Endogenous synthesis of peptidoglycan in eukaryotic cells; a novel concept involving its essential role in cell division, tumor formation and the biological clock

Cephalopod ink: production, chemistry, functions and applications

One of the most distinctive and defining features of coleoid cephalopods—squid, cuttlefish and octopus—is their inking behavior. Their ink, which is blackened by melanin, but also contains other constituents, has been used by humans in various ways for millennia. This review summarizes our current knowledge of cephalopod ink. Topics include: (1) the production of ink, including the functional organization of the ink sac and funnel organ that produce it; (2) the chemical components of ink, with a focus on the best known of these—melanin and the biochemical pathways involved in its production; (3) the neuroecology of the use of ink in predator-prey interactions by cephalopods in their natural environment; and (4) the use of cephalopod ink by humans, including in the development of drugs for biomedical applications and other chemicals for industrial and other commercial applications. As is hopefully evident from this review, much is known about cephalopod ink and inking, yet more striking is how little we know. Towards closing that gap, future directions in research on cephalopod inking are suggested.

A high-performance liquid chromatography method for the detection of diaminopimelic acid in urine

We describe a quantitative assay for diaminopimelic acid (DAP) in urine. It involves (i) hydrolysis of urine samples, (ii) purification by several different liquid chromatography steps, and (iii) analysis by high-performance liquid chromatography on a reversed-phase C18 column. Tritiated-DAP, the internal standard, allows one to precisely follow the DAP-containing fractions and to determine the yield during purification. Sensitive and relatively accurate quantification of DAP, with a threshold of 50 fmol, is based on ion-pairing properties of eluants and ortho-phthaldialdehyde derivatization. The presence of DAP in relevant fractions was confirmed by combined gas chromatography and mass spectrometry. The DAP concentration in adult human urine pooled over 24 h ranges from 0.69 to 2.01 microM, a result in fair agreement with previously published values obtained by ninhydrin derivatization or gas chromatography.

Cloning of the gene for monogalactosyldiacylglycerol synthase and its evolutionary origin

Monogalactosyldiacylglycerol (MGDG) synthase (UDPgalactose:1,2-diacylglycerol 3-beta-D-galactosyltransferase; EC 2.4.1.46) catalyzes formation of MGDG, a major structural lipid of chloroplast. We cloned a cDNA for the synthase from cucumber cDNA library. The full-length cDNA clone was 2142 bp, and it contains a 1575-bp open reading frame encoding 525 aa. The open reading frame consists of the regions for a mature protein (422 aa; Mr of 46,552) and transit peptide to chloroplast (103 aa). Although the molecular weight of mature protein region matched that purified from cucumber cotyledons, it was quite different from those purified from spinach (approximately 20 kDa) reported by other groups. The mature region of the protein was expressed in Escherichia coli as a fusion protein with glutathione S-transferase. The expression in E. coli showed that the protein catalyzed MGDG synthesis very efficiently. Therefore, we concluded that the cDNA encodes MGDG synthase in cucumber. In addition, the deduced amino acid sequence of the MGDG synthase cDNA showed homology with MurG of Bacillus subtilis and E. coli, which encode a glycosyltransferase catalyzing the last step of peptidoglycan synthesis in bacteria. This sequence homology implies that the machinery of chloroplast membrane biosynthesis is evolutionarily derived from that of cell wall biosynthesis in bacteria. This is consistent with the endosymbiotic hypothesis of chloroplast formation.

Genetic ecology: a new interdisciplinary science, fundamental for evolution, biodiversity and biosafety evaluations

Genetic ecology is the extension of our modern knowledge in molecular genetics to studies of viability, gene expression and gene movements in natural environments like soils, aquifers and digestive tracts. In such milieux, the horizontal transfer of plasmid-borne genes between phylogenetically distant species has already been found to be much more frequent than had been expected from laboratory experience. For the study of exchanges involving chromosomally-located genes, more has to be learned about the behaviour of transposons in such environments. The results expected from studies in genetic ecology are relevant for considerations of evolution, biodiversity and biosafety. The role of this new field of research in restoring popular confidence in science and in its biotechnological applications is stressed.

The gene of the N-acetylglucosaminidase, a Bacillus subtilis 168 cell wall hydrolase not involved in vegetative cell autolysis

lytD, the structural gene of the Bacillus subtilis 168 N-acetylglucosaminidase was localized at 310 degrees, next to the tagABC operon. Sequence analysis revealed a monocistronic operon encoding a 95.6 kDa protein endowed with an export signal, the cleavage of which yields the monomer polypeptide (92.8 kDa) of the dimeric active form of the enzyme. Transcription is initiated at a sigma-D (sigma D)-dependent promoter and ends at a terminator common to lytD and the divergently transcribed tagABC operon. In addition, we report the sequence of the adjacent upstream ORF, transcribed in the same direction as lytD, which shows significant homology to phosphomannose isomerase-encoding genes. Cell separation, motility, autolysis, cell wall turnover and growth were not affected in strains devoid of the N-acetylglucosaminidase. A mutant deficient in the two most abundant autolysins, i.e. the LytC amidase and the glucosaminidase, exhibited the phenotype of the amidase-deficient strains, revealing their non-requirement for growth. This conclusion raises two fundamental questions: how does the cell undo the highly cross-linked peptidoglycan so as to be able to grow, and what is the role of the considerable amount of autolysin normally present? Possible answers to these questions are discussed.

Biological properties of bacterial peptidoglycan

Synthetic and natural muramyl peptides have a variety of biological actions in mammals, including the abilities to enhance sleep and body temperature. Although muramyl peptides can be detected constitutively in mammalian organisms, no biochemical synthetic pathways are known for muramyl peptides in mammals. However, muramyl peptides are well known as components of bacterial cell wall peptidoglycan (synonym: murein). Isolated bacterial cell walls elicit host responses similar to those produced by bacterial infections or by purified muramyl peptides. Mammalian cells which phagocytize bacteria can digest bacterial cell walls and release biologically active muramyl peptides. The released muramyl peptides then express some or all of the biological effects observed with synthetic muramyl peptides. Also, cell-free systems consisting of isolated bacterial cell walls and lysozyme produce substances with similar biological activities.