Treponema bryantii sp. nov., a rumen spirochete that interacts with cellulolytic bacteria

A saccharolytic spirochete that associated and interacted with cellulolytic bacteria was isolated from bovine rumen fluid. Isolation was accomplished by means of a procedure involving serial dilution of a sample of rumen fluid into a cellulose-containing agar medium. Clear zones appeared within the medium as a result of cellulose hydrolysis by rumen bacteria. The saccharolytic spirochete and a cellulolytic bacterium later identified as a strain of Bacteroides succinogenes were isolated from the clear zones. The spirochete did not utilize cellulose, but grew in coculture with the cellulolytic bacterium in cellulose-containing media. When cocultured in these media the spirochete used, as fermentable substrates, soluble sugars released from cellulose by the cellulolytic bacterium. In cellulosecontaining agar medium the spirochete enhanced cellulose breakdown by the B. succinogenes strain. Electron microscopy showed that the helical spirochete cells possessed an outer sheath, a protoplasmic cylinder, and two periplasmic fibrils. Under a CO₂ atmosphere, in a reduced medium containing inorganic salts, rumen fluid, glucose, and NaHCO₃, the spirochete grew to a final density of 1.9×10⁹ cells/ml. Succinate, acetate, and formate were products of the fermentation of glucose by growing cells. CO₂ (HCO₃ ^-), branched short-chain fatty acids, folic acid, biotin, niacinamide, thiamine, pyridoxal, and a carbohydrate were required for growth of the spirochete. The results of this study indicated that the rumen spirochete represents a new species of Treponema. It is proposed that the new species be named Treponema bryantii.Abbreviations cpm counts per minute - GC guanine plus cytosine - T_m melting temperature - PC protoplasmic cylinder - PF pertplasmic fibrils (axial fibrils) - OS outer sheath - ID insertion disk     

Spirochaeta halophila sp. n., a facultative anaerobe from a high-salinity pond

A facultatively anaerobic spirochete isolated from a high-salinity pond grew optimally when 0.75 M NaCl, 0.2 M MgSO₄, and 0.01 M CaCl₂ were present in media containing yeast extract, peptone, and a carbohydrate. The organism failed to grow when any one of these three salts was omitted from the medium. Aerobically-grown colonies of the spirochete were red, whereas anaerobically-grown colonies showed no pigmentation. Non-pigmented mutants of the spirochete were isolated.The spirochete used carbohydrates, but not amino acids, as energy sources. Glucose was fermented to CO₂, H₂, ethanol, acetate, and a small amount of lactate. Determinations of radioactivity in products formed from glucose-1-¹⁴C and enzymatic assays indicated that glucose was dissimilated to pyruvate mainly via the Embden-Meyerhof pathway. Pyruvate was metabolized through a clostridial-type clastic reaction.Cells growing acrobically performed an incomplete oxidation of glucose mainly to CO₂ and acetate. Comparison of aerobic and anaerobic growth yields indicated that oxidative phosphorylation occurred in cells growing aerobically. The guanine + cytosine content of the DNA of the spirochete was 62 moles%. It is proposed that the spirochete described herein be considered a new species and that it be namedSpirochaeta halophila.     

Variable cellular composition of Chromatium in growing cultures

Summary A strictly anaerobic spirochete was isolated from a sample of marine mud. The organism possessed two axial fibrils entwined with the regularly coiled protoplasmic cylinder. An outer envelope or sheath enclosed both protoplasmic cylinder and axial fibrils. The spirochete grew in chemically defined media containing glucose, amino acids or NH₄Cl, sulfide, NaCl, vitamins, coenzyme A, and in-organic salts. A reducing agent, such as sodium sulfide or l-cysteine, as well as exogenous supplements of biotin, niacin and coenzyme A were required for growth. Pantothenate replaced coenzyme A as an exogenous growth factor, but the resulting cell yields were low. The spirochete grew in media prepared with sea water, but not in fresh water media containing less than 0.05 M NaCl (optimum concentration 0.35 M). Both Na⁺ and Cl^- were required. Carbohydrates served as fermentable substrates. Amino acids, sugar alcohols, tricarboxylic acid cycle intermediates, and other organic acids and alcohols were not fermented. Glucose was fermented to ethyl alcohol, acetate, CO₂, H₂, and small amounts of lactate, formate and pyruvate. The guanine + cytosine content of the DNA of the spirochete was 50.5 moles-% (buoyant density). It is proposed that the marine isolate be considered a new species and that it be named Spirochaeta litoralis.     

Capnocytophaga: New genus of Gram-negative gliding bacteria. III. Physiological characterization

Sixty-eight strains of capnophilic fusiform Gram-negative rods from the human oral cavity were subjected to extensive physiologic characterization, tested for susceptibility to various antibiotics, and the mol-percent guanine plus cytosine of each isolate determined. The characteristics of the isolates were compared with 10 fresh and 2 stock isolates of Fusobacterium nucleatum. The isolates clearly differed from the Fusobacterium species on the basis of molpercent guanine plus cytosine, end products, growth in a capnophilic environment and fermentation of carbohydrates.All of the gliding isolates required CO₂ and formed acetate and succinate, but not H₂S, indole or acetylmethylcarbinol. All fermented glucose, sucrose, maltose and mannose. The organisms may be differentiated on the basis of fermentation of additional carbohydrates, hydrolysis of polymers and reduction of nitrate. Three species are proposed: Capnocytophaga ochracea, Capnocytophaga sputigena and Capnocytophaga gingivalis. Ten isolates did not fit into the proposed species.     

Autotrophic growth of four Sulfolobus strains on tetrathionate and the effect of organic nutrients

Autotrophic growth yields of four strains of Sulfolobus using tetrathionate as sole energy substrate fell in the range 6.2–7.8 g dry weight (mol tetrathionate oxidized)^-1. Autotrophic organisms lacked ribulose 1,5-bis-phosphate carboxylase, but contained pyruvate and phosphoenolpyruvate carboxylases. S. brierleyi and strains B6-2 and LM exhibited mixotrophic growth, with tetrathionate oxidation, CO₂-fixation and organic substrate assimilation occurring concurrently, using media containing glucose or acetate. Yeast extract or succinate supported heterotrophic growth and showed strain-dependent repression of one or both of tetrathionate oxidation and CO₂-fixation resulting in biphasic growth. All four carbon atoms of succinate were assimilated to cell-carbon during growth. Acetate was the major source of cell-carbon during mixotrophic growth. These observations are not inconsistent with the possibility of a reductive carboxylic acid cycle in these organisms. Radiorespirometric analysis of glucose oxidation indicated CO₂ release to occur by means of an Entner-Doudoroff pathway (followed by pyruvate decarboxylation) and oxidative pentose phosphate pathway reactions. There was little evidence from the glucose radiorespirometry of the large-scale use of an oxidative tricarboxylic acid cycle for terminal oxidation of acetate derived from pyruvate. These results demonstrate the considerable metabolic versatility of Sulfolobus strains and show that there is significant variation among them.Abbreviations PIPES Piperazine-N,N-bis (2-ethane sulphonic acid)     

Utilization of aminoaromatic acids by a methanogenic enrichment culture and by a novel<Emphasis Type="Italic"> Citrobacter freundii</Emphasis> strain

Following incubation of mesophilic methanogenic floccular sludge from a lab-scale upflow anaerobic sludge bed reactor used to treat cattle manure wastewater, a stable 5-aminosalicylate-degrading enrichment culture was obtained. Subsequently, a Citrobacter freundii strain, WA1, was isolated from the 5-aminosalicylate-degrading methanogenic consortium. The methanogenic enrichment culture degraded 5-aminosalicylate completely to CH₄, CO₂ and NH₄ ⁺, while C. freundii strain WA1 reduced 5-aminosalicylate with simultaneous deamination to 2-hydroxybenzyl alcohol during anaerobic growth with electron donors such as pyruvate, glucose or serine. When grown on pyruvate, C. freundii WA1 converted 3-aminobenzoate to benzyl alcohol and also reduced benzaldehyde to benzyl alcohol. Pyruvate was fermented to acetate, CO₂, H₂ and small amounts of lactate, succinate and formate. Less lactate (30%) was produced from pyruvate when C. freundii WA1 grew with 5-aminosalicylate as co-substrate.     

Autotrophic growth and CO2 fixation of Chloroflexus aurantiacus

Chlorofluexus aurantiacus OK-70 fl was grown photoautotrophically with hydrogen as the electron source. The lowest doubling time observed was 26 h.The mechanism of CO₂ fixation in autotrophically grown cells was studied. The presence of ribulose-1,5-bis-phosphate carboxylase and phosphoribulokinase could not be demonstrated. Carbon isotope fractionation (¹³C) was small, and alanine and aspartate but not 3-phosphoglycerate were the major labelled compounds in short term ¹⁴CO₂ labelling. Thus CO₂ is not fixed by the Calvin cycle.Fluoroacetate (FAc) completely inhibited protein synthesis in cultures and caused a slight citrate accumulation. However, CO₂ fixation continued and increased polyglucose formation occurred. Under these conditions added acetate was metabolized to polyglucose, as were glycine, serine, glyoxylate and succinate, but to a lesser extent; little or no formate or CO was utilised.Glyoxylate inhibited CO₂ fixation in vivo, indicating that pyruvate is formed from acetyl-CoA and CO₂ by pyruvate synthase. Two key enzymes of the reductive TCA cycle, citrate lyase and -ketoglutarate synthase were not detected in cell free extracts, but pyruvate synthase and phosphoenolpyruvate carboxylase were demonstrated. It is concluded that acetyl-CoA is a central intermediate in the CO₂ fixation process, but the mechanism of its synthesis is not clear.Abbreviations Rubisco ribulose-1,5-bisphosphate carboxylase - TCA cycle tricarboxylic acid cycle - FAc monofluoroacetate - PEP phosphoenolpyruvate - MV methyl viologen - TTC triphenyltetrazolium chloride - PMS phenazine methosulfate     

Amino acid and glucose fermentation by Treponema denticola

Summary Treponema denticola was grown in serum-containing media to which ¹⁴C-labelled compounds were added. Determinations of radioactivity in the products formed indicated that the organism fermented alanine, cysteine, glycine, serine, and glucose. Fermentation products included acetate, lactate, succinate, formate, pyruvate, ethanol, CO₂, H₂S, and NH₃. The products formed from glucose constituted a small portion of the total products. Assays of enzymatic activities in cell extracts indicated that the organism degraded glucose via the Embden-Meyerhof pathway. T. denticola possessed a coenzyme A-dependent CO₂-pyruvate exchange activity associated with a clostridial-type clastic system for pyruvate metabolism. Phosphotransacetylase and acetate kinase activities were present in cell extracts. Acetyl phosphate formation and benzyl viologen reduction were detected when cell extracts were incubated with pyruvate, serine or cysteine. The data indicate that T. denticola is an amino acid fermenter and that it possesses the enzymes needed for the fermentation of glucose. However, glucose does not serve as the primary substrate when the organism grows in media including both this carbohydrate and amino acids.     

RNA synthesis during morphogenesis of the fungusMucor racemosus

Bacteroides succinogenes produces acetate and succinate as major products of carbohydrate fermentation. An investigation of the enzymes involved indicated that pyruvate is oxidized by a flavin-dependent pyruvate cleavage enzyme to acetyl-CoA and CO₂. Active CO₂ exchange is associated with the pyruvate oxidation system. Reduction of flavin nucleotides is CoASH-dependent and does not require ferredoxin. Acetyl-CoA is further metabolized via acetyl phosphate to acetate and ATP. Reduced flavin nucleotide is used to reduce fumarate to succinate by a particulate flavin-specific fumarate reductase reaction which may involve cytochrome b. Phosphoenolpyruvate (PEP) is carboxylated to oxalacetate by a GDP-specific PEP carboxykinase. Oxalacetate, in turn, is converted to malate by a pyridine nucleotide-dependent malate dehydrogenase. The organism has a NAD-dependent glyceraldehyde-3-phosphate dehydrogenase. The data suggest that reduced pyridine nucleotides generated during glycolysis are oxidized in malate formation and that the electrons generated during pyruvate oxidation are used to reduce fumarate to succinate.     

Acetyl CoA,a central intermediate of autotrophic CO2 fixation in Methanobacterium thermoautotrophicum

The pathway of autotrophic CO₂ fixation in Methanobacterium thermoautotrophicum has been investigated by long term labelling of the organism with isotopic acetate and pyruvate while exponentially growing on H₂ plus CO₂. Maximally 2% of the cell carbon were derived from exogeneous tracer, 98% were synthesized from CO₂. Since growth was obviously autotrophic the labelled compounds functioned as tracers of the cellular acetyl CoA and pyruvate pool during cell carbon synthesis from CO₂. M. thermoautotrophicum growing in presence of U-¹⁴C acetate incorporated ¹⁴C into cell compounds derived from acetyl CoA (N-acetyl groups) as well as into compounds derived from pyruvate (alanine), oxaloacetate (aspartate), -ketoglutarate (glutamate), hexosephosphates (galactosamine), and pentosephosphates (ribose). The specific radioactities of N-acetylgroups and of the three amino acids were identical. The hexosamine exhibited a two times higher specific radioactivity, and the pentose a 1.6 times higher specific radioactivity than e.g. alanine. M. thermoautotrophicum growing in presence of 3-¹⁴C pyruvate, however, did not incorporate ¹⁴C into cell compounds directly derived from acetyl CoA. Those compounds derived from pyruvate, dicarboxylic acids and hexosephosphates became labelled. The specific radioactivities of alanine, aspartate and glutamate were identical; the hexosamine had a specific radioactivity twice as high as e.g. alanine.The finding that pyruvate was not incorporated into compounds derived from acetyl CoA, whereas acetate was incorporated into derivatives of acetyl CoA and pyruvate in a 1:1 ratio demonstrates that pyruvate is synthesized by reductive carboxylation of acetyl CoA. The data further provide evidence that in this autotrophic CO₂ fixation pathway hexosephosphates and pentosephosphates are synthesized from CO₂ via acetyl CoA and pyruvate.     

Malonomonas rubra gen. nov. sp. nov., a microaerotolerant anaerobic bacterium growing by decarboxylation of malonate

From anoxic marine sediment samples, new anaerobic, microaerotolerant, Gram-negative, non-sporeforming bacteria were isolated which grew in mineral medium with malonate as sole source of carbon and energy. Cells were motile thin rods, often forming large aggregates. Malonate was decarboxylated to acetate with concomitant growth yields of 1.9–2.1 g dry cell matter per mol malonate degraded. Fumarate and malate were fermented to succinate and CO₂. No other substrates were used. No inorganic electron acceptors were reduced. At least 150 mM NaCl was required for growth with either substrate. High amounts of a periplasmic cytochrome c were detected, as well as small amounts of a membrane-bound cytochrome b. All enzymes of the citric acid cycle were found to be present. The DNA base ratio was 48.3 mol% guanine plus cytosine. Since this new bacterium cannot be affiliated with any of the known genera and species, a new genus and species, Malonomonas rubra is proposed.     

CO2 fixation in halobacteria

Seven strains of extremely halophilic bacteria (Halobacterium spp., Halococcus spp., and Haloarcula sp.) fixed CO₂ under light and dark conditions. Light enhanced CO₂ fixation in Halobacterium halobium but inhibited it in Halobacterium volcanii and Haloarcula strain GN-1. Propionate stimulated ¹⁴CO₂ incorporation in some strains, but inhibited it in others. Semi-starvation in basal salts plus glycerol induced enhanced CO₂ fixation rates. ¹⁴CO₂ fixation in semi-starved cells was stimulated by NH ₄ ⁺ or pyruvate and inhibited by succinate and acetate in most strains. No possible reductant was found. In cell-free extracts of H. halobium, NH ₄ ⁺ but not propionate stimulated ¹⁴CO₂ fixation. No RuBP carboxylase activity was detected. The main ¹⁴C-labeled -keto acid detected after a 2-min incubation with ¹⁴CO₂ and pyruvate was pyruvate. Little or no -ketobutyrate was detected among the early products of propionate-stimulated CO₂ fixation. Glycine was the major amino acid synthesized during a 2-min incubation with NH ₄ ⁺ , propionate, and ¹⁴CO₂. Propionate-stimulated CO₂ fixation was sensitive to trimethoprim and insensitive to avidin. A novel pathway for non-reductive CO₂ fixation involving a glycine synthase reaction with CO₂, NH ₄ ⁺ , and a methyl carbon derived from the -carbon cleavage of propionate is tentatively proposed.Abbreviations used BBS buffered basal salts - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - MOPS 3-(N-morpholino)propanesulfonic acid - DNPH 2,4-dinitrophenylhydrazine - DNP dinitrophenyl - TLC thin-layer chromatography - FH₄ tetrahydrofolate This work was supported by National Science Foundation grant PCM-8116330 and Petroleum Research Fund grant PRF 13704-AC2     

Capnocytophaga: New genus of gram-negative gliding bacteria I. General characteristics,taxonomic considerations and significance

The characteristics of gliding bacteria isolated from both healthy and diseased sites in the oral cavity are, summarized and the taxonomic position of the bacteria discussed. Uniform attributes of the fusiform isolates include gliding motility, strictly fermentative metabolism dependent on the presence of CO₂ (or HCO ₃ ^- ), under either anaerobic or aerobic conditions, presence of benzidine-reactive components, and the production of acetic and succinic acids as the major or sole, acidic, metabolic and products. Given the guanine and cytosine content of DNA, their gliding motility, and the ability of many strains to attack polysaccharide a relationship to the cytophagas is suggested. This relationship, along with the CO₂-dependent growth is recognized by the generic name Capnocytophaga given them. Many of the isolates are grouped into three species C. ochracea, C. Sputigena, and C. gingivalis, separated on the basis of morphological and physiological traits.     

Respiration of blue-green algae in the light

The CO₂ evolution in the light of Anabaena as well as several other blue-green algae is below 10% of the dark control. Addition of DCMU restores CO₂ evolution in the light almost to the dark level. Furthermore, by adding unlabeled NaHCO₃, a ¹⁴CO₂ release is observed with prelabeled algal cells attaining 15 to 100% of dark control. Analysis by double-reciprocal plots exhibits a competitive relationship between added and endogenously released carbon dioxide. We conclude that CO₂ evolved by respiration is immediately refixed in the light without being liberated.The degree of ¹⁴CO₂ release induced by unlabeled bicarbonate in the light allows to determine true photoinhibition of respiration. Anabaena variabilis Kütz. exhibits almost no inhibition while in eight other species respiration is light-inhibited between 50 and 85% of the dark control.Abbreviations CCCP carbonyl cyanide m-chlorophenylhydrazone - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - TCA trichloroacetic acid     

pH and base counterion affect succinate production in dual-phase <Emphasis Type="Italic">Escherichia coli</Emphasis> fermentations

Succinate production was studied in Escherichia coli AFP111, which contains mutations in pyruvate formate lyase (pfl), lactate dehydrogenase (ldhA) and the phosphotransferase system glucosephosphotransferase enzyme II (ptsG). Two-phase fermentations using a defined medium at several controlled levels of pH were conducted in which an aerobic cell growth phase was followed by an anaerobic succinate production phase using 100% (v/v) CO₂. A pH of 6.4 yielded the highest specific succinate productivity. A metabolic flux analysis at a pH of 6.4 using ¹³C-labeled glucose showed that 61% of the PEP partitioned to oxaloacetate and 39% partitioned to pyruvate, while 93% of the succinate was formed via the reductive arm of the TCA cycle. The flux distribution at a pH of 6.8 was also analyzed and was not significantly different compared to that at a pH of 6.4. Ca(OH)₂ was superior to NaOH or KOH as the base for controlling the pH. By maintaining the pH at 6.4 using 25% (w/v) Ca(OH)₂, the process achieved an average succinate productivity of 1.42 g/l h with a yield of 0.61 g/g.     

Spirochaeta halophila sp. n., a facultative anaerobe from a high-salinity pond.

A facultatively anaerobic spirochete isolated from a high-salinity pond grew optimally when 0.75 M NaCl, 0.2 M MgSO4, and 0.01 M CaCl2 were present in media containing yeast extract, peptone, and a carbohydrate. The organism failed to grow when any one of these three salts was omitted from the medium. Aerobically-grown colonies of the spirochete were red, whereas anaerobically-grown colonies showed no pigmentation. Non-pigmented mutants of the spirochete were isolated. The spirochete used carbohydrates, but not amino acids, as energy sources. Glucose was fermented to CO2, H2, ethanol, acetate, and a small amount of lactate. Determinations of radioactivity in products formed from glucose-1-14C and enzymatic assays indicated that glucose was dissimilated to pyruvate mainly via the Embden-Meyerhof pathway. Pyruvate was metabolized through a clostridial-type clastic reaction. Cells growing aerobically performed an incomplete oxidation of glucose mainly to CO2 and acetate. Comparison of aerobic and anaerobic growth yields indicated that oxidative phosphorylation occurred in cells growing aerobically. The guanine + cytosine content of the DNA of the spirochete was 62 moles %. It is proposed that the spirochete described herein be considered a new species and that it be named Spirochaeta halophila.     

Fermentation of 2-methoxyethanol by Acetobacterium malicum sp. nov. and Pelobacter venetianus

Anaerobic bacteria degrading 2-methoxyethanol were enriched from freshwater sediments, and three strains were isolated in pure culture. Two of them were Grampositive non-spore-forming rods and grew strictly anaerobically by acetogenic fermentation. Optimal growth occurred at 30°C, initial pH 7.5–8.0. 2-Methoxyethanol and 2-ethoxyethanol were fermented to acetate and corresponding alcohols. Hydrogen plus carbon dioxide, formate, acetoin, l-malate, lactate, pyruvate, fructose, and methoxyl groups of 3,4,5-trimethoxybenzoate and 3,4,5-trimethoxycinnamate were fermented to acetate. 1,2-Propanediol was fermented to acetate, propionate, and propanol. Strain MuME1 was described as a new species, Actetobacterium malicum. It had a DNA base composition of 44.1 mol% guanine plus cytosine. The third strain, which was identified as Pelobacter venetianus, fermented 2-methoxyethanol to methanol, ethanol, and acetate.     

The role of carbon dioxide in glucose metabolism of Bacteroides fragilis

The effect of CO₂ concentration on growth and glucose fermentation of Bacteroides fragilis was studied in a defined mineral medium. Batch culture experiments were done in closed tubes containing CO₂ concentrations ranging from 10% to 100% (with appropriate amounts of bicarbonate added to maintain the pH at 6.7). These experiments revealed that CO₂ had no influence on growth rate or cell yield when the CO₂ concentration was above 30% CO₂ (minimum available CO₂–HCO ₃ ^- , 25.5 mM), whereas a slight decrease in these parameters was observed at 20% and 10% CO₂ (available CO₂–HCO ₃ ^- , 17 and 8.5 mM, respectively). If CO₂–HCO ₃ ^- concentrations were below 10 mM, the lag phase lengthened and a decrease in maximal growth rate and cell yield were observed. The amount of acetate made decreased, while d-lactate concentration increased. A net production of CO₂ allowed growth under conditions of extremely low concentrations of added CO₂.When B. fragilis was grown in continuous culture with 100% CO₂ or 100% N₂, the dilution rate influenced the concentrations of acetate, succinate, propionate, d-lactate, l-malate and formate formed. Decreasing the dilution rate favored propionate and acetate production under both conditions. When the organism was grown with 100% N₂, the amount of propionate formed was greater than the amount of succinate formed at all dilution rates. Except at slow dilution rates the reverse was true when 100% CO₂ was used. B. fragilis was unable to grow at dilution rates faster than 0.154 h^-1 when grown with 100% N₂; the Y _glc ^max was 67.9 g DW cells/mol glucose and m _s was 0.064 mmol glucose/g DW·h. If the gas atmosphere was 100% CO₂ the organism was washed out of the culture when the dilution rate exceeded 0.38 h^-1; the Y _glc ^max was 59.4 g DW cells/mol glucose and m _s was 0.094 mmol glucose/g DW·h.Measurement of the phosphoenolpyruvate (PEP) carboxykinase (E.C. 4.1.1.49) with whole, permeabilized cells of B. fragilis showed an increase of specific enzyme activity with decreasing CO₂ concentrations. The mechanisms used by B. fragilis to adjust to low levels of CO₂ are discussed.     

Light-induced accumulation of lactate and succinate in Anabaena cylindrica

In the cyanobacterium Anabaena cylindrica lactate accumulated in large amounts when the cells were exposed to light. The presence or absence of oxygen, or a change in CO₂ concentration did not affect the lactate accumulation. The cellular succinate level also increased in the light when CO₂ was supplied at the high concentration of 1%. 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU), an inhibitor of photosynthetic electron flow, inhibited the increase in the concentration of lactate and succinate. Photosynthesis is a prerequisite for the increase of these organic acids. Thenoyltrifluoroacetone, an inhibitor of succinate dehydrogenase, inhibited the increase of succinate, suggesting that the succinate is formed via fumarate by the reverse of reactions of tricarboxylic acid (TCA) cycle. Upon addition of ammonium to the cell suspension in the light under high CO₂ concentration, the increases in the concentrations of lactate and succinate were inhibited while those of glutamine, glutamate and aspartate were stimulated. Ammonium apparently changed the products of metabolism of pyruvate and oxaloacetate from lactate and succinate to amino acids.Abbreviations Chl chlorophyll - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethyl urea - TTFA thenoyltrifluoroacetone - PCA perchloric acid     

Effects of nucleic acid compounds on viability and cell composition of Bdellovibrio bacteriovorus during starvation

The effects of various exogenous nucleic acid compounds on the viability and cell composition of Bdellovibrio bacteriovorus starved in buffer were measured. In decreasing order of effectiveness, these compounds were found to decrease the rate of loss of viability and the loss of cell carbon, cell ribonculeic acid, and cell protein: glutamate > ribonucleoside monophosphates > ribonucleosides > deoxyribonucleoside monophosphates. Similar sparing effects were not observed with nucleic acid bases, deoxyribonucleosides, ribose, ribose-5-phosphate, deoxyribose, and deoxyribose-5-phosphate. Appreciable increases in the respiration rate over the endogenous rate did not occur when cell suspensions were incubated with individual or mixtures of nucleic acid compounds. Formation of ¹⁴CO₂ by cell suspensions incubated with carbon 14-labeled nucleic acid compounds indicated ribonucleosides and ribonucleoside monophosphates were respired and to a small extent, were incorporated into cell material of non-growing cells. The respired ¹⁴CO₂ was derived mainly from the ribose portion of these molecules. No respired ¹⁴CO₂ or incorporated carbon 14 was found with bdellovibrios incubated with other nucleic acid compounds tested, including free ribose. During growth of B. bacteriovorus on Escherichia coli in the presence of exogenous UL-¹⁴C-ribonucleoside monophosphates, 10–16% of the radioactivity was in the respired CO₂ and of the radioactivity incorporated into the bdellovibrios, only 40 to 50% resided in the cell nucleic acids. However, during growth on ¹⁴C-adenine,-uracil, or-thymidine labeled E. coli, only trace amounts of ¹⁴CO₂ were found and 90% or more of the incorporated radioactivity was in the bdellovibrio nucleic acids. It is concluded that bdellovibrio can use ribonucleoside monophosphates during growth and starvation as biosynthetic precursors for synthesis of both nucleic acids and other cell materials as well as catabolizing the ribose portion for energy purposes.Abbreviations HM buffer 5 mM N-2-hydroxyethyl-piperazine-N-2-ethanesulfonic acid (pH 7.6) containing 0.1 mM CaCl₂ and MgCl₂ - DNA deoxyribonucleic acid - RNA ribonucleic acid - Ar, Cr, Gr, Ur ribonucleosides of adenine, cytosine, guanine, uracil, respectively - dTr deoxythymidine - AMP, CMP, GMP, UMP ribonucleoside monophosphates of adenine, cytosine, guanine, and uracil, respectively - dTMP deoxythymidine monophosphate - ATP adenosine triphosphate - PFU plaque-forming units