Metabolism of Pyridine Compounds by Phthalate-Degrading Bacteria

Bacteria were isolated from marine sediments that grew aerobically on m-phthalate, p-phthalate, or dipicolinate (2,6-pyridine dicarboxylate [2,6-PDCA]). Strain OP-1, which grew on o-phthalate and was previously obtained from a marine source, was also studied. Intact cells of each organism demonstrated Na⁺-dependent oxidation of their growth substrates. Strain PCC5M grew on dipicolinate but did not metabolize m-phthalate. The phthalate degraders, however, demonstrated Na⁺-dependent metabolism of the appropriate PDCA analogs. 2,6-PDCA was transformed by strain CC9M when this strain was grown on m-phthalate, 2,5-PDCA was metabolized by strain PP-1 grown on p-phthalate, and 2,3-PDCA (quinolinate) was oxidized by strain OP-1 grown on o-phthalate. Spectral changes accompanying the Na⁺-dependent transformations of the PDCA analogs suggest the formation of hydroxylated compounds. Metabolism probably occurred via phthalate hydroxylases; this is a previously unrecognized route for the environmental transformation of pyridine compounds. Hydroxylated products may feed into known pathways for the catabolism of pyridines or be photochemically degraded because of their absorbance in the solar actinic range (wavelengths > 300 nm). The results reinforce recent evidence for the broad potential of aromatic hydroxylase systems for the destruction of pollutants.     

Metabolism of Explosive Compounds by Sulfate-Reducing Bacteria

The metabolism of various explosive compounds—1,3,5-trinitrobenzene (TNB), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine (HMX)—by a sulfate-reducing bacterial consortium, Desulfovibrio spp., was studied. The results indicated that the Desulfovibrio spp. used all of the explosive compounds studied as their sole source of nitrogen for growth. The concentrations of TNB, RDX, and HMX in the culture media dropped to below the detection limit (<0.5 ppm) within 18 days of incubation. We also observed the production of ammonia from the nitro groups of the explosive compounds in the culture media. This ammonia served as a nitrogen source for the bacterial growth, and the concentration of ammonia later dropped to <0.5 mg/L. The sulfate-reducing bacteria may be useful in the anaerobic treatment of explosives-contaminated soil. Received: 23 January 1998 / Accepted: 5 March 1998     

Metabolism of Di- and Mono-n-Butyl Phthalate by Soil Bacteria

Samples for mycological analysis were collected from surfaces in the Skylab spacecraft before launch and during flight for each manned mission. Fungal contamination levels were low during the first two flights; however, the species recovered were different for each mission. On the third mission, widespread contamination of the Skylab spacecraft with Aspergillus and Pencillium spp. was detected. This contamination was traced to several contaminated space suit undergarments.     

Catch-Bond Behavior of Bacteria Binding by Slip Bonds

It is shown that multipili-adhering bacteria expressing helix-like pili binding by slip bonds can show catch-bond behavior. When exposed to an external force, such bacteria can mediate adhesion to their hosts by either of two limiting means: sequential or simultaneous pili force exposure (referring to when the pili mediate force in a sequential or simultaneous manner, respectively). As the force is increased, the pili can transition from sequential to simultaneous pili force exposure. Since the latter mode of adhesion gives rise to a significantly longer bacterial adhesion lifetime than the former, this results in a prolongation of the lifetime, which shows up as a catch-bond behavior. The properties and conditions of this effect were theoretically investigated and assessed in some detail for dual-pili-adhering bacteria, by both analytical means and simulations. The results indicate that the adhesion lifetime of such bacteria can be prolonged by more than an order of magnitude. This implies that the adhesion properties of multibinding systems cannot be directly conveyed to the individual adhesion-receptor bonds.     

Carbohydrate Metabolism by the Acetic Acid Bacteria

A general review of the acetic acid bacteria belonging to the intermediate type was accomplished physiologically, biochemically and morphologically. Conclusively, it was clarified that these were clearly a specific group and different from both Acetobacter and Gluconobacter, These were intermediate between lactaphilic and glycophilic, besides, on the carbohydrate oxidizability, these were intermediate between Acetobacter and Gluconobacter as mentioned previously.¹⁾ These showed the same result as Acetobacter on the vitamin requirement for the growth, but were closely related to Gluconobacter on the carbohydrate availability. And on the oxidative activity for amino acid, accompanying the deamination, these were also clearly distinguished from both Acetobacter and Gluconobacter, particularly these oxidized strongly l-serine. Differing from the observations by other investigators, these showed single flagellation, with the exception of multi-polar, but never multi-peritrichous.     

Carbohydrate Metabolism by the Acetic Acid Bacteria

Vitamin requirements for the growth of the acetic acid bacteria were investigated extensively on a. taxonomical viewpoint and the following new findings were pointed out. Neither Acetobacter nor Intermediate strain required vitamin for the growth.

Gluconobacter required generally pantothenic acid. And some strains belonging to it did moreover somewhat of thiamine, nicotinic acid and p-aminobenzoic acid, although there was a difference of requirements between strains even in the same species. Riboflavin, pyridoxine, vitamin B₁₂, folic acid, biotin and inositol were unnecessary for the growth of the acetic acid bacteria. A taxonomical division of the acetic acid bacteria based on the vitamin requirements agreed well with that on basis of the oxidative activities for carbohydrates.     

Metabolism of Inorganic N Compounds by Ammonia-Oxidizing Bacteria

ABSTRACT

Ammonia oxidizing bacteria extract energy for growth from the oxidation of ammonia to nitrite. Ammonia monooxygenase, which initiates ammonia oxidation, remains enigmatic given the lack of purified preparations. Genetic and biochemical studies support a model for the enzyme consisting of three subunits and metal centers of copper and iron. Knowledge of hydroxylamine oxidoreductase, which oxidizes hydroxylamine formed by ammonia monooxygenase to nitrite, is informed by a crystal structure and detailed spectroscopic and catalytic studies. Other inorganic nitrogen compounds, including NO, N₂O, NO₂, and N₂ can be consumed and/or produced by ammonia-oxidizing bacteria. NO and N₂O can be produced as byproducts of hydroxylamine oxidation or through nitrite reduction. NO₂ can serve as an alternative oxidant in place of O₂ in some ammonia-oxidizing strains. Our knowledge of the diversity of inorganic N metabolism by ammonia-oxidizing bacteria continues to grow. Nonetheless, many questions remain regarding the enzymes and genes involved in these processes and the role of these pathways in ammonia oxidizers.     

Glutathione-S-Transferase Activity and Metabolism of Glutathione Conjugates by Rhizosphere Bacteria

Glutathione-S-transferase (GST) activity was determined in 36 species of rhizosphere bacteria with the substrate 1-chloro-2,4-dinitrobenzene (CDNB) and in 18 strains with the herbicide alachlor. Highest levels of CDNB-GST activity (60 to 222 nmol (middot) h(sup-1) (middot) mg(sup-1)) were found in gram-negative bacteria: Enterobacter cloacae, Citrobacter diversus, Klebsiella planticola, Pseudomonas cepacia, Pseudomonas fluorescens, Pseudomonas putida, and Xanthomonas campestris. There was very low CDNB-GST activity in the gram-positive strains. Rapid metabolism of CDNB-glutathione conjugates, attributable to high levels of (gamma)-glutamyltranspeptidase, also occurred in the gram-negative bacteria, especially pseudomonads. Alachlor-GST activity detected in cell extracts and whole-cell suspensions of some strains of the families Enterobacteriaceae and Pseudomonaceae was 50- to 100-fold lower than CDNB-GST activity (0.5 to 2.5 nmol (middot) h(sup-1) (middot) mg(sup-1)) and was, for the most part, constitutive. The glutathione-alachlor conjugate was rarely detected. Cysteineglycine and/or cysteine conjugates were the major products of alachlor-GST metabolism. Whole-cell suspensions of certain Pseudomonas spp. dechlorinated from 20 to 75% of 100 (mu)M alachlor in 24 h. Results indicate that rhizosphere bacteria, especially fluorescent pseudomonads, may play an important role in the degradation of xenobiotics such as alachlor via GST-mediated reactions.     

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 ¹⁴CO₂ 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. ¹⁴CO₂ was incorporated into pyruvate when propionate and n-propylamine were oxidized in the presence of NaAsO₂, 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 ¹⁴CO₂ incorporation studies with several propane-utilizing organisms indicate that the methylmalonyl-succinate pathway is the predominant one for the metabolism of propionate.     

Surface Binding of Aflatoxin B1 by Lactic Acid Bacteria

Specific lactic acid bacterial strains remove toxins from liquid media by physical binding. The stability of the aflatoxin B₁ complexes formed with 12 bacterial strains in both viable and nonviable (heat- or acid-treated) forms was assessed by repetitive aqueous extraction. By the fifth extraction, up to 71% of the total aflatoxin B₁ remained bound. Nonviable bacteria retained the highest amount of aflatoxin B₁. Lactobacillus rhamnosus strain GG (ATCC 53103) and L. rhamnosus strain LC-705 (DSM 7061) removed aflatoxin B₁ from solution most efficiently and were selected for further study. The accessibility of bound aflatoxin B₁ to an antibody in an indirect competitive inhibition enzyme-linked immunosorbent assay suggests that surface components of these bacteria are involved in binding. Further evidence is the recovery of around 90% of the bound aflatoxin from the bacteria by solvent extraction. Autoclaving and sonication did not release any detectable aflatoxin B₁. Variation in temperature (4 to 37°C) and pH (2 to 10) did not have any significant effect on the amount of aflatoxin B₁ released. Binding of aflatoxin B₁ appears to be predominantly extracellular for viable and heat-treated bacteria. Acid treatment may permit intracellular binding. In all cases, binding is of a reversible nature, but the stability of the complexes formed depends on strain, treatment, and environmental conditions.     

Metabolism of l-Selenomethionine and Selenite by Probiotic Bacteria: In Vitro and In Vivo Studies

Since selenium supplements have been shown to undergo biotransformation in the gut, probiotic treatment in combination with selenium supplements may change selenium disposition. We investigated the metabolism of L-selenomethionine (SeMet) and selenite by probiotic bacteria in vitro and the disposition of selenium after probiotic treatment followed by oral dosing with SeMet and selenite in rats. When SeMet was incubated anaerobically with individual antibiotic-resistant probiotic strains (Streptococcus salivarius K12, Lactobacillus rhamnosus 67B, Lactobacillus acidophilus L10, and Bifidobacterium lactis LAFTI? B94) at 37°C for 24 h, 11-18% was metabolized with 44-80% of SeMet lost being converted to dimethyldiselenide (DMDSe) and dimethylselenide (DMSe). In similar incubations with selenite, metabolism was more extensive (26-100%) particularly by the lactobacilli with 0-4.8% of selenite lost being converted to DMSe and DMDSe accompanied by the formation of elemental selenium. Four groups of rats (n?=?5/group) received a single oral dose of either SeMet or selenite (2 mg selenium/kg) at the time of the last dose of a probiotic mixture or its vehicle (lyoprotectant mixture used to maintain cell viability) administered every 12 h for 3 days. Another three groups of rats (n?=?3/group) received a single oral dose of saline or SeMet or selenite at the same dose (untreated rats). Serum selenium concentrations over the subsequent 24 h were not significantly different between probiotic and vehicle treated rats but appeared to be more sustained (SeMet) or higher (selenite) than in the corresponding groups of untreated rats. Probiotic treated rats given SeMet also had selenium concentrations at 24 h that were significantly higher in liver and lower in kidney than untreated rats given SeMet. Thus, treatment with probiotics followed by SeMet significantly affects tissue levels of selenium.     

Microcalorimetric Measurements of Glucose Metabolism by Marine Bacterium Vibrio alginolyticus

Microcalorimetric measurements of heat production from glucose by Vibrio alginolyticus were made to assess the viability of calorimetry as a technique for studying the metabolism of marine bacteria at organic nutrient concentrations found in marine waters. The results show that the metabolism of glucose by this bacterium can be measured by calorimetry at submicromolar concentrations. A linear correlation between glucose concentration and total heat production was observed over a concentration range of 8 mM to 0.35 μM. It is suggested that these data indicate a constant efficiency of metabolism for this bacterium over the wide range of glucose concentrations studied.     

Caffeic Acid Metabolism by Bacteria of the Human Gastrointestinal Tract

The metabolism of caffeic acid, previously shown to be carried out by the intestinal microbiota of man and experimental animals, has now been examined in a number of bacteria isolated from human feces. It has been found that of the 12 organisms isolated none has the ability to catalyze more than one reaction of the series leading from caffeic acid to either m-hydroxyphenylpropionic acid or 4-ethylcatechol.     

Inhibition of Settlement by Larvae of Balanus amphitrite and Ciona intestinalis by a Surface-Colonizing Marine Bacterium

In an attempt to isolate bacteria with inhibitory effects against settlement by larvae of sessile invertebrates, 40 marine bacterial isolates were screened for effects against laboratory-reared barnacle larvae (Balanus amphitrite) and ascidian larvae (Ciona intestinalis). Five isolates displayed non-pH-dependent inhibitory effects against the larvae. The initial characterization of a toxic component released from an isolate, designated D2 (CCUG 26757), and its effect on laboratory-reared barnacle and ascidian larvae were studied. D2 is a facultative, anaerobic, gram-negative bacterium isolated from the surface of C. intestinalis from waters off the Swedish west coast at a depth of 10 m. Results suggest that the toxic component is released by D2 during the stationary phase. Aged biofilms were more toxic to the larvae than unaged films. The biologically active compound was in the supernatant of D2 and was heat stable and <500 Da in molecular mass. No evidence of protein or peptide moieties was found. On the basis of two phase and chromatography separations, the component is polar and neutral and contains or binds to carbohydrate moieties. Metaperiodate treatment increased toxicity; undiluted supernatant from a 24-h growth culture of D2 killed barnacle and ascidian larvae within a few hours of exposure, whereas after metaperiodate treatment, the larvae were killed in approximately 30 min.     

Differential Light Scattering Measurements of Heat-Treated Bacteria

Effects of heat on diameter, size distribution, and refractive index of Staphylococcus epidermidis suspensions were determined accurately by computer analysis of differential light scattering data.     

Velocity Measurements of Motile Bacteria by Use of a Videotape Recording Technique

A method has been developed to measure accurately the velocity of motile bacteria     

Potential of Siderophore Production by Bacteria Isolated from Heavy Metal: Polluted and Rhizosphere Soils

Recently, heavy metals have been shown to have a stimulating effect on siderophore biosynthesis in various bacteria. In addition, several studies have found that siderophore production is greater in bacteria isolated from soil near plant roots. The aim of this study was to compare the production of siderophores by bacterial strains isolated from heavy metal-contaminated and uncontaminated soils. Chrome azurol sulphonate was used to detect siderophore secretion by several bacterial strains isolated from heavy metal-contaminated and rhizosphere-uncontaminated soils with both a qualitative disc diffusion method and a quantitative ultraviolet spectrophotometric method. Siderophore production by rhizosphere bacteria was significantly greater than by bacteria isolated from contaminated soil. The Pearson’s correlation test indicated a positive correlation between the amount of siderophore produced by bacteria isolated from the rhizosphere using the quantitative and qualitative detection methods and the amount of heavy metal in the soil. However, a significant negative correlation was observed between the amount of siderophore produced by bacteria isolated from heavy metal-contaminated soil and the amount of heavy metal (r value of ?0.775, P < 0.001).