Repression of Pyruvate Kinase in Candida utilis and Rat Liver by Sclerin through Energy Charge

Though sclerin (SCL) only slightly inhibited the activity of pyruvate kinase (PK) in crude extract of Candida utilis, markedly repressed the level of that in the growing cells in a glucose medium. The repression of PK was largely recovered by 2,4-dinitrophenol (DNP), and SCL rather raised the level in the cells growing on gluconate.

SCL also slightly inhibited the activity of a partially purified PK from rat liver, and, when orally administered, or incubated with the liver slices, obviously lowered the level of PK in the liver and liver slices. The effect of SCL in the liver slices was reversed by DNP. SCL stimulated the oxidative phosphorylation in mitochondria prepared from the fresh liver, and served to maintain the activity in the liver slices during incubation.

Both activity of PK from Candida utilis and rat liver was remarkably inhibited by adenylate energy charge in vitro.

It is concluded that SCL represses the level of PK in these cells and tissues through a high energy charge by stimulating the oxidative phosphorylation.     

Microbial diversity in ostrich ceca as revealed by 16S ribosomal RNA gene clone library and detection of novel Fibrobacter species

The ostrich (Struthio camelus) is a herbivorous bird and although the hindgut is known as the site for fiber digestion, little is known about the microbial diversity in the ostrich hindgut. Our aim was to analyze the microbial diversity in ostrich ceca using a 16S ribosomal RNA gene (rDNA) clone library approach. A total of 310 clones were sequenced and phylogenetically analyzed and were classified into 110 operational taxonomy units (OTUs) based on a 98% similarity criterion. The similarity of the sequences ranged from 86 to 99% and 95 OTUs had less than 98% similarity to the sequences in the public databases. Coverage and the Shannon–Wiener index (H′) of the library were 83.9% and 4.29, respectively. The sequences were assigned to the following 6 phyla: Firmicutes (50.9% of the total number of sequences), Bacteroidetes (39.4%), Fibrobacteres (6.5%), Euryarchaeota (1.9%), Spirochaetes (1.0%), and Verrucomicrobia (0.3%); approximately 90% of the sequences were affiliated with Firmicutes and Bacteroidetes. The only OTU of Fibrobacteres (OTU 107), had 93 and 90% similarity to Fibrobacter succinogenes and F. intestinalis, respectively, suggesting a new species of Fibrobacter in ostrich ceca. Clostridium coccoides and C. leptum formed major groups within the Firmicutes. There was no OTU with high similarity (≥98%) to the 16S rDNA of cultivated fibrolytic bacteria in our library. Although two OTUs were affiliated with Euryarchaeota, no sequence was affiliated with methanogenic Archaea. This study presents the very complex ostrich cecal microbial community, in which the majority of the bacterial species have not yet been cultivated.     

Genetic mapping in Bacillus subtilis 168 of the aadK gene which encodes aminoglycoside 6-adenylyltransferase

Abstract Bacillus subtilis 168 has an aadK gene, which encodes aminoglycoside 6-adenylyltransferase, a streptomycin-modifying enzyme, on its chromosome. To characterize the aadK gene, we con tructed a B. subtilis 168 strain that carried the chloramphenicol resistance gene near the aadK on the chromosome and an aadK deletion mutant using an integration technique. The aadK gene was mapped between azlB and pheA on the chromosome of B. subtilis 168. The aadK deletion mutant was slightly more susceptible to streptomycin than the original strain. The result indicates that the aadK gene contributes low-level resistance to streptomycin in B. subtilis 168.     

A New Approach to AIDS Research and Prevention: The Use of Gene-Mutated HIV-1/SIV Chimeric Viruses for Anti-HIV-1 Live-Attenuated Vaccines

The lack of a suitable animal model is a major obstacle to developing anti-HIV-1 vaccines. We successfully generated an SIVmac/HIV-1 chimeric virus (SHIV) (designated as NM-3rN) that contains the HIV-1 env gene and is infectious to macaque monkeys. Challenging the vaccinated macaque monkeys with NM-3rN, we developed an evaluation system for anti-HIV-1 Env-targeted vaccines. For the purpose of making the vaccine, a series of gene-mutated SHIVs were constructed. The monkeys vaccinated with these SHIVs had long-term anti-virus immunities without manifesting the disease, and became resistant to a challenge inoculation with NM-3rN. The sera from a monkey showed that, after the vaccination, the neutralizing antibodies not only against the parental HIV-1 but also against an antigenically different HIV-1 were raised. In vivo experiments confirmed that the vaccinated monkeys were protected from the challenge inoculum of an antigenically different SHIV-MN. Vaccination of monkeys with the attenuated SHIVs showed that further gene-deletion of the SHIV resulted in less immunogenicity. Nevertheless, the attenuated SHIVs had a vaccine effect against the challenge inoculation. In addition to specific immunities including neutralizing antibodies and cytotoxic T cells, a more complicated immune mechanism induced by live vaccine appears to play a role in this protection. Our data suggest that the live vaccine can induce strong and wide-range immunity against HIV-1. These SHIVs should contribute to understanding the pathogenicity of AIDS and to the development of future anti-HIV-1 live vaccines for humans.     

Pale and dark dichromatism related to microhabitats in a herbivorous tanganyikan cichlid fish,Telmatochromis temporalis

Dichromatism and habitat utilization of a small herbivorous cichlid fish,Telmatochromis temporalis, were studied in a littoral rocky area of Lake Tanganyika. Individuals of both sexes had either pale or dark body coloration that did not change for long periods. Both sexes defended territories from consexuals, and a male had a harem of several females. Pale fish had territories in exposed areas and dark fish in shaded ones. Larger fish were dominant over smaller consexuals and occupied well-illuminated areas. When pale and dark fish were kept in areas with shaded and lighted backgrounds, respectively, they changed body colour within a few weeks. When pale fish were in well-illuminated areas and dark ones in shaded areas, they were cryptic. BecauseTelmatochromis temporalis are very vulnerable prey in coastal areas, dichromatism may function as antipredator camouflage.     

The Density of a Homogeneous Population of Cells Controls Resetting of the Program for Swarmer Formation in the Unicellular Marine MicroorganismNoctiluca scintillans

Noctiluca scintillansis a luminescent marine dinoflagellate. The life cycle ofNoctilucaconsists of a vegetative stage and a swarmer stage. The swarmer stage ofNoctilucais initiated by formation of a swarmer-mother cell instead of binary fission of vegetative cells. We studied the formation of swarmers under various conditions and became convinced that the cells have a strict program for the formation of swarmers which starts to operate in every cell after a defined number of cell cleavages. The probability that the program will be executed appeared to be affected by the presence of other cells. In other words, a high density of cells suppressed the expression of the program. Suppression was achieved by resetting the mechanism and was related to the number of cell divisions. Our findings provide one of the simplest examples of a mechanism by which a large population produces individuality in a group of genetically homogeneous organisms.     

A possible role of histidine in a nickel resistant mechanism of Saccharomyces cerevisiae

When a nickel resistant strain N08 of S. cerevisiae was grown in a Ni-supplemented medium, approximately 70% of the nickel is distributed in the soluble fraction. The soluble fraction was chromatographed on Sephadex G-10 and the fraction contained both nickel and large amounts of histidine. When cells were grown in medium containing various combinations of nickel and magnesium and which exhibited approximately 50% growth inhibition, a molar ratio of intracellular histidine and nickel contents remained constant at 1.2-1.4, indicating that the increase in histidine content is correlated with nickel accumulation. The wild type strain 0605-S6, however, exhibits no increase in histidine content when grown in a Ni-supplemented medium, and, therefore, a nickel-resistant mechanism of yeast appears to be the formation of histidine-nickel complexes.     

A gene cluster for the synthesis of serotype g-specific polysaccharide antigen in Aggregatibacter actinomycetemcomitans

Aggregatibacter actinomycetemcomitans is an important pathogen related to aggressively progressive periodontal breakdown in adolescents and adults. The species can be divided into six serotypes (a–f) according to their surface carbohydrate antigens. Recently, a new serotype g of A. actinomycetemcomitans was proposed. The aim of the present study was to sequence the gene cluster associated with the biosynthesis of the serotype g-specific polysaccharide antigen and develop serotype-specific primers for PCR assay to identify serotype g strains of A. actinomycetemcomitans. The serotype-specific polysaccharide (SSPS) gene cluster of the NUM-Aa 4039 strain contained 21 genes in 21,842-bp nucleotides. The similarity of the SSPS gene cluster sequence was 96.7 % compared with that of the serotype e strain. Seventeen serotype g genes showed more than 90 % homology both in nucleotide and amino acids to the serotype e strain. Three additional genes with 1,579 bp in NUM-Aa 4039 were inserted into the corresponding ORF13 of the serotype e strain. The serotype g-specific primers were designed from the insertion region of NUM-Aa 4039. Serotypes of the a–f strains were not amplified by serotype-specific g primers; only NUM-Aa 4039 showed an amplicon band. The NUM-Aa 4039 strain was three genes in the SSPS gene cluster different from those of serotype e strain. The specific primers derived from these different regions are useful for identification and distribution of serotype g strain among A. actinomycetemcomitans from clinical samples.