-induced anthroyl stearate fluorescence change as a function of pH is qualitatively similar to that observed with other probes for a proton gradient (e.g. 9-aminoacridine). Furthermore, anthroyl stearate does not monitor H⁺ uptake per se because (a) the pH dependence of H⁺ transport is different from that of the anthroyl stearate fluorescence change, and (b) tetraphenylboron, which does not inhibit H⁺ uptake, reduces anthroyl stearate fluorescence.

Thus, anthroyl stearate appears to be a useful probe of a proton gradient supported by phenazine methosulfate or Diquat catalyzed electron flow and is the first “non-amine” fluorescence probe utilized for this purpose in chloroplasts.     

Effect of glutamate on extracellular potassium activity in isolated retina of cyprinid fish

The effect of ( -)glutamate on extracellular K⁺ activity of the isolated retina of the cyprinid fish, roach, was investigated using double-barrelled K⁺-sensitive micro-electrodes. Application of μM-mM glutamate to the retina as a “puff” from an atomizer induced a transient rise in extracellular K⁺ activity, which was maximal 50–100 μm below the photoreceptor surface. The effect was concentration-dependent, but not related to the state of light adaptation of the retina. In the presence of dinitrophenol or ouabain, the glutamate-induced increase in extracellular K⁺ activity was maintained.

The following conclusions are made. (1) The most likely cellular origin(s) of the glutamate-induced rise in extracellular K⁺ activity are the photoreceptors and/or the Muller (glial) cells. (2) The mechanism responsible for returning the extracellular K⁺ activity to normal depends strongly on metabolic, Na⁺, K⁺ pump activity. (3) The effect parallels the action of endogenous glutamate, and may be important for modulation of neurotransmission in the intact retina.     

A versatile colony assay based on NADH fluorescence

Direct visualization of the activity of enzymes expressed by bacterial colonies attached to a solid support, often referred to as “filter assay”, is a powerful strategy for the identification of new or improved biocatalysts. In this work we demonstrate the usefulness of NAD⁺/NADH coupled enzymatic reactions as visualization tool in such experimental setups. Dehydrogenases, capable of oxidizing or reducing the reaction product released from the bacterial colony were supplemented to the screening solution, together with the screening substrate and a sufficient amount of NAD⁺ or NADH, respectively. We also examined the screening of directly NAD⁺/NADH coupled reactions. The release or consumption of NADH in the area of colonies was monitored on behalf of its fluorescence at 450 nm. Excitation was achieved by standard “black-light” UV tubes (340–360 nm). The visible fluorescence signal was recorded using a CCD-camera. We got excellent results for the screening of threonine aldolases and esterases and were able to show the principle utility for amidase, nitrilase, nitrile hydratase, hydroxynitrile lyase and benzaldehyde dehydrogenase active colonies.     

Effects of moderate short-term potassium depletion in normal humans the role of prostaglandins

The role of prostaglandins (PG) in the effects of potassium (K⁺)depletion was studied in six normal women. A mean K⁺-deficit of 220 mEq was induced with and without concomitant treatment with indomethacin (150 mg/day). Mean serum K⁺ concentration decreased from 4.2 ± (S.E.) 0.1 to 3.2 ± 0.1 mEq/L without indomethacin and from 4.1 ± 0.1 to 3.2 ± 0.1 mEq/L with indomethacin. “Supine” and “upright” plasma renin activity (PRA) and plasma norepinephrine concentration (NE) were unaltered by K⁺ -depletion alone but decreased with indomethacin. Plasma aldosterone (PA) was suppressed during K⁺-depletion (control: 7.2 ± 2.6 ng/dl supine, 19.3 ± 8.1 ng/dl upright; K⁺-depletion: 2.6 ± 0.3 ng/dl supine, 5.5 ± 1.3 ng/dl upright) and was paralleled by a decrease in urinary aldosterone. K⁺-depletion decreased urinary PGE₂ from 667 ± 133 to 343 ± 60 ng/day (P < 0.025) without a change in PGF₂. The dose of exogenous angiotensin II (A II) which increased diastolic blood pressure by 20 mm Hg (pressor dose) was 7.1 ± 1.4 ng/kg/min during control and increased to 11.0 ± 0.7 ng/kg/min during K⁺-depletion (P < 0.05). Indomethacin increased the sensitivity to A II both during control (pressor dose: 4.9 ± 0.6 ng/kg/min) and K⁺- depletion (pressor dose: 6.0 ± 1.0 ng/kg/min). These results indicate that in healthy subjects, moderate short-term K⁺-depletion does not affect PRA or NE but decreases production of aldosterone and PGE₂ by the kidney. The changes in vascular sensitivity to exogenous A II during K⁺-depletion and indomethacin and the decreases in plasma NE and PRA during indomethacin may be explained by changes in vascular vasodilator PG.     

The Ca 2+ leak paradox and rogue ryanodine receptors: SR Ca 2+ efflux theory and practice

Ca²⁺ efflux from the sarcoplasmic reticulum (SR) is routed primarily through SR Ca²⁺ release channels (ryanodine receptors, RyRs). When clusters of RyRs are activated by trigger Ca²⁺ influx through L-type Ca²⁺ channels (dihydropyridine receptors, DHPR), Ca²⁺ sparks are observed. Close spatial coupling between DHPRs and RyR clusters and the relative insensitivity of RyRs to be triggered by Ca²⁺ together ensure the stability of this positive-feedback system of Ca²⁺ amplification. Despite evidence from single channel RyR gating experiments that phosphorylation of RyRs by protein kinase A (PKA) or calcium-calmodulin dependent protein kinase II (CAMK II) causes an increase in the sensitivity of the RyR to be triggered by [Ca²⁺]_i there is little clear evidence to date showing an increase in Ca²⁺ spark rate. Indeed, there is some evidence that the SR Ca²⁺ content may be decreased in hyperadrenergic disease states. The question is whether or not these observations are compatible with each other and with the development of arrhythmogenic extrasystoles that can occur under these conditions. Furthermore, the appearance of an increase in the SR Ca²⁺ “leak” under these conditions is perplexing. These and related complexities are analyzed and discussed in this report. Using simple mathematical modeling discussed in the context of recent experimental findings, a possible resolution to this paradox is proposed. The resolution depends upon two features of SR function that have not been confirmed directly but are broadly consistent with several lines of indirect evidence: (1) the existence of unclustered or “rogue” RyRs that may respond differently to local [Ca²⁺]_i in diastole and during the [Ca²⁺]_i transient; and (2) a decrease in cooperative or coupled gating between clustered RyRs in response to physiologic phosphorylation or hyper-phosphorylation of RyRs in disease states such as heart failure. Taken together, these two features may provide a framework that allows for an improved understanding of cardiac Ca²⁺ signaling.     

Effect of filipin on Rat-liver and yeast mitochondria

1. Under the appropriate conditions intact yeast and mammalian mitochondria exhibit a heretofore unobserved sensitivity to the polyene antibiotic, filipin. The activity of the “filipin complex” (Filipins I, II, III and IV) is shown to be primarily due to the component designated Filipin II.

2. Yeast mitochondria treated with filipin complex, or purified Filipin II, exhibit “uncoupled” succinate oxidation and inhibited -ketoglutarate oxidation. Maximum filipin effect is observed at a concentration of 4 mM Filipin II. Rat-liver mitochondria are more sensitive to filipin than yeast mitochondria, and respiratory inhibition is observed regardless of substrate.

3. In liver mitochondria filipin-inhibited respiration is not relieved by Mg²⁺, K⁺, Ca²⁺ or 2,4-dinitrophenol, but is reversed by cytochrome c.

4. It is proposed that filipin treatment leads to altered membrane permeability and that respiratory inhibition is due to a loss of endogenous respiratory cofactors or an inactivation of primary dehydrogenases. The filipin-uncoupled yeast respiration may likewise be attributed to an altered phosphate permeability of the yeast mitochondrial membranes.     

Réoxydation du quencher de fluorescence “Q” en présence de 3-(3,4-dichlorophényl)-1,1-diméthylurée

Reoxidation of the fluorescence quencher “Q” in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea

Reoxidation of the fluorescence quencher Q in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea shows the following properties:

It is sensitive to very low concentrations of hydroxylamine (a few μM).

It corresponds to a back reaction between Q⁻ and the primary oxidant Z⁺ formed in the light. A part of this back reaction gives rise to luminescence emission.

Within the range we studied the kinetic of reoxidation is second order with regards to Q⁻.     

Combination of u.v.-B. and ozone reduces pollen tube growth more than either stress alone

The rate of in vitro Nicotiana tabacum L. “Bel-W3” pollen tube growth was reduced 62 and 44%, respectively, when pollen tubes were exposed to 120 ppb ozone (O₃) for 3 hr or 300 μW/cm² ultraviolet-B (u.v.-B) radiation for 30 min. Petunia hybrida Vilm. “White Cascade” pollen tube growth was reduced 34 and 59%, respectively, upon exposure to O₃ or u.v.-B at the above doses. The combination of u.v.-B at 300 μW/cm² for 30 min, followed by O₃ at 120 ppb for 3 hr, reduced pollen tube growth by 79% for “Bel-W3” and 75% for “White Cascade”. The effect appeared to be additive, implying that different target areas may be affected by the two stressors. In the Northeast, plants are exposed to both u.v.-B and O₃ during the normal growing season. This may result in an unexpectedly higher stress on the reproductive system than had been previously suspected based on these two stressors acting individually.     

Improved salt tolerance of melon (Cucumis melo L.) by the addition of proline and potassium nitrate

A pot experiment was carried out under glasshouse conditions with melon (Cucumis melo) cv. “Tempo F1” in a mixture of peat, perlite and sand (1:1:1) to investigate the effects of external proline and potassium nitrate applications to salinity-treated (150 mM) plants with respect to fruit yield, plant growth, some physiological parameters and ion uptake. Treatments were—(i) control (C): plants receiving nutrient solution, (ii) salinity treatment, as for control plus 150 mM NaCl. Salinity treatment was combined with or without either 5 mM supplementary KNO₃ or 10 mM proline. The salt treatment (150 mM NaCl) led to significant decreases in plant growth, fruit yield, relative water content (RWC), stomatal density, uptake of Ca²⁺, K⁺ and N, and chlorophyll a and b contents, accompanied by significant increases in Na⁺ uptake, proline concentration and membrane permeability. Supplementary KNO₃ and proline treatments significantly ameliorated the adverse effects of salinity on plant growth, fruit yield and the physiological parameters examined. This could be attributed to the effects of all the external supplements in maintaining membrane permeability, and increasing concentrations of Ca²⁺, N and K⁺ in the leaves of plants subjected to salt stress.     

A low-temperature-sensitive intermediate state between S2 and S3 in photosynthetic water oxidation deduced by means of thermoluminescence measurements

The temperature dependence of S-state transitions in Photosystem II was measured by means of thermoluminescence using two different protocols for low-temperature flash excitation: protocol A, “last flash at low temperature”, and protocol B, “all flashes at low temperature”. Comparison of the temperature-dependence curves obtained by these two protocols revealed a marked difference particular for the three-flash experiments. The difference was attributed to the formation of a low-temperature sensitive precursor state between S₂ and S₃. The state is formed by two flash illumination given at −5 to −50°C, spontaneously transforms to normal S₃ on dark warming, and is not converted to S₀ by the 3rd flash. The precursor state was tentatively assigned to an S₃ in which H⁺ release is not completed.     

Binding of divalent copper and calcium ions to poly I

The effect ot Cu²⁺ and Ca²⁺ ions, on the ultraviolet differential (UVD) spectra of single-stranded poly I was studied and the coordination (Δε_b) and conformation (Δε_c) conponents of the spectra calculated The comparison of Δε_b and the UVD spectrum of protonated IMP leads to the conclusion that N(7) ot inosine-5'-monophosphate (IMP) is a coordinating site tor Ca²⁺ and Cu²⁺ ions on the polymer bases. The binding ot Ca²⁺ and Cu²⁺ ions causes differently directed displacements of the four absorption bands of poly I, which are observed in the wavenumber range (50-34) × 10³ cm⁻¹ The calculation of concentration dependencies tor the association constants (K“) ot Ca²⁺ and Cu²⁺ ions binding to poly I bases shows that the binding is cooperative The K“ values for the poly I + Ca²⁺ complex are two orders of magnitude lower than those for the poly 1 + Cu²⁺ complex At low ion concentrations, binding to the poly I phosphates predominates and increases the degree of the polynucleotide helicity. At higher concentrations the spectra are mainly affected by the ion binding to bases, which results in melting of the helical parts of poly I At Ca²⁺ concentrations exceeding 10⁻³ M light-scattering aggregates are formed. The degree of monomer order in them is close to that observed in multistranded helices of poly I     

Pigment systems and electron transport in chloroplasts I. Quantum requirements for the two light reactions in spinach chloroplasts

From studies of electron-transport reactions of isolated spinach chloroplasts, we observe the following quantum requirements: (A) For the photoreduction of NADP⁺, measured both aerobically and anaerobically, in a 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) poisoned system with ascorbate and reduced 2,6-dichlorophenolindophenol (DCIPH₂) present as electron donors, the quantum requirements are 1.0 ± 0.05 at wavelengths longer than 700 nm of actinic light, and 1.5–2.5 for wavelengths between 620 and 680 nm. (B) For the photoreduction of 2,6-dichlorophenolindophenol (DCIP) with water as the electron donor, the quantum requirements are 1.0 ± 0.05 in the range 630–660 nm. (C) For the photoreduction of NADP⁺ with water as the electron donor, the quantum requirements are 2.0 ± 0.1 in the wavelength range 640–678 nm of actinic light, increasing to 6 or greater at wavelengths beyond 700 nm. These results are shown to be inconsistent with the “separate package” model for the two pigment systems in higher plant photosynthetic electron transport. The evidence is most easily interpreted using a “controlled spillover” model, in which the transfer of electronic excitation energy from one pigment system to the other is under the control of incompletely identified factors in the reaction mixture.

At moderate light intensities the steady state rate of the [ascorbate + DCIPH₂ → NADP⁺] reaction (A) in the presence of DCMU and added ferredoxin can be increased more than 3 times when saturating amounts of plastocyanin and ferredoxin-NADP reductase are added to the chloroplasts. Similarly, the steady-state rate of the [H₂O → DCIP] Hill reaction (B) is increased about 3-fold by added MgCl₂ and plastocyanin, but added ferredoxin or ferredoxin-NADP reductase have no effect on this reaction. Plastocyanin appears to be the electron transport component which couples to DCIP, either in the oxidized or in the reduced form, in the reaction media. The steady-state rate of the [H₂O → NADP⁺] reaction (C) with saturating amounts of ferredoxin can be further increased more than 3-fold when MgCl₂, plastocyanin and ferredoxin-NADP reductase are added.     

Impact of vitamin E supplement in standard laboratory animal diet on microvascular manifestation of ischemia/reperfusion injury

Aimed at improving animal fertility and health, diets for farm and laboratory animals have over the last few years been supplemented with increasing amounts of the antioxidant vitamin E. We now demonstrate by intravital microscopy that feeding hamsters with a vitamin E-supplemented “standard” rodent diet (60 ppm vitamin E) significantly reduces the microvascular manifestations of ischemia/reperfusion injury when compared to animals fed a nonsupplemented diet. Postischemic leukocyte adhesion to venular endothelium was reduced from 770 ± 204 cells/mm² at 24 h after reperfusion in control animals on the nonsupplemented diet to 403 ± 105 cells/mm² in animals on the “standard” rodent diet (means ± SD, N = 7 animals per group, p < 0.01). Animals on the nonsupplemented diet showed a dramatic loss of capillary perfusion density until 7 days after reperfusion (to 21 ± 13% of preischemic baseline values), whereas this loss was significantly attenuated (to 71 ± 12% of preischemic values, p < 0.01) in animals on the “standard” rodent diet. No difference in the extent of reperfusion injury was seen between animals on the “standard” rodent diet and animals on diets with substantially higher vitamin E supplements (300 ppm–30.000 ppm). Besides underscoring the benefit of vitamin E in reducing the extent of ischemia/reperfusion injury, this study raises the concern that vitamin E supplements in “standard” laboratory animal diets may have a far-reaching impact on biomedical research by jeopardizing established animal models of disease.     

Effect of gamma radiation and alpha particles on gene recombination in Chlamydomonas reinhardi

Low doses of ⁶⁰Co γ radiation, which kill no more than about 5% of the zygospores, change gene recombination at only 2 short stages during the course of meiosis in Chlamydomonas reinhardi, but higher doses, which kill more than 10% of the spores, depress recombination at all stages up to pachytene. Irradiation with particles having a mean linear energy transfer (LET) of about 1300 and 1600 MeV g⁻¹ cm² changes recombination in a manner which appears to combine the effects characteristic of both low and high doses of γ-radiation simultaneously. The “γ high-dose” type of response has a relative biological effectiveness (RBE) of between 20 and 35, and the “γ low-dose” RBE is greater than 1 although precise evaluation is impossible due to the complexity of the response. The RBE for survival was 16.5 at the low dose levels studied.     

Self-reduction of the iron(III)-doxorubicin complex

The Fe³⁺-doxorubicin complex undergoes reactions that suggest that the complex self-reduces to a ferrous oxidized-doxorubicin free radical species. The Fe³⁺-doxorubicin system is observed to reduce ferricytochrome c, consume O₂ and react with 2,2′-bipyridine. Bipyridine acts as a “ferrous ion scavenger” as it reacts with the ferrous ion produced by Fe³⁺-doxorubicin self-reduction. In the absence of O₂, a ferrous doxorubicin complex accumulates. In the presence of oxygen, Fe²⁺ recycles back to Fe³⁺. The rates of these reactions were measured and the Fe³⁺-doxorubicin self-reduction was determined to be the rate-determining step. The Fe³⁺-doxorubicin induced inactivation of cytochrome c oxidase and NADH cytochrome c reductase on beef heart submitochondrial particles occurs at a rate similar to Fe³⁺-doxorubicin self-reduction. Thus the rate at which damage to these mitochondrial enzymes occurs may be controlled by a nonezymatic Fe³⁺-doxorubicin self-reduction.     

Mutation induction by thymine deprivation in Escherichia coli B/R. II. Mutation in the repressed and derepressed tryptophan operon.

True Trp⁺ reversions are induced by thymine deprivation in cells with repressed trp operons as efficiently as in derepressed cells. At least part of the mutations are fixed during thymine starvation, i.e. in the absence of net DNA synthesis. The hypothesis is put forward that thymineless mutagenesis is due to repair-replication under limited concentrations of 5′-dTTP, performed by an inducible error-prone “DNA-polymerizing activity” on single-strand gaps.     

Zooplankton feeding ecology: bacterivory by metazoan microzooplankton

Bacterivory by the rotifer Brachionus plicatilis Müller, nauplii and copepodites of the copepods Centropages Krøyer sp. and Acartia tonsa Dana, and the tintinnid Favella panamensis Kofoid & Campbell was examined using fluorescently labelled bacteria (FLB) and epifluorescence microscopy. FLB were < 1 μm in diameter, and were offered at environmental concentrations (1.47−9.08 × 10⁶ cells·ml⁻¹). FLB were visible within rotifers, nauplii, copepodites, and tintinnids, confirming ingestion. Rotifer clearance rates (32–418 μl·animal⁻¹·h⁻¹) exhibited no relation with FLB concentration. In some cases rates of clearance of FLB by rotifers were different with alternative phytoplankton food (Nanochloris Naumann sp.) than in replicates with FLB alone, whereas in other cases presence of alternative food exhibited no clear effects on rates of ingestion of FLB. Clearance rates for all six naupliar stages of A. tonsa nauplii (0–320 μl·animal⁻¹·h⁻¹) were stage-related, with higher rates by NIII-VI nauplii than NI-II nauplii. Nauplii had higher rates of clearance of FLB in the absence of alternative phytoplankton food (Isochrysis Parke sp.). Clearance rates of FLB by a single stage of Centropages sp. nauplii, A. tonsa CI copepodites and F. panamensis (each obtained at only a single food concentration of either 1.5 or 5.0 × 10⁶ cells·ml⁻¹) were within the range of 85–142 μl·animal⁻¹·h⁻¹. These ranges were similar to those of rotifers and A. tonsa nauplii. This is the first report of FLB ingestion by metazoan marine microzooplankton. Although rotifers and ciliates might be expected to ingest small particles such as FLB using ciliary induced feeding currents, the means by which nauplii and copepodites eat FLB is less clear. We propose that they may “eat” bacteria as they “drink” to osmoregulate.