Stationary Phase Of Cell Growth Research Articles

Isolation and characterization of thermophilic bacteria capable of lysing microbial cells in activated sludge

To find an efficient biological method to solubilize waste activated sludge (WAS) from the biological wastewater treatment process, several strains of thermophilic bacteria capable of solubilizing WAS were isolated from sewage sludge compost. The culture supernatants of the isolates were able to lyse vegetable bacterial cells and the lytic activity mainly came from the exoenzyme produced by the isolates. The culture supernatants of the different isolates showed different lysis characteristics. The factors affecting bacterial cell lysis were investigated using E. coli as a model bacterium. The E. coli cells were lysed easily at higher temperature (60 degrees C or 70 degrees C) while little lytic activity by the supernatants of isolates was observed at lower temperature (50 degrees C). The level of pH also had great influence on the lysis of E. coli cells. The E. coli cells in the early stationary growth phase were easier to lyse than those in the late stationary growth phase or death phase.

Growth Phase-dependent Activation of Nitrogen-related Genes by a Control Network of Group 1 and Group 2 σ Factors in a Cyanobacterium

It has been reported that an RNA polymerase sigma factor, SigC, mainly contributes to specific transcription from the promoter PglnB-54,-53 under nitrogen-deprived conditions during the stationary phase of cell growth in the cyanobacterium Synechocystis sp. strain PCC 6803 (Asayama, M., Imamura, S., Yoshihara, S., Miyazaki, A., Yoshida, N., Sazuka, T., Kaneko, T., Ohara, O., Tabata, S., Osanai, T., Tanaka, K., Takahashi, H., and Shirai, M. (2004) Biosci. Biotechnol. Biochem. 68, 477-487). In this study, we further examined the functions of group 2 sigma factors of RNA polymerase in NtcA-dependent nitrogen-related gene expression in PCC 6803. Results indicated that SigB and SigC contribute to the transcription from PglnB-54,-53 with a sigma factor replaced in a growth phase-dependent manner. We also confirmed the contribution of SigB and SigC to the transcription of other NtcA-dependent genes, glnA, sigE, and amt1, as in the case of glnB. On the other hand, the transcription of glnN was dependent on SigB and SigE. In the SigB and SigC-based regulation, the level of SigB increased, but that of SigC was constant under conditions of nitrogen deprivation. Furthermore, it was found that SigC negatively and positively regulates the level of SigB in the log and stationary phase, respectively. SigC also had a positive effect on the level of sigB transcript during the stationary phase. In contrast, SigB acts positively on SigC levels in both growth phases. These results and previous findings indicated that multiple group 2 sigma factors take part in the control of NtcA-dependent nitrogen-related gene expression in cooperation with a group 1 sigma factor, SigA.

Characterization of a Counterpart to Mammalian Ornithine Decarboxylase Antizyme in Prokaryotes

The degradation of mammalian ornithine decarboxylase (ODC) (EC 4.1.1.17) by 26 S proteasome, is accelerated by the ODC antizyme (AZ), a trigger protein involved in the specific degradation of eukaryotic ODC. In prokaryotes, AZ has not been found. Previously, we found that in Selenomonas ruminantium, a strictly anaerobic and Gram-negative bacterium, a drastic degradation of lysine decarboxylase (LDC; EC 4.1.1.18), which has decarboxylase activities toward both L-lysine and L-ornithine with similar K(m) values, occurs upon entry into the stationary phase of cell growth by protease together with a protein of 22 kDa (P22). Here, we show that P22 is a direct counterpart of eukaryotic AZ by the following evidence. (i) P22 synthesis is induced by putrescine but not cadaverine. (ii) P22 enhances the degradation of both mouse ODC and S. ruminantium LDC by a 26 S proteasome. (iii) S. ruminantium LDC degradation is also enhanced by mouse AZ replacing P22 in a cell-free extract from S. ruminantium. (iv) Both P22 and mouse AZ bind to S. ruminantium LDC but not to the LDC mutated in its binding site for P22 and AZ. In this report, we also show that P22 is a ribosomal protein of S. ruminantium.

Improvement of α-Amylase Production by Modulation of Ribosomal Component Protein S12 in Bacillus subtilis 168

The capacity of ribosomal modification to improve antibiotic production by Streptomyces spp. has already been demonstrated. Here we show that introduction of mutations that produce streptomycin resistance (str) also enhances alpha-amylase (and protease) production by a strain of Bacillus subtilis as estimated by measuring the enzyme activity. The str mutations are point mutations within rpsL, the gene encoding the ribosomal protein S12. In vivo as well as in vitro poly(U)-directed cell-free translation systems showed that among the various rpsL mutations K56R (which corresponds to position 42 in E. coli) was particularly effective at enhancing alpha-amylase production. Cells harboring the K56R mutant ribosome exhibited enhanced translational activity during the stationary phase of cell growth. In addition, the K56R mutant ribosome exhibited increased 70S complex stability in the presence of low Mg2+ concentrations. We therefore conclude that the observed increase in protein synthesis activity by the K56R mutant ribosome reflects increased stability of the 70S complex and is responsible for the increase in alpha-amylase production seen in the affected strain.

The whcE gene of Corynebacterium glutamicum is important for survival following heat and oxidative stress

In this study, we have analyzed an ORF from Corynebacterium glutamicum, which codes for a homologue of the Streptomyces coelicolor WhiB-family of proteins known to be involved in sporulation. This ORF encoded a putative protein which harbors a helix–turn–helix DNA-binding motif and a probable redox-sensing motif, and has been designated whcE. We constructed a whcE mutant strain and analyzed the strain under a variety of growth conditions. This mutant strain exhibited a prolonged lag phase and earlier death within the stationary phase, suggesting that the relevant gene may play a role in both growth adaptation and stress responses. Further analysis determined that the mutant strain was not only sensitive with regard to survival under heat stress, but was also markedly susceptible to thiol-specific oxidant diamide and redox cycling compounds, including menadione and plumbagin. The mutant strain also exhibited reductions in thioredoxin reductase activity, which indicates that the trxB gene encoding thioredoxin reductase is under the control of WhcE. Expression of whcE was stimulated during the stationary phase of cell growth and could be modulated by diamide. We also delineated the relationship between whcE and the sigH gene, which is located downstream of whcE, and has been shown to be involved in heat stress responses, via the encoding of an ECF σ factor. In a sigH mutant strain, the whcE gene was no longer expressed, thereby suggesting that the σ H sigma factor is involved in whcE expression. Our results suggest that WhcE functions as a transcription factor which can activate the trxB gene, as well as other genes, possibly by sensing redox changes during the metabolic downshifting of cells from exponential growth to the stationary phase, whereas σ H appears to function as the sigma factor for these genes, including whcE.

Activation of the plant plasma membrane H + -ATPase by phosphorylation and binding of 14-3-3 proteins converts a dimer into a hexamer

Plant plasma membrane H+-ATPases (PMAs) can be activated by phosphorylation of their penultimate residue (a Thr) and the subsequent binding of regulatory 14-3-3 proteins. Although 14-3-3 proteins usually exist as dimers and can bind two targets, the in vivo effects of their binding on the quaternary structure of H+-ATPases have never been examined. To address this question, we used a Nicotiana tabacum cell line expressing the Nicotiana plumbaginifolia PMA2 isoform with a 6-His tag. The purified PMA2 was mainly nonphosphorylated and 14-3-3-free, and it was shown by blue native gel electrophoresis and chemical cross-linking to exist as a dimer. Fusicoccin treatment of the cells resulted in a dramatic increase in Thr phosphorylation, 14-3-3 binding, and in vivo and in vitro ATPase activity, as well as in the conversion of the dimer into a larger, possibly hexameric, complex. PMA2 phosphorylation and 14-3-3 binding were observed also when cells in stationary growth phase were metabolically activated by transfer to fresh medium. When expressed in yeast, PMA2 was also phosphorylated and formed a complex with 14-3-3 proteins without requiring fusicoccin; no complex was observed when phosphorylation was prevented by mutagenesis. Single-particle analysis by cryoelectron microscopy showed that the PMA2-14-3-3 complex is a wheel-like structure with a 6-fold symmetry, suggesting that the activated complex consists of six H+-ATPase molecules and six 14-3-3 molecules.

Phosphorylation by Pho85 Cyclin-dependent Kinase Acts as a Signal for the Down-regulation of the Yeast Sphingoid Long-chain Base Kinase Lcb4 during the Stationary Phase

Sphingoid long-chain base 1-phosphates (LCBPs) act as bioactive lipid molecules in eukaryotic cells. In yeast, LCBPs are synthesized mainly by the long-chain base kinase Lcb4p. Until now, the regulatory mechanism for Lcb4p has been unclear. In the present study, we found that Lcb4p is post-translationally modified by phosphorylation. Using a protein kinase mutant yeast collection, we further demonstrated that the cyclin-dependent kinase Pho85p is involved in this phosphorylation. Pho85p functions in a number of cellular processes, especially in response to environmental changes. Two of 10 Pho85p cyclins, Pcl1p and Pcl2p had overlapping functions in the phosphorylation of Lcb4p. Site-directed mutagenesis identified the phosphorylation sites in Lcb4p as Ser(451) and Ser(455). Additionally, pulse-chase experiments revealed that Lcb4p is degraded via the ubiquitin-dependent pathway. The protein was stabilized in Deltapho85 cells, suggesting that phosphorylation acts as a signal for the degradation. Lcb4p is down-regulated in the stationary phase of cell growth, and both phosphorylation and ubiquitination appear to be important for this process. Moreover, we demonstrated that Lcb4p is delivered to the vacuole for degradation via the multivesicular body. Since forced accumulation of LCBPs results in prolonged growth during the stationary phase, down-regulation of Lcb4p may be physiologically important for proper cellular responses to nutrient deprivation.

Two-dimensional electrophoresis database of Listeria monocytogenes EGDe proteome and proteomic analysis of mid-log and stationary growth phase cells.

Listeria monocytogenes is the causative agent of listeriosis, one of the most significant foodborne diseases in industrialized countries. The complete genome of the L. monocytogenes EGDe strain, belonging to the serogroup 1/2a, has been sequenced and is comprised of 2853 open reading frames. The objective of the current study was to construct a two-dimensional (2-D) database of the proteome of this strain. The soluble protein fractions of the microorganism were recovered either in the mid-log or in the stationary phase of growth at 37 degrees C. These fractions were analyzed by 2-D electrophoresis (2-DE), using immobilized pH gradient strips of various pH values (3-10, 3-6, and 5-8) for the first-dimensional separations and 12.5% acrylamide gels for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). 201 protein spots corresponding to 126 different proteins were identified by matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). The 2-DE maps presented here provide a first basis for further investigations of protein expression in L. monocytogenes. In this way, the comparison of proteome between cells in the exponential or stationary phase of growth at 37 degrees C allowed us to characterize 161 variations in protein spot intensity, of which 38 were identified. Among the differentially expressed proteins were ribosomal proteins (RpsF, RplJ, and RpmE), proteins involved in cellular metabolism (GlpD, PdhD, Pgm, Lmo1372, Lmo2696, and Lmo2743) or in stress adaptation (GroES and ferritin), a fructose-specific phosphotransferase enzyme IIB (Lmo0399) and different post-translational modified forms of listeriolysin (LLO).

Direct Pathway to RNA Polymerase II

Cellular responses to the extracellular environment can involve changes in gene expression, often the end point of signaling cascades that originate at the cell surface. Some signaling pathways regulate RNA polymerase II enzyme activity to control transcription. Many pathways impinge on transactivator proteins poised at gene promoters. These transactivators recruit the RNA polymerase II by interacting with regulator proteins of the Srb and Mediator complexes that also make up the polymerase holoenzyme. Chang et al. report that the Ras-protein kinase A (PKA) signaling pathway of the yeast Saccharomyces cerevisiae , which controls cell proliferation, targets the Srb9p protein in the Srb complex. Srb proteins and the Ras-PKA pathway are known to repress the expression of genes during the stationary phase of cell growth. Srb9p was phosphorylated by PKA in vitro and in vivo. Expression of a constitutively activated form of Ras also increased phosphorylation of Srb9p and the modification modulated the effect of the Srb complex on cell growth. The authors propose that by directly targeting proteins of the polymerase complex, cells could rapidly induce broad changes in gene expression. Y.-W. Chang, S. C. Howard, P. K. Herman, The Ras/PKA signaling pathway directly targets the Srb9 protein, a component of the general RNA polymerase II transcription apparatus. Mol. Cell 15 , 107-116 (2004). [Online Journal]

Comparative analysis of transcriptional regulatory elements of glutamate-dependent acid-resistance systems of Shigella flexneri and Escherichia coli O157:H7

The ability to withstand an acid-challenge of pH 2.5 or less by Shigella flexneri is a necessary trait for virulence and is generally believed to be restricted to the stationary-phase of growth. Earlier reports indicated the glutamate-dependent acid-resistance (GDAR) system of S. flexneri is under the regulation of rpoS, the gene encoding alternative sigma factor that is induced in the stationary-growth phase. The present study reports that unlike Escherichia coli O157:H7, S. flexneri cells when grown in minimal medium, require acid-induction in the stationary-growth phase for a functional GDAR. When grown on complex medium at pH 5.5, GDAR of S. flexneri was vigorous compared to the cells grown at pH 7.5. No acid-induction was required for the stationary phase E. coli cells grown on either minimal or complex growth media. Distinct differences in the gadA, gadBC, gadE, and hdeA (but not in rpoS) transcript levels were observed in the stationary-growth phase cells between the two pathogens grown on minimal medium. Additionally, rpoS-independent acid-induction of GDAR in the logarithmic growth phase that has been recently observed in E. coli strains [FEMS Microbiol. Lett. 227 (2003) 39–45] was not detected in the S. flexneri rpoS mutant. Although some differences in the DNA sequence at the upstream regulatory elements of gadBC were noticed, they do not appear to be significant and involvement of additional regulators in S. flexneri is anticipated, which also may explain the observed differences in the GDAR of two enteric pathogens.

Gts1p Activates SNF1-dependent Derepression of HSP104 and TPS1 in the Stationary Phase of Yeast Growth

We previously reported that the GTS1 product, Gts1p, plays an important role in the regulation of heat tolerance of yeast under glucose-limited conditions in either batch or continuous culture. Here we show that heat tolerance was decreased in GTS1-deleted and increased in GTS1-overexpressing cells under glucose-derepressed conditions during the batch culture and that the disruption of SNF1, a transcriptional activator of glucose-repressible genes, diminished this effect of GTS1. Intracellular levels of Hsp104 and trehalose, which were reportedly required for the acquisition of heat tolerance in the stationary phase of cell growth, were affected in both GTS1 mutants roughly in proportion to the gene dosage of GTS1, whereas those of other Hsps were less affected. The mRNA levels of genes for Hsp104 and trehalose-6-phosphate synthase 1 changed as a function of GTS1 gene dosage. The Q-rich domain of Gts1p fused with the DNA-binding domain of LexA activated the transcription of the reporter gene LacZ, and Gts1p lacking the Q-rich domain lost the activation activity of HSP104 and TPS1. Furthermore, Gts1p bound to subunits of Snf1 kinase, whereas it did not bind to DNA. Therefore, we suggested that GTS1 increases heat tolerance by mainly activating Snf1 kinase-dependent derepression of HSP104 and TPS1 in the stationary phase of yeast growth.

Coumarin inhibits the growth of carrot ( Daucus carota L. cv. Saint Valery) cells in suspension culture

We used a carrot (Daucus carota L. cv. Saint Valery) cell suspension culture as a simplified model system to study the effects of the allelochemical compound coumarin (1,2 benzopyrone) on cell growth and utilisation of exogenous nitrate, ammonium and carbohydrates. Exposure to micromolar levels of coumarin caused severe inhibition of cell growth starting from the second day of culture onwards. At the same time, the presence of 50 mumol/L coumarin caused accumulation of free amino acids and of ammonium in the cultured cells, and stimulated their glutamine synthetase, glutamate dehydrogenase, glucose-6-phosphate dehydrogenase and phosphoenolpyruvate carboxylase activities. Malate dehydrogenase, on the other hand, was inhibited under the same conditions. These effects were interpreted in terms of the stimulation of protein catabolism and/or interference with protein biosynthesis induced by coumarin. This could have led to a series of compensatory changes in the activities of enzymes linking nitrogen and carbon metabolism. Because coumarin seemed to abolish the exponential phase and to accelerate the onset of the stationary phase of cell growth, we hypothesise that such allelochemical compounds may act in nature as an inhibitor of the cell cycle and/or as a senescence-promoting substance.

Cytotoxicity and apoptotic inducibility of Vitex agnus-castus fruit extract in cultured human normal and cancer cells and effect on growth.

A crude extract was prepared with ethanol from dried ripened Vitex agnus-castus fruits growing in Israel (Vitex extract). Cytotoxicity of the extract against human uterine cervical canal fibroblast (HCF), human embryo fibroblast (HE-21), ovarian cancer (MCF-7), cervical carcinoma (SKG-3a), breast carcinoma (SKOV-3), gastric signet ring carcinoma (KATO-III), colon carcinoma (COLO 201), and small cell lung carcinoma (Lu-134-A-H) cells was examined. After culture for 24 h (logarithmic growth phase) or 72 h (stationary growth phase), the cells were treated with various concentrations of Vitex extract. In both growth phases, higher growth activity of cells and more cytotoxic activity of Vitex extract were seen. The cytotoxic activity against stationary growth-phase cells was less than that against logarithmic growth-phase cells. DNA fragmentation of Vitex extract-treated cells was seen in SKOV-3, KATO-III, COLO 201, and Lu-134-A-H cells. The DNA fragmentation in Vitex extract-treated KATO-III cells was inhibited by the presence of the antioxidative reagent pyrrolidine dithiocarbamate or N-acetyl-L-cysteine (NAC). Western blotting analysis showed that in Vitex extract-treated KATO-III cells, the presence of NAC also inhibited the expression of heme oxygenase-1 and the active forms of caspases-3, -8 and -9. It is concluded that the cytotoxic activity of Vitex extract may be attributed to the effect on cell growth, that cell death occurs through apoptosis, and that this apoptotic cell death may be attributed to increased intracellular oxidation by Vitex extract treatment.

Protective effects of cold temperature and surface-contact on acid tolerance of Salmonella spp.

To determine the effect of cold-storage temperature and surface contact on the survival of Salmonella spp. during acid challenge. To determine the contribution of sigma transcriptional factor (encoded by rpoS) in surface contact-mediated acid tolerance. Salmonella serovar Typhimurium cells in exponential and stationary growth phase were subjected to acid challenge in planktonic and surface-associated states. Low temperatures offered protection against acid challenge to cells which were in stationary growth phase (but not to those in exponential growth phase). The cells from stationary, as well as logarithmic growth phase, acquired increased acid tolerance upon surface contact with various surfaces, such as fresh-cut apples, agar and polyethersulphone membranes. The alternative sigma transcription factor was not required to acquire surface contact-mediated acid tolerance. Salmonella spp. take advantage of low temperature and surface association to overcome acid challenge. Some of the acid tolerance mechanisms are independent of the sigma transcription factor regulon. Effective control measures during produce processing must take into account the different susceptibilities of planktonic vs surface-associated food-borne pathogens.

Propionibacterium acnes and inflammation in acne; P. acnes has T-cell mitogenic activity.

Circumstantial evidence suggests that Propionibacterium acnes has a role in the inflammation of acne. This could be effected by antigenic or superantigenic or mitogenic reactions. The purpose of this investigation was to determine whether P. acnes had only antigenic activity or additional superantigenic and mitogenic activity. A lymphocyte transformation assay was used to detect responses to a mixture of eight P. acnes whole cell isolates, and their supernatant culture fluids. In order to determine the nature of T-cell reactions to P. acnes cells a mouse-antihuman major histocompatibility complex class II monoclonal antibody was used in the lymphocyte transformation assay to inhibit the antigenic stimulation of lymphocytes. An analysis of the T-cell receptor (TCR) variable region beta (BV) repertoire was undertaken using flow cytometry of the unstimulated and stimulated cells. Peripheral blood mononuclear cells (PBMNC) from adults with no history of acne responded strongly to stationary growth phase cells of P. acnes, less strongly to cells in the exponential growth phase. No response was detected to supernatant culture fluids. PBMNC from five cord blood samples (CBMNC) responded maximally after 3 and 7 days of incubation with stationary growth phase cells of P. acnes. The reaction of CBMNC to P. acnes cells was not suppressed completely by the blocking antibody. The analysis of the TCRBV repertoire indicated that P. acnes induced no deletion or over-representation of certain BV element-bearing T cells. The TCRBV analysis was repeated after preincubation with the blocking antibody. Deletion of T cells bearing certain BV components occurred and there was no over-representation of T cells carrying certain BV components. Two mechanisms of lymphocyte activation by P. acnes cells are proposed, antigen and mitogen driven. These results are consistent with the histological evidence of inflammation in acne lesions.

Identification of a 22-kDa protein required for the degradation of Selenomonas ruminantium lysine decarboxylase by ATP-dependent protease.

In Selenomonas ruminantium, a strictly anaerobic, Gram-negative bacterium isolated from sheep rumen, a rapid degradation of lysine decarboxylase (LDC) occurred on entry into the stationary phase of cell growth. Here, we identified a 22-kDa protein as a stimulating factor for the degradation of LDC, which was catalyzed by ATP-dependent protease(s) in S. ruminantium. The purified 22-kDa protein preparation itself had no degradation activity towards LDC but it was required for the degradation of LDC by ATP-dependent proteases in a cell-free system. The 22-kDa protein had similar biochemical and biophysical characteristics to those of antizyme, the regulator for the degradation of mammalian ODC, which had been reported only in mammalian cells. From the sequencing data of the N-terminal 30 amino acid residues of the 22-kDa protein preparation, 22-kDa protein was found to be a new protein which was distinguished from antizyme. This is the first report of the presence of an antizyme-like regulator protein in a prokaryote.

CHARACTERIZATION OF THE ADHESIVE MUCILAGES SECRETED BY LIVE DIATOM CELLS USING ATOMIC FORCE MICROSCOPY

Higgins, M. J., Mulvaney, P. & Wetherbee, R.Schools of Botany and Chemistry, University of Melbourne, Victoria 3052, AustraliaAtomic Force Microscopy (AFM) resolved the topography and mechanical properties of the adhesive mucilages secreted by living cells of the fouling diatom Craspedostauros australis. Tapping mode images of live cells revealed a soft, cohesive mucilage layer that encased most of the diatom silica cell wall. Force curves revealed that this type of mucilage had an adhesion strength of 71.2 mN m‐1 and a compressibility of 5.7 x 106 N m‐2. High force contact mode imaging (i.e., increased set‐point voltage) resulted in the ‘raking’ of the cohesive mucilage to reveal the underlying, silicified wall structures. Further imaging of cantilever ‘cleaned’ cell walls of live cells in stationary growth phase revealed the active secretion of soft mucilage via pore openings in the girdle bands. A second adhesive mucilage in the form of distinct strands was found to project through the silica valve walls at the raphes, and to be involved in cell adhesion and motility. Single force spectroscopy measurements revealed that an adhesive strand (or strands) was resistant to breaking forces greater than 40 nN and could only be detached from the AFM cantilever probe using mechanical retraction of the piezo. Using the Worm‐like Chain model (WLC) the chain length and persistence length of the strands were calculated to be 3μm and 0.04Å, respectively. These values imply that the strands are very adhesive and strong compared to other single biological polymers, and could account for the complex interactions between diatom cells and their substratum.

Dynamics of serine/threonine protein kinase activity during the growth of the wild-typeStreptomyces avermitilis strain and its chloramphenicol-resistant mutant

The dynamics of serine/threonine protein kinase activity during the growth of the wild-type Streptomyces avermitilis strain and its chloramphenicol-resistant (Cmlr) pleiotropic mutant with an enhanced production of avermectins was studied by measuring the transfer of radiolabeled phosphate from [gamma-32P]ATP to the serine and threonine residues of proteins in cell-free extracts. In both of the strains studied, radiolabeled phosphate was found to incorporate into polypeptides with molecular masses of 32, 35, 41, 68, 75, 79, 83, and 137 kDa; however, the degree and the dynamics of phosphorylation of particular peptides were different in these strains. The differences revealed could not be accounted for by the interference of ATPases or phosphoprotein phosphatases. The data obtained may be interpreted as evidence that Cmlr mutation activates the protein kinase signalling system of S. avermitilis cells in the early stationary growth phase and thus enhances the production of avermectins and leads to some other physiological changes in the mutant strain.

Leucine incorporation by Microcystis aeruginosa

In experiments with axenic cultures of Microcystis aeruginosa, we tested whether this cyanobacterium incorporates leucine, a compound that is often used for the measurement of heterotrophic bacterioplankton production. Microcystis showed significant leucine incorporation, and the uptake of exponentially growing cells was higher than the uptake of cells in stationary growth phase. Therefore, the leucine method may not be suitable for measuring bacterial production in highly eutrophic waters with a dominance of cyanobacteria.

Simultaneous uptake of ammonium and nitrate salts by an aerobic culture of Bacillus licheniformis No. 40-2

A one-step elimination of NO 3 − and NH 4 + through aerobic culture of Bacillus licheniformis is proposed. The cell growth markedly increased in a medium containing 1.5 mM of FeSO 4 under aerobic conditions. At the stationary phase of cell growth, the NO 3 − and NH 4 + disappeared entirely from the medium. This bacterial culture could be applied to bioremediation systems.