Journal of Microbiology

Research Support, Non-U.S. Gov'ts

The GntR-Type Regulators GtrA and GtrB Affect Cell Growth and Nodulation of Sinorhizobium meliloti: Yi Wang , Ai-Min Chen , Ai-Yuan Yu , Li Luo , Guan-Qiao Yu , Jia-Bi Zhu , Yan-Zhang Wang; J. Microbiol. 2008;46(2):137-145. Published online June 11, 2008; DOI: https://doi.org/10.1007/s12275-007-0145-0

Abstract: GntR-type transcriptional regulators are involved in the regulation of various biological processes in bacteria, but little is known about their functions in Sinorhizobium meliloti. Here, we identified two GntR-type transcriptional regulator genes, gtrA and gtrB, from S. meliloti strain 1021. Both the gtrA1 mutant and the gtrB1 mutant had lower growth rates and maximal cell yields on rich and minimal media, as well as lower cell motility on swimming plates, than did the wild-type strain. Both mutants were also symbiotically deficient. Alfalfa plants inoculated with wild-type strain 1021 formed pink elongated nodules on primary roots. In contrast, the plants inoculated with the gtrA1 and gtrB1 mutants formed relatively smaller, round, light pink nodules mainly on lateral roots. During the first 3~4 weeks post-inoculation, the plants inoculated with the gtrA1 and gtrB1 mutants were apparently stunted, with lower levels of nitrogenase activity, but there was a remarkable increase in the number of nodules compared to those inoculated with the wild-type strain. Moreover, the gtrA1 and gtrB1 mutants not only showed delayed nodulation, but also showed markedly reduced nodulation competition. These results demonstrated that both GtrA and GtrB affect cell growth and effective symbiosis of S. meliloti. Our work provides new insight into the functions of GntR-like transcriptional regulators.

Axenic Culture of Gyrodinium impudicum Strain KG03, a Marine Red-tide Microalga that Produces Exopolysaccharide: Joung Han Yim , Hong Kum Lee; J. Microbiol. 2004;42(4):305-314.; DOI: https://doi.org/2106 [pii]

Abstract: An exopolysaccharide-producing microalgal dinoflagellate was isolated from a red-tide bloom and designated strain KG03. A bacteria-free culture of strain KG03 was achieved using a modified wash with phototaxis and antibiotic treatment. Combined treatment with neomycin and cephalosporin was the most effective for eliminating the bacteria associated with the microalgae. Strain KG03 was identified as Gyrodinium impudicum by analyzing the ITS regions of the 5.8S rDNA, 18S rDNA, morphological phenotype and fatty acid composition. The exopolysaccharide production and cell growth in a 300-ml photobioreactor were increased 2.7- and 2.4-fold, respectively, compared with that in a flask culture at the first isolation step.

Detection of L-xylosone and its physiological effects in saccharomyces cerevisiae: Seok, Yeong Jae , Yang, Kap Seok , Kang, Ju Gyeong , Kim, Seong Tae , Huh, Won Ki , Kang, Sa Ouk; J. Microbiol. 1996;34(2):192-197.

Abstract: L-Xylosone was detected as its quinoxaline derivative in the degradation solution of dehydro-L-ascorbic acid. The production rate of L-xylosone was much faster in aerated phosphate-cirate buffer (pH 5. 6) than in pure water. L-Xylosone and dehydro-L-ascorbic acid were identified in the crude extracts of Saccharomyces cerevisiae. The concentration of L-xylosone in the crude cell extracts was calculated to be about 0.2 nmol (mg protein)^-1. When L-xylosone was added to asynchronous culture of S. cerevisiae, it inhibited primarily the synthesis of protein and RNA. Examination of the effect of L- xylosone on synchronous culture of the yeast indicated that L-xylosone inhibited the initiation of DNA replication and that the cells were arrested at G₁stage of cell division cycle. These results suggested a possibility that L-xylosone can act as an inhibitor of cell growth.

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