Differentiation of a free-living alga into forms with ecto- and endosymbiotic associations with heterotrophic organisms in a 5-year microcosm culture.

The ecological mechanisms underlying the diversification of autotrophic species into endosymbiotic lifestyles and the ways in which the evolution of endosymbiotic species is ecologically and evolutionarily affected by sister lineages/lines that are adapted to extra-host environments remain unclear. In this paper, we investigated a differentiation process of algal species in which an endosymbiotic type was differentiated phenotypically from a free-living ancestral clone, by using an experimental model called the CET microcosm, which contains a green alga (Micractinium sp.), a bacterium (Escherichia coli), and a ciliate (Tetrahymena thermophila) cultured together without an external resource supply for over 5 years.

Exploitation or cooperation? Evolution of a host (ciliate)-benefiting alga in a long-term experimental microcosm culture.

Controversy persists as to whether the acquisition of beneficial metabolic functions via endosymbiosis can occur suddenly on an evolutionary time scale. In this study, an early stage of endosymbiotic associations, which evolved from previously unassociated auto (photo)- and heterotrophic unicellular organisms was analyzed using an experimental ecosystem model, called CET microcosm. This ecosystem model was composed of a green alga (Micractinium sp.

The effects of single nucleotide polymorphisms in CYP2A13 on metabolism of 5-methoxypsoralen.

A number of studies have demonstrated that cytochrome P450 (P450) converts furanocoumarin derivatives into reactive molecules, which form covalent bonds to biomolecules. 5-Methoxypsoralen (5-MOP) is a natural furanocoumarin from apiaceous plants. In this study, we examined the effect on 5-MOP metabolism of single nucleotide polymorphisms (SNPs) in CYP2A13.

Crystal structure and desulfurization mechanism of 2'-hydroxybiphenyl-2-sulfinic acid desulfinase.

The desulfurization of dibenzothiophene in Rhodococcus erythropolis is catalyzed by two monooxygenases, DszA and DszC, and a desulfinase, DszB. In the last step of this pathway, DszB hydrolyzes 2'-hydroxybiphenyl-2-sulfinic acid into 2-hydroxybiphenyl and sulfite. We report on the crystal structures of DszB and an inactive mutant of DszB in complex with substrates at resolutions of 1.

Dibenzothiophene desulfurizing enzymes from moderately thermophilic bacterium Bacillus subtilis WU-S2B: purification, characterization and overexpression.

The moderately thermophilic bacterium Bacillus subtilis WU-S2B desulfurized dibenzothiophene (DBT) at 50 degrees C through the selective cleavage of carbon-sulfur bonds. In this study, three enzymes involved in the microbial DBT desulfurization were purified and characterized. The first two enzymes, DBT monooxygenase (BdsC) and DBT sulfone monooxygenase (BdsA), were purified from the wild-type strain, and the last one, 2'-hydroxybiphenyl 2-sulfinic acid desulfinase (BdsB), was purified from the recombinant Escherichia coli overexpressing the gene, bdsB, with chaperonin genes, groEL/ES.

Atmospheric nitrogen dioxide gas is a plant vitalization signal to increase plant size and the contents of cell constituents.

We report the unexpected novel finding that exogenously supplied atmospheric NO2 at an ambient concentration is a plant vitalization signal to double shoot size and the contents of cell constituents. When seedlings of Nicotiana plumbaginifolia were grown for 10 wk under natural light and irrigation with 10 mm KNO3 in air containing (+NO2 plants) or not containing (-NO2 plants) 15NO2 (150 +/- 50 ppb), shoot biomass, total leaf area, and contents per shoot of carbon (C), nitrogen (N), sulphur (S), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), free amino acids and crude proteins were all approximately 2 times greater in +NO2 plants than in -NO2 plants. In mass spectrometric analysis of the 15N/14N ratio, it was found that NO2-derived N (NO2-N) comprised < 3% of total plant N, indicating that the contribution of NO2-N to total N was very minor.

Novel metabolism of nitrogen in plants.

Our previous study showed that approximately one-third of the nitrogen of 15N-labeled NO2 taken up into plants was converted to a previously unknown organic nitrogen (hereafter designated UN) that was not recoverable by the Kjeldahl method (Morikawa et al., 2004). In this communication, we discuss metabolic and physiological relevance of the UN based on our newest experimental results.

Crystallization and preliminary X-ray analyses of desulfurization enzyme DszB and its C27S mutant complexed with biphenyl-2-sulfinic acid.

DszB is a hydrolase involved in the biodegradation of dibenzothiophene in the soil bacterium Rhodococcus sp. IGTS8. DszB catalyzes the hydrolysis of 2'-hydroxybiphenyl-2-sulfinic acid to sulfite and biphenyl-2-ol.

Thermostable flavin reductase that couples with dibenzothiophene monooxygenase, from thermophilic Bacillus sp. DSM411: purification, characterization, and gene cloning.

Flavin reductase is essential for the oxygenases involved in microbial dibenzothiophene (DBT) desulfurization. An enzyme of the thermophilic strain, Bacillus sp. DSM411, was selected to couple with DBT monooxygenase (DszC) from Rhodococcus erythropolis D-1.

Three distinct Arabidopsis hemoglobins exhibit peroxidase-like activity and differentially mediate nitrite-dependent protein nitration.

All plants examined to date possess non-symbiotic hemoglobin whose physiological role remains unclear. The present study explored the catalytic function of three representative classes of the plant hemoglobin from Arabidopsis thaliana: AtGLB1, AtGLB2, and AtGLB3. Purified recombinant proteins of these hemoglobins displayed hydrogen peroxide-dependent oxidation of several peroxidase substrates that was sensitive to cyanide, revealing intrinsic peroxidase-like activity.

Formation of unidentified nitrogen in plants: an implication for a novel nitrogen metabolism.

Plants take up inorganic nitrogen and store it unchanged or convert it to organic forms. The nitrogen in such organic compounds is stoichiometrically recoverable by the Kjeldahl method. The sum of inorganic nitrogen and Kjeldahl nitrogen has long been known to equal the total nitrogen in plants.

A novel enzyme, 2'-hydroxybiphenyl-2-sulfinate desulfinase (DszB), from a dibenzothiophene-desulfurizing bacterium Rhodococcus erythropolis KA2-5-1: gene overexpression and enzyme characterization.

Dibenzothiophene (DBT), a model of organic sulfur compound in petroleum, is microbially desulfurized to 2-hydroxybiphenyl (2-HBP), and the gene operon dszABC was required for DBT desulfurization. The final step in the microbial DBT desulfurization is the conversion of 2'-hydroxybiphenyl-2-sulfinate (HBPSi) to 2-HBP catalyzed by DszB. In this study, DszB of a DBT-desulfurizing bacterium Rhodococcus erythropolis KA2-5-1 was overproduced in Escherichia coli by coexpression with chaperonin genes, groEL/groES, at 25 degrees C.