Microbial utilization of electrically reduced neutral red as the sole electron donor for growth and metabolite production.

Electrically reduced neutral red (NR) served as the sole source of reducing power for growth and metabolism of pure and mixed cultures of H2-consuming bacteria in a novel electrochemical bioreactor system. NR was continuously reduced by the cathodic potential (-1.5 V) generated from an electric current (0.3 to 1.0 mA), and it was subsequently oxidized by Actinobacillus succinogenes or by mixed methanogenic cultures. The A. succinogenes mutant strain FZ-6 did not grow on fumarate alone unless electrically reduced NR or hydrogen was present as the electron donor for succinate production. The mutant strain, unlike the wild type, lacked pyruvate formate lyase and formate dehydrogenase. Electrically reduced NR also replaced hydrogen as the sole electron donor source for growth and production of methane from CO2. These results show that both pure and mixed cultures can function as electrochemical devices when electrically generated reducing power can be used to drive metabolism. The potential utility of utilizing electrical reducing power in enhancing industrial fermentations or biotransformation processes is discussed.     

A photoregulated ligand for the nuclear import receptor karyopherin alpha.

The ability to orchestrate the transport of proteins between nucleus and cytoplasm provides cells with a powerful regulatory mechanism. Selective translocation between these compartments is often used to propagate cellular signals, and it is an intimate part of the processes that control cell division, viral replication, and other cellular events. Therefore, precise experimental control over protein localization, through the agency of light, would provide a powerful tool for the study and manipulation of these events. To this end, a prototype photoregulated nuclear localization signal (NLS) was derived from a native NLS. A library of 30 mutants of the bipartite NLS from Xenopus laevis nucleoplasmin containing a novel, photoisomerizable amino acid was prepared by parallel, solid-phase synthesis and screened in vitro for binding to the nuclear import receptor karyopherin alpha, which mediates the nuclear import of cellular proteins. A single peptide was identified in which the cis and trans photoisomers bind the receptor differentially. The strategy used to obtain this peptide is systematic and empirical; therefore, it is potentially applicable to any peptide-receptor system.     

Plant gene responses to frequency-specific sound signals

We identified a set of sound-responsive genes in plants using a sound-treated subtractive library and demonstrated sound regulation through mRNA expression analyses. Under both light and dark conditions, sound up-regulated expression of rbcS and ald. These are also light-responsive genes and these results suggest that sound could represent an alternative to light as a gene regulator. Ald mRNA expression increased significantly with treatment at 125 and 250 Hz, whereas levels decreased significantly with treatment at 50 Hz, indicating a frequency-specific response. To investigate whether the ald promoter responds to sound, we generated transgenic rice plants harboring a chimeric gene comprising a fusion of the ald promoter and GUS reporter. In three independent transgenic lines treated with 50 or 250 Hz for 4 h, GUS mRNA expression was up-regulated at 250 Hz, but down-regulated at 50 Hz. Thus, the sound-responsive mRNA expression pattern observed for the ald promoter correlated closely with that of ald, suggesting that the 1,506 bp ald promoter is sound-responsive. Therefore, we propose that in transgenic plants, specific frequencies of sound treatment could be used to regulate the expression of any gene fused to the ald promoter.     

Characterization of a T-cell subset prevalent in immunoregulatory disorders in humans

T cells from individuals with certain autoimmune diseases (rheumatoid arthritis, graft-versus-host disease, acquired immunodeficiency syndrome) express high levels of a cell surface sialoglycoprotein with a molecular weight of 140 kDa (gp140). Although a low frequency of gp 140+ T cells was detected in the blood of normal individuals, upon stimulation with autologous EBV-transformed B cells (AMLR), the frequency of expression of gp140 was increased threefold. To further characterize gp 140+ T cells, rosetting techniques with ox erythrocytes coated with monoclonal anti-gp 140 antibody were used to isolate T-cell subsets for phenotypic, cell cycle, and functional analysis. The majority of gp140+ T cells expressed cytotoxic/suppressor (CD8+) phenotype in both normal and AMLR-activated states. Unstimulated gp140+ T cells had significantly greater nucleic acid content, as measured by acridine orange and flow cytometry, than gp140- T cells. Surprisingly, the gp140+ T-cell subset had a less proliferative response in vitro to pokeweed or phytohemaglutinin mitogens. These results suggest that gp140+ T cells in normal individuals and in patients with autoimmune diseases may have been activated previously in vivo and that they are relatively resistant to reactivation in vitro.