Studies on some methane-utilizing bacteria

Cleavage of malyl-Coenzyme A into acetyl-Coenzyme A and glyoxylate by Pseudomonas AM1 and other C1-unit-utilizing bacteria

1. Malyl-CoA lyase was found in high activity in extracts of Pseudomonas AM1, Pseudomonas MA, Pseudomonas MS, Hyphomicrobium X and Methylosinus trichosporium. 2. The enzyme cleaves (2S)-malyl-CoA into equimolar amounts of acetyl-CoA and glyoxylate in the presence of Mg(2+). 3. The specific activity of malyl-CoA lyase was several-fold higher in Pseudomonas AM1 when grown on C(1) compounds than when grown on C(2), C(3) or C(4) compounds. This suggests that the enzyme plays a specially important role in C(1) metabolism. 4. It is suggested that its role in C(1) metabolism, in organisms utilizing the serine pathway, is to provide the glyoxylate necessary to sustain operation of this pathway. 5. The activity of malyl-CoA lyase in extracts of Pseudomonas MA, Pseudomonas MS and Hyphomicrobium X is 27-50 times higher than the activity of ATP- and CoA-dependent cleavage of malate, suggesting that the latter activity may be due to coupling of two enzymes, malate thiokinase and malyl-CoA lyase. 6. Methane-grown Pseudomonas methanica and Methylococcus capsulatus, which are not known to use the serine pathway, possess appreciable amounts of malyl-CoA lyase. Instead of being used primarily for carbon assimilation, the enzyme may here serve as a route to glycine during biosynthesis of purines and proteins.

Physiological studies on Vitreoscilla stercoraria

Vitreoscilla stercoraria ATCC 15218 was studied to elucidate some of its physiological characteristics. The initial optimal pH for the organism was found to be 7.5 to 7.7. The characteristics of the growth curve of the organism showed that its growth in shake cultures is by increasing trichome number up to approximately 15 hr and by increasing trichome length after 15 hr. Nutritional studies indicated that it is auxotrophic for biotin, thiamine, and l-arginine, and it appears to be an obligate amino acid utilizer because only protein hydrolysates or known amino acid mixtures would support growth.

Metabolism of Propane, n -Propylamine, and Propionate by Hydrocarbon-Utilizing Bacteria

Studies were conducted on the oxidation and assimilation of various three-carbon compounds by a gram-positive rod isolated from soil and designated strain R-22. This organism can utilize propane, propionate, or n -propylamine as sole source of carbon and energy. Respiration rates, enzyme assays, and 14 CO 2 incorporation experiments suggest that propane is metabolized via methyl ketone formation; propionate and n -propylamine are metabolized via the methylmalonyl-succinate pathway. Isocitrate lyase activity was found in cells grown on acetate and was not present in cells grown on propionate or n -propylamine. 14 CO 2 was incorporated into pyruvate when propionate and n -propylamine were oxidized in the presence of NaAsO 2 , but insignificant radioactivity was found in pyruvate produced during the oxidation of propane and acetone. The n -propylamine dissimilatory mechanism was inducible in strain R-22, and amine dehydrogenase activity was detected in cells grown on n -propylamine. Radiorespirometer and 14 CO 2 incorporation studies with several propane-utilizing organisms indicate that the methylmalonyl-succinate pathway is the predominant one for the metabolism of propionate.

New pseudomonad utilizing methanol for growth

A bacterium capable of rapid growth on methanol as sole carbon source was isolated and classified as a new pseudomonad. Its doubling time was about 100 min at 32 to 37 C, and it grew well at methanol concentrations up to 2%. The organism was sensitive to phosphate, but reasonable cell densities could be obtained by using pH control. Cell yields of about 31%, based on methanol consumed, were obtained. The amino acid pattern of the protein indicated that the bacterium holds promise as a source of single-cell protein.

Physiological studies of methane and methanol-oxidizing bacteria: oxidation of C-1 compounds by Methylococcus capsulatus

Methylococcus capsulatus grows only on methane or methanol as its sole source of carbon and energy. Some amino acids serve as nitrogen sources and are converted to keto acids which accumulate in the culture medium. Cell suspensions oxidize methane, methanol, formaldehyde, and formate to carbon dioxide. Other primary alcohols are oxidized only to the corresponding aldehydes. Oxidation of formate by cell suspensions is more sensitive to inhibition by cyanide than is the oxidation of other one carbon compounds. This is due to the cyanide sensitivity of a soluble nicotinamide adenine dinucleotide-specific formate dehydrogenase. Oxidation of formaldehyde and methanol is catalyzed by a nonspecific primary alcohol dehydrogenase which is activated by ammonium ions and is independent of pyridine nucleotides. Some comparisons are made with a strain of Pseudomonas methanica.

Batch production of protein from ethane and ethane-methane mixtures

A culture of Graphium grows upon natural gas and a mineral salt solution. Ethane is the preferred substrate but methane is co-utilized. A stirred-tank type fermentor was used to study batch growth. Maximum production rate of biomass was 80 mg/liter.hr, at pH 4, using simple synthetic supporting medium with ammonium sulfate as a nitrogen source. This rate was observed after 40 hr of fermentation. A doubling time of 3.7 hr was observed. The corresponding specific growth rate was 0.187 per hr. A magnetic drive fermentor was used to study the effect of continuous recycle of gases in a gas-tight system. The rate of oxygen utilization is approximately 2.1 times higher than for ethane. Oxygen must not be allowed to become limiting in recycle gases. The calculated efficiency of overall biomass synthesis averages 30%. Hyphal and unicellular tissue of Graphium contains 52% protein. It compares favorably with standard FAO protein in its content of amino acids.

Bacterial metabolism of arylsulfonates. I. Benzene sulfonate as growth substrate for Pseudomonas testosteroni H-8

Pseudomonas testosteroni H-8 utilizes as sole carbon source benzene sulfonate (BS), p-toluene sulfonate (pTS), and ethylbenzene sulfonate (EBS) but not higher homologs. Growth on BS was rapid (generation time, 3 hr) and efficient (Y = 57), and resulted in accumulation of sulfate. As the culture is acid-sensitive, the medium must be heavily buffered to permit extensive growth. The BS oxidase system is inducible. Cells grown on BS, but not glutamate, oxidized BS, pTS, or EBS without lag (QO(2) = 50 to 100). Oxygen uptake on BS is temperature-dependent and sensitive to cyanide. Complete oxidation of 1 mumole of BS consumed approximately 5.7 mumoles of oxygen.

Oxygenation of methane by methane-grown Pseudomonas methanica and Methanomonas methanooxidans

1. Experimental conditions have been found in which small amounts of methanol (approximately 2.5mm) accumulated when washed cell suspensions of methane-grown Pseudomonas methanica and Methanomonas methanooxidans were incubated with methane+oxygen mixtures in Warburg flasks. 2. The methanol formed could be separated completely from water by fractional distillation through glass helices followed by gas chromatography using 20% polyethylene glycol 400 on a Celite 545 support. 3. By using (18)O-enriched oxygen gas the abundance of (18)O in the methanol formed from oxidation of methane was measured with a Perkin-Elmer 270 combined gas chromatograph/mass spectrometer. The results showed that the oxygen in methanol was derived exclusively from gaseous oxygen in both micro-organisms. 4. Control experiments using [(18)O]water in incubation mixtures confirmed that there was negligible incorporation of the oxygen atom from water into methanol.

Automatic assessment of respiration during growth in stirred fermentors

An apparatus for the continuous and automatic measurement of respiration during growth of micro-organisms in stirred aerated culture is described. The effluent atmosphere from the culture vessels is passed through commercially available oxygen and carbon dioxide gas analyzers, and their electrical output is fed to a multipoint recorder. The apparatus has been used to measure the respiration of Escherichia coli, Pseudomonas aeruginosa, Bacillus thuringiensis, and Methylococcus capsulatus during growth on complex and defined media. In addition, pH values and dissolved oxygen concentrations were measured. Growth of P. thuringiensis in glucose-limited media showed unexpected interruptions in the oxygen consumption curves which resembled diauxic growth; growth of B. thuringiensis in complex media showed similar discontinuities of respiration. These results are explained as the sequential utilization of preferred substrates which, in the case of P. aeruginosa were provided as transient intermediates of glucose.

Divergent metabolic pathways for propane and propionate utilization by a soil isolate

The metabolism of propane and propionate by a soil isolate (Brevibacterium sp. strain JOB5) was investigated. The presence of isocitrate lyase in cells grown on isopropanol, acetate, or propane and the absence of this inducible enzyme in n-propanol- and propionate-grown cells suggested that propane is not metabolized via C-terminal oxidation. Methylmalonyl coenzyme A mutase and malate synthase are constitutive in this organism. The incorporation of (14)CO(2) into pyruvate accumulated during propionate utilization suggests that propionate is metabolized via the methyl-malonyl-succinate pathway. These results were further substantiated by radiorespirometric studies with propionate-1-(14)C, -2-(14)C, and -3-(14)C as substrate. Propane -2-(14)C was shown, by unlabeled competitor experiments, to be oxidized to acetone; acetone and isopropanol are oxidized in this organism to acetol. Cleavage of acetol to acetate and CO(2) would yield the inducer for the isocitrate lyase present in propane-grown cells.

Role of alcoholic intermediates in formation of isomeric ketones from n-hexadecane by a soil Arthrobacter

A soil Arthrobacter species isolated from an Oregon soil was capable of transforming n-hexadecane to a series of ketonic products, the 2-,3-, and 4-hexadecanones, with evidence for accumulation of 2- and 3-hexadecanols as oxidative intermediates when yeast extract or peptone was used as a growth substrate. The accumulation and participation of internal alcohols in this type of hydrocarbon transformation has not been previously reported. In the absence of yeast extract or peptone, growth from low-level inocula was not observed when n-hexadecane or two oxidation products, 2-hexadecanol and 3-hexadecanone, were used as substrates. However, washed resting cell suspensions of the organism transformed 2-hexadecanol, or a mixture of 2-,3-, and 4-hexadecanols, to the corresponding ketones without lag, indicating the possible constitutive nature of the alcohol dehydrogenase enzyme(s) carrying out this reaction. The addition of glucose to these resting cells stimulated transformation of n-hexadecane to alcoholic and ketonic oxidation products. Formation of isomeric internal alcohols appears to be a limiting step in ketone formation by this Arthrobacter isolate.

Effect of substrate on the fatty acid composition of hydrocabon-utilizing microorganisms

The fatty acid pattern in three hydrocarbon-utilizing bacteria during growth on various substrates was examined. The predominant fatty acids in acetate-grown cells were C(16), C(16:1), C(18:1), and Br-C(19) and the major fatty acids in propane-grown cells were C(15), C(17), C(17:1), C(18:1), and Br-C(18). When one organism (Mycobacterium sp. strain OFS) was grown on the n-alkanes from C(13) to C(17), the major fatty acid in the cells was of the same chain length as the substrate. Studies on the incorporation of acetate into the cellular fatty acids of microorganisms growing on C(15) and C(17)n-alkanes suggest that the oxidative products of the substrate are incorporated into the cellular fatty acids without degradation to acetate.

Oxidation and assimilation of carbohydrates by Micrococcus sodonensis

Perry, Jerome J. (North Carolina State University, Raleigh), and James B. Evans. Oxidation and assimilation of carbohydrates by Micrococcus sodonensis. J. Bacteriol. 91:33-38. 1966.-Micrococcus sodonensis is a biotin-requiring strict aerobe that cannot utilize carbohydrates as sole sources of carbon and energy. However, addition of mannose, glucose, sucrose, or maltose to a medium on which the organism can grow resulted in an increase in total growth. M. sodonensis oxidized these sugars without induction, thus indicating the presence of constitutive enzymes for their transport, activation, and metabolism. Under appropriate nonproliferating cell conditions, glucose was readily incorporated into essential constituents of the cell. When glucose-1-C(14) and glucose-6-C(14) were oxidized by nonproliferating cells, the label was found in both the protein and nucleic acid fractions of the cell. The respiratory quotients of cells oxidizing glucose in saline and in phosphate buffer indicated assimilation of sugar carbon in buffer and virtually no assimilation in saline. The ability of M. sodonensis to completely oxidize glucose and to grow on intermediates of glucose oxidation but not on glucose suggests that glucose may suppress or repress some reaction(s) necessary for growth, and that growth substrates either derepress or circumvent this block.

ATMOSPHERIC NITROGEN FIXATION BY METHANE-OXIDIZING BACTERIA

Davis , J. B. (Socony Mobil Oil Co., Inc., Dallas, Tex.), V. F. Coty, and J. P. Stanley . Atmospheric nitrogen fixation by methane-oxidizing bacteria. J. Bacteriol. 88: 468–472. 1964.—Methane-oxidizing bacteria capable of fixing atmospheric nitrogen were isolated from garden soil, pond mud, oil field soil, and soil exposed to natural gas, indicating a rather wide prevalence in nature. This may explain the high concentration of organic nitrogen commonly found in soils exposed to gas leakage from pipelines or natural-gas seeps. Added molybdenum was a requirement for growth in a nitrogen-free mineral salts medium. All nitrogen-fixing, methane-oxidizing bacteria isolated were gram-negative, nonsporeforming, usually motile rods. Colonies were light yellow, yellow, or white. The most common isolate, which formed light-yellow colonies, is referred to as Pseudomonas methanitrificans sp. n., and is distinguished from Pseudomonas ( Methanomonas ) methanica by nitrogen-fixing ability and a preponderance of poly-β-hydroxybutyrate in the cellular lipid fraction.