Construction of shuttle vectors derived fromAcetobacter xylinum for cellulose-producing bacteriumAcetobacter xylinum

Summary Shuttle vector pUF106 was constructed by ligation ofAcetobacter xylinum plasmid pFF6 toEscherichia coli plasmid pUC18. It had unique restriction sites suitable for insertion of a foreign DNA fragment and conferred ampicillin resistance to a host. pUF106 transformed cellulose-producingA. xylinum ATCC10245 as well asE. coli JM109.     

cDNA sequence and expression of a phosphoenolpyruvate carboxylase gene from soybean

A full-length cDNA encoding a subunit of phosphoenolpyruvate carboxylase (PEPC) was isolated from a developing seed expression library of the C₃ plant Glycine max. The corresponding mRNA is present at similar levels in leaf, stem, root and developing seed. Two potential start codons exist, and the activity of protein initiated from the first such codon could be subject to regulation by protein kinase. Sequence comparison shows a similar upstream start codon in the case of the Ppc2 gene from Mesembryanthemum crystallinum, previously assumed to lack the sequences necessary for phosphorylation. The soybean encoded protein tends to resemble other C₃-type PEPC proteins more closely than those implicated in C₄ or crassulacean acid metabolism.     

Molecular cloning of cDNA for the import precursor of human subunit B of H(+)-ATP synthase in mitochondria.

The nucleotide sequence of the import precursor of subunit b of human H(+)-ATP synthase has been determined from a recombinant cDNA clone isolated by screening a human kidney cDNA library with a cDNA for rat subunit b as a probe. The sequence was composed of 1,134 nucleotides including a coding region for the import precursor of subunit b and noncoding regions on the 5'- and 3'-sides. The import precursor of subunit b and its mature polypeptide deduced from the open reading frame were found to consist of 256 and 214 amino acid residues with molecular weights of 28,893 and 24,610, respectively. The presequence of 42 amino acids could be the import signal peptide for directing the protein into the mitochondrial matrix.     

Budding-specific lectin induced in epithelial cells is an extracellular matrix component for stem cell aggregation in tunicates.

We have examined immunocytochemically the expression, localization and in vivo function of a calcium-dependent and galactose-binding 14 x 10(3) Mr lectin purified from the budding tunicate, Polyandrocarpa misakiensis. Lectin granules first appeared in the inner epithelium of a double-walled bud vesicle. Soon after the bud entered the developmental phase, the granules were secreted into the mesenchymal space, where the lectin-positive extracellular matrix (ECM) developed. The lectin was also produced and secreted by granular leucocytes during budding. Hemoblasts, pluripotent stem cells in the blood, were often found in association with the ECM and they aggregated with epithelial cells to form organ rudiments. The lectin showed a high binding affinity for hemoblast precursors. The blockage of epithelial transformation of stem cells by galactose in in vivo bioassy was ineffective in the presence of the lectin. Polyclonal anti-lectin antibody prevented the hemoblasts spreading on the ECM and moving toward the epithelium, but it did not block the cell-cell adhesion of hemoblasts. By three days of bud development, lectin granules and ECM have almost disappeared from the developing bud together with a cessation of hemoblast aggregation. These results show that Polyandrocarpa lectin is a component of the ECM induced specifically in budding and suggest strongly that it plays a role in bud morphogenesis by directing the migration of pluripotent stem cells to the epithelium.     

Cloning of genes responsible for acetic acid resistance in Acetobacter aceti.

Five acetic acid-sensitive mutants of Acetobacter aceti subsp. aceti no. 1023 were isolated by mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. Three recombinant plasmids that complemented the mutations were isolated from a gene bank of the chromosome DNA of the parental strain constructed in Escherichia coli by using cosmid vector pMVC1. One of these plasmids (pAR1611), carrying about a 30-kilobase-pair (kb) fragment that conferred acetic acid resistance to all five mutants, was further analyzed. Subcloning experiments indicated that a 8.3-kb fragment was sufficient to complement all five mutations. To identify the mutation loci and genes involved in acetic acid resistance, insertional inactivation was performed by insertion of the kanamycin resistance gene derived from E. coli plasmid pACYC177 into the cloned 8.3-kb fragment and successive integration into the chromosome of the parental strain. The results suggested that three genes, designated aarA, aarB, and aarC, were responsible for expression of acetic acid resistance. Gene products of these genes were detected by means of overproduction in E. coli by use of the lac promoter. The amino acid sequence of the aarA gene product deduced from the nucleotide sequence was significantly similar to those of the citrate synthases (CSs) of E. coli and other bacteria. The A. aceti mutants defective in the aarA gene were found to lack CS activity, which was restored by introduction of a plasmid containing the aarA gene. A mutation in the CS gene of E. coli was also complemented by the aarA gene. These results indicate that aarA is the CS gene.     

Occurrence of D-rhamnan as the common antigen reactive against monoclonal antibody E87 in Pseudomonas aeruginosa IFO 3080 and other strains.

S. Sawada and co-workers reported that a monoclonal antibody (MAb), E87, interacted with about 80% of Pseudomonas aeruginosa isolates, and they separated a rhamnose-rich polysaccharide as the probable antigen for MAb E87 from P. aeruginosa IFO 3080 (S. Sawada, T. Kawamura, Y. Masuho, and K. Tomibe, J. Infec. Dis. 152:1290-1299, 1985). In the present study, the rhamnose-rich polysaccharide was shown to be structurally and immunologically identical to the D-rhamnan of P. aeruginosa IID 1008 (S. Yokota, S. Kaya, S. Sawada, T. Kawamura, Y. Araki, and E. Ito, Eur. J. Biochem. 167:203-209, 1987). Furthermore, a set of enzymes responsible for the formation of GDP-rhamnose (probably in a D-form) from GDP-D-mannose was found in the 100,000 x g supernatant fractions obtained from all of nine P. aeruginosa strains reactive against MAb E87. The result strongly supports a possibility that lipopolysaccharides having a D-rhamnan chain widely occur as the common antigen among various P. aeruginosa isolates.     

Comparison of the intestinal bacteria in specific pathogen free mice from different breeders

Specific pathogen free BALB/c mice from 3 commercial laboratory animal breeders in Japan were compared on the composition of caecal flora revealed by selective and nonselective cultivation as well as direct microscopical observation on smears, and relative caecal weight. Large differences were detected in viable counts of total bacteria and almost all bacterial groups, while direct microscopical counts which consisted mainly of fusiform bacteria were almost equal, resulting in diverse recovery rates among 3 breeders. Eubacterium and spiral shaped organisms were not detected from all breeders. There also existed variations within breeders, especially those in the number of Enterobacteriaceae. Relative caecal weight also differed among breeders, suggesting the participation of variety of caecal bacteria in determining this parameter. As these variations in bacteriological status of animals can influence experimental results, standardization of intestinal microbial flora is required.     

Characteristics of a circadian pacemaker in the suprachiasmatic nucleus

Summary The nature of the circadian rhythms of the SCN in a hypothalamic island was examined in male rats by recording multiple unit activity from the SCN for longer durations. Successful continuous recording lasted up to 35 days. Neural activity of the SCN inside the island showed free-running rhythms whose periods were slightly longer than 24 h (Figs. 2, 3, Table 1). When the retino-hypothalamic pathway was spared, re-entrainment to a displaced light and dark cycle was attained following a transition period of a few days (Fig. 4). Phases of the rhythms shifted in a phase-dependent manner in response to single light pulses interrupting constant darkness (Fig. 5 and Fig. 6). These results suggest an endogenous nature of the circadian rhythm of the SCN within the hypothalamic island. Thus, neurons or neuronal networks in the SCN may have not only an inherent ability to generate a circadian rhythm, but also an intricate machinery to regulate its phase. Simultaneous recordings from the left and right SCN showed a slight but visible discrepancy in their phases between the two rhythms in 3 out of 12 cases (Fig. 7).Abbreviations LL constant light - LD light-dark - DD constant darkness - SCN Suprachiasmatic nucleus     

Cytological studies on the mosaic silkworms induced by low temperature treatment

Mosaic silkworms were induced when the hybrid eggs of two strains with different egg color and larval markings were exposed to low temperature. Cytological studies were conducted to find out the relation between mosaic larval pattern and ploidy in reproductive cells along with demonstration of chromosomes in the mosaic embryos. — Mosaic eggs eith the characters of both the father and the hybrid were two types, one with large serosa nuclei (LN-mosaic) and the other with small serosa nuclei (SN-mosaic). The cytological studies demonstrated that LN-mosaic individuals were 2n/4n, while SN-mosaic ones were n/2n. In both types of silkworms, cell ploidy level in nuclei of synkaryon origin was two times that of androgenic ones. — From the results obtained in the present studies as well as in the previous studies, a possible mechanism of induction of mosaicism in silkworms by cold shock is contemplated.