The biological inactivity of glucose 6-phosphite, inorganic phosphites and other phosphites.
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Glucose↗
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Tandem addition of trialkyl phosphites to alpha,beta-unsaturated imines: a comparison with silylated phosphites.
Trialkyl phosphites were evaluated for addition reactions to alpha,beta-unsaturated imines. An acidic medium is required to allow consecutive 1,4- and 1,2-addition to occur. In this manner, 3-phosphonyl-1-aminophosphonates, phosphonic acid analogues of glutamate, are obtained in good yields (32-90%). The reaction is mainly influenced by the steric bulk of the nitrogen substituent: less steric N-substituents lead to better yields of the tandem adducts.
Glutamic Acid↗
Letter: Silyl phosphites. I. The reaction of silyl phosphites with diphenyl disulfide. Synthesis of S-phenyl nucleoside phosphorothioates.
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Chemical Phenomena↗
Inhibition and pH dependence of phosphite dehydrogenase.
Phosphite dehydrogenase (PTDH) catalyzes the NAD-dependent oxidation of phosphite to phosphate, a reaction that is 15 kcal/mol exergonic. The enzyme belongs to the family of D-hydroxy acid dehydrogenases. Five other family members that were analyzed do not catalyze the oxidation of phosphite, ruling out the possibility that this is a ubiquitous activity of these proteins. PTDH does not accept any alternative substrates such as thiophosphite, hydrated aldehydes, and methylphosphinate, and potential small nucleophiles such as hydroxylamine, fluoride, methanol, and trifluoromethanol do not compete with water in the displacement of the hydride from phosphite. The pH dependence of k(cat)/K(m,phosphite) is bell-shaped with a pK(a) of 6.8 for the acidic limb and a pK(a) of 7.8 for the basic limb. The pK(a) of 6.8 is assigned to the second deprotonation of phosphite. However, whether the dianionic form of phosphite is the true substrate is not clear since a reverse protonation mechanism is also consistent with the available data. Unlike k(cat)/K(m,phosphite), k(cat) and k(cat)/K(m,NAD) are pH-independent. Sulfite is a strong inhibitor of PTDH that is competitive with respect to phosphite and uncompetitive with respect to NAD(+). Incubation of the enzyme with NAD(+) and low concentrations of sulfite results in a covalent adduct between NAD(+) and sulfite in the active site of the enzyme that binds very tightly. Fluorescent titration studies provided the apparent dissociation constants for NAD(+), NADH, sulfite, and the sulfite-NAD(+) adduct. Substrate isotope effect studies with deuterium-labeled phosphite resulted in small normal isotope effects (1.4-2.1) on both k(cat) and k(cat)/K(m,phosphite) at pH 7.25 and 8.0. Solvent isotope effects (SIEs) on k(cat) are similar in size; however, the SIE of k(cat)/K(m,phosphite) at pH 7.25 is significantly larger (4.4), whereas at pH 8.0, it is the inverse (0.6). The pH-rate profile of k(cat)/K(m,phosphite), which predicts that the observed SIEs will have a significant thermodynamic origin, can account for these effects.
Amino Acid Sequence↗
NTP Toxicology and Carcinogenesis Studies of Dimethyl Hydrogen Phosphite (CAS No. 868-85-9) in F344/N Rats and B6C3F1 Mice (Gavage Studies).
Dimethyl hydrogen phosphite (DMHP) is used as an intermediate in the production of insecticides and herbicides, as an additive to lubricants, and as a stabilizer in oil and plaster and was considered for use as a chemical to simulate the physical (but not the biologic) properties of anticholinesterase agents. Results of 13-week gavage studies in F344/N rats (0-400 mg DMHP/kg body weight) and in B6C3F1 mice (0-1,500 mg DMHP/kg body weight) were used to identify short-term toxicity and to establish doses for the 2-year toxicology and carcinogenesis studies. In these studies, dimethyl hydrogen phosphite (greater than 97% pure) was administered for 103 weeks in corn oil by gavage to groups of 50 male F344/N rats and to groups of 50 male and female B6C3F1 mice at doses of 0, 100, or 200 mg/kg and to groups of 50 female F344/N rats at doses of 0, 50, or 100 mg/kg. In the 2-year studies, survival of high dose male rats and high dose male mice was lower (P<0.05) than that of the vehicle controls (male rats: vehicle control, 39/50; low dose, 29/50; high dose, 23/50; male mice: 42/50; 34/50; 32/50). At the end of the studies, mean body weights were lower than those of the corresponding vehicle controls for high dose male rats (-15%), for high dose female rats (-5%), and for high dose male mice (-5%). Dimethyl hydrogen phosphite caused dose-related increases in nonneoplastic and neoplastic lesions of the lung in male and female rats. In high dose male rats, there were increased incidences of lung neoplasms, including squamous cell carcinomas (0/50; 0/50; 5/50), alveolar/bronchiolar adenomas (0/50; 0/50; 5/50), and alveolar/bronchiolar carcinomas (0/50; 1/50; 20/50). In high dose female rats, there was a marginal increase in the incidence of alveolar/bronchiolar carcinomas of the lung (0/50; 1/49; 3/50). Hyperplasia of the lung and chronic interstitial pneumonia were increased in dosed male rats and in high dose female rats. Dimethyl hydrogen phosphite caused increases in forestomach lesions in male and female rats. In male rats, there was an increased incidence of forestomach neoplasms, including squamous cell papillomas (0/50; 1/50; 3/50) and squamous cell carcinomas (0/50; 0/50; 3/50). High dose male rats had increased incidences of hyperkeratosis and hyperplasia of the forestomach. In high dose female rats, the incidence of forestomach hyperplasia was increased. Neoplastic lesions of the forestomach (a squamous cell papilloma and a squamous cell carcinoma) were found in two high dose female rats. Mineralization of the cerebellum was seen in high dose male rats (12/49) and in no other group. Focal calcification of the testis occurred at increased incidence in dosed male mice in the 2-year studies (2/50; 9/47; 24/50). Compound-related testicular atrophy was seen in male mice in the 13-week study. Dimethyl hydrogen phosphite did not induce any neoplasms in male or female mice. Dimethyl hydrogen phosphite was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 in the presence or absence of Aroclor 1254-induced male Sprague-Dawley rat or Syrian hamster liver S9. This chemical did not induce sex-linked recessive lethal mutations in Drosophila melanogaster. An audit of the experimental data was conducted for these carcinogenic studies on dimethyl hydrogen phosphite. No data discrepancies were found that influenced the final interpretations. Under the conditions of these gavage studies, there was clear evidence of carcinogenicity in male rats receiving dimethyl hydrogen phosphite, as shown by increased incidences of alveolar/bronchiolar adenomas, alveolar/bronchiolar carcinomas, and squamous cell carcinomas of the lung and of neoplasms of the forestomach. There was equivocal evidence of carcinogenicity in female F344/N rats receiving dimethyl hydrogen phosphite, as shown by marginally increased incidences of alveolar/bronchiolar carcinomas of the lung and of neoplasms of the stomach. There was no evidence of carcinogenicity in male or female B6C3F1 mice receiving dimethyl hydrogen phosphite at doses of 100 ogen phosphite at doses of 100 or 200 mg/kg for 103 weeks. Synonyms: phosphonic acid, dimethyl ester (9CI); dimethyl phosphite; dimethyl phosphorus acid; methyl phosphonate; dimethyl phosphonate; dimethoxyphosphine oxide; TL 585; DMHP; phosphorous acid, dimethyl ester; dimethylphosphite; dimethyl phosphonate; dimethylphosphorous acid; bis(hydroxymethyl) phosphine oxide
Journal Article↗
Molecular genetic analysis of phosphite and hypophosphite oxidation by Pseudomonas stutzeri WM88.
The first molecular and genetic characterization of a biochemical pathway for oxidation of the reduced phosphorus (P) compounds phosphite and hypophosphite is reported. The pathway was identified in Pseudomonas stutzeri WM88, which was chosen for detailed studies from a group of organisms isolated based on their ability to oxidize hypophosphite (+1 valence) and phosphite (+3 valence) to phosphate (+5 valence). The genes required for oxidation of both compounds by P. stutzeri WM88 were cloned on a single ca. 30-kbp DNA fragment by screening for expression in Escherichia coli and Pseudomonas aeruginosa. Two lines of evidence suggest that hypophosphite is oxidized to phosphate via a phosphite intermediate. First, plasmid subclones that conferred oxidation of phosphite, but not hypophosphite, upon heterologous hosts were readily obtained. All plasmid subclones that failed to confer phosphite oxidation also failed to confer hypophosphite oxidation. No subclones that conferred only hypophosphite expression were obtained. Second, various deletion derivatives of the cloned genes were made in vitro and recombined onto the chromosome of P. stutzeri WM88. Two phenotypes were displayed by individual mutants. Mutants with the region encoding phosphite oxidation deleted (based upon the subcloning results) lost the ability to oxidize either phosphite or hypophosphite. Mutants with the region encoding hypophosphite oxidation deleted lost only the ability to oxidize hypophosphite. The phenotypes displayed by these mutants also demonstrate that the cloned genes are responsible for the P oxidation phenotypes displayed by the original P. stutzeri WM88 isolate. The DNA sequences of the minimal regions implicated in oxidation of each compound were determined. The region required for oxidation of phosphite to phosphate putatively encodes a binding-protein-dependent phosphite transporter, an NAD+-dependent phosphite dehydrogenase, and a transcriptional activator of the lysR family. The region required for oxidation of hypophosphite to phosphite putatively encodes a binding-protein-dependent hypophosphite transporter and an alpha-ketoglutarate-dependent hypophosphite dioxygenase. The finding of genes dedicated to oxidation of reduced P compounds provides further evidence that a redox cycle for P may be important in the metabolism of this essential, and often growth-limiting, nutrient.
Base Sequence↗
Phosphite disrupts the acclimation of Saccharomyces cerevisiae to phosphate starvation.
The influence of phosphite (H2PO3-) on the response of Saccharomyces cerevisiae to orthophosphate (HPO4(2-); Pi) starvation was assessed. Phosphate-repressible acid phosphatase (rAPase) derepression and cell development were abolished when phosphate-sufficient (+Pi) yeast were subcultured into phosphate-deficient (-Pi) media containing 0.1 mM phosphite. By contrast, treatment with 0.1 mM phosphite exerted no influence on rAPase activity or growth of +Pi cells. 31P NMR spectroscopy revealed that phosphite is assimilated and concentrated by yeast cultured with 0.1 mM phosphite, and that the levels of sugar phosphates, pyrophosphate, and particularly polyphosphate were significantly reduced in the phosphite-treated -Pi cells. Examination of phosphite's effects on two PHO regulon mutants that constitutively express rAPase indicated that (i) a potential target for phosphite's action in -Pi yeast is Pho84 (plasmalemma high-affinity Pi transporter and component of a putative phosphate sensor-complex), and that (ii) an additional mechanism exists to control rAPase expression that is independent of Pho85 (cyclin-dependent protein kinase). Marked accumulation of polyphosphate in the delta pho85 mutant suggested that Pho85 contributes to the control of polyphosphate metabolism. Results are consistent with the hypothesis that phosphite obstructs the signaling pathway by which S. cerevisiae perceives and responds to phosphate deprivation at the molecular level.
Acclimatization↗
Laser flash photolysis evidence for styryl radical cation cyclization in the SET-induced photorearrangement of a p-methoxy-substituted 2-phenylallyl phosphite.
The SET-induced photorearrangement of dimethyl 2-(4-methoxyphenyl)allyl phosphite, 9 (UV light, uranium glass filter, 9,10-dicyanoanthracene (DCA), biphenyl), gives phosphonate 12 in 83% isolated yield. Laser flash irradiation at 355 nm of oxygen saturated solutions of phosphite 9 containing DCA and biphenyl generates the transient UV spectrum of the biphenyl radical cation that is quenched by electron transfer from phosphite 9 (k(q) = 8.9 x 10(9) M(-1) s(-1) at 20 degrees C) to form the 4-methoxystyryl cation 10. The UV spectrum of 10 decays by a measured first-order rate constant of 8.0 x 10(6) s(-1), presumably to generate the cyclic distonic radical cation 11. Intermediate 10 was further characterized by measurement of the second-order rate constants for its reaction with azide, chloride, and bromide ions and with the neutral nucleophile trimethyl phosphite. This study provides the first spectroscopic evidence regarding the proposed mechanism (Schemes 1 and 2) for the SET-induced photorearrangements of dimethyl 2-arylallyl phosphites to the corresponding 2-arylallylphosphonates. Moreover, absolute rate constants for the intramolecular trapping of alkene radical cations have seldom been measured. The removal of the electron from the styryl moiety of phosphite 9, rather than from phosphorus, and the detectability of 10 arise from the stabilizing effect of the 4-methoxy substituent. These results, however, do not allow conclusions to be made concerning the site of removal of an electron in the SET-induced photorearrangement of dimethyl 2-phenylallyl phosphite 1 to phosphonate 6.
Allyl Compounds↗
A convenient approach to the synthesis of medium size oligodeoxyribonucleotides by improved new phosphite method.
Improvement of the new phosphite method for the synthesis of oligodeoxyribonucleotides using the deoxyribonucleoside 3'-bis(1,1,1,3,3,3- hexafluoro-2-propyl) phosphite unit has been carried out via the hydrolysis and capping steps, without any side reaction products. The new phosphite unit and capping agent, bis(1,1,1,3,3,3-hexafluoro-2-propyl)-2-propyl phosphite, is readily activated by N-methylimdazole under very mild condition on a solid support. This operation involves a one pot reaction, which is an advantage over both the phosphite and H- phosphonate approaches. The mechanism of internucleotidic bond formation of the new phosphite method is also discussed.
Electrophoresis, Polyacrylamide Gel↗
Tuning of the structures of chiral phosphane-phosphites: application to the highly enantioselective synthesis of alpha-acyloxy phosphonates by catalytic hydrogenation.
A family of new chiral phosphane-phosphites 5 has been prepared and employed in the synthesis of rhodium complexes of formulation [Rh(cod)(5)]BF4 (7). The use of bulky phosphane or phosphite groups in the preparation of 7 avoids the formation of undesired disubstituted complexes, one of which (9 a) has been isolated and characterized. Ligands 5 display important differences from the bulkier phosphane-phosphites 1: complexes 7-unlike their rigid [Rh(cod)(1)]BF4 counterparts-show fluxional behaviour in solution, consistent with backbone oscillation around the coordination plane. A detailed screening of ligands 1 and 5 in catalytic asymmetric hydrogenations of enol phosphonates 12 demonstrated a critical influence of the steric characteristics of the phosphane-phosphite in the course of the reaction, and optimization of the two phosphorus functionalities resulted in the production of versatile and efficient catalysts for this class of hydrogenations: enantioselectivities of up to 98% ee were thus obtained with substrates bearing an alkyl substituent in the beta-position, while for their challenging aryl counterparts values of up to 92% ee were achieved. The coordination mode of phosphonate 12 a towards a Rh phosphane-phosphite fragment has also been investigated and a preference of the olefin fragment to occupy the position cis to the phosphite group has been observed. From this observation an interpretation of the configurations of the hydrogenated phosphonates has also been made.
Journal Article↗
Anaerobic utilization of phosphite and hypophosphite by Bacillus sp.
A Bacillus sp. capable of utilizing phosphite and hypophosphite under anaerobic conditions was isolated from Cape Canerval soil samples. The organism was isolated on a glucose-mineral salts medium with phosphate deleted. Anaerobic cultivation of this isolate resulted in decreases in the hypophosphite or phosphite concentration, increases in turbidity, cell count, and dry-cell weight, and decreases in pH and glucose concentration. The optimum hypophosphite concentration for this isolate was 60 microgram/ml, whereas the optimum phosphate concentration was greater than 1,000 microgram/ml, suggesting that higher concentrations of hypophosphite may be toxic to this isolate. Hypophosphite or phosphite utilization was accompanied by little or no detectable accumulation of phosphate in the medium, and 32P-labeled hypophosphite was incorporated into the cell as organic phosphate. When phosphate was present in the medium, the isolate failed to metabolize phosphite. In the presence of phosphite and hypophosphite, the isolate first utilized phosphite and then hypophosphite.
Anaerobiosis↗
[Suppression of the human immunodeficiency virus in cultured cells by 5'-phosphites of 3'-azido-2',3'-dideoxynucleosides].
5'-Phosphites (5'-hydrogenphosphonates) of 3'-azido-2'-, 3'-dideoxynucleosides are shown to be effective inhibitors of the human immunodeficiency virus (HIV-1) in MT4 cell culture. 5'-Phosphite of 3'-azido-2', 3'-dideoxythymidine was the most active among these compounds and even a little more active as compared to the well-known anti-AIDS drug 3'-azido-2',3'-dideoxythymidine; at the same time 5'-phosphites of 3'-azido-2',3' -dideoxynucleosides with adenine, guanine and cytosine bases were more active than the corresponding nucleosides. The toxicity of all four phosphites was comparatively low and the equimolar mixture of all four phosphites was 2-3 fold less toxic than each of them separately. Data on the decreased toxicity of the phosphite mixture are explained from the viewpoint of a decreased pool disbalance of natural 2'-deoxynucleoside 5'-triphosphates in cells; a significant pool disbalance is developed in the case of 3'-azido-2',3'-dideoxythymidine action.
Antiviral Agents↗
Lithosyntrophy: Obligate syntrophy in a phosphite-oxidizing, methanogenic culture.
The anaerobic conversion of organic matter to methane and carbon dioxide typically relies on obligate syntrophic interactions between bacteria and methanogenic archaea, where interspecies electron transfer enables thermodynamically constrained reactions to proceed near equilibrium. Syntrophs often couple the oxidation of fermentation products such as fatty acids and alcohols to the reduction of protons to form hydrogen (H2). These reactions can only proceed if low H2 concentrations are maintained by H2-consuming syntrophic partners. Here, we describe "lithosyntrophy," a mode of syntrophic interaction in which electrons that drive hydrogenotrophic methanogenesis originate from an inorganic compound rather than from the canonical organic substrates. Candidatus Phosphitivorax anaerolimi Phox-21 oxidizes phosphite (HPO32-, oxidation state +3) to phosphate coupled to hydrogenogenesis in an obligate energetic dependency on a hydrogenotrophic methanogen, Methanoculleus sp. Physiology experiments, thermodynamic calculations, genomic annotation, and metaproteomics analysis collectively revealed a mechanism for syntrophic phosphite oxidation in Phox-21. In this pathway, electrons derived from phosphite drive H2 production via an electron-confurcating hydrogenase. Unlike previously characterized acetogenic phosphite oxidizers, Phox-21 is a mixotroph that assimilates acetate to form biomass. Lithosyntrophic phosphite oxidizers may play important roles both in transferring reducing equivalents as well as biologically available phosphorus to other members of their surrounding microbial communities, establishing a previously unrecognized metabolic and biogeochemical link between the phosphorus and carbon redox cycles in anoxic ecosystems.
Oxidation-Reduction↗
Photo-Arbuzov rearrangements of 1-arylethyl phosphites: stereochemical studies and the question of radical-pair intermediates.
The direct UV irradiation of the 1-arylethyl phosphites 7, 8, and 9 was carried out in acetonitrile, benzene, and cyclohexane, as was the triphenylene-sensitized reaction of 9. Dimethyl 1-phenylethyl phosphite, 7, gives the photo-Arbuzov rearrangement product, dimethyl 1-phenylethylphosphonate (10), in 67% average yield and minor amounts (2%) of 2,3-diphenylbutane (11a) in quantum yields of 0.32 and 0.02, respectively. The photorearrangement of optically active, predominantly (R)-1-phenylethyl phosphite 7 (R/S = 97/3; 94% ee), at 35-40 degrees C proceeds with a high degree of stereospecificity at the stereogenic migratory carbon to give predominantly (R)-10 (R/S = 86/14, 72 +/- 2% ee). Use of the nitroxide radical trap TEMPO affords phosphonate 10, presumably all cage product, from predominantly (R)-7 (R/S = 97/3; 94% ee) in 64% yield (80% ee, R/S = 90/10). By contrast, the 1-(4-acetylphenyl)-ethyl phosphite, predominantly (S)-8 (S/R = 98/2, 96% ee), on direct irradiation gives the corresponding phosphonate (12) in only 20% yield along with dimer 11b in 40% accountability yield. Phosphonate 12 is nearly racemic (R/S = 52/48). Direct irradiation of predominantly (R)-9 (R/S = 98/2, 96% ee), a 1-(1-naphthyl)ethyl phosphite, results in a product distribution similar to that from predominantly (R)-7, but with a somewhat higher degree of retention of configuration in the product phosphonate 13 (R/S = 93/7, 86 +/- 3 ee). By contrast, the triplet triphenylene-sensitized photorearrangement of largely (R)-9 (R/S = 98/2, 96% ee) leads to product distributions similar to those from direct irradiation of predominantly (S)-8 and is accompanied by almost total loss of stereochemistry in its product phosphonate, 13 (R/S = 51/49). The partial loss of stereochemistry on direct irradiation of 7 and 9 provides evidence for radical pair formation. Furthermore, these stereochemical results are diagnostic of the multiplicity of the initial radical pair formed. Values for kcomb/krot for the proximate free radical pairs from 7 and 9, derived experimentally, are severalfold larger than those for the proximate singlet pair from Ph2C=C=N-CHPhMe, corrected to 35 degrees C. The possibility that kcomb is increased for the pairs from 7 and 9 is proposed.
Phosphites↗
Phosphite additives and their transformation products in polyethylene packaging for gamma-irradiation.
Infrared (IR) spectroscopy has been used to identify and quantify the phosphite antioxidant, tris(2,4-di-tert.butylphenyl) phosphite, and its corresponding phosphate in high density polyethylene (HDPE) food trays, both in the original, commercial trays and also as a function of gamma-irradiation and post-irradiation, storage conditions. This direct method of inhibitor analysis complements time-consuming (some times non-quantitative) extraction methods, which for organo-phosphites are complicated by their facile conversion to phosphates by peroxidic impurities in the solvent. Because of the complete destruction of phosphite to give mainly phosphate at quite low gamma-irradiation doses (approximately 5 kGy) and phosphate formation during melt processing and radiation sterilization of these HDPE trays must take into account products from the irradiation of phosphate. Any residual phosphite is lost progressively in post-irradiation reactions, which are complex, producing a less than-quantitative yield of phosphate.
Chromatography, High Pressure Liquid↗
[Acute toxic effects of trimethyl and triethyl phosphites].
The studies on toxic properties of trimethyl and triethyl phosphities involved: determination of acute general toxic effect on white rats following intragastric and intraperitoneal administration of these compounds, based on DL50 test, determination of damaging effect direction, by histopathological examination of animals' internal organs, determination of intensity of primarily irritating action on the skin, eye and conjunctiva, as well as sensitizing effect on guinea-pigs. DL50 value for trimethyl phosphite following intragastric administration was found to be 2.45 g/kg and following intraperitoneal administration--2.25 g/kg; for triethyl phosphite these values were: 4.00 g/kg after intragastric administration and 1.50 g/kg after intraperitoneal administration, respectively. In local action both phosphites mildly irritate the skin, eye and conjunctiva. A weak sensitizing effect of triethyl phosphite was found. Trimethyl and triethyl phosphites have general toxic effects. A particular direction of their action is demonstrated by acroparalysis. Apart from general action they were found to show systemic action and induce parenchymatous degeneration of the liver and kidneys, whatever route of administration. Administered intragastrically, they result in mucosa necrosis, ulceration and fibrino-purulent exudate, exfoliating the mucosa.
Animals↗
Alterations of alkaline phosphatase activity during adaptation of Escherichia coli to phosphite and hypophosphite.
When Escherichia coli cells were grown in media containing either phosphite or hypophosphite as the sole source of phosphorus, the responded to this situation primarily in the same way as phosphate-limited cultures: The activity of alkaline phosphatase increased drastically, which under natural conditions would enable the cells to compensate for the shortage of phosphate. Subsequent transfers, however, resulted in a quite different response: While the phosphatase activity of phosphate-limited cells stays at a high derepressed level, its increase was followed by a gradual decline in organisms grown on phosphite of hypophosphite. After eight to ten transfers on these P-compounds, phosphatase activity was back to its initial, repressed, low level, indicating that the cells were fully adapted to these substrates. Adaptation to either PO3-3 or PO3-2 was completely abolished if the cells were again grown with PO3-3 as P-source, whereafter the entire process of adaptation had to be repeated. The observed adaptation pattern, reflected by the alterations of phosphatase activity, was qualitatively equal with PO3-3 and PO3-2, but quantitatively different, because the response to hypophosphite gave much higher values than the increase obtained with phosphite. Phosphite-adapted cells are not simultaneously adapted to hypophosphite, but their response to the latter was less intense than observed after direct transfers from PO3-4 to PO3-2. Adaptation to hypophosphite, however, led simultaneously to phosphite adaptation, so that these cells can utilize both P-compounds as a substitute for phosphate.
Adaptation, Physiological↗
Desulfotignum phosphitoxidans sp. nov., a new marine sulfate reducer that oxidizes phosphite to phosphate.
A new sulfate-reducing bacterium was isolated from marine sediment with phosphite as sole electron donor and CO(2) as the only carbon source. Strain FiPS-3 grew slowly, with doubling times of 3-4 days, and oxidized phosphite, hydrogen, formate, acetate, fumarate, pyruvate, glycine, glutamate, and other substrates nearly completely, with concomitant reduction of sulfate to sulfide. Acetate was formed as a side product to a small extent. Glucose, arabinose, and proline were partly oxidized and partly fermented to acetate plus propionate. Growth with phosphite, hydrogen, or formate was autotrophic. Also, in the presence of sulfate, CO dehydrogenase was present, and added acetate did not increase growth rates or growth yields. In the absence of sulfate, phosphite oxidation was coupled to homoacetogenic acetate formation, with growth yields similar to those in the presence of sulfate. Cells were small rods, 0.6 - 0.8 x 2-4 microm in size, and gram-negative, with a G+C content of 53.9 mol%. They contained desulforubidin, but no desulfoviridin. Based on sequence analysis of the 16S rRNA gene and the sulfite reductase genes dsrAB, strain FiPS-3 was found to be closely related to Desulfotignum balticum. However, physiological properties differed in many points from those of D. balticum. These findings justify the establishment of a new species, Desulfotignum phosphitoxidans.
Anaerobiosis↗