Uric acid degradation by Bacillus fastidiosus strains.

Seven Bacillus strains including one of the original Bacillus fastidiosus strains of Den Dooren de Jong could grow on urate, allantoin, and, except one, on allantoate. No growth could be detected on adenine, guanine, hypoxanthine, xanthine, and on degradation products of allantoate. Some strains grew very slowly in complex media. The metabolic pathway from urate to glyoxylate involved uricase, S(+)-allantoinase, allantoate amidohydrolase, S(-)-ureidoglycolase, and, in some strains, urease.     

Purine uptake by Alcaligenes eutrophus H16

The uptake of adenine, guanine, xanthine, hypoxanthine and uric acid by whole cells was studied, using spectrophotometric techniques, ¹⁴C-labelled compounds and metabolic inhibitors. Three different non-constitutive systems were shown to maintain the uptake of adenine and that of the pairs guanine/hypoxanthine and xanthine/uric acid. —Active transport of adenine was induced by adenine only, but passive uptake was also involved. Maximum K _T values of 110–131 M were observed at the pH optimum of 8.0. —Guanine and hypoxanthine were translocated by one single mechanism as indicated by K _T and K _I values. This system was induced by both these substances but its affinity was 51/2-times higher for guanine than for hypoxanthine; it was noncompetitively stimulated by Mg²⁺. — A further system, induced by xanthine and uric acid, catalyzed the uptake of both these compounds. It exhibited two pH optima (at pH 6.6 and 7.9); inactivation by heat and stimulation or inhibition by several compounds indicated that two separate mechanisms might be involved in the uptake of xanthine and uric acid.     

A comparison of purine metabolism and nucleotide pools in normal and hypoxanthine-guanine phosphoribosyltransferase-deficient neuroblastoma cells

Purine nucleotide synthesis and interconversion were examined over a range of purine base and nucleoside concentrations in intact N4 and N4TG (hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficient) neuroblastoma cells. Adenosine was a better nucleotide precursor than adenine, hypoxanthine or guanine at concentrations greater than 100 μM. With hypoxanthine or guanine, N4TG cells had less than 2% the rate of nucleotide synthesis of N4 cells. At substrate concentrations greater than 100 μM the rates for deamination of adenosine and phosphorolysis of guanosine exceeded those for any reaction of nucleotide synthesis. Labelled inosine and guanosine accumulated from hypoxanthine and guanine, respectively, in HGPRT-deficient cells and the nucleosides accumulated to a greater extent in N4 cells indicating dephosphorylation of newly synthesized IMP and GMP to be quantitatively significant. A deficiency of xanthine oxidase, guanine deaminase and guanosine kinase activities was found in neuroblastoma cells. Hypoxanthine was a source for both adenine and guanine nucleotides, whereas adenine or guanine were principally sources for adenine (>85%) or guanine (>90%) nucleotides, respectively. The rate of [¹⁴C]formate incorporation into ATP, GTP and nucleic acid purines was essentially equivalent for both N4 and N4TG cells. Purine nucleotide pools were also comparable in both cell lines, but the concentration of UDP-sugars was 1.5 times greater in N4TG than N4 cells.     

Urate oxidase of Chlamydomonas reinhardii

Urate oxidase (EC 1.7.3.3) of Chlamydomonas reinhardii cells grown on purines and purine derivatives has been partially characterized. Crude enzyme preparations have a pH optimum of 9.0, require O₂ for activity, have an apparent K_m of 12 μ M for urate, and are inhibited by high concentrations of this substrate. Enzyme activity was particularly sensitive to metal ion chelating agents like cyanide, cupferron, diethyldithiocarbamate and o -phenanthroline, and to structural analogues of urate like hypoxanthine and xanthine. Chlamydomonas cells grow phototrophically on adenine, guanine, hypoxanthine, xanthine, urate, allantoin or allantoate as sole nitrogen source, indicating that in this alga the standard pathway of aerobic degradation of purines of higher plants, animals and many microorganisms operates. As deduced from experiments in vivo , urate oxidase from Chlamydomonas is repressed in the presence of ammonia or nitrate.     

Profiles of purine biosynthesis, salvage and degradation in disks of potato (Solanum tuberosum L.) tubers

To find general metabolic profiles of purine ribo- and deoxyribonucleotides in potato (Solanum tuberosum L.) plants, we looked at the in situ metabolic fate of various ¹⁴C-labelled precursors in disks from growing potato tubers. The activities of key enzymes in potato tuber extracts were also studied. Of the precursors for the intermediates in de novo purine biosynthesis, [¹⁴C]formate, [2-¹⁴C]glycine and [2-¹⁴C]5-aminoimidazole-4-carboxyamide ribonucleoside were metabolised to purine nucleotides and were incorporated into nucleic acids. The rates of uptake of purine ribo- and deoxyribonucleosides by the disks were in the following order: deoxyadenosine > adenosine > adenine > guanine > guanosine > deoxyguanosine > inosine > hypoxanthine > xanthine > xanthosine. The purine ribonucleosides, adenosine and guanosine, were salvaged exclusively to nucleotides, by adenosine kinase (EC 2.7.1.20) and inosine/guanosine kinase (EC 2.7.1.73) and non-specific nucleoside phosphotransferase (EC 2.7.1.77). Inosine was also salvaged by inosine/guanosine kinase, but to a lesser extent. In contrast, no xanthosine was salvaged. Deoxyadenosine and deoxyguanosine, was efficiently salvaged by deoxyadenosine kinase (EC 2.7.1.76) and deoxyguanosine kinase (EC 2.7.1.113) and/or non-specific nucleoside phosphotransferase (EC 2.7.1.77). Of the purine bases, adenine, guanine and hypoxanthine but not xanthine were salvaged for nucleotide synthesis. Since purine nucleoside phosphorylase (EC 2.4.2.1) activity was not detected, adenine phosphoribosyltransferase (EC 2.4.2.7) and hypoxanthine/guanine phosphoribosyltransferase (EC 2.4.2.8) seem to play the major role in salvage of adenine, guanine and hypoxanthine. Xanthine was catabolised by the oxidative purine degradation pathway via allantoin. Activity of the purine-metabolising enzymes observed in other organisms, such as purine nucleoside phosphorylase (EC 2.4.2.1), xanthine phosphoribosyltransferase (EC 2.4.2.22), adenine deaminase (EC 3.5.4.2), adenosine deaminase (EC 3.5.4.4) and guanine deaminase (EC 3.5.4.3), were not detected in potato tuber extracts. These results suggest that the major catabolic pathways of adenine and guanine nucleotides are AMP → IMP → inosine → hypoxanthine → xanthine and GMP → guanosine → xanthosine → xanthine pathways, respectively. Catabolites before xanthosine and xanthine can be utilised in salvage pathways for nucleotide biosynthesis.     

Biosynthesis of Ureides from Purines in a Cell-free System from Nodule Extracts of Cowpea [Vigna unguiculata (L) Walp.

The synthesis of ¹⁴C-labeled xanthine/hypoxanthine, uric acid, allantoin, allantoic acid, and urea from [8-¹⁴C]guanine or [8-¹⁴C]hypoxanthine, but not from [8-¹⁴C]adenine, was demonstrated in a cell-free extract from N₂-fixing nodules of cowpea (Walp.). The ¹⁴C recovered in the acid/neutral fraction was present predominantly in uric acid and allantoin (88-97%), with less than 10% of the ¹⁴C in allantoic acid and urea. Time courses of labeling in the cell-free system suggested the sequence of synthesis from guanine to be uric acid, allantoin, and allantoic acid. Ureide synthesis was confined to soluble extracts from the bacteroid-containing tissue, was stimulated by pyridine nucleotides and intermediates of the pathways of aerobic oxidation of ureides, but was completely inhibited by allopurinol, a potent inhibitor of xanthine dehydrogenase (EC 1.2.1.37). The data indicated a purine-based pathway for ureide synthesis by cowpea nodules, and this suggestion is discussed.     

Absorption and metabolism of purines by the small intestine of the chicken.

1. Absorption of purines and their metabolism by the small intestine were estimated by using the everted gut sacs from the duodenum, jejunum and ileum of the chicken. 2. When no purine was added to the mucosal fluid, large amounts of uric acid, much less but appreciable adenine, hypoxanthine and xanthine and no detectable guanine were released from both sides of all segments of the small intestine, and these released amounts were largest in the duodenum. 3. Similar absorption rates of adenine from the jejunum and ileum were about 1.7-3.0 times as high as those of hypoxanthine and uric acid from these intestines and those of adenine and uric acid from the duodenum (P less than 0.05). 4. Guanine was not absorbed unchanged from any segments of the intestine and a little xanthine was absorbed only from the jejunum and ileum. 5. Guanine and xanthine seem to be absorbed in uric acid form, hypoxanthine in xanthine and uric acid forms and adenine in hypoxanthine form, from the small intestine especially from the jejunum. 6. Adenine, guanine, xanthine and hypoxanthine were greatly metabolized in the mucosa of the duodenum, and the conversions of hypoxanthine to xanthine and uric acid were most active.     

Purine degradation in Pseudomonas aeruginosa and Pseudomonas testosteroni.

1. Adenine, hypoxanthine, xanthine and guanine are broken down in Pseudomonas aeruginosa and Pseudomonas testosteroni to allantoin by the concerted action of the enzymes adenine deaminase, guanine deaminase, NAD+-dependent xanthine dehydrogenase and uricase. 2. Uric acid is broken down by an unstable, membrane-bound uricase with an unusually low pH optimum. 3. In both strains adenine inhibits growth and xanthine dehydrogenase. A second type of inhibition is manifest only in Ps. testosteroni and concerns the regulation of the biosynthesis of amino acids of the aspartate family. Enzymic studies showed that in this strain aspartate kinase is inhibited by AMP.     

Metabolism of hypoxanthine in isolated rat hepatocytes.

The hepatic metabolism of hypoxanthine was investigated by studying both the fate of labelled hypoxanthine, added at micromolar concentrations to isolated rat hepatocyte suspensions, and the kinetic properties of purified hypoxanthine/guanine phosphoribosyltransferase from rat liver. More than 80% of hypoxanthine was oxidized towards allantoin; less than 5% of the label was incorporated into the purine mononucleotides, and a similar proportion appeared transiently in inosine. The maximal velocity of oxidation (approx. 750nmol/min per g of cells) was in close agreement with the known activity of xanthine oxidase in liver extracts. In contrast, the maximal velocity of the incorporation of labelled hypoxanthine into mononucleotides reached only 30nmol/min per g of cells, compared with an activity of hypoxanthine/guanine phosphoribosyltransferase, measured at substrate concentrations analogous to those prevailing intracellularly, of 500nmol/min per g of cells. Hypoxanthine incorporation into the mononucleotides was decreased by allopurinol, anoxia and ethanol, despite inhibition of its oxidation under these conditions; it was increased by incubation of the cells in supraphysiological concentrations of Pi. Allopurinol and anoxia decreased the concentration of phosphoribosyl pyrophosphate inside the cells by respectively 40 and 60%, ethanol had no effect on the concentration of this metabolite and Pi increased its concentration up to 10-fold. The kinetic study of purified hypoxanthine/guanine phosphoribosyltransferase showed that a mixture of ATP, IMP, GMP and GTP, at the concentrations prevailing in the liver cell, decreased the V max. of the enzyme 6-fold, increased its Km for hypoxanthine from 1 to 4 microM and its Km for phosphoribosyl pyrophosphate from 2.5 to 25 microM. In the presence of 5 microM-hypoxanthine and 2.5 microM-phosphoribosyl pyrophosphate, the mixture of nucleotides inhibited the activity of purified hypoxanthine/guanine phosphoribosyltransferase by 95%. It is concluded that this inhibition results in a limited participation of hypoxanthine/guanine phosphoribosyltransferase in the control of the production of allantoin by the liver.     

Trichosporon adeninovorans sp. nov., a yeast species utilizing adenine,xanthine, uric acid,putrescine and primary n-alkylamines as the sole source of carbon,nitrogen and energy

A new yeast species, Trichosporon adeninovorans, was isolated from soil by the enrichment culture method. Apart from adenine, the strain utilized uric acid, guanine, xanthine, hypoxanthine, 6,8-dihydroxypurine, putrescine, propylamine, butylamine, pentylamine, hexylamine and octylamine as sole source of carbon, nitrogen and energy.The structure of the cell wall of Tr. adeninovorans was ascomycetous. On the subcellular level growth on adenine or uric acid was accompanied with the development of microbodies in the cell. These cell organelles probably were the site of urate oxidase, an enzyme that, after growth on purine substrates, together with allantoinase was present at high activities. Low activities of adenine amidohydrolase and xanthine dehydrogenase were also demonstrated.     

Utilization of organic compounds as the sole source of nitrogen by Thiobacillus thiooxidans

Thiobacillus thiooxidans DSM 504 was shown to grow with adenine, hypoxanthine, xanthine and uric acid as sole sources of nitrogen. Growth with these compounds was observed after lag periods of varying lengths, unless the cells had been previously grown with the same purine base. The disappearance of adenine was accompanied by a temporary accumulation of hypoxanthine in the medium. The utilization of purines was inhibited by ammonia (1 mM). Guanine, pyrimidines and some other organic compounds were not utilized.Non-standard abbreviation U-¹⁴C uniformly labeled by ¹⁴C     

Characterization of guanine and hypoxanthine phosphoribosyltransferases in Methanococcus voltae.

Phosphoribosyltransferase (PRTase) and nucleoside phosphorylase (NPase) activities were detected by radiometric methods in extracts of Methanococcus voltae. Guanine PRTase activity was present at 2.7 nmol min(-1) mg of protein(-1) and had an apparent Km for guanine of 0.2 mM and a pH optimum of 9. The activity was inhibited 50% by 0.3 mM GMP. IMP and AMP were not inhibitory at concentrations up to 0.6 mM. Hypoxanthine inhibited by 50% at 0.16 mM, and adenine and xanthine were not inhibitory at concentrations up to 0.5 mM. Guanosine NPase activity was present at 0.01 nmol min(-1) mg of protein(-1). Hypoxanthine PRTase activity was present at 0.85 nmol min(-1) mg of protein(-1) with an apparent Km for hypoxanthine of 0.015 mM and a pH optimum of 9. Activity was stimulated at least twofold by 0.05 mM GMP and 0.2 mM IMP but was unaffected by AMP. Guanine inhibited by 50% at 0.06 mM, but adenine and xanthine were not inhibitory. Inosine NPase activity was present at 0.04 nmol min(-1) mg of protein(-1). PRTase activities were not sensitive to any base analogs examined, with the exception of 8-azaguanine, 8-azahypoxanthine, and 2-thioxanthine. Fractionation of cell extracts by ion-exchange chromatography resolved three peaks of activity, each of which contained both guanine and hypoxanthine PRTase activities. The specific activities of the PRTases were not affected by growth in medium containing the nucleobases. Mutants of M. voltae resistant to base analogs lacked PRTase activity. Two mutants resistant to both 8-azaguanine and 8-azahypoxanthine lacked activity for both guanine and hypoxanthine PRTase. These results suggest that analog resistance was acquired by the loss of PRTase activity.     

Guanine uptake and metabolism in Neurospora crassa

Guanine is transported into germinated conidia of Neurospora crassa by the general purine base transport system. Guanine uptake is inhibited by adenine and hypoxanthine but not xanthine. Guanine phosphoribosyltransferase (GPRTase) activity was demonstrated in cell extracts of wild-type germinated conidia. The Km for guanine ranged from 29 to 69 micro M in GPRTase assays; the Ki for hypoxanthine was between 50 and 75 micro M. The kinetics of guanine transport differ considerably from the kinetics of GPRTase, strongly suggesting that the rate-limiting step in guanine accumulation in conidia is not that catalyzed by GPRTase. Efflux of guanine or its metabolites appears to have little importance in the regulation of pools of guanine or guanine nucleotides since very small amounts of 14C label were excreted from wild-type conidia preloaded with [8-14C]guanine. In contrast, excretion of purine bases, hypoxanthine, xanthine, and uric acid appears to be a mechanism for regulation of adenine nucleotide pools (Sabina et al., Mol. Gen. Genet. 173:31-38, 1979). No label from exogenous [8-14C]guanine was ever found in any adenine nucleotides, nucleosides, or the base, adenine, upon high-performance liquid chromatography analysis of acid extracts from germinated conidia of wild-type of xdh-l strains. The 14C label from exogenous [8-14C]guanine was found in GMP, GDP, GTP, and the GDP sugars as well as in XMP. Xanthine and uric acid were also labeled in wild-type extracts. Similar results were obtained with xdh-l extracts except that uric acid was not present. The labeled xanthine and XMP strongly suggest the presence of guanase and xanthine phosphoribosyltransferase in germinated conidia.     

Utilization of adenine and guanine as nitrogen sources by Chlamydomonas reinhardtii cells

Chlamydomonas reinhardtü Dangeard, adenine or guanine can be used as the sole nitrogen source for growth by means of an inducible system which is repressed by ammonia. Cells grown on either adenine or guanine were able to take up both purines, although the adenine uptake rate was always about 40% of the guanine uptake rate. Both adenine and guanine were taken up by an inducible system(s) exhibiting hyperbolic kinetics with identical apparent A, values of 3-2 mmol m^?3 for adenine and 3-2mmol m^?3 for guanine. Adenine and guanine utilization depended on pH, with similar optimal pH values of 7·3 and 7·4, respectively. Adenine and guanine each acted as a competitive inhibitor of the other's uptake, and their utilization was also inhibited by hypoxanthine, xanthine and urate. Inhibition of adenine uptake by guanine and hypoxanthine was competitive, with A′, values of 5·5 and 1. 6 mmol m^?3 respectively. Guanine uptake was also inhibited competitively by adenine (K₁= 1·3mmol m^?3) and hypoxanthine (K₁= 3. 3 mmol m^?3). Utilization of both adenine and guanine was inhibited by cyanide, azide, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea, 2,4-dinitrophenol and carbonylcyanide m-chlorophenylhydrazone, and was also sensitive to p-hydroxymercuribenzoate and N-ethyl-maleimide. On the basis of these results, taken together, the possibility that adenine and guanine are translocated into Chlamydomonas by a common system is discussed.     

Entry of Escherichia coli into stationary phase is indicated by endogenous and exogenous accumulation of nucleobases.

Endogenous and exogenous accumulation of nucleobases was observed when Escherichia coli entered the stationary phase. The onset of the stationary phase was accompanied by excretion of uracil and xanthine. Except for uracil and xanthine, other nucleobases (except for minor amounts of hypoxanthine), nucleosides, and nucleotides (except for cyclic AMP) were not detected in significant amounts in the culture medium. In addition to exogenous accumulation of nucleobases, stationary-phase cells increased the endogenous concentrations of free nucleobases. In contrast to extracellular nucleobases, hypoxanthine was the dominating intracellular nucleobase and xanthine was present only in minor concentrations inside the cells. Excretion of nucleobases was always connected to declining growth rates. It was observed in response to entry into the stationary phase independent of the initial cause of the cessation of cell growth (e.g., starvation for essential nutrients). In addition, transient accumulation of exogenous nucleobases was observed during perturbations of balanced growth conditions such as energy source downshifts. The nucleobases uracil and xanthine are the final breakdown products of pyrimidine (uracil and cytosine) and purine (adenine and guanine) bases, respectively. Hypoxanthine is the primary degradation product of adenine, which is further oxidized to xanthine. The endogenous and exogenous accumulation of these nucleobases in response to entry into the stationary phase is attributed to degradation of rRNA.     

Purine ribonucleotide biosynthesis, interconversion and catabolism in mouse brain in vitro

The relative rates of the synthetic, interconversion and catabolic reactions of purine metabolism in chopped mouse cerebrum were studied. The rates of incorporation of [(14)C]adenine and [(14)C]hypoxanthine into purine ribonucleotides were much less than the potential activities of adenine phosphoribosyltransferase and hypoxanthine phosphoribosyltransferase, and the rates of incorporation were stimulated by the addition of guanosine to the incubation mixture. The availability of ribose phosphates may be a limiting factor for the formation of ribonucleotides from purine bases. The rate of incorporation of [(14)C]adenosine into purine ribonucleotides was at least seven- to eight-fold higher than that of adenine. The radioactivity in adenine ribonucleotides synthesized from adenine and hypoxanthine was about 100- and ten-fold respectively higher than that in the radioactive guanine ribonucleotides. The conversion of inosinate into guanine ribonucleotides was probably limited by the amount of inosinate available, and the conversion of adenine ribonucleotides into guanine ribonucleotides was probably limited by the activity of adenylate deaminase. The rate of catabolism of [(14)C]adenosine was low in comparison with its rate of utilization for ribonucleotide synthesis. A fraction of the [(14)C]hypoxanthine was catabolized to xanthine and urate. [(14)C]Guanine was completely converted into xanthine, mostly by the guanine deaminase that was released during incubation of chopped mouse cerebrum.     

Genetic modification of substrate specificity of hypoxanthine phosphoribosyltransferase in Salmonella typhimurium.

Salmonella typhimurium strain GP660 (proAB-gpt deletion, purE) lacks guanine phosphoribosyltransferase and hence cannot utilize guanine as a purine source and is resistant to inhibition by 8-azaguanine. Strain GP660 was mutagenized and a derivative strain (GP36) was isolated for utilization of guanine and hypoxanthine, but not xanthine, as purine sources. This alteration was designated sug. The strain was then sensitive to inhibition by 8-azaguanine. Column chromatographic analysis revealed the altered phosphoribosyltransferase peaks for both hypoxanthine and guanine to be located together, in the same position as hypoxanthine phosphoribosyltransferase (hpt gene product) of the wild-type strain. Genetic analysis showed the sug mutation to be allelic with hpt. Therefore sug represented a modification of the substrate specificity of the hpt gene product.     

Nitrogen Metabolism in Paramecium aurelia

Nitrogen in cell fractions of Paramecium aurelia varied according to the growth medium. Trichloroacetic acid-soluble fractions of cells were chromatographer. Adenine, adenosine, guanine, guanosine, hypoxanthine, aspartic acid, glutamic acid, histidine, lysine, proline, and phenylalanine were identified. Fyrimidines and xanthine, or their respective ribosides and ribotides, were not detected. Ammonia was released into the medium by both actively growing and "resting" cells. Culture fluids of "resting"cells also contained hypoxanthine and lesser amounts of adenine and guanine. Urea, uric acid, creatine, cretonne, and ailantoin were absent.
Pyrimidine nitrogen seems excreted as dihydrouracil. The following enzymes were detected in homogenates and cell-free preparations: nucleotidases, nucleoside hydrolases, and cytidine deaminase. Urease, uricase, adenase, guanase, xanthine oxidase, adenosine deaminase, and 5'-adenylic acid deaminase were not present in this organism.
Purine and pyrimidine incorporation into nucleic acids was investigated by the use of radioactive tracers. Guanosine gives rise to nucleic-acid guanine and adenine; adenosine was precursor to nucleic acid adenine only. Formate was incorporated into purines; glycine was not. P. aurelia can interconvert cytidine and uridine; both give rise to nucleic acid thymine. The methyl group of thymine may be derived from formate.     

Adenosine phosphyorylase activity as distinct from inosine-guanosine phosphorylase activity in Sarcoma 180 cells and rat liver.

Adenosine phosphorylase (EC 2.4.2.-) activity present in Sarcoma 180 cells grown in culture and in rat liver, is shown to be distinct from inosine-guanosine phosphorylase by several criteria: (a) treatment of Sarcoma 180 cell extract with p-chloromercuribenzoate inhibited the two activities to a different extent, (b) adenine selectively protected the adenosine phosphorylase activity of Sarcoma 180 and rat liver extract against heat inactivation, while hypoxanthine selectively protected inosine-guanosine phosphorylase activity, (c) at nearly saturating substrate concentrations and using Sarcoma 180 extract, the rates of ribosylation of a mixture of adenine + hypoxanthine or adenine + guanine, but not of hypoxanthine + guanine, were found to be almost equal to the sum of their individual rates as measured separately, (d) inosine selectively inhibited the ribosylation of hypoxanthine and guanine catalysed by Sarcoma 180 and rat liver extract while 2-chloroadenosine selectively inhibited the ribosylation of adenine and N6-furfuryladenine, (e) pH vs. activity curves were similar with hypoxanthine or guanine as the substrate but they were markedly different from the curve with adenine as the substrate. The potential role of adenosine phosphorylase activity in vivo is discussed.     

Nature of the Nitrogen Compounds Supporting Phototrophic Growth of the Marine Cryptomonad Hemiselmis virescens*

SYNOPSIS. Previous claims of a specific amino add-nitrogen requirement for growth of Hemiselmis virescens have been disproved. The photosynthetic cryptomonad grows well on ammonium ion (at subtoxic concentrations) as sole N-source but cannot utilize nitrate-or nitrite-N. Although the organism utilizes glycine efficiently, other amino acids are poor N-sources, and only L-glutamine, L-cysteine, L-cystine, and L-tryptophan gave evidence of limited growth. Glycine peptides, derivatives (sarcosine, hippuric acid), and homologous relatives (β-alanine, taurine) gave no growth. Among other amino compounds tested, only D-glucosamine and D-galactosamine supported some growth. Urea and some of its derivatives (alloxan, parabanic acid) were efficiently utilized, while other derivatives (biuret, guanidine, hydantoin, hydantoic acid, allantoin, creatinine) failed to support growth. All purines tested (adenine, hypoxanthine, xanthine, guanine, uric acid) gave moderate to good growth, while the pyrimidines cytosine, uracil, thymine were not utilized. No dark growth was obtained from any of the compounds supporting phototrophic growth. The capacity for efficient utilization of glycine, urea, and some of the purines may have ecologic significance.