• Proceedings of the Botanical Society of Korea Conference
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• 1999.08a
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• pp.55-67
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• 1999

A puc -deleted cell of Rhodobacter sphaeroides grows with a doubling time longer than 160 h under the light-limiting photoheterotrophic ( 3 Watts [W]/㎡) conditions due to an absence of the peripheral light-harvesting B800-850 complex. A spontaneous fast-growing mutant, R.sphaeroides SK101 was ioslate dto have∼40-h doubling at 3 Watts/㎡, while the growth of the mutant was not distinguished from its parental strain during both aerobic and light-saturating photoheterotrphic (10W/㎡) growth. The B875 complex of SK101 under the light-limiting conditions was elevated by 20 to 30% compared with that of the puc -deleted cell, reflecting parallel increase of bacteriochlorophyll and carotenoid contents of the mutant. The formation of B875 complex of SK101 under the anaerobic dark conditions with dimethylsulfoxide was the same as that of the puc-deleted cell. suggesting that the mutation of SK101 result in the altered control of B875 complex formation by light. When puc is restored in SK101 , it is not B875 complex but B800-850 complex which formation is elevated. The mutation of SK101 affected the bchF transcription most drastically to show two to tenfold increase during both aerobic and photoheterotrophic growth. The mutated phenotype of SK101 was complemented with pW2, which contains approximately 100-kb HNA of the photosynthetic gene clusters. The complementing DNA was narrowed down to a 1.1-kb DNA containing orfQ and pufKBA . The mutation of SK101 appeared to be exerted through the mutation of the orfQ gene encoding a putative bacteriochlorophyll -mobilizing protein.

• Journal of Microbiology and Biotechnology
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• v.11 no.2
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• pp.310-316
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• 2001

Poly-3-hydroxybutyrate (PHB) synthase catalyzed the last enzymic step to synthesize the intracellular PHB of Rhodobacter sphaeroides. No PHB was detected when the phbC coding for PhB synthase was interrupted, and its expression was regulated at the level of transcription. The cellular PHB content increased about four- to six-fold during the growth transition from the exponential to the early stationary phase under both aerobic and photoheterotrophic conditions. The PHB content during the aerobic growth seemed to be determined by the PhB synthase activity. However, the PHB synthase activity of photoheterotrophically grown cells did not correlate with the PhB content, suggesting a photoheterotrophic regulation different from the aerobic control. Thus, the PHB content of R. sphaeroides was regulated at the transcription level only under aerobic conditions.

• Journal of Microbiology and Biotechnology
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• v.9 no.5
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• pp.604-612
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• 1999

A puc-deleted cell of Rhodobacter sphaeroides grows with a doubling time longer than 160 h under light-limiting photoheterotrophic (3 Watts [W]/㎡) conditions due to an absence of the peripheral light-harvesting B800-850 complex. A spontaneous fast-growing mutant, R. sphaeroides SK101, was isolated from the puc-deleted cells cultured photoheterotrophically at 3 W/㎡. This mutant grew with an approximately 40-h doubling time. The growth of the mutant, however, was indistinguishable from its parental strain during photoheterotrophic growth at 10 W/㎡ as well as during aerobic growth. The membrane of SK101 grown aerobically did not reveal the presence of any spectral complex, while the amounts of the B875 complex and photosynthetic pigments of SK101 grown anaerobiclly in the dark with dimethylsulfoxide (DMSO) were the same as those of the parental cell. These results indicate that the oxygen control of the photosynthetic complex formation remained unaltered in the mutant. The B875 complex of SK101 under light-limiting conditions was elevated by 20％ to 30％ compared with that of the parental cell, which reflected the parallel increase of the bacteriochlorophyll and carotenoid contents of the mutant. When the puc was restored in SK101, the B875 complex level remained unchanged, but that of the B800-850 complex increased. The mutated phenotype of SK101 was complemented with orfQ encoding a putative bacteriochlorophyll-mobilizing protein. Accordingly, it is proposed that the mutated OrfQ of SK101 should have an altered affinity towards the assembly factor specific to the most peripheral light-harvesting complex, which could be either the B875 or the B800-850 complex.

• Microbiology and Biotechnology Letters
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• v.22 no.2
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• pp.197-202
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• 1994

Microalga, Spirulina platensis has been cultivated in a pilot scale photo-bioreactor to treat wastewater and to produce high protein feedstocks from swine waste containing medium. 0.31(1/day) of specific growth rate and 0.170 of bioenergeric yield were obtanined from batch cultivation in 30% waster containing medium, compared to 0.71(1/day) and 0.545 from clean culture. An optimal dilution concentration was decided as 20% of working volume, based upon the cell growth and biomass productivity. The removal rate of nitrates in the wastewater was decreased as the adding concentration of wastewater was increased while the decrease of total phosphates was reversed, showing 0.33(1/day) and 0.30(1/day) of rate constants for nitrate removal in 10% addition and for phosphate removal in 30% addition, respectively. The chemical composition and amino acid profile of the biomass were superior to those of commerically available health food product, Spirulina sp.

• Journal of Microbiology and Biotechnology
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• v.17 no.2
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• pp.373-377
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• 2007

No phosphatidylcholine (PC) was detected in the membrane of Rhodobacter sphaeroides pmtA mutant (PmtAl) lacking phosphatidylethanolamine (PE) N-methyltransferase, whereas PE in the mutant was increased up to the mole % comparable to the combined level of PE and PC of wild type. Neither the fatty acid composition nor the fluidity of membrane was altered by pmtA mutation. Consistently, aerobic and photoheterotrophic growth of PmtAl were not different from wild type. However, PmtAl showed an extended lag phase (15 h) after the growth transition from aerobic to photoheterotrophic conditions, indicating the PC requirement for the efficient formation of intracytoplasmic membrane (ICM). Interestingly, the B800-850 complex of PmtAl was decreased more than twofold in comparison with wild type, whereas the level of the B875 complex comprising the fixed photosynthetic unit was not changed. Since puc expression is not affected by pmtA mutation, PC appears to be required for the proper formation of the B800-850 complex in the ICM of R. sphaeroides.

• KSBB Journal
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• v.20 no.6
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• pp.413-417
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• 2005

The purple sulfur phototrophic bacterium, Thiocapsa roseopersicina NCIB 8347 has been studied on hydrogen production and cell growth under different culture conditions, such as light source, light intensity, and growth temperature. T. roseopersicina showed maximum cell growth of 1.38 and 1.42 g-DCW/L under 7.5-10 klux of halogen and fluorescent light, respectively, and produced maximum amount of hydrogen with values of 0.90 and 0.48 $mL-H_2/mg$-DCW under the irradiation of 10 klux of halogen and fluorescent light, respectively. The optimum growth temperature for hydrogen production was $26^{\circ}C$, and hydrogen production rate was lowered over $30^{\circ}C$. When T. roseopersicina was grown photoheterotrophically under irradiation of 8-9 klux of halogen lamp, the generation time was 4.2 hr. The strains started producing hydrgen from the middle of the logarithmic growth phase and continued until succinate concentration leveled out.

• Journal of Microbiology and Biotechnology
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• v.15 no.5
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• pp.1115-1119
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• 2005

The photoheterotrophic $H_2$ production of Rhodobacter sphaeroides was significantly increased through disruption of the genes coding for uptake hydrogenase and poly-${\beta}$-hydroxybutyrate (PHB) synthase (Lee et al., Appl. Microbiol. Biotechnol. 60: 147-153, 2002). In this work, we further removed the B800-850 light-harvesting (LH) complex from the strain and found an increase in $H_2$ production at the light-saturating cell growth (${\ge}10$ Watts $[W]/m^2$). Neither the mutant nor the wild-type produced more $H_2$ at the brighter light. Accordingly, light does not appear to be limited for the $H_2$ production by the presence of B800-850. However, increase in the level of the spectral complexes resulted in decrease of $H_2$ production. Thus, although the B875 is essential for light harvesting, the consumption of cellular energy for the synthesis of B800-850 and the surplus LH complexes may reduce the energy flow into the $H_2$ production of R. sphaeroides.

• Journal of Microbiology and Biotechnology
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• v.11 no.6
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• pp.1031-1037
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• 2001

By a sequential action of ${\beta}$-ketothiolase and acetoacetyl-CoA reductase, two molecules of acetyl-CoA re converted into D-3-hydroxybutyryl-CoA, a substrate for PHB synthase to form poly-3-hydroxybutyryl-CoA, a substrate for PHB synthase to form poly-3-hydroxybutyrate (PHB) of rhodobacter sphaeroides. The ${\beta}$-ketothiolase gene, phbA, and acetoacetyl-CoA reductase gene, phbB, were cloned and analyzed for their expression. Enzyme activities of ${\beta}$-ketothiolase and acetoacetyl-CoA reductase showed constitutive levels during aerobic and photoheterotrophic growth of R. sphaeroides. In addition, no difference of each enzyme activity was observed between cells grown aerobically and photoheterotrophically. The constitutive level of the enzyme activities are regulated according to the growth phases along with growth conditions. Thus, phbAB expression is not determinative in regulating the PB content. On the other hand, phbA-deleted cell AZI accumulated only $10\%$ PHB of the wild-type, and an elevated dosage of phbAB in trans in R. sphaeroides resulted in a higher content of PHB, indicating that phbAB codes for the enzymes responsible for providing the main supply of subsyrate for PHB synthase. PHB formation by an alternative pathway that does not does not depend on the phbA-and phbB-coding enzymes is also proposed.

• Journal of Microbiology and Biotechnology
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• v.7 no.2
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• pp.127-131
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• 1997

Alkaline phosphatase (APase) was found to be inducible in Anabaena sp. strain CA Growth was less than control in presence of most amino acids except glycine and serine, but most amino acids enhanced APase activity. Highest APase activity was recorded in tyrosine supplemented culture followed by hydroxyproline, cystein, valine and glutamic acid. Threonine supplemented material showed lowest APase level (1.8 nmol/mg protein/min). Lactose, glucose, sodium pyruvate and succinate stimulated growth but not APase activity. APase activity was high in the presence of sucrose, mellibiose, mannitol, arabinose, maltose and sorbose, even though the growth in these supplements was less than in control. Organic phosphate sources supported good growth of the organism. Best growth occurred in presence of inorganic phosphate, adenosine diphosphate, fructose 1,6-diphosphate or ribulose 1,5-diphosphate, followed by other phosphorus sources tested. APase activity in presence of any of the organic phosphate sources was 3 to 5 fold low as compared to phosphate limited culture. Also, there was no APase activity in cultures grown on inorganic phosphate. These data indicate that most amino acids and a few carbohydrates (sucrose, mellibiose, arabinose and sorbose) are suitable for APase production. Lactose, glucose, pyruvate or succinate may be used as a carbon source during photoheterotrophic growth of the cyanobacterium. Glycine and serine are preferred nitrogen sources for its growth. Phosphate repressible APase activity has been found in Anabaena sp. strain CA.

• KSBB Journal
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• v.31 no.3
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• pp.158-164
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• 2016

Plant growth promoting (PGP) hormones, which are produced in a small quantity by bacteria, affect in plant growth and development. PGPs play an important role on the crop productivity in agricultural field. In this study, a photosynthetic bacterial strain producing the PGP was isolated from paddy soil. Bacterial isolate was gram negative, rod-shaped and motility positive. From the 16s rRNA gene sequence analysis, the isolate was identified as Rhodobacter capsulatus PS-2. The mass cultivation of R. capsulatus PS-2 was optimized by considering of the carbon, nitrogen and inorganic salt sources. Optimal medium composition was determined as Na-succinate 4.5 g, yeast extract 5 g, $K_2HPO_4$ 1 g, $MgSO_4$ 5 g, per liter. From the result of 500 L fermentation for 2 days using the optimal medium, the viable cells were $8.7{\times}10^9cfu/mL$. R. capsulatus PS-2 strain produced the carotenoid and indole-3-acetic acid (IAA). The carotenoid extraction and quantitative analysis were performed by HCl-assisting method. Total carotenoid contents from R. capsulatus PS-2 culture broth were measured as $7.02{\pm}0.04$ and $6.93{\pm}0.05mg/L$ under photoheterotrophic and chemoheterotrophic conditions, respectively. To measure the productivity of IAA, colorimetric method was employed using Salkowski reagent at optical density 535 nm. The results showed that the highest content of IAA was $197.44{\pm}5.92mg/L$ in the optimal medium supplemented with 0.3% tryptophan.