Diauxic growth of Penicillium camembertii on glucose and arginine

The growth of Penicillium camembertii during batch culture in a synthetic medium containing glucose and arginine was examined. The diauxic growth observed can be well characterized. Indeed, in a first phase, glucose and arginine were, respectively, assimilated as carbon and nitrogen sources, with an acidification of the medium (until 3.5), since arginine was taken up in exchange for protons. During this phase of growth, arginine, in addition to glucose, was also assimilated as an energy source, resulting in the release of the arginine carbon content as CO₂. Then, in a second phase, characterized by reduced growth rates after glucose depletion, arginine was assimilated as a carbon and nitrogen source, as well as an energy source, resulting in ammonium release which raised the pH (final pH 6.3), despite the amino acid/H⁺ exchange, since amino acids contain excess nitrogen in relation to their carbon content for fungi.     

Utilization of Organic Nitrogen Sources by Two Phytoplankton Species and a Bacterial Isolate in Pure and Mixed Cultures

Algal production of dissolved organic carbon and the regeneration of nutrients from dissolved organic carbon by bacteria are important aspects of nutrient cycling in the sea, especially when inorganic nitrogen is limiting. Dissolved free amino acids are a major carbon source for bacteria and can be used by phytoplankton as a nitrogen source. We examined the interactions between the phytoplankton species Emiliania huxleyi and Thalassiosira pseudonana and a bacterial isolate from the North Sea. The organisms were cultured with eight different amino acids and a protein as the only nitrogen sources, in pure and mixed cultures. Of the two algae, only E. huxleyi was able to grow on amino acids. The bacterium MD1 used all substrates supplied, except serine. During growth of MD1 in pure culture, ammonium accumulated in the medium. Contrary to the expectation, the percentage of ammonium regenerated from the amino acids taken up showed no correlation with the substrate C/N ratio. In mixed culture, the algae grew well in those cultures in which the bacteria grew well. The bacterial yields (cell number) were also higher in mixed culture than in pure culture. In the cultures of MD1 and T. pseudonana, the increase in bacterial yield (number of cells) over that of the pure culture was comparable to the bacterial yield in mixed culture on a mineral medium. This result suggests that T. pseudonana excreted a more-or-less-constant amount of carbon. The bacterial yields in mixed cultures with E. huxleyi showed a smaller and less consistent difference than those of the pure cultures of MD1. It is possible that the ability of E. huxleyi to use amino acids influenced the bacterial yield. The results suggest that interactions between algae and bacteria influence the regeneration of nitrogen from organic carbon and that this influence differs from one species to another.     

Raoultella planticola, a new strain degrading 2,4,5-trichlorophenoxyacetic acid

A new strain that degrades the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) was isolated from soil, which was exposed to factors related to the petrochemical industry. According to its physiological, biochemical, cultural, and morphological traits, together with the sequence of the 16S rRNA gene, the strain was identified as Raoultella planticola 33-4ch. The strain could consume 2,4,5-T as a sole source of carbon and energy. The amount of 2,4,5-T in the culture medium decreased by 51% after five days of incubation. Raoultella planticola 33-4ch consumes 2,4,5-T to produce 4-chlorophenoxyacetic, phenoxyacetic, and 3-methyl-2,6-dioxo-4-hexenoic acids.     

Raoultella planticola, a new strain degrading 2,4,5-trichlorophenoxyacetic acid

A new strain that degrades the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) was isolated from soil, which was exposed to factors related to the petrochemical industry. According to its physiological, biochemical, cultural, and morphological traits, together with the sequence of the 16S rRNA gene, the strain was identified as Raoultella planticola 33-4ch. The strain could consume 2,4,5-T as a sole source of carbon and energy. The amount of 2,4,5-T in the culture medium decreased by 51% after five days of incubation. Raoultella planticola 33-4ch consumes 2,4,5-T to produce 4-chlorophenoxyacetic, phenoxyacetic, and 3-methyl-2,6-dioxo-4-hexenoic acids.     

Fatty acids ofPseudomonas aeruginosa grown on media affecting polymyxin susceptibility

The readily extractable lipids ofPseudomonas aeruginosa 015 were significantly altered by growth on branched-chain amino acids and their acyl derivatives as sole carbon source. These cultural conditions, especially growth on the acyl derivatives, resulted in decreased amounts of unsaturated fatty acids and concomitant increases in cyclopropyl acids. The shift in the ratio of unsaturated to cyclopropyl acids was primarily due to the carbon source and did not correlate to the physiological or temporal age of the culture. Growth on carbon sources catabolized to propionyl-CoA affected the synthesis of odd-chain fatty acids. Growth on substrates metabolized to isobranched carbon skeletons resulted in the synthesis of branched-chain fatty acids. The carbon sources caused minor changes in the cellular percentage and phosphate content of the readily extractable lipids.     

Isolation and properties of new strains of obligate methanotrophs

New strains of obligate methanotrophic bacteria which assimilate only methane or methanol as the source of carbon and energy have been isolated. According to their morphology, ultrastructure, cultural and physiologo-biochemical characteristics, the bacteria were classed as Methylobacter vinelandii, Methylobacter bovis, Methylobacter chroococcum and Mehylosinus sporium. A new species Methylocystis echinoides sp. nov. is described; it differs from other methanotrophs in certain morphological and physiological properties. The subspecies Methylosinus trichosporium var. methanolicum is recommended to be termed as Methylocytis methanolicus sp. nov.     

嗜热子囊菌利用短链有机酸生产角质酶

以嗜热子囊菌(Thermobifida fusca WSH03-11)发酵生产角质酶为模型,研究微生物利用市政污泥厌氧酸化所产短链有机酸为碳源发酵生产高附加值产品的可能。发现：(1)以丁酸、丙酸和乙酸为碳源时,有机酸和氮元素浓度分别为8.0 g/L和1.5 g/L有利于角质酶的生产;而以乳酸为碳源时,最适有机酸和氮源浓度分别为3.0 g/L和1.0 g/L;(2)改变诱导物角质的浓度,以丁酸、丙酸、乙酸和乳酸为碳源,分别比优化前提高了31.0%、13.3%、43.8%和73.2%;(3)在四种有机酸中,T. fusca WSH03-11利用乙酸的速率最快,平均比消耗速率是丙酸的1.3倍,丁酸的2.0倍及乳酸的2.2倍;以丁酸为碳源时的酶活(52.4 U/mL)是乳酸的1.7倍、乙酸的2.5倍和丙酸的3.2倍;角质酶对乳酸的得率(12.70 u/mg)分别是丁酸的1.4倍、丙酸的3.0倍和乙酸的3.8倍;(4)以混合酸为碳源生产角质酶,T. fusca WSH03-11优先利用乙酸,而对丁酸的利用受到抑制。进一步研究发现,混合酸中0.5 g/L的乙酸将导致丁酸的消耗量降低66.7%。这是首次利用混合酸作碳源发酵生产角质酶的研究报道。这一研究结果进一步确证了利用市政污泥厌氧酸化所产有机酸为碳源发酵生产高附加值产品的可行性,为以廉价碳源生产角质酶奠定了良好的基础。     

嗜热子囊菌利用短链有机酸生产角质酶

以嗜热子囊菌(Thermobifida fusca WSH03-11)发酵生产角质酶为模型,研究微生物利用市政污泥厌氧酸化所产短链有机酸为碳源发酵生产高附加值产品的可能。发现：(1)以丁酸、丙酸和乙酸为碳源时,有机酸和氮元素浓度分别为8.0 g/L和1.5 g/L有利于角质酶的生产;而以乳酸为碳源时,最适有机酸和氮源浓度分别为3.0 g/L和1.0 g/L;(2)改变诱导物角质的浓度,以丁酸、丙酸、乙酸和乳酸为碳源,分别比优化前提高了31.0%、13.3%、43.8%和73.2%;(3)在四种有机酸中,T. fusca WSH03-11利用乙酸的速率最快,平均比消耗速率是丙酸的1.3倍,丁酸的2.0倍及乳酸的2.2倍;以丁酸为碳源时的酶活(52.4 U/mL)是乳酸的1.7倍、乙酸的2.5倍和丙酸的3.2倍;角质酶对乳酸的得率(12.70 u/mg)分别是丁酸的1.4倍、丙酸的3.0倍和乙酸的3.8倍;(4)以混合酸为碳源生产角质酶,T. fusca WSH03-11优先利用乙酸,而对丁酸的利用受到抑制。进一步研究发现,混合酸中0.5 g/L的乙酸将导致丁酸的消耗量降低66.7%。这是首次利用混合酸作碳源发酵生产角质酶的研究报道。这一研究结果进一步确证了利用市政污泥厌氧酸化所产有机酸为碳源发酵生产高附加值产品的可行性,为以廉价碳源生产角质酶奠定了良好的基础。     

Influence of amino acids on nitrogen fixation ability and growth of Azospirillum spp

The utilization of amino acids for growth and their effects on nitrogen fixation differ greatly among the several strains of each species of Azospirillum spp. that were examined. A. brasiliense grew poorly or not at all on glutamate, aspartate, serine, or histidine as the sole nitrogen and carbon sources. Nitrogen fixation by most A. brasiliense strains was inhibited only slightly even by 10 mM concentrations of these amino acids. In contrast, A. lipoferum and A. amazonense grew very well on glutamate, aspartate, serine, or histidine as the sole nitrogen and carbon sources; nitrogen fixation, which was measured in the presence of malate or sucrose, was severely inhibited by these amino acids. It was concluded that growth on histidine as the sole source of nitrogen, carbon, and energy may be used for the taxonomic characterization of Azospirillum spp. and for the selective isolation of A. lipoferum. The different utilization of various amino acids by Azospirillum spp. may be important for their establishment in the rhizosphere and for their associative nitrogen fixation with plants. The physiological basis for the different utilization of glutamate by Azospirillum spp. was investigated further. A. brasiliense and A. lipoferum exhibited a high affinity for glutamate uptake (Km values for uptake were 8 and 40 microM, respectively); the Vmax was 6 times higher in A. lipoferum than in A. brasiliense. At high substrate concentrations (10 mM), the nonsaturable component of glutamate uptake was most active in A. lipoferum and A. amazonense.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of amino acids on nitrogen fixation ability and growth of Azospirillum spp.

The utilization of amino acids for growth and their effects on nitrogen fixation differ greatly among the several strains of each species of Azospirillum spp. that were examined. A. brasiliense grew poorly or not at all on glutamate, aspartate, serine, or histidine as the sole nitrogen and carbon sources. Nitrogen fixation by most A. brasiliense strains was inhibited only slightly even by 10 mM concentrations of these amino acids. In contrast, A. lipoferum and A. amazonense grew very well on glutamate, aspartate, serine, or histidine as the sole nitrogen and carbon sources; nitrogen fixation, which was measured in the presence of malate or sucrose, was severely inhibited by these amino acids. It was concluded that growth on histidine as the sole source of nitrogen, carbon, and energy may be used for the taxonomic characterization of Azospirillum spp. and for the selective isolation of A. lipoferum. The different utilization of various amino acids by Azospirillum spp. may be important for their establishment in the rhizosphere and for their associative nitrogen fixation with plants. The physiological basis for the different utilization of glutamate by Azospirillum spp. was investigated further. A. brasiliense and A. lipoferum exhibited a high affinity for glutamate uptake (Km values for uptake were 8 and 40 microM, respectively); the Vmax was 6 times higher in A. lipoferum than in A. brasiliense. At high substrate concentrations (10 mM), the nonsaturable component of glutamate uptake was most active in A. lipoferum and A. amazonense.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dark and light metabolism of amino acids inChlorella vulgaris

An investigation was made of the suitability of 27 amino acids to serve as source of nitrogen, carbon and energy forChlorella vulgaris in the dark. Only leucine led to profuse growth. Eight other amino acids were moderately effective.In the light, almost all of the amino acids tested proved to be suitable nitrogen sources. Histidine and tryptophane, however, damaged the cells and killed them after a few weeks cultivation in the light, the cultures turning black with histidine and brown with tryptophane. The effect of histidine could be abolished by including pyridoxine or nicotinamide in the culture medium.     

Organic or mineral nitrogen source during Penicillium camembertii growth on a glucose limited medium

Penicillium camembertii was cultivated on a carbon-limited medium (glucose). Two nitrogen sources were compared, a mineral, ammonium, and an organic nitrogen source, lysine. Among the amino acids convenient nitrogen sources for P. camembertii, lysine was chosen since it cannot be assimilated as a carbon source for cell biosynthesis. During culture on glucose and ammonium, a decline phase immediately followed growth after glucose depletion, since no energy source remained in the medium. On the contrary, on glucose and lysine, a stationary state was recorded after glucose depletion, since lysine was used as the energy supply for cell maintenance, leading to the release of the corresponding carbon as CO₂, while nitrogen from lysine was released as ammonium.     

Morphological and physiological characteristics ofSpirillum gracile sp.n.

Spirilla measuring 0.25 to 0.30 µ in diameter and generally 5 to 10 µ in length were selectively isolated from pond and stream water. The isolation procedure involved the use of cellulose ester filter discs (0.45 µ pore size) which allowed the thin spirilla to migrate onto the surface of culture plates, but retained larger organisms. The spirilla isolated formed distinctive subsurface, spreading, semi-transparent colonies. The organisms exhibited a microaerophilic behavior; however, they did not grow anaerobically. Nutritional studies indicated that amino acids served both as carbon and nitrogen sources for the organisms and that organic acids and carbohydrates were suitable as carbon sources. NH₄Cl was utilized poorly as a nitrogen source and KNO₃ not at all. An exogenous supply of vitamins was not needed for growth. On the basis of their cell diameter, their microaerophilic growth and other physiological characteristics, the spirilla could not be identified with any of the previously described species of the genusSpirillum. It is proposed that these thin spirilla be recognized as a new species to be designatedSpirillum gracile.     

高等植物对氨基酸态氮的吸收与利用研究进展

植物能够在不经矿化的情况下直接吸收利用环境中的分子态氨基酸.氨基酸作为植物和微生物的优良碳源和氮源,二者对其吸收存在着激烈竞争,氨基酸态氮来源广、半衰期短的特点使其具有巨大的流通量.运用氮同位素示踪方法研究氨基酸对植物的氮营养贡献一直是国内外学者研究的热点,对揭示土壤肥力本质具有重要意义.本文对不同生态系统中氨基酸形态特征、代谢机制及营养贡献进行了简要综述,分析了氨基酸态氮在植物-土壤-微生物系统中的循环机制及生物有效性等方面研究现状和发展趋势,并提出了土壤氨基酸生物有效性环境调控、氨基酸碳-氮代谢及提高农田生态系统有机氮管理等待解决的科学问题.     

Kinetics of amino acid uptake by ectomycorrhizal roots

It is well established that ectomycorrhizal fungi can use amino acids as nitrogen and carbon sources, but data on the kinetic properties of amino acid uptake systems of ectomycorrhizal systems are scarce. Using ¹⁴C-labelled compounds we have determined the kinetics of uptake of amino acids by excised ectomycorrhizal roots for a range of distinct mycorrhizal types from three tree species, beech, spruce, and pine. All mycorrhizal types examined took up amino acids via high-affinity transport systems ( K _M values ranging from 19 to 233 mmol m^–3). A comparative analysis of kinetic parameters for uptake of amino acids and the ammonium analogue methylammonium showed that ectomycorrhizal roots have similar or even higher affinities (lower K _M values) for the amino acids, indicating that absorption of these organic forms of nitrogen (N) can contribute significantly to total N uptake by ectomycorrhizal plants. Analysis of amino acid uptake by ectomycorrhizal roots collected along a European north/south gradient of increasing mineral N pollution from northern Sweden to south Germany revealed no obvious trend in the uptake capabilities for amino acids by ectomycorrhizal roots in relation to the location of the sampling site on this gradient. Rather, the fungal species forming a particular morphotype was the factor determining uptake kinetics. It can therefore be deduced that the species composition of the fungal community will contribute significantly to the functional diversity of a population of mycorrhizal roots.     

Studies on the biosynthesis of biotin. Production of biotin and biotin-like compounds by a pseudomonad

1. Filtrates from cultures of a strain of Pseudomonas aeruginosa, grown in a basal glucose-ammonium chloride-vitamins-salts medium, possessed biotin activity as detected by microbiological assays. Exponential-phase culture filtrates contained biotin and desthiobiotin in the approximate ratio 1:3, with smaller amounts of biotin sulphoxide and three unidentified compounds with biotin activity. 2. The addition of malonate, adipate or pimelate to the basal medium stimulated the production of compounds with biotin activity; this effect was enhanced when these compounds were included in the medium as the major carbon source. Succinate, glutarate, suberate, fumarate or oxaloacetate did not stimulate the production of compounds with biotin activity. The ratio of biotin to desthiobiotin in filtrates from cultures grown in medium containing malonate as the carbon source was about 1:1. Experiments in which mixtures of malonate and pimelate were included in the medium as the carbon sources showed that these acids probably make a similar contribution in biotin biosynthesis. 3. A number of heterocyclic compounds, including several containing the ureido group (-NH-CO-NH-), were included in the basal medium but none of them stimulated the production of compounds with biotin activity to any marked degree. 4. Several amino acids, particularly cysteine (or cystine) and lysine, when added individually as supplements to the basal medium, stimulated the production of compounds with biotin activity. Filtrates from cultures grown in medium supplemented with cysteine contained approximately equal proportions of biotin and desthiobiotin. A much greater stimulation in the production of compounds with biotin activity was obtained when certain amino acids were included in the medium as the major source of nitrogen or carbon and nitrogen; ornithine, citrulline and argininosuccinate had the most marked effect. The ratio of biotin to desthiobiotin in filtrates from these cultures was usually greater than in filtrates from cultures grown in basal medium. 5-Aminovalerate also caused some stimulation when used as the nitrogen source, but urea was inactive. The effect of binary mixtures of certain amino acids was also examined. 5. The results are discussed in relation to the possible role of the stimulatory compounds during biotin biosynthesis.     

Physiological and biochemical characteristics and capacity for polyhydroxyalkanoates synthesis in a glucose-utilizing strain of hydrogen-oxidizing bacteria, Ralstonia eutropha B8562

The physiological, biochemical, genetic, and cultural characteristics of the glucose-utilizing mutant strain Ralstonia eutropha B8562 were investigated in comparison with the parent strain R. eutropha B5786. The morphological, cultural, and biochemical characteristics of strain R. eutropha B8562 were similar to those of strain R. eutropha B5786. Genetic analysis revealed differences between the 16S rRNA gene sequences of these strains. The growth characteristics of the mutant using glucose as the sole carbon and energy source were comparable with those of the parent strain grown on fructose. Strain B8562 was characterized by high yields of polyhydroxyalkanoate (PHA) from different carbon sources (CO2, fructose, and glucose). In batch culture with glucose under nitrogen limitation, PHA accumulation reached 90% of dry weight. In PHA, beta-hydroxybutyrate was predominant (over 99 mol %); beta-hydroxyvalerate (0.25-0.72 mol %) and beta-hydroxyhexanoate (0.008-1.5 mol %) were present as minor components. The strain has prospects as a PHA producer on glucose-containing media.     

Carbon and nitrogen yields during batch cultures of Geotrichum candidum and Penicillium camembertii

Batch cultures of Geotrichum candidum and Penicillium camembertii were carried out on peptones as carbon and nitrogen source and in the presence of lactate as a second carbon source. Unless growth ceased, carbon and nitrogen yields remained constants, except yields involving lactate consumption by G. candidum, since this fungus preferentially metabolized peptones as a carbon source. For both fungi, nearly 40% of the available carbon was metabolized for cellular biosynthesis and the remainder (about 60%) as carbon dioxide, for the energy supply of both biosynthesis and viable cell maintenance. Moreover, in relation to their carbon content, amino acids contain excess nitrogen, which was released as ammonium. From all these, the yields of ammonium nitrogen on cellular nitrogen were in all cases higher than 1, and were especially high when the medium contained only peptones as a carbon source, 4.4 and 5.7 for G. candidum and P. camembertii respectively. Indeed, in this case, the excess nitrogen was especially pronounced.