Among the 70 family bacterial factors, group 2 factors have similar promoter recognition specificity to group 1 (principal) factors and express and function under specific environmental and physiological conditions. In general, the cyanobacterial genome encodes more than four group 2 factors, and the unicellular Synechococcus elongatus PCC 7942 (Synechococcus) has five group 2 factors (RpoD2-6). In this study, we analyzed expression of group 2 factors of Synechococcus at both mRNA and protein levels, and we showed that the rpoD3 expression was activated only by high light (1,500 mol photons m ؊2 s ؊1 ) among the various stress conditions examined. After high light shift, rpoD3 mRNA accumulated transiently within the first 5 min and diminished subsequently, whereas RpoD3 protein increased gradually during the first several hours. We also found that the rpoD3 deletion mutant rapidly lost viability under the same conditions. Analysis of the rpoD3 promoter structure revealed the presence of an HLR1 (high light-responsive element 1) sequence, which was suggested to be responsible

Although regulation of sigma factors has been intensively investigated, anti-sigma factors have not been identified in oxygenic photosynthetic organisms. A previous study suggested that the sigma factor, SigE, of the cyanobacterium Synechocystis sp. PCC 6803, a positive regulator of sugar catabolism, is posttranslationally activated by light-to-dark transition. In the present study, we found that the H subunit of Mg-chelatase ChlH interacts with sigma factor SigE by yeast two-hybrid screening, and immunoprecipitation analysis revealed that ChlH associates with SigE in a lightdependent manner in vivo. We also found that Mg 2؉ promotes the interaction of SigE and ChlH and determines their localization in vitro. In vitro transcription analysis demonstrated that ChlH inhibits the transcription activity of SigE. Based on these results, we propose a model in which ChlH functions as an anti-sigma factor, transducing light signals to SigE in a process mediated by Mg 2؉ .cyanobacteria ͉ transcription

Cyanobacterial principal r factor, r A , includes a specifically conserved cluster of basic amino acids in the amino-terminal extension called region 1.1. We found that the r A in a thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 binds DNA in the absence of the core RNA polymerase and that r A lacking region 1.1 is not able to bind DNA. This indicates that, in the cyanobacterium, region 1.1 participates in DNA-binding, rather than inhibiting the interaction between free r and DNA, as found in other principal r factors of eubacteria. The results of in vitro transcription assays with the reconstituted RNA polymerase showed that region 1.1 reduces transcription activity from the cpc promoter.

Two novel antifungal antibiotics, PF1 163A and B, were isolated from the fermentation broth of Penicillium sp. They were purified from the solid cultures of rice media using ethyl acetate extraction, silica gel and Sephadex LH-20 column chromatographies. PF1 163A and B showed potent growth inhibitory activity against pathogenic fungal strain Candida albicans but did not show cytotoxic activity against mammalian cells. These compounds inhibited the ergosterol biosynthesis in Candida albicans.The incidence of life-threatening systemic infections caused by opportunistic yeasts and fungi has increased in patients infected by HIV or received cancer chemotherapy1^The most prevalently used antifungal drugs include the polyenes and the azoles. All these agents, however, have problems in, for example, potency, toxicity and resistance development2'3). Therefore, the discovery and development of novel antifungal agents are required to resolve these problems. As part of an antifungal screening program, we searched for compoundsfrom the fermentation broths that inhibited the fungal ergosterol biosynthesis. In this paper, we describe the taxonomy of the producing strain, fermentation, isolation and biological activities of the novel compounds designated PF1 163A and B isolated from the microbial broths of Penicillium sp.

No abstract