Jeong-Kyung Lee

Lysine decarboxylase expression by Vibrio vulnificus, which is up-regulated by CadC in response to acid stress, is also induced by SoxR in response to superoxide stress. SoxR binds to the promoter region of the cadBA operon, coding for a lysine-cadaverine antiporter (CadB) and a lysine decarboxylase (CadA). The induction of cadBA transcription by SoxR is independent of CadC. Cadaverine, which neutralizes the external medium, also appears to scavenge superoxide radicals, since increasing cellular

Both site-directed and spontaneous mutagenesis have been used to investigate the role of the cis-acting regulatory region between -92 and -1 base pair (bp) of the puc operon of Rhodobacter sphaeroides. The DNA sequence from -84 to -66 bp upstream of the 5' end of the start site of puc operon transcription is essential for normal puc operon expression. This regulatory effect was exerted irrespective of the presence or absence of additional upstream regulatory sequences extending from -629 to -93

The manganese-containing superoxide dismutase (MnSOD) of Vibrio vulnificus, normally detected after the onset of the stationary phase, is expressed during the lag that immediately follows the transfer of cells grown exponentially to a fresh medium acidified to pH 5.0, whereas Fe-containing SOD is constitutively expressed. The signal triggering the growth lag and MnSOD induction therein is not low pH but intracellular superoxide accumulated under these conditions, since addition of a superoxide s

An electron paramagnetic resonance (EPR) signal characteristic of the 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO)-OH spin adduct, which is formed from the reaction of DMPO with superoxide radicals generated by xanthine oxidase-mediated reaction, was significantly reduced by the cadaverine or Escherichia coli Mn-containing superoxide dismutase (MnSOD). Likewise, cytochrome c reduction by superoxide was inhibited by cadaverine, and the inhibition level increased in proportion to the level of cadaveri

Chlorophyllide a reductase of Rhodobacter sphaeroides, which were reconstituted with the purified subunits of BchX, BchY, and BchZ, reduced ring B of chlorophyllide a using NADH under anaerobic conditions. Interestingly, suppressor mutations rescuing the inability of R. sphaeroides Fe-SOD mutant to grow in succinate-based minimal medium were predominantly mapped to BchZ subunit of chlorophyllide a reductase. The enzyme is labile in the presence of O(2). However, it generates superoxide at low O(

The photosynthetic growth of Synechocystis sp. strain PCC 6803 is hampered by exogenously added bacteriochlorophyllide a (Bchlide a) in a dose-dependent manner. The growth inhibition caused by Bchlide a, however, is relieved by an increased level of exogenously added chlorophyllide a (Chlide a). The results are explained by the competitive inhibition of chlorophyll synthase by Bchlide a, with inhibition constants (K(I)s) of 0.3 mM and 1.14 mM in the presence of sufficient geranylgeranyl pyrophos

Rhodobacter sphaeroides has a cuprozinc-containing superoxide dismutase (CuZnSOD) in its periplasm in addition to the cytoplasmic SOD that appears to contain iron (FeSOD). The FeSOD is constitutively expressed under the growth conditions examined, whereas the CuZnSOD is detected only when the light-harvesting complexes are found. The CuZnSOD expression is regulated post-transcriptionally, and the enzyme appears to protect the photoheterotrophic cells from periplasmic superoxide that may be gener

The photosynthetic growth of Synechocystis sp. PCC6803 ceased upon expression of Rhodobacter sphaeroides chlorophyllide a reductase (COR). However, an increase in cytosolic superoxide dismutase level in the recombinant Synechocystis sp. PCC6803 completely reversed the growth cessation. This demonstrates that COR generates superoxide in Synechocystis sp. PCC6803. Considering the dissolved oxygen (DO) level suitable for COR, the intracellular DO of this oxygenic photosynthetic cell appears to be l

OBJECTIVE: To evaluate the usefulness of low-dose CT (LDCT) for the diagnosis of acute lower respiratory infection (ALRI) in elderly patients in the emergency room (ER). METHODS: A total of 160 consecutive patients (mean age: 75.9 ± 9.2 years; range: 60-97 years), who were diagnosed to have ALRI by LDCT in the ER, were enrolled in this study. Initial chest radiograph (CR) and CT patterns of ALRI were analysed, and clinical courses of patients were assessed. RESULTS: 49 patients showed negative C

The cellular fatty acid composition is important for metabolic plasticity in Rhodobacter sphaeroides. We explored the effects of changing the cellular ratio of unsaturated fatty acids (UFAs) to saturated fatty acids (SFAs) in R. sphaeroides by overexpressing several key fatty acid biosynthetic enzymes through the use of expression plasmid pRK415. Bacteria containing the plasmid pRKfabI1 with the fabI1 gene that encodes enoyl-acyl carrier protein (ACP) reductase showed a reduction in the cellular

Vibrio vulnificus contains two coproporphyrinogen III oxidases (CPOs): O2-dependent HemF and O2-independent HemN. The growth of the hemF mutant HF1 was similar to wild-type cells at pH 7.5 under 2% O2 conditions where HemN was active and had a half-life of 64 min. However, HF1 did not grow when the medium pH decreased to pH 5.0, where oxidative stress affects endogenous S-adenosylmethionine (SAM) levels. The growth of HF1 was restored not only by elevating the expression of MnSOD but also throug

Chlorophyll synthase (ChlG) and bacteriochlorophyll synthase (BchG) have a high degree of substrate specificity. The BchG mutant of Rhodobacter sphaeroides, BG1 strain, is photosynthetically incompetent. When BG1 harboring chlG of Synechocystis sp. PCC 6803 was cultured photoheterotrophically, colonies arose at a frequency of approximately 10(-8). All the suppressor mutants were determined to have the same mutational change, ChlGI44F. The mutated enzyme ChlGI44F showed BchG activity. Remarkably,

Long-chain free fatty acids (FFAs) are a type of backbone molecule that can react with alcohol to produce biodiesels. Various microorganisms have become potent producers of FFAs. Efforts have focused on increasing metabolic flux to the synthesis of either neutral fat or fatty acyl intermediates attached to acyl carrier protein (ACP), which are the source of FFAs. Membrane lipids are also a source of FFAs. As an alternative way of producing FFAs, exogenous phospholipase may be used after heterolo

The production of phytylated chlorophyll a (Chl aP) in Rhodobacter sphaeroides, which uses phytylated bacteriochlorophyll a (BChl aP), is the first step in expanding the light absorption spectra. Unlike the chlorophyll synthase (ChlG) of the Synechocystis sp. PCC6803, ChlGs of angiosperms, including Arabidopsis thaliana, Nicotiana tabacum, Avena sativa, and Oryza sativa, showed bacteriochlorophyll synthase activity and resistance to inhibition by bacteriochlorophyllide a (BChlide a), geranylgera