Biomedical subjects

Haruko Takeyama

Publications and source records attributed to Haruko Takeyama.

39 records · Page 3Linked to original sources

PubMed2002

Cadmium recovery by a sulfate-reducing magnetotactic bacterium, Desulfovibrio magneticus RS-1, using magnetic separation.

Cadmium recovery by a sulfate-reducing magnetotactic bacterium, Desulfovibrio magneticus strain RS-1, was investigated. D. magneticus precipitated >95% of cadmium at an initial concentration of 1.3 ppm in the growth medium. Electron microscopic analysis revealed that D. magneticus formed electron-dense particles on its surface when cultivated in the presence of cadmium ions (Cd2+). Sulfide was also found in the precipitate, and the composition ratio of sulfide/cadmium was 0.7. Sixty percent of viable RS-1 cells was recovered by a simple magnetic separation revealing the removal of 58% cadmium from the culture medium.

Cadmium↗

PubMed1999

UV-A-induced expression of GroEL in the UV-A-resistant marine cyanobacterium Oscillatoria sp. NKBG 091600.

The authors have examined the response to UV-A irradiation of the UV-A-resistant marine cyanobacterium Oscillatoria sp. NKBG 091600, which produces the UV-A-absorbing compound biopterin glucoside. The expression of a 60 kDa protein was markedly induced at 500 min after UV-A irradiation. This protein was identified by N-terminal amino acid sequence analysis as GroEL. Northern blot analysis demonstrated that GroEL synthesis was controlled by UV-A at the transcriptional level. A CIRCE element and a putative SOS consensus sequence were found upstream of the groESL operon, overlapping two putative promoter sequences. Primer extension analysis revealed that groESL transcription in UV-A-induced cells starts from the proximal promoter overlapped by the SOS consensus sequence. This indicates that an SOS response regulation is instrumental in UV-A-induced GroEL expression of Oscillatoria sp. NKBG 091600. Furthermore, this UV-A-inducible GroEL may function to upregulate biopterin glucoside biosynthesis, thereby allowing growth under UV-A irradiation.

Base Sequence↗

PubMed1997

Expression of the eicosapentaenoic acid synthesis gene cluster from Shewanella sp. in a transgenic marine cyanobacterium, Synechococcus sp.

The eicosapentaenoic acid (EPA) synthesis gene cluster isolated from a marine bacterium, Shewanella putrefaciens strain SCRC-2738, was cloned and expressed in the marine cyanobacterium Synechococcus sp. A broad-host-range cosmid vector, pJRD215 (10.2 kb, Smr Kmr), was used to clone a 38 kb insert, pEPA, containing the EPA synthesis gene cluster, creating plasmid pJRDEPA (approx. 48 kb). This plasmid was transferred to the cyanobacterial host at a frequency of 2.2 x 10(-7). Cyanobacterial transconjugants grown at 29 degrees C produced 0.12 mg EPA (g dry weight)-1, whereas those grown at 23 degrees C produced 0.56 mg EPA (g dry weight)-1. The yield was further improved to 0.64 mg (g dry weight)-1 by incubation for 1 d at 17 degrees C. This is believed to be the first successful cloning and expression of such a large heterologous gene cluster in a marine cyanobacterium.

Conjugation, Genetic↗