The Influence of Extremely High Concentrations of Inorganic P at Varying pH on the Growth and Photosynthesis of Unicellular Algae

An increase in the phosphate concentration due to severe pollution is without real toxic effect for the phytoplankton in eutrophic lakes, although the various species have a variable tolerance against high concentrations. Experiments on photosynthesis and growth were made with cultures of two algae, Chlorella pyrenoidosa and Nitzcshia palea, using phosphate concentrations much higher than ever found in nature. The tolerance decreases with rising pH. This seems not to be due to a higher ratio of secondary phosphate at a high pH. Nor is the rise in the osmotic pressure apparently the cause of the decrease in the growth rate at high phosphate concentrations.     

Response of Rhizobium leguminosarum bv phaseoli to acidity

Soil acidity constraints grain legume production in tropical soils, both limiting Rhizobium survival and reducing nodulation. Strains of rhizobia with greater tolerance to hydrogen-ion concentration have been identified, but the basis for strain differences in pH tolerance has yet to be determined. In this study, strains of Rhizobium leguminosarum by phaseoli which differed in their tolerance to acidity were exposed to acid pH, then cell levels of potassium and calcium determined, and specific ‘acid-shock’ proteins identified. Lowering the external pH to 4.6–4.7 resulted in an immediate efflux of calcium from the cell of both acid tolerant and sensitive bean strains. Change in cell potassium levels on exposure to acidity varied with the strain. Strain UMR 1899 and an acid-sensitive mutant derived from it maintained high cytoplasmic potassium at acid pH, whereas an acid-sensitive strain UMR 1632 underwent a marked decline in cell potassium at pH 4.6. Exposure of these strains to pH 4.5 in the presence of [³⁵S]-labeled methionine enhanced production of a number of proteins, while synthesis of other proteins at this pH was significantly reduced. Differences in banding pattern were also evident between UMR1899 and the Tn5-induced pH-sensitive mutant UMR5005 derived from it, and between cells grown in the presence and absence of calcium and phosphorus.     

Sensitivity to H- and Al ions limiting growth and distribution of the woodland grass Bromus benekenii

One pH experiment and two aluminium experiments were conducted in order to investigate the effects of H- and Al ions on growth of Bromus benekenii. Continuously flowing solution cultures were used with ion concentrations simulating natural soil solutions. In all experiments, treatment effects were more pronounced on root than on shoot growth. In the pH experiment, root growth decreased with decreasing pH within the pH range 4.5 to 3.5. The critical pH for root growth of Bromus benekenii was between 3.8 and 4.0. In the Al experiments, root growth started to decrease at 20 M of quickly reacting Al and almost ceased at 70 M Al. This characterizes Bromus benekenii as an Al sensitive species. In the pH experiment, shoot concentrations of Ca, Mg, K and P decreased with decreasing pH, but root concentrations were not affected. In the Al experiments, the Al concentrations of both shoots and roots increased with Al in the nutrient solution. At treatments of 70 M Al or higher, Ca, Mg, K and P concentrations in the shoots were reduced. The critical concentrations of H- and Al ions in the experiments were similar to the highest concentrations found at field sites of Bromus benekenii, analysed in soil solutions obtained by centrifugation technique. Both Al and H toxicity were considered to be of importance as limiting factors for the distribution of Bromus benekenii in south Sweden. Probably, Al toxicity starts to limit growth when also pH itself influences growth negatively. The importance of simulating natural soil solutions in experiments is emphazised, in order to obtain information on the importance of chemical soil factors to the distribution of plants.     

Aluminium tolerance in triticale,wheat and rye as measured by root growth characteristics and aluminium concentration

Summary Screening large populations of plant species for Al tolerance requires simple and rapid tests. In this study, root characteristics of 12 cultivars of triticale (X Triticosecale, Witt Mack), wheat (Triticum aestivum L.), and rye (Secale cereale L.) were measured in nutrient solution with 0 or 6 ppm Al added. Aluminum injury to roots of triticale and wheat was characterized by decreases in root length, increases in the number of roots, and in Al-sensitive Redcoat and Arthur wheats by decrease in root weight. Root length and number of roots were correlated in triticale (r=−0.73^*) and in wheat (r=−0.85^*). Root length was also correlated with root weight in wheat (r=0.65^*); there was no relationship between the number of roots and weight. Differences in Al tolerance of cultivars of the three species were greater when the solution was adjusted to pH 4.8 only on the first day of the experiment than when pH was maintained at pH 4.8 throughout the growing period. Triticale and rye cultivars low in ability to increase solution pH gradually overcame Al toxicity by increasing the nutrient solution pH between 12 and 22 days. Aluminum sensitive triticale and wheat accumulated more Al in roots than tolerant cultivars when the solution pH was not adjusted daily; but no differences in Al accumulation were obtained between wheat cultivars at constant pH value. This study indicated that root length and number of roots can be reliably used for screening triticales for Al tolerance within 12 days of exposure to Al. Root length, Al concentration, and dry weight after 22 days of Al treatment were also reliable criteria for evaluating differential Al tolerances among triticale cultivars.     

Effect of pH and phosphate on soluble soil aluminium and on growth and composition of kikuyu grass

Summary Kikuyu (Pennisetum clandestinium Hochst) grew relatively poorly on the Wollongbar krasnozem at soil pH values below 4.36. At these low pH values dry matter yields were increased by raising the pH or by application of high rates of phosphate. Both treatments decreased the concentration of soluble soil-Al on which the concentration of Al in tops was linearly dependent (r=0.95). The inverse relationship found between plant growth and Al concentration, when present in excess of ∼1.5 μg/g soil and ∼90 μg/g tops, is suggestive of Al toxicity. However, at Al concentrations causing severe yield reductions, the Ca concentration in kikuyu tops was approaching deficiency levels. The Al-Ca antagonism was further demonstrated by the reduction in Ca-uptake caused by increased concentrations of soluble soil-Al under constant conditions of exchangeable Ca and of pH. The yield-reducing effects of Al toxicity per se and Al-induced Ca deficiency are therefore confounded.     

Effects of Interspecific Interactions between Microcystis aeruginosa and Chlorella pyrenoidosa on Their Growth and Physiology

Interactions between Microcystis aeruginosa and Chlorella pyrenoidosa were analyzed by flow cytometry and by phytoplankton pulse‐amplitude‐modulated fluorimetry (Phyto‐PAM) in joint cultures as well as in cultures separated by dialysis membranes. Results showed that the growth of C. pyrenoidosa was greater than that of M. aeruginosa, and that the growth of M. aeruginosa but not the growth of C. pyrenoidosa was significantly inhibited by the interactions between M. aeruginosa and C. pyrenoidosa. Culture filtrates of these two algae showed no apparent effects on the growth of the competing species. For M. aeruginosa, decreases in esterase activity, chlorophyll a fluorescence, and maximum quantum yield were observed in joint cultures, indicating that the metabolic activity and photosynthetic capacity of M. aeruginosa were suppressed. Light limitation from the shading effect of C. pyrenoidosa may be the main reason for such inhibition. For C. pyrenoidosa, esterase activity was suppressed in membrane‐separated and joint cultures, suggesting that C. pyrenoidosa was probably affected by allelopathic substances secreted by M. aeruginosa. However, no significant difference was observed in the chlorophyll a fluorescence and maximum quantum yield of C. pyrenoidosa in the two cultures. In addition, interspecific interactions induced a reduction in size in both M. aeruginosa and C. pyrenoidosa, which may contribute to the development of C. pyrenoidosa dominance in the present study. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Isolation of bisphenol A-tolerant/degrading <Emphasis Type="Italic">Pseudomonas monteilii</Emphasis> strain N-502

Bisphenol A (BPA) is a highly biotoxic compound that kills many microorganisms at a low concentration (1,000 ppm). We isolated BPA-tolerant/degrading Pseudomonas monteilii strain N-502 from about 1,000 samples collected from a field, sewage, and pond water. The isolated strain had strong BPA tolerance and high BPA-degrading activity. This strain was able to grow in a minimum medium containing BPA as the sole carbon source. Strain N-502 is an aerobic, motile, gram-negative, nonspore-forming, rod-shaped bacterium and was identified as P. monteilii, based on 16 S rRNA gene analysis. Strain N-502 completely degraded BPA 500 ppm in a 10-day, in culture system and was able to degrade BPA 100 ppm in a 2-h resting cell system. This strain also showed potent ability to degrade BPA 500 and 1,000 ppm in the resting cell system. Moreover, the initial BPA degradation rate was accelerated with the addition of Ca²⁺, Mg²⁺, and folic acid.     

Effect of various metal ions on growth of two wheat lines known to differ in aluminium tolerance

The effects of aluminium (Al), manganese (Mn), zinc (Zn), copper (Cu), boron (B), iron (Fe), gallium (Ga), scandium (Sc) and lanthanum (La) on growth of an Al-tolerant and an Al-sensitive line of wheat (Triticum aestivum L.) were measured in solution culture. The concentrations of nutrients in the basal nutrient solution were (M) 500 Ca, 100 Mg, 300 K, 600 N (150 NH₄, 450 NO₃), 600 SO₄, 2.5 P, 3 B, 2.5 Fe, 0.5 Zn, 0.5 Mn, 0.1 Cu at a pH of 4.7. The major solution nutrient concentrations were maintained at the nominal concentration with monitoring, frequent additions and weekly renewal. Differentiation in yield between the Al-tolerant and Al-sensitive line only occurred in the presence of Al indicating that, in the long term, none of the other metals tested could be used as an analog for Al. The visual symptoms in the roots of Cu toxicity (in both lines) and Al toxicity (in the sensitive line) were similar. The solution concentration (M) at which yield of the roots of the tolerant line was reduced by 50% was, in order of increasing tolerance, Cu 0.5, Sc 1.1, La 7.1, Ga 8.6, Al 15, Zn 19, Fe 84, B 490 and Mn 600.     

Cultivation of Chlorella pyrenoidosa in soybean processing wastewater

Chlorella pyrenoidosa was cultivated in soybean processing wastewater (SPW) in batch and fed-batch cultures without a supply of additional nutrients. The alga was able to remove 77.8 ± 5.7%, 88.8 ± 1.0%, 89.1 ± 0.6% and 70.3 ± 11.4% of soluble chemical oxygen demand (SCOD_Cr), total nitrogen (TN), NH₄⁺-N and total phosphate (TP), respectively, after 120 h in fed-batch culture. C. pyrenoidosa attained an average biomass productivity of 0.64 g L⁻¹ d⁻¹, an average lipid content of 37.00 ± 9.34%, and a high lipid productivity of 0.40 g L⁻¹ d⁻¹. Therefore, cultivation of C. pyrenoidosa in SPW could yield cleaner water and useful biomass.     

Extracellular Carbohydrates and Polysaccharides of the Alga Chlorella pyrenoidosa Chick S-39

In the growing culture of the thermophilic alga Chlorella pyrenoidosa Chick S-39, the amount of extracellular carbohydrates in the medium reached 5–17% of their content in the cells and 20–40% of the total content of extracellular organic matter. Experiments with the enrichment and synchronous algal cultures showed that the accumulation of extracellular carbohydrates and polysaccharides in the media occurred due to their release from the cells, rather than to cell lysis, and depended on cell photosynthetic activity and reproduction. Chromatographic determination of free sugars revealed the presence of saccharose, glucose, and fructose in the culture medium. Extracellular carbohydrates in C. pyrenoidosa cultures were represented mainly by water-soluble polysaccharides containing galactose, mannose, arabinose, xylose, ribose, fucose, and rhamnose.     

The effects of sodium chloride,potassium chloride and glycerol on the activity of nitrate reductase of a salt-tolerant and two non-tolerant plants

Summary The activity of nitrate reductase from the salt-tolerant alga Dunaliella parva is inhibited by sodium chloride and potassium chloride, but not by glycerol. The activity of the enzyme from Chlorella pyrenoidosa Chick 611-8b and from the XD line of tobacco (Nicotiana tabacum L. cv. Xanthi) cells is inhibited by all three solutes. Salt tolerance in Dunaliella parva, which is due to internal formation of glycerol, is accompanied by the adaptation of the activity of the enzyme to elevated glycerol concentrations.     

Phosphorus deficiency enhances aluminum tolerance of rice (Oryza sativa) by changing the physicochemical characteristics of root plasma membranes and cell walls

The negative charge at the root surface is mainly derived from the phosphate group of phospholipids in plasma membranes (PMs) and the carboxyl group of pectins in cell walls, which are usually neutralized by calcium (Ca) ions contributing to maintain the root integrity. The major toxic effect of aluminum (Al) in plants is the inhibition of root elongation due to Al binding tightly to these negative sites in exchange for Ca. Because phospholipid and pectin concentrations decrease in roots of some plant species under phosphorus (P)-limiting conditions, we hypothesized that rice (Oryza sativa L.) seedlings grown under P-limiting conditions would demonstrate enhanced Al tolerance because of their fewer sites on their roots. For pretreatment, rice seedlings were grown in a culture solution with (+P) or without (−P) P. Thereafter, the seedlings were transferred to a solution with or without Al, and the lipid, pectin, hemicellulose, and mineral concentrations as well as Al tolerance were then determined. Furthermore, the low-Ca tolerance of P-pretreated seedlings was investigated under different pH conditions. The concentrations of phospholipids and pectins in the roots of rice receiving −P pretreatment were lower than those receiving +P pretreatment. As expected, seedlings receiving the −P pretreatment showed enhanced Al tolerance, accompanied by the decrease in Al accumulation in their roots and shoots. This low P-induced enhanced Al tolerance was not explained by enhanced antioxidant activities or organic acid secretion from roots but by the decrease in phospholipid and pectin concentrations in the roots. In addition, low-Ca tolerance of the roots was enhanced by the −P pretreatment under low pH conditions. This low P-induced enhancement of low-Ca tolerance may be related to the lower Ca requirement to maintain PM and cell wall structures in roots of rice with fewer phospholipids and pectins.     

The effect of maleic hydrazide on growth and mutation of a blue-green alga

Summary Maleic hydrazide is mutagenic to the blue-green alga Anacystis nidulans at pH 5.0, producing mutations to streptomycin-resistance and penicillin-resistance, and is non-mutagenic at pH 8.0, promoting growth in low concentrations. The maleic hydrazide-induced increases in the levels of streptomycin- and penicillin-resistance are 1000 and 500 times respectively over the parental strain. The resistant strains can further mutate spontaneously to give rise to strains resistant to still higher concentrations of the antibiotic.Cultures growing with manganese are more sensitive to maleic hydrazide-induced inhibition of growth than are those growing without manganese. However, cultures of the alga in maleic hydrazide grown in the presence of two different concentrations of manganese differ in the extent of growth which is better in those with the higher manganese concentration than in those with the lower. These results suggest different modes of interaction between manganese and maleic hydrazide, controlled primarily by manganese concentration.     

Early effect of sodium pentachlorophenate on photosynthetic activity of the alga <Emphasis Type="Italic">Chlorella pyrenoidosa</Emphasis> Chick. S-39

Early effects of 0.0001–10 mM sodium pentachlorophenate (PCP-Na) on the green alga Chlorella pyrenoidosa Chick. S-39 involves a rapid (within 1–2 min) decrease in the light-induced oxygen evolution by algal cells. The suppressed relative yield of variable chlorophyll fluorescence in C. pyrenoidosa in the presence of high PCP-Na concentrations and its dynamics provide evidence for rapid inactivation of photosystem 2, which is not observed at low concentrations of the toxicant. An analysis of the induction curve of delayed chlorophyll fluorescence in algal cells suggests that PCP-Na at low concentrations disturbs the coupling of electron transport and phosphorylation, whereas at high concentrations it inhibits electron transport and decreases the energy potential of photosynthetic membranes. The early toxic effect of PCP-Na is responsible for subsequent impairment of C. pyrenoidosa productivity.     

Comparison of population dynamics between slow- and fast-growing strains of the rotifer Brachionus calyciflorus pallas in continuous culture

Summary The population dynamics of a slow- and a fast-growing strain of the rotifer Brachionus calyciflorus are compared. Rotifers were grown in steady-states, at various specific growth rates (), in both two-stage chemostat and turbidostat cultures on the green alga Chlorella pyrenoidosa. Population variables, including specific ingestion (I), loss (L) and filtration (F) rates, yield (Y), production (P) and half-saturation coefficient of growth (K _g), were calculated using a growth model based on saturation kinetics. I, L, F and K _g were shown to be higher and Y and P lower for the fast-growing strain. Differences between the two strains with regard to these variables may represent tradeoffs associated with the faster potential growth rate. Steady-state relationships between these values and for the fast-growing strain, however, deviated from model predictions which suggest a possible shift from carbon to non-carbon growth limitation.     

The extremely high Al resistance of Penicillium janthineleum F-13 is not caused by internal or external sequestration of Al

Penicillium janthinellum F-13 has been isolated in previous work as a fungus tolerating the presence of high concentrations of Al (as high as 100 mM AlCl₃). Here its growth rate and yield in three acidic (pH 3.0) media of different composition with varying concentrations of Al are reported. The presence of Al did not affect these parameters, except that the growth yield was somewhat lower in GM (a glucose/peptone/yeast extract-containing medium) with the highest concentration tested (100 mM AlCl₃). The amount of Al found in the mycelium was so low that it cannot lead to a significant decrease in the medium for the higher Al concentrations applied. Although citric acid was excreted at growth on GM, and the presence of Al even promoted this, the concentration of this was far too low to diminish (by chelation) the high Al concentrations in the medium to a non-toxic level, i.e. the level (of approx. 1 mM) that is tolerated by low-resistance fungi. At growth on SLBM (a peptone/yeast extract/soil extract-containing medium), a rise in pH occurred. The same was found for SM (a glucose/mineral salts-containing medium), although in this case the picture was more complicated because the initial rise in pH was followed by a lowering due to the excretion of oxalic acid. Although both phenomena can diminish Al toxicity (by decreasing the external concentration of monomeric Al, regarded to be the toxic species), again the decrease is far too low to attain a non-toxic level when high Al concentrations are applied. Therefore, although in principal the metabolic phenomena observed for P. janthinellum F-13 at growth on different media can diminish Al toxicity, the tolerance of this organism for high external Al concentrations must be caused by another mechanism.     

Pseudomonas azotoformans F77和Pseudomonas paracarnis P1风化黑云母的效应及机制比较

【目的】比较高效矿物风化固氮假单胞菌(Pseudomonas azotoformans) F77及其亲缘关系较近的假单胞菌(Pseudomonas paracarnis) P1风化黑云母的效应和机制。【方法】通过检测两株菌在不同时间点的发酵液中细胞数量、pH值、葡萄糖剩余量、葡萄糖酸浓度和可溶性Fe、Al释放量,比较它们对黑云母的风化效果与生理机制。采用RNA-seq技术研究这两株菌风化黑云母过程中出现差异的分子机制。【结果】在持续5 d的风化试验中,菌株F77发酵液中的细胞数量和pH值低于菌株P1,葡萄糖酸浓度是菌株P1的27.3-53.9倍,Fe和Al元素的释放量是菌株P1的3.3-23.3倍。比较转录组数据表明,菌株F77特有的基因数量(2 872)和差异基因数量(1 832)均多于菌株P1 (分别为1 903和1 258)。菌株F77在胞内物质跨膜转运与碳代谢、细胞运动、趋化与信号诱导等途径中基因数量也高于菌株P1。此外,菌株F77的超氧化物歧化酶和过氧化氢酶基因差异表达倍数、葡萄糖酸合成基因数量和差异表达倍数也明显高于菌株P1。【结论】菌株F77风化黑云母以及合成葡萄糖酸的能力显著高于菌株P1。菌株F77通过产生葡萄糖酸来促进黑云母的风化。添加黑云母显著促进了菌株F77胞内与矿物风化相关基因的表达,如物质跨膜转运、细胞运动与趋化、信号诱导、碳代谢及能量代谢等途径基因。此外,葡萄糖酸合成途径基因、超氧化物歧化酶基因以及过氧化氢酶基因在矿物风化中可能发挥重要作用。     

Responses of Al-tolerant Dayton and Al-sensitive Kearney barley cultivars to calcium and magnesium during al stress

Summary Two barley cultivars differing in Al tolerance, Kearney (Al-sensitive) and Dayton (Al-tolerant) were exposed to Al stress with varied Ca and Mg concentrations in the nutrient solution. Increase in calcium and magnesium supply protected root meristems and root growth from Al toxicity more effectively in the Al-tolerant cultivar than in the Al-sensitive one. Lateral roots were much more sensitive to Al than adventitious roots. Exposure to 0.33 mM Al with low concentrations of Ca (1.3 mM) and Mg (0.3 mM) caused damage to root tips in both cultivars. Increasing the Ca concentration to 4.3 and 6.3 mM prevented root tip damage in Dayton but not in Kearney. In the Al-tolerant cultivar Dayton, however, the root tips regenerated even at the low Ca concentration of 1.3 mM, whereas 6.3 mM Ca was necessary for this to occur in Kearney. This difference was due to the fact that Dayton's root meristem cells were more resistant to damage. Magnesium responses also varied between the two cultivars. At the lowest Ca concentration an increase in Mg to 6.3 mM permitted regeneration of damaged Kearney root tips and completely prevented any damage in Dayton. It is to be assumed that the different responses of the two cultivars are due to differences in plasma membrane properties.     

Growth inhibition by high light intensities in algae from lakes undergoing acidification

Blooms ofChrysochromulina breviturrita Nich. (Prymnesiophyceae) have been found to be restricted to lakes above pH 5.5 even though the alga is able to tolerate pH 4.0 in laboratory culture. A possible explanation is the increased transparency in acidifying lakes and a sensitivity ofC. breviturrita to high light intensities. A comparison was made withMougeotia sp., a filamentous green alga which co-occurs in moderately acidic lakes and has a similar pH tolerance range. This alga forms dense, floating mats or amorphous clouds in the upper littoral zone, where it would be exposed to full sunlight irradiances. In cultures ofC. breviturrita, prolonged exposures to 1600 μE · m⁻² · s⁻¹ (I₀′) resulted in reductions in cell yield which were dependent age at the onset of exposure to high light intensity. Only cultures exposed to high light intensities during late stationary phase were able to recover to control levels and no recovery occurred if these cultures were nitrogen deficient.Mougeotia was more tolerant of both high light intensity and nitrogen limitation during the recovery period. The inability ofC. breviturrita to recover from the effects of high light intensity during nitrogen deprivation may be particularly important in small, stratified lakes which are undergoing acidification. The slow rate of vertical circulation, and increasing transparency, would prolong exposure of the alga to the high irradiance levels of nutrient-deficient epilimnetic waters. This suggests that the geographic distribution ofC. breviturrita may be explained in part by the increasing light intensities in lakes undergoing acidification.     

Aluminium effects on Scenedesmus obtusiusculus with different phosphorus status. I. Mineral uptake

Synchronously growing cultures of the unicellular green alga Scenedesmus obtusiusculus were cultivated for 24 and 72 h in the presence or absence of phosphorus. Aluminium chloride (37, 74, 111, 148, 185, or 222 μmol) was added daily to 1 l cell suspension at the end of the cell division phase. As AlCl₃ decreases the pH of the growth medium, controls were run in media with low pH in the absence of AlCl₃. Samples for analysis of the internal (net uptake) and external (bound to cell surface) levels of Al, Mg, P, Ca, and Fe were taken every second hour during a 24 h period or once after 72 h. The investigation shows that the intracellular aluminium in Scenedesmus affects the nutrient status of the cells. A high intracellular level of Al is in consort with an enhancement of the intracellular fractions of Mg, P, Ca and Fe. The increase in net uptake of the minerals measured in the presence of Al is not due to an Al-induced lowering of the pH, caused by Al. The concentrations of Al, Mg, P, Ca and Fe in the cells are generally lower during the dark period of the cell cycle, when the cells are dividing, than during the light period. A peak in mineral concentration of the cells could be monitored in the middle of the 24 h life cycle of the cells. The intracellular Al level is higher when the growth medium is low in P than in phosphorus-rich medium, due to precipitation of aluminium-phosphate both in medium and at cell surfaces. The extracellular Al and P fractions are thus higher in the presence than in the absence of P. The highest Al content monitored in the cells is about 100 nmol Al (10⁶ cells)^?1. A large fraction of Al initially taken up after addition to the medium is subsequently released from the cells during the 24 h cell cycle. The results are interpreted as Al effects on the plasma membrane, thus indirectly affecting various mechanisms for ion transport across the membrane. There are also indications that a surface covered with aluminium-phosphate, formed at high P level in the medium, may prevent ion uptake.