Binding of adenovirus and its external proteins to Triton X-114. Dependence on pH

35S-Labeled adenovirus type 2 (Ad2) (10 ng/ml) was incubated with 1% Triton X-114 at various pH values varying from 3.0 to 8.0. The detergent phase was separated from the aqueous phase by centrifugation, and the amounts of Ad2 were determined in the two phases. At pH 7.0-8.0, less than 5% of Ad2 was associated with the detergent phase; at pH 5.0 or below, about 60% of Ad2 was associated with the detergent phase. When a mixture of 35S-labeled capsid proteins was used at pH 7.0, 60-70% of the total proteins were associated with the detergent at pH 5.0, but less than 5% of the proteins interacted with detergent at pH 7.0. Among the three major external proteins (hexon, penton base, and fiber), penton base had the highest association with Triton X-114 at pH 5.0. Both intact virus and the capsid proteins that were associated with Triton X-114 at pH 5.0 were released into the aqueous phase on subsequent incubation at pH 7.0. On the basis of these results, it is suggested that mildly acidic pH induces amphiphilic properties in adenovirus capsid proteins and may help Ad2 escape from acidic endocytic vesicles.     

Dynamic changes of intracellular pH in individual lactic acid bacterium cells in response to a rapid drop in extracellular pH

We describe the dynamics of changes in the intracellular pH (pH(i)) values of a number of lactic acid bacteria in response to a rapid drop in the extracellular pH (pH(ex)). Strains of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, and Lactococcus lactis were investigated. Listeria innocua, a gram-positive, non-lactic acid bacterium, was included for comparison. The method which we used was based on fluorescence ratio imaging of single cells, and it was therefore possible to describe variations in pH(i) within a population. The bacteria were immobilized on a membrane filter, placed in a closed perfusion chamber, and analyzed during a rapid decrease in the pH(ex) from 7.0 to 5.0. Under these conditions, the pH(i) of L. innocua remained neutral (between 7 and 8). In contrast, the pH(i) values of all of the strains of lactic acid bacteria investigated decreased to approximately 5.5 as the pH(ex) was decreased. No pronounced differences were observed between cells of the same strain harvested from the exponential and stationary phases. Small differences between species were observed with regard to the initial pH(i) at pH(ex) 7.0, while different kinetics of pH(i) regulation were observed in different species and also in different strains of S. thermophilus.     

分阶段pH调控提高2-酮基-L-古龙酸生产

为了提高酮古龙酸菌Ketogulonicigenium vulgare和巨大芽胞杆菌Bacillus megaterium生产2-酮基-L-古龙酸(2-KLG)的生产效率,分析了pH对K.vulgare和B.megaterium生长和产酸的影响,发现K.vulgare和B.megaterium的最适生长pH值分别为6.0和8.0,但是K.vulgare的糖酸转化活力在pH7.0时达到最大值,因此提出了三阶段pH控制策略(第一阶段:0～8h,pH8.0;第二阶段:8～20h,pH6.0;第三阶段:20h至发酵结束,pH7.0)以促进K.vulgare生长和2-KLG生产。结果表明,三阶段pH控制策略的实施进一步提高了2-KLG的产量(77.3g/L)、生产强度(1.38g/(L·h))和L-山梨糖消耗速率(1.42g/(L·h)),分别比恒定pH7.0时提高了9.7%、33.2%和25.7%。     

Effect of pH on Bacillus thermoamylovorans Growth and Glucose Fermentation

The effect of pH on the growth and physiology of Bacillus thermoamylovorans, a new moderately thermophilic and non-spore-forming bacterium isolated from palm wine, was studied. Growth occurred from pH 5.4 to 8.5, with optimum growth at 7.0. During the exponential growth phase at optimum pH, glucose was consumed at the maximum rate (qs), 17.87 mmol g(sup-1) h(sup-1), and was mainly fermented into acetate, ethanol, and formate (76.5% of metabolites produced). In acidic or alkaline conditions, glucose specific consumption rates were considerably reduced (qs = 8.06 mmol g(sup-1) h(sup-1) at pH 5.6 and 2.85 mmol g(sup-1) h(sup-1) at pH 8.4), and a switch in glucose metabolism toward lactate production (62.6% of metabolites produced at pH 5.6 and 41.2% of those produced at pH 8.4) was observed. Moreover, optimum cellular yield (Y(infx/ATP)), 14.8 g mol(sup-1), and optimum energy yield (Y(infATP/s)), 2.65 mol mol(sup-1), were observed at neutrality. The results of this study were compared with published data about lactic acid bacteria; this comparison allowed us to complement our previous taxonomic study of B. thermoamylovorans and to identify additional phenotypic differences between B. thermoamylovorans and lactobacilli.     

Combined action of redox potential and pH on heat resistance and growth recovery of sublethally heat-damaged Escherichia coli

The combined effect of redox potential (RP) (from −200 to 500 mV) and pH (from 5.0 to 7.0) on the heat resistance and growth recovery after heat treatment of Escherichia coli was tested. The effect of RP on heat resistance was very different depending on the pH. At pH 6.0, there was no significant difference, whereas at pH 5.0 and 7.0 maximum resistance was found in oxidizing conditions while it fell in reducing ones. In sublethally heat-damaged cells, low reducing and acid conditions allowed growth ability to be rapidly regained, but a decrease in the redox potential and pH brought about a longer lag phase and a slower exponential growth rate, and even led to growth failure (pH 5.0, ≤−100 mV). Received: 28 June 1999 / Received revision: 22 October 1999 / Accepted: 22 October 1999     

甜瓜幼苗生长及光合特性与育苗基质pH相关性研究

以新疆厚皮甜瓜皇后为试材,在泥炭珍珠岩复合基质中,按一定比例加入CaCO3,构成pH梯度值分别为5.0、5.5、6.0、6.5、7.0、7.5和8.0的7种基质类型,研究了基质pH对甜瓜幼苗生长及其光合特性的影响。结果表明,基质酸碱性对甜瓜幼苗的光合特性、根系活力、单株叶面积、根系和地上部干物重都产生显著影响,酸性和微酸性基质(pH<6.0)时,幼苗叶片叶绿体超微结构发生降解,叶绿素堆积,叶片净光合速率下降,单株叶面积减小,根和地上部干重降低;pH为6.0～7.0的各处理在叶面积以及根和地上部干重指标上,F检验不显著;pH>7.0的微碱性和碱性基质虽然对幼苗产生不利影响,但与pH<6.0的处理比较,其影响要小些。鉴于此,甜瓜幼苗生长的基质pH范围为6.0～7.0,偏碱不会对幼苗产生严重的生理障碍。采用CaCO3调节基质pH时,最佳调节范围为pH6.0～6.5。     

Dimethyl-and monomethyloxyluciferins as analogs of the product of the bioluminescence reaction catalyzed by firefly luciferase

The absorption and fluorescence spectra of dimethyloxyluciferin (DMOL) and monomethyloxyluciferin (MMOL) were studied at pH 3.0-12.0. In the range of pH 3.0-8.0, the fluorescence spectrum of DMOL exhibits a maximum at lambda(em) = 639 nm. At higher pH values an additional emission maximum appears at lambda(em) = 500 nm (wavelength of excitation maximum lambda(ex) = 350 nm), which intensity increases with time. It is shown that this peak corresponds to the product of DMOL decomposition at pH > 8.0. The absorption spectra of MMOL were studied in the range of pH 6.0-9.0. At pH 8.0-9.0, the absorption spectrum of MMOL exhibits one peak at lambda(abs) = 440 nm. At pH 7.3-7.7, an additional band appears with maximum at lambda(abs) = 390 nm. At pH 6.0-7.0 two maxima are observed, at lambda(abs) = 375 and 440 nm. The fluorescence spectra of MMOL (pH 6.0-9.7, lambda(ex) = 440 or 375 nm) exhibit one maximum. It is shown that decomposition of DMOL and MMOL in aqueous solutions results in products of similar structure. DMOL and MMOL are rather stable at the pH optimum of luciferase. It is suggested that they can be used as fluorescent markers for investigation of the active site of the enzyme.     

New Strains of Bacillus licheniformis and Bacillus coagulans producing Thermostable α-Amylase Active at Alkaline pH

Two species of Bacillus producing thermostable α-amylase with activity optima at alkaline pH are reported here. These organisms were isolated from soil and have been designated as Bacillus licheniformis CUMC 305 and B. coagulans CUMC 512. The enzymes released by these two species were partially purified up to about 81- and 72-fold respectively of the initial activity. The enzyme from B. licheniformis showed a wide temperature-range of activity, with optimum at 91°C. At this temperature it remained stable for 1 h. It retained 40–50% activity at 110°C and showed only 60% of its activity at 30°C. The enzyme showed a broad pH range of activity (4–10) retaining substantial activity on the alkaline side. The optimum pH was 9·5. The enzyme of B. coagulans showed activity up to 90°C, with optimum at 85°C and had a wide pH range with optimum at 7·5–8·5. The hydrolysis pattern of the substrate starch by these enzymes indicated that glucose, maltose, maltotriose and maltotetraose are the principal products rather than higher oligosaccharides.     

Optimization of culture conditions of probiotic bifidobacteria for maximal adhesion to hexadecane

Culture growth conditions were optimized for adhesion to hexadecane of the probiotic Bifidobacterium bifidum HI 39 and HI 48. Among three growth media used, MILS lactose broth was the best medium to obtain maximum cell adhesion, followed by MRS and TPY lactose broth for B. bifidum HI 39 and HI 48. Increasing the incubation time from 6 to 18 h resulted in a gradual increase in percentage adhesion at 37 °C of both organisms in MILS, MRS and TPY media. Thereafter, incubation up to 48 h showed a marked reduction in adhesion of B. bifidum HI 39 and B. bifidum HI 48. When the test cultures were grown at pH values from 5.0 to 8.0 in MILS lactose broth at 37 °C for 18 h, there was a gradual enhancement in cell adhesion up to pH 7.0; but higher pH values retarded the bacterial adhesion. The study showed that the optimum conditions for adhesion to hexadecane of the selected bifidobacterial strains were pH 7.0 and incubation at 37 °C for 18 h in MILS broth.     

Kinetic study on pH dependence of growth and death of Streptococcus faecalis

A chemostat culture was used for lactic acid fermentation with Streptococcus faecalis at various pH values (8.0, 7.0, 6.0, 5.5, 5.0) and glucose concentrations (10, 20, 30 g/l). At every pH value, the reciprocals of the specific consumption rate of glucose and the specific production rate of lactic acid were linearly correlated to the reciprocal of the specific growth rate. The product, lactic acid, caused non-competitive inhibition of the specific growth rate at every pH value. Moreover, it was found that the cell death rate was dependent on pH and lactic acid. The death rate was smallest at pH 7.0 and increased with increasing lactic acid concentration. The kinetic equations of growth and death are proposed in a broader pH range. Correspondence to: H. Ohara     

The response of GS-NS0 myeloma cells to pH shifts and pH perturbations

The perceived sensitivity of animal cells to hydrodynamic shear has limited agitation and aeration at large-scale. This makes it difficult to ensure adequate mixing of the vessel contents and may lead to inhomogeneities in operational parameters such as temperature, dissolved oxygen concentration, and especially pH. The effect of pH shifts and pH perturbations on the cellular responses, in batch culture, of a GS-NS0 mouse myeloma cell line, expressing a recombinant antibody, was investigated. In addition, the effect of extreme pH on the structure of the purified antibody product was studied using isoelectric focusing. The fermentation pH value was shifted abruptly from pH 7.3 to pH values ranging from 6.5 to 9.0. Culture pH was maintained at this new value for the remainder of the fermentation. All pH shifts of above 0.2 units caused a transient increase in apoptosis. However, cultures shifted to pH values between 7.0 and 8.0 continued to grow and the apoptotic fraction returned to initial levels. Cultures shifted to pH values above pH 8.0 and below pH 7.0 did not recover resulting in culture death. For example, a shift to pH 8.5 caused accumulation of cells in the G(2)/M phase of the cell cycle followed by apoptotic death. After the pH shift, maximum specific growth rate was observed over the range pH 7.3 to 7.5 and maximum viable cell number was seen at pH 7.3. Maximum volumetric antibody production, resulting from increased culture longevity, was seen at pH 7.0. It was also observed that glucose consumption increased with increasing pH. In a separate set of experiments cells were subjected to a single pH perturbation ranging in duration from 0 to 600 minutes. Exposure of cells to a pH value greater than 8.5 for more than 10 minutes caused a decrease in the proportion of viable cells and induced a lag in cell growth. At very low pH (6.5) similar effects were seen, but only for extended perturbations (600 min). However, after recovery from the pH perturbation, growth, product secretion and metabolism all returned to original levels. Incubation of the antibody, at the range of pH values investigated, indicated no alterations in the structure of the antibody as determined by the isoelectric focusing pattern.     

Low-pH-induced effects on patterns of protein synthesis and on internal pH in Escherichia coli and Salmonella typhimurium

Escherichia coli and Salmonella typhimurium were grown in a supplemented minimal medium (SMM) at a pH of 7.0 or 5.0 or were shifted from pH 7.0 to 5.0. Two-dimensional gel electrophoretic analysis of proteins labeled with H2(35)SO4 for 20 min during the shift showed that in E. coli, 13 polypeptides were elevated 1.5- to 4-fold, whereas in S. typhimurium, 19 polypeptides were increased 2- to 14-fold over the pH 7.0 control. Upon long-term growth at pH 5.0, almost double the number of polypeptides were elevated twofold or more in S. typhimurium compared with E. coli. In E. coli, there was no apparent induction of heat shock proteins upon growth at pH 5.0 in SMM. However, growth of E. coli in a complex broth to pH 5.0, or subsequent growth of fresh E. coli cells in the filtrate from this culture, showed that a subset of five polypeptides is uniquely induced by low pH. Two of these polypeptides, D60.5, the inducible lysyl-tRNA synthetase, and C62.5, are known heat shock proteins. Measurements of the internal pH (pHi) and growth rates of both organisms were made during growth in SMM at pH 7.0, pH 5.0, and upon the pH shift. The data show that the pHi of E. coli decreases more severely than that of S. typhimurium at an external pH of 5.0; the growth rate of E. coli is about one-half that of S. typhimurium at this pH, whereas the two organisms have the same growth rate at pH 7.0. The two-dimensional gel, growth, and pHi experiments collectively suggest that, at least in SMM, S. typhimurium is more adaptive to low-pH stress than is E. coli.     

Low-pH-induced effects on patterns of protein synthesis and on internal pH in Escherichia coli and Salmonella typhimurium.

Escherichia coli and Salmonella typhimurium were grown in a supplemented minimal medium (SMM) at a pH of 7.0 or 5.0 or were shifted from pH 7.0 to 5.0. Two-dimensional gel electrophoretic analysis of proteins labeled with H2(35)SO4 for 20 min during the shift showed that in E. coli, 13 polypeptides were elevated 1.5- to 4-fold, whereas in S. typhimurium, 19 polypeptides were increased 2- to 14-fold over the pH 7.0 control. Upon long-term growth at pH 5.0, almost double the number of polypeptides were elevated twofold or more in S. typhimurium compared with E. coli. In E. coli, there was no apparent induction of heat shock proteins upon growth at pH 5.0 in SMM. However, growth of E. coli in a complex broth to pH 5.0, or subsequent growth of fresh E. coli cells in the filtrate from this culture, showed that a subset of five polypeptides is uniquely induced by low pH. Two of these polypeptides, D60.5, the inducible lysyl-tRNA synthetase, and C62.5, are known heat shock proteins. Measurements of the internal pH (pHi) and growth rates of both organisms were made during growth in SMM at pH 7.0, pH 5.0, and upon the pH shift. The data show that the pHi of E. coli decreases more severely than that of S. typhimurium at an external pH of 5.0; the growth rate of E. coli is about one-half that of S. typhimurium at this pH, whereas the two organisms have the same growth rate at pH 7.0. The two-dimensional gel, growth, and pHi experiments collectively suggest that, at least in SMM, S. typhimurium is more adaptive to low-pH stress than is E. coli.     

An organic solvent-, detergent-, and thermo-stable alkaline protease from the mesophilic, organic solvent-tolerant Bacillus licheniformis 3C5

Bacillus licheniformis 3C5, isolated as mesophilic bacterium, exhibited tolerance towards a wide range of non-polar and polar organic solvents at 45 degrees C. It produced an extracellular organic solvent-stable protease with an apparent molecular mass of approximately 32 kDa. The inhibitory effect of PMSF and EDTA suggested it is likely to be an alkaline serine protease. The protease was active over abroad range of temperatures (45-70 degrees C) and pH (8-10) range with an optimum activity at pH 10 and 65 degrees C. It was comparatively stable in the presence ofa relatively high concentration (35% (v/v)) of organic solvents and various types of detergents even at a relatively high temperature (45 degrees C). The protease production by B. licheniformis 3C5 was growth-dependent. The optimization of carbon and nitrogen sources for cell growth and protease production revealed that yeast extract was an important medium component to support both cell growth and the protease production. The overall properties of the protease produced by B. licheniformis 3C5 suggested that this thermo-stable, solvent-stable, detergent-stable alkaline protease is a promising potential biocatalyst for industrial and environmental applications.     

pH regulates genes for flagellar motility, catabolism, and oxidative stress in Escherichia coli K-12

Gene expression profiles of Escherichia coli K-12 W3110 were compared as a function of steady-state external pH. Cultures were grown to an optical density at 600 nm of 0.3 in potassium-modified Luria-Bertani medium buffered at pH 5.0, 7.0, and 8.7. For each of the three pH conditions, cDNA from RNA of five independent cultures was hybridized to Affymetrix E. coli arrays. Analysis of variance with an alpha level of 0.001 resulted in 98% power to detect genes showing a twofold difference in expression. Normalized expression indices were calculated for each gene and intergenic region (IG). Differential expression among the three pH classes was observed for 763 genes and 353 IGs. Hierarchical clustering yielded six well-defined clusters of pH profiles, designated Acid High (highest expression at pH 5.0), Acid Low (lowest expression at pH 5.0), Base High (highest at pH 8.7), Base Low (lowest at pH 8.7), Neutral High (highest at pH 7.0, lower in acid or base), and Neutral Low (lowest at pH 7.0, higher at both pH extremes). Flagellar and chemotaxis genes were repressed at pH 8.7 (Base Low cluster), where the cell's transmembrane proton potential is diminished by the maintenance of an inverted pH gradient. High pH also repressed the proton pumps cytochrome o (cyo) and NADH dehydrogenases I and II. By contrast, the proton-importing ATP synthase F1Fo and the microaerophilic cytochrome d (cyd), which minimizes proton export, were induced at pH 8.7. These observations are consistent with a model in which high pH represses synthesis of flagella, which expend proton motive force, while stepping up electron transport and ATPase components that keep protons inside the cell. Acid-induced genes, on the other hand, were coinduced by conditions associated with increased metabolic rate, such as oxidative stress. All six pH-dependent clusters included envelope and periplasmic proteins, which directly experience external pH. Overall, this study showed that (i) low pH accelerates acid consumption and proton export, while coinducing oxidative stress and heat shock regulons; (ii) high pH accelerates proton import, while repressing the energy-expensive flagellar and chemotaxis regulons; and (iii) pH differentially regulates a large number of periplasmic and envelope proteins.     

Effects of pH on feeding responses in the apple maggot fly,Rhagoletis pomonella (Diptera: Tephritidae)

Phagostimulatory effects of pH values of sucrose on Rhagoletis pomonella adults were studied in the laboratory. Flies were standardized for age, diet and food deprivation. Two presentation schemes were employed. The first varied pH value (3.0-10.0) with sucrose concentration kept constant at 40%. The second varied both sucrose concentration (8%, 24% and 40%) and pH value (5.0-8.0). Fly feeding propensity was evaluated by observation of fly acceptance or rejection of sucrose and duration of feeding. When tested on red wooden spheres treated with 40% sucrose, fly feeding acceptance was significantly greater when pH ranged from 5.0 to 8.0, and duration of feeding was significantly longer at pH 6.0-7.0. At pH /=8.0, feeding propensity was significantly reduced. Decrease in sucrose concentration significantly increased fly sensitivity to pH. Males were more responsive to varying pH than females. The sucrose pH shown to stimulate maximal feeding response was 6.4. Such information is relevant to formulation improvement of a coating mixture of sucrose and insecticide applied to red spheres as part of apple maggot fly control programs.     

Effects of pH strategy on endo- and exo-metabolome profiles and sodium potassium hydrogen ports of beta-lactamase-producing Bacillus licheniformis

The effects of pH strategy on endo- and exo-metabolome profiling of beta-lactamase-producing Bacillus licheniformis were investigated at controlled-pH (pH(C) = 6.5, 6.75, 7.0, 7.25, 7.5) and uncontrolled-pH (pH(UC) = 7.5) values using a glucose-based defined medium. The cell concentration profiles were not affected by the pH considerably within the investigated range. The highest enzyme activities were obtained as A = 54 U cm(-)(3) at pH(C) = 6.75 among the controlled-pH operations and as A = 57 U cm(-3) at the uncontrolled-pH pH(UC) = 7.5. At all conditions, oxygen transfer resistances were more effective, whereas the limitation increased in the beta-lactamase production phase. Total intracellular amino acid concentrations ranged between 0.142 and 6.766 kg m(-3) (0.0058-0.277 g g(cell)(-1)), and their concentrations in terms of kg m(-3) were, at most, 580-fold higher than the extracellular concentrations. Methionine/cysteine concentrations were generally higher than the other intracellular amino acids, whereas asparagine concentration was the highest in the fermentation broth. From Na(+), K(+), and H(+) ion profiles, Na(+)-K(+) antiport and Na(+)-H(+) symport were found to be present within the system, and a correlation was found between organic acid transport and Na(+)-H(+) symport. Intracellular organic acid concentrations in terms of kg m(-3) were, at most, 20-fold higher than that of the extracellular, and with the increase in pH, extracellular acetic acid concentration increased and lactic acid concentration decreased. Average permeability coefficient values of organic acids were found to be in the range from 4.10 x 10(-7) to 4.32 x 10(-6) cm s(-1) for the growth phase (0 < t < 6 h) and decreased at least 3-fold in the beta-lactamase production phase (8 < t < 15 h), indicating the considerable structural change of the lipid membrane during the fermentation.     

The effect of temperature,pH, and initial glucose concentration on the kinetics of ethanol production by Zymomonas mobilis in batch fermentation

Summary Zymomonas mobilis, strain ATCC 10988, was used to evaluate the effects of pH (5.0 to 8.0), temperature (30°C to 40°C), and initial glucose concentration (75 g/l to 150 g/l) on the kinetics of ethanol production from glucose using batch fermentation. Specific ethanol production rate was maximum and nearly constant over a pH range of 6.0 to 7.5. End-of-batch ethanol yield and specific growth rate were insensitive to pH in the range of 5.0 to 7.5. End-of-batch ethanol yield was maximum and nearly constant between 30°C and 37°C but decreased by 24% between 37°C and 40°C. All other kinetic parameters are greatest at 34°C. End-of-batch ethanol yield is maximum at an initial glucose concentration of 100 g/l. Specific growth rate reaches a maximum at 75 g/l, but specific ethanol production rate decreases throughout the range. The optimum initial glucose concentration of 100 g/l gives the highest ethanol yield at a specific ethanol production rate less than 10% below the maximum observed.     

Propionic acid fermentation of lactose by Propionibacterium acidipropionici: effects of pH

Batch propionic acid fermentation of lactose by Propionibacterium acidipropionici were studied at various pH values ranging from 4.5 to 7.12. The optimum pH range for cell growth was between 6.0 and 7.1, where the specific growth rate was approximately 0.23 h(-1). The specific growth rate decreased with the pH in the acids have been identified as the two major fermentation products from lactose. The production of propionic acid was both growth and nongrowth associated, while acetic acid formation was closely associated with cell growth. The propionic acid yield increased with decreasing pH; It changed from approximately 33% (w/w) at pH 6.1-7.1 to approximately 63% at pH 4.5-5.0. In contrast, the acetic acid yield was not significantly affected by the pH; it remained within the range of 9%-12% at all pH values. Significant amounts of succinic and pyruvic acids were also formed during propionic acid fermentation of lactose. However, pyruvic acid was reconsumed and disappeared toward the end of the fermentation. The succinic acid yield generally decreased with the pH, from a high value of 17% at pH 7.0 to a low 8% at pH 5.0 Effects of growth nutrients present in yeast ex-tract on the fermentation were also studied. In general, the same trend of pH effects was found for fermentations with media containing 5 to 10 g/L yeast extract. However, More growth nutrients would be required for fermentations to be carried out efficienytly at acidic pH levels.     

Induction of Cell Division in Leaf Cells of Coconut Palm by Alteration of pH and its Correlation with Glyoxalase-I Activity

Cell division in suspension cultures obtained from leaf cellsof coconut was influenced by pH of the culture media. A 3-foldincrease in cell number was obtained at pH 7.0 compared to suspensionsgrowing at pH 5.0. The pH of both cells and media changed after48 h of growth. Internal cell pH showed a significant increasewhen cultures were grown at pH 7.0 and 8.0 and increased onlyslightly at pH 5.0 and 6.0. Glyoxalase-I activity of cells insuspension culture was found to be pH-depcndent, showing maximumactivity at pH 7.0. Glutathione, a co-enzyme for the substratemethylglyoxaJ for glyoxalase-I, produced a 2-fold increase incell number at a concentration of 5 x 10^–3 mol dm ^–3.The polyamine, spermidine, promoted cell division maximallyat a concentration of 10^–6 mol dm^–3. Methylglyoxal-bis(guanylhydrazone), an inhibitor of spermidine biosynthesis,strongly inhibited cell division giving maximum inhibition ata concentration of 3 x 10^–6 mol dm ^–3. These resultsindicate a positive correlation between cell division and glyoxalase-Iactivity. Key words: Cocos nucifera, glyoxalase-I, pH, spermidine