In vitro salinity resistance of three ectomycorrhizal fungi

The growth models, diameter growth rates, biomass yield and Na⁺ contents of three ectomycorrhizal (ECM) fungi, Suillus bovinus (L. ex Fr.) O. Kuntze, Suillus luteus (L. ex Fr.) Gray, Boletus luridus Schaeff ex Fr., were investigated at nine NaCl levels (0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 mol/L). The results showed that the growth models of the three ECM fungal species were not affected by the NaCl concentration, but the growth rates reduced with the increasing NaCl concentration. The growth rates of B. luridus and S. bovinus were significantly higher than that of S. luteus at the same NaCl level; the biomass yields of three ECM fungal species were different, S. bovinus < S. luteus < B. luridus. Of the three species, B. luridus exhibited the highest growth rates, best biomass yield, and greatest Na⁺ concentration in the mycelia over the NaCl gradient tested, indicating B. luridus has the most tolerance to NaCl stress and assimilation to Na⁺ under salt stress. The growth rate of S. luteus was the lowest, but the biomass yield and Na⁺ concentration in the mycelia were only lower than those of B. luridus. S. bovinus was the most sensitive to NaCl stress and its growth rate was faster than that of S. luteus, but the biomass yield and Na⁺ concentration in the mycelia were the lowest.     

Effects of aluminium ions on uptake of calcium,magnesium and nitrogen in Betula pendula seedlings growing at high and low nutrient supply rates

The effects of aluminium on plant nutrition in small birch plants (Betula pendula Roth) were investigated. By using relative addition rate (r _A, g g^?1 d^?1) of nutrients as the growth-controlling variable, it was possible to grow the plants at very low external nutrient concentrations and to simulate plant requirements at two different fertility levels. Before aluminium addition the plants were at steady-state relative growth rate, (R _G, g g^?1 d^?1). The two addition rates were free access of nutrients with R _G ≈ 0.215 d^?1, or nutrient-limited, R _Aand R _G=0.10 d^?1. Internal concentrations of calcium and magnesium decreased with increasing Al³⁺ conncentration in the nutrient solution while nitrogen concentrations in the plants remained unchanged or increased. It was demonstrated in both nutrition treatments that calcium and magnesium decrease per se does not reduce plant growth and that uptake has to be considered in relation to plant requirement at different growth rates. The interpretation of the effects of aluminium on Ca and Mg uptake and plant biomass development suggested that processes other than disturbances in Ca and Mg uptake are the cause of the decrease in growth.     

Bioaccumulation of Copper by Zea mays: Impact on Root, Shoot and Leaf Growth

In the present study, the growth and the Cu²⁺accumulation by roots, shoots and leaves of Zea mays were examined using copper sulphate in the range of 10^?4 to 10^?2 M. Plants of Z. mays did not show inhibition of growth in the presence of 10^?4 to 10^?2 M Cu²⁺; however, it was observed growth effects on root when different Cu²⁺ solution concentrations were used. Only the seedlings exposed to 10^?2 M exhibited substantial root growth reduction, yielding only 56% of length with respect to the control. Seedlings exposed to 10^?4 M Cu²⁺ exhibited 16% and 42% growth increase in shoots and leaves, respectively, when compared with the controls. The seedlings treated with 10^?3 and 10^?2 M Cu²⁺ were inhibited in shoot and leaf growth. The fresh weights in roots, shoots and leaves significantly decreased at 10^?2 M Cu²⁺. The tolerance index, based on root length, was not significantly different for the three different treatments with copper. However, the total accumulation rate was very low at 10^?4 and 10^?3 M compared to 10^?2 Cu treatments. The capacity of copper accumulation by roots, shoots and leaves of Z. mays plants increased concomitant to the copper concentration, arriving to 382 times more in roots, 157 in shoots and only 16 in leaves, all compared to the controls. Cu could be accumulated by roots, shoots and leaves when the initial concentrations were 10^?3 and 10^?4 M. However, when it was 10^?2 M, the metal could not be accumulated by leaf and shoot levels; the roots could increase their copper accumulation capacity three times compared to the control. Z. mays has potential ability to accumulate Cu without being overly sensitive to Cu toxicity.     

Some effects of montmorillonite on the growth of mixed microbial cultures

A defined starch urea-mineral-salts medium was used to study the effect of montmorillonite on the growth of pairs of microorganisms. The pairs of microorganisms used were Bacillus 3B-Klebsiella U34 and Bacillus 3B-Candida N2. When Bacillus 3B and Klebsiella U34 were grown together between montmorillonite concentrations of 0.4 mg·ml^?1 and 10 mg·ml^?1, linear relationships existed between logio (montmorillonite concentration) and the maximum yield of both Bacillus 3B and Klebsiella U34 and the final $\text{3B}\text{U34}$ ratio. At montmorillonite concentrations of greater than 10 mg·ml^?1 growth of both Bacillus 3B and Klebsiella U34 was reduced, possibly due to complete binding of starch to montmorillonite. Montmorillonite reduced the growth of Bacillus 3B and Candida N2 when they were grown together, possibly due to reduced urea hydrolysis.In these well defined systems, the analysis of the effects of clay minerals on microbial growth was complex. This complexity was due to the large number of points in the system at which the mineral could affect the system. The use of mathematical tools for analysis helped to quantify the exact relationships between Bacillus 3B, Klebsiella U34 and montmorillonite.     

Stenotrophomonas rhizophila DSM14405T promotes plant growth probably by altering fungal communities in the rhizosphere

Stenotrophomonas rhizophila DSM14405^T is of high biotechnological interest as plant growth stimulator, especially for salinated conditions. The objective of this study was to determine the effect of plant species (cotton, tomato, and sweet pepper) on colonisation and plant growth promotion of this beneficial bacterium in gnotobiotic systems and in non-sterile soil. All plant structures (leaves, stems, and roots) were densely colonised by DSM14405^T reaching up to 10⁹ cells g^?1 fresh weight; under gnotobiotic conditions the abundances were 4–5 orders of magnitude higher than in non-sterile soil. Under non-sterile conditions and ambient humidity, tomato shoots were more densely colonised than shoots of sweet pepper and cotton. S. rhizophila DSM14405^T was shown to grow endophytically and colonise the vicinity of root hairs of tomato. Plant growth promotion was particularly apparent in tomato. In general, the impact of plant species on colonisation and plant growth promotion was more pronounced in soil than under gnotobiotic conditions and likely due to the control of diseases and deleterious microorganisms. S. rhizophila DSM14405^T was shown to control diseases in sweet pepper and in cotton. Molecular profiling via single strand conformation polymorphism of internal transcribed spacers and 16S rRNA genes (PCR-single strand conformational polymorphism (SSCP)) revealed that S. rhizophila DSM14405^T strongly affected fungal, but not bacterial communities in the rhizosphere of tomato and sweet pepper. Major SSCP bands related to uncultured fungi and Candida subhashii, disappeared in tomato rhizosphere after Stenotrophomonas treatment. This suggests an indirect, species-specific plant growth promotion effect of S. rhizophila via the elimination of deleterious rhizosphere organisms.     

Isotopic evidence of significant assimilation of atmospheric-derived nitrogen fixed by Azospirillum brasilense co-inoculated with phosphate-solubilising Pantoea dispersa in pepper seedling

The contribution of plant growth-promoting bacteria (PGPB) of the genus Azospirillum to the plant N budget through biological nitrogen fixation (BNF) is still controversial. The aim of this study was to determine the contribution of BNF by Azospirillum brasilense on pepper grown at different N levels, attained using the ¹⁵N natural abundance method. To this end, pepper plants were grown in a growth chamber and treated with A. brasilense combined with Pantoea dispersa and then irrigated at four different N levels (0, 1, 3 and 7 mM NO₃⁻). The assimilation of fixed N was clear from the lower δ¹⁵N values observed in bacteria-treated plants compared with those of non-bacteria treated plants. The percentage of BNF-derived N decreased with decreasing NO₃⁻ levels in the growth medium. BNF contribution to the total nitrogen content of plants was found to be as high as 46%. The results suggest that the bacteria have a potential to supply a considerable amount of N to pepper seedlings, as well as to stimulate plant growth and N uptake when Azospirillum–Pantoea treatment is combined with low NO₃⁻ levels.     

Effects of aluminum on mineral content of mycorrhizal fungi in vitro

The influence of Al³⁺ on the mineral content of mycorrhizal fungi was studied in vitro. Amanita muscaria (L. ex Fr.) Pers. ex Hooker whose growth is reduced and Lactarius piperatus (L. ex Fr.) S.F. Gray whose growth is stimulated by Al³⁺ where chosen for the experiments. 0, 0.1, 1, and 10mM A³⁺ were added as Al₂(SO₄)₃ · 18H₂O to modified M-40 medium. Al³⁺ drastically affected the mineral contents of the mycelia of both fungi: the Al, Ca, and Na contents increased while P, Mg, and K decreased with the increasing Al³⁺ concentrations in the media. On the other hand, some important differences between the two mycelia were detected. In the mycelia of Lacterius piperatus grown on the control media, there was about twice as much Ca content and a three times lower P content than in the Amanita muscaria mycelia. The Al³⁺ content in the mycelia of Lactarius piperatus grown on 10mM Al³⁺ was six times higher than in Amanita muscaria at the same concentration.     

Improvement of Brassica napus growth under cadmium stress by cadmium-resistant rhizobacteria

This study focuses on the characterization of four bacterial isolates from heavy metal-polluted rhizosphere in order to examine their plant growth promoting (PGP) activity. The PGP activity on the canola (Brassica napus) of the strains which showed cadmium resistance and multiple PGP traits was assessed in the presence and in the absence of Cd²⁺. The strains, Pseudomonas tolaasii ACC23, Pseudomonas fluorescens ACC9, Alcaligenes sp. ZN4 and Mycobacterium sp. ACC14 showed 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity. They also synthesized ACCD enzyme in vitro when 0.4 mM Cd²⁺ was added to the growth medium. The presence of the metal, however, reduced the ACCD activity in Alcaligenes sp. ZN4 and Mycobacterium sp. ACC14, while it did not affect the ACCD activity of P. tolaasii ACC23 and P. fluorescens ACC9. ACC9 and ACC23 produced indole acetic acid (IAA) and siderophores, while ACC14 produced only IAA. IAA and siderophores were produced more actively under Cd-stress.Root elongation assays conducted on B. napus under gnotobiotic conditions demonstrated increases (from 34% up to 97%) in root elongation of inoculated canola seedlings compared to the control plants. Subsequently, the effect of inoculation with these strains on growth and uptake of Cd²⁺ in roots and shoots of canola was studied in pot experiments using Cd-free and Cd-treated (15 μg Cd²⁺ g^?1 dw) soil. Inoculation with P. tolaasii ACC23, P. fluorescens ACC9 and Mycobacterium sp. ACC14 promoted the growth of plants at concentrations of 0 and 15 μg Cd²⁺ g^?1 soil. The maximum growth was observed in the plants inoculated with P. tolaasii ACC23. The strains did not influence the specific accumulation of cadmium in the root and shoot systems, but all increased the plant biomass and consequently the total cadmium accumulation.The present observations showed that the bacterial strains used in this study protect the plants against the inhibitory effects of cadmium, probably due to the production of IAA, siderophores and ACCD activity.     

Potential phytotoxicity of diquat accumulated by aquatic plants and sediments

The adsorption and desorption of Reglone A^R to freshwater algae, Myriophyllum spicatum and a soil-sand mixture, singly and in combination was examined to investigate the potential for phytotoxicity of diquat residues in aquatic sediments. The diquat adsorption capacity of the aquatic plants ranged from 0.6 to 2.4 mg diquat g dry wt^?1. Forty to seventy percent of the adsorbed diquat could be desorbed with 5 M ammonium chloride. The adsorption capacity of the soil system was about 2.5 mg diquat g dry wt^?1 and approximately 35% of this diquat could be desorbed. Reglone^R inhibited the growth of blue-green algae (Anabaena flos-aquae and Anacystis nidulans) at concentrations greater than 0.03 ppm. Eukaryotic algae were less sensitive, growth of Navicula pelliculosa was inhibited at concentrations exceeding 0.3 ppm and Chlorella vulgaris was unaffected by 3 ppm Reglone. In the presence of soil, growth inhibition by Reglone was eliminated. Reglone was added to a water-soil mixture system at levels up to 334 ppm to simulate chronic usage. Anabaena flos-aquae or Lemna sp. were used to bioassay the availability of the diquat adsorbed to this soil system. Significant growth inhibition of both bioassay plants was observed in soil treated with 33.4 ppm Reglone and the 334 ppm treatment was lethal. These experiments suggest that residual phytotoxicity becomes apparent in this soil system at about 7% of the diquat adsorption capacity. The Reglone adsorption-desorption isotherm of a natural, organic lake sediment was measured to predict the number of Reglone treatments at the recommended application rate before residual phytotoxicity would become apparent.     

Factors limiting colonization of unsterilized filter-paper by cereal root-infecting fungi

Five cereal root-infecting fungi were found to produce colonies of limited size (from 5 mm agar inoculum disks) on unsterilized Whatman No. 3 filter paper; the optimal volume of mineral nutrients solution was that required for saturation of the paper circles. Under these conditions, further expansion of colonies was halted, after 22 days or less at 20°C, by growth of commensal bacteria. Optimal concentration of sodium nitrate in the minerals solution was 82.5mgl^?1 for Phialophora grammicola, 330 mgl^?1 for Fusarium culmorum, and 660 mgl^?1 for Cochliobolus sativus, Curvularia ramosa and Gaeumannomyces graminis var, tritici. Final colony size could be predicted from that after 8 days from inoculation, and so was determined by speed of initiation of cellulolysis and early mycelial growth.Under these conditions, adventitious colonies of other cellulolytic fungi rarely developed on the wet, unsterilized filter-paper. But when the constraint imposed by growth of associated bacteria was removed by addition of streptomycin sulphate (at 150 mgl^?1) to the minerals solution, then colony size of inoculant fungi was increased, generally by a factor of 2 × or more, and this increase was accompanied by appearance of numerous adventitious fungal colonies on the paper circles.     

Interactive effects of N fertilizer source and timing of fertilization leave specific N isotopic signatures in Chinese cabbage and soil

Natural ¹⁵N abundances (δ¹⁵N) in plant and soil can be used as a powerful marker to reveal the history of N fertilization. To investigate whether N fertilizer source and timing of fertilization leave specific δ¹⁵N signals in plant tissue and soil inorganic N, Chinese cabbage (Brassica campestris L. cv. Maeryok), one of the most popular vegetables in Asia, was grown in pots for 60 days with a single or split N applications of organic (composted manure; δ¹⁵N=+16.4‰) or inorganic N (urea; δ¹⁵N=−0.7‰). Seven N treatments were studied: (1) a single basal fertilization with compost or (2) urea; (3) a basal urea application followed by an additional (at 40 days after transplant, same below) compost or (4) urea application; (5) a basal compost application followed by an additional compost or (6) urea application; and (7) no N fertilization. Regardless of the time of N application, δ¹⁵N of cabbage treated with compost was higher (>+9.0‰) than that (< +1.0‰) treated with urea, reflecting the effect of isotopically different N sources. In split N fertilization, only the addition of isotopically different N sources in the middle of the growth period significantly affected the δ¹⁵N of the whole plant. Specific δ¹⁵N signals of basal N inputs were detected in outer cabbage parts formed in the early growth stage, while those of additional N inputs were detected in inner cabbage parts formed in the latter growth stage. We conclude that measurements of temporal variations in δ¹⁵N of plant parts formed in different growth stages could reveal the history of N fertilization.     

Growth promotion and protection against damping-off of wheat by two rock phosphate solubilizing actinomycetes in a P-deficient soil under greenhouse conditions

Micromonospora aurantiaca- and Streptomyces griseus-related strains isolated from Moroccan phosphate mines (MA^MPM and SG^MPM) were previously selected for their rock phosphate (RP) solubilizing abilities and their multiple plant growth promoting properties demonstrated in laboratory conditions. In order to assess whether these interesting properties could have a direct effect on plant growth and fitness, seeds of the wheat plant (Triticum durum L. cv. Vitron) coated or not with mycelium of these strains and of the reference strain S. griseus M1323, were grown in a sterile soil deficient in soluble phosphate supplemented or not with soluble phosphate or with the insoluble RP, under greenhouse conditions. These studies revealed that the presence of the actinomycete strains in the soil supplemented with RP significantly promoted the growth of the wheat plants. MA^MPM and SG^MPM had the greatest stimulatory effect on plant growth with 50–47% and 80–78% weight increase of shoots and roots, respectively, in comparison with the sterile control. This increase correlated with a significant increase in the N and P content of plant tissues. The MA^MPM- and SG^MPM-dependent growth promotion in the RP supplemented soil was on average 10–13% lower than that achieved by the soluble phosphate supplement. Furthermore, in a soil infested with Pythium ultimum, the mediator of damping-off disease, the coating of wheat seeds with the mycelium of MA^MPM strain resulted in a clear protection of the plant. The level of protection achieved by MA^MPM was 14% lower than that conferred by the commercial bio-fungicide agent (Mycostop^®). This study demonstrated that MA^MPM in association with pulverized RP could constitute a novel and non-polluting bio-fertilizer/biocontrol product useful for the development of sustainable agriculture.     

Response of Pinus Sylvestris Seedlings to Cadmium and Mycorrhizal Colonisation

Effects of Cd and mycorrhizal colonisation on seedling growth and Cd accumulation in Pinus sylvestris seedlings were studied. While colonisation by Suillus bovinus improved shoot growth, colonisation by Paxillus involutus had no effect on growth of seedlings. There was no Cd-ameliorating effect of colonisation in terms of either shoot or root growth. Colonisation by P. involutus did not decrease Cd transport from roots to shoots, whereas colonisation by S. bovinus significantly reduced the level of Cd in shoots in the 100 mg Cd kg^-1 treatment. The proportion of healthy mycorrhizal root tips of S. bovinus-inoculated seedlings was reduced as a result of Cd addition. However, no such effect was found in P. involutus-inoculated seedlings.     

Effect of fluoride on axenic cultures of diatoms

Algal bioassay studies on the effect of F concentrations on diatoms Nitzschia palea (freshwater) and Amphora coffeaeformis (brackishwater) were conducted in the laboratory. Significant enhancement of growth occurred in N. palea at F concentrations between 10 and 110 mg L^?1. In A. coffeaeformis statistically significant stimulation occurred at 70 mg L^?1 F and above 90 mg L^?1 F the growth declined. The results indicate that the diatom N. palea and A. coffeaeformis can tolerate high F concentration.     

Effect of SO2 and NH3 on growth behavior of some phylloplane fungi of wheat in in vitro

The colony growth of some phylloplane fungi of wheat viz. Alternaria alternata, Aspergillus favus, Amiger, Cladosportium cladosporioides, Curvularia lunata, Drechslera australiensis, Epicoccum purpurascens, Fusarium oxysporum, Penicillium chrysogenum and P. citrinum were studied in chamber fumigation experiments exposed to 2669 ± 105 μg SO₂ m^?3 and 708.33 ± 55 μg NH3 m^?3 air, separately, for 10, 30 and 60 min. The colony growth of all the test fungi was significantly (P=0.01/0.005) inhibited on prolonged period of SO₂/NH₃ exposure. However, some of the test fungi namely A. favus, A. niger, E. purpurascens and F. oxysporum showed growth stimulation after 10 min exposure of SO₂. Similarly, the growth of C. lunata and F. oxysporum increased only after 10 min exposure of NH3. The inhibitory effect of SO₂/NH₃ was directly correlated with the exposure times.     

Effects of a chromated-copper-arsenate wood preservative on the growth of a pentachlorophenol degrading bacterium

A chromated-copper-arsenate (CCA) wood preservative was tested for toxic effects on the growth of a bacterial culture (Flavobactenum sp. ATCC 53874) capable of biodegrading pentachlorophenol, another wood preservation chemical. Both a commercially available CCA preparation and a laboratory-prepared CCA solution were tested. Each had an inhibitory effect on the growth of Flavobacterium at diluted CCA levels as low as 1.0×10^?4 to 1.0×10^?5% wt vol^?1. The commercial formulation was generally more toxic. EC₅₀ values calculated after 96 hr of incubation were 1.2 ×10^?4% wt vol^?1 for the commercial material (containing 0.15/0.097/0.14 μg mL^?1 of Cr/Cu/As, respectively) and 3.8×10^?4% for the laboratory solution (containing 0.51/0.31/0.49 μg mL^?1 of Cr/Cu/As, respectively). CCA toxicity increased during the first 7 to 8 days and then slowly decreased for the balance of the 21 day incubation period. Biodegradation of pentachlorophenol residues in contaminated soil will be negatively affected by the presence of CCA as a co-contaminant.     

Short-Term Effects of Arsenate-Induced Toxicity on Growth, Chlorophyll and Carotenoid Contents, and Total Content of Phenolic Compounds of Azolla filiculoides

This study evaluated the toxic effects of arsenic (As) on the growth, total antioxidant activity, total content of phenolic compounds, and content of photosynthetic pigments of Azolla filiculoides. The aquatic fern was propagated and exposed to Yoshida nutrient solution contaminated with sodium arsenate (Na₂HAsO₄??7H₂O) at six concentrations (5, 10, 20, 30, 60, and 120???g?As?mL^?1), including the control without As contamination. Azolla cultures were kept under environmental chamber conditions?26??C, 12?h photoperiod and 80% HR for 96?h. Increased As concentrations (>30???g?mL^?1) significantly diminished growth of A. filiculoides and the total content of chlorophyll and total phenolic compounds, but significantly enhanced of total carotenoid?+?xanthophylls content. The concentrations of 5 and 10???g?As?mL^?1 significantly stimulated the growth of A. filiculoides. This aquatic fern tolerates As concentrations lower than 30???g?mL^?1, and its maximum As accumulation (28???g?g^?1 dry weight) was achieved when exposed to 60???g As mL^?1, but showing clear symptoms of As toxicity.     

Colonization of wheat roots by Gaeumannomyces graminis inhibited by specific soils,microorganisms and ammonium-nitrogen

Lineal extension of Gaeumannomyces graminis var. tritici hyphae along roots of intact wheat plants growing in soils was measured. Hyphal growth rates were lower in soils treated with NH₄⁺-N than with NO₃^?-N. In a soil that is suppressive to the take-all disease, the controlling influence of NH₄⁺-N was eliminated by soil fumigation (methyl bromide), and reintroduced to fumigated soil by additions of 1% nonsterile soil. Effects of fumigation on hyphal growth were absent in a nonsuppressive soil, and in NO₃^?-treatments of the suppressive soil. When inocula of selected groups of wheat rhizoplane microflora were reintroduced into a fumigated or a soil-reinoculated soil via a root-food base, the Pseudomonas spp. consistently appeared more suppressive in NH₄⁺-N treatments than the general bacterial flora, Bacillus spp. spores, streptomycetes, and fungi.     

Regulation of parasitism by host density: The Bdellovibrio-Rhizobium interrelationship

Rhizobium strains of the cowpea group did not lose viability readily when added to soil, but Bdellovibrio acting on these rhizobia were found in 32 of 90 soils examined. Bdellovibrio did not initiate replication in liquid media at low host densities, but it did multiply once the Rhizohium numbers increased through growth to about 10⁸ ml^?1. From about 10⁴ to 6 × 10⁵ ml^?1Rhizohium cells survived attack by the parasites in liquid media. In nutrient-free buffer, no significant increase in vibrio abundance was evident if the rhizobial frequency was low. whereas Rhizobium populations containing 6 × 10⁸ cells ml^?1 were lysed rapidly. Bdellovibrio did not multiply when introduced into sterile soil with small numbers of the host, but it replicated when the rhizobia were abundant because of the latter's use of soil organic matter for growth or because of the deliberate addition of 10⁸Rhizohium g^?1. Nevertheless, the host persisted in such vibrio-rich soil samples. The abundance of indigenous bdellovibrios increased appreciably in nonsterile soil if the rhizobia were introduced in large but not small numbers. It is suggested that a major reason for the lack of elimination of the host population in soil by its parasites is the need for a critical host cell frequency, large Rhizobium numbers being required for Btiellovibrio to initiate replication and low numbers of surviving hosts no longer being able to support the parasite.     

Assessment of the Phytoremediation Potential of Salvinia minima Baker Compared to Spirodela polyrrhiza in High-strength Organic Wastewater

Salvinia minima combines several advantages for being used in aquatic phytoremediation. The objectives of this work were to compare the growth kinetics and productivity of S. minima and Spirodela polyrrhiza in high-strength synthetic organic wastewater (HSWW) and to evaluate the growth characteristics of S. minima in various culture media, including anaerobic effluents from pig wastewater (PWAE). It was found that the Relative Growth Rate (RGR) of S. minima was significantly higher (p?<?0.05) compared to the RGR of S. polyrrhiza in Hutner Medium (HM) and in HSWW. Also, S. minima showed a 1.5 fold productivity and a 2.3 fold productivity, compared to S. polyrrhiza in HM and HSWW, respectively. Diauxic growth of S. minima was observed preferentially under pH control and there was a simultaneous consumption of two nitrogen sources. Productivity of S. minima was similar in pig waste anaerobic effluents (PWAE) and in HM without ammonium nitrate and amended with ammonium sulphate (MHM?+?AS), at an initial NH₄ concentration of 35 mg l^?1. Above this level, the productivity was found to decrease as the initial ammonium concentration increased, in both media. Growth was completely inhibited at 140 mg l^?1 in the PWAE. In summary, S. minima is a better option than S. polyrrhiza for treating high-strength organic wastewater and lagoons should be operated at a maximum initial ammonium–nitrogen concentration of 70 mg l^?1 and at a pH of 5.0 or 6.0. Likewise, the initial density should be maintained in the range of 7 to 15 g dw m^?2.