Secretion of lipids induced by inhibition of peptidoglycan synthesis in streptococci.

Inhibition of peptidoglycan synthesis causes an immediate and massive secretion of both newly synthesized and "old" lipids from several species of bacteria, including streptococci, Staphylococcus epidermidis, and Bacillus subtilis. Lipid secretion occurs in the absence of detectable bacterial lysis. This novel phenomenon was examined in more detail in three strains of streptococci: S. sanguis (group H), S. pyogenes (group A), And S. pneumoniae. The secretion of lipids is specifically induced by inhibitors of peptidoglycan synthesis; it is not caused by inhibitors of protein, ribonucleic acid, or deoxyribonucleic acid synthesis. The occurrence appears to be reversible since penicillin-induced secretion comes to a halt upon the timely addition of penicillinase, correlating with resumption of culture growth. All cellular lipids are secreted in essentially the same proportions as those found in the drug treated bacteria. It is suggested that continued peptidoglycan synthesis may be essential for the integration and retention of lipid material in the plasma membrane.     

Choline-containing bacteriophage receptors in Streptococcus pneumoniae.

Choline-containing teichoic acid seems to be essential for the adsorption of bacteriophage Dp-1 to pneumococci. This conclusion is based on the following observations: In contrast to pneumococci grown in choline-containing medium, cells grown in medium containing ethanolamine or other submethylated aminoalcohols instead of choline were found to be resistant to infection by Dp-1. Live choline-grown bacteria and heat- or UV-inactivated cells and purified cell walls prepared from these cells were capable of adsorbing phage Dp-1; ethanolamine-grown pneumococci or cell wall preparations were unable to do so. Adsorption of Dp-1 to choline-containing cell walls was competitively inhibited by phosphorylcholine and by several choline-containing soluble cell surface components, such as the Forssman antigen and the teichoic acid-glycan complexes formed by autolytic cell wall degradation. Cell walls prepared from pneumococci grown in ethanolamine or phosphorylethanolamine were inactive. Electron microscopic studies with pneumococci that had segments of choline-containing cell wall material amid ethanolamine-containing regions indicated that the Dp-1 phage particles adsorbed exclusively to the choline-containing surface areas. We suggest that the choline residues of the pneumococcal teichoic acid are essential components of the Dp-1 phage receptors in this bacterium.     

Isolation and characterization of a Tn551-autolysis mutant of Staphylococcus aureus.

A Lyt- mutant with reduced autolytic activity was isolated after Tn551 mutagenesis of the methicillin-susceptible Staphylococcus aureus laboratory strain RN450. The Lyt- phenotype could be transferred back into the parent and into a variety of other S. aureus strains by transduction of the transposon marker. Southern analysis has located the Tn551 insert to a 3.2-kb HindIII DNA fragment on the SmaI B fragment of the staphylococcal chromosome. The Lyt- phenotype included reduced rates of cell wall turnover and autolysis induced by detergent or methicillin treatment; however, the rate of methicillin-induced killing was not affected. Peptidoglycans prepared from the parental and mutant cells showed identical muropeptide compositions, as resolved by a high-resolution high-pressure liquid chromatography technique. On the other hand, LiCl extracts of the mutant cells contained reduced amounts of total protein and lower specific cell wall-degrading activity compared with those of extracts of parental cells. The profile of bacteriolytic enzymes as detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed multiple band differences between mutant and parental cells; a major lytic band with properties characteristic of the staphylococcal endo-beta-N-acetylglucosaminidase was completely absent from the Lyt- cells. The Lyt- phenotype transduced into a series of methicillin-resistant strains of both homogeneous and heterogeneous phenotypes caused only a modest decrease in the level of methicillin resistance, as determined by population analysis.     

Specificity of DNA uptake in genetic transformation of gonococci

Genetic transformation of gonococci to streptomycin resistance was inhibited by homologous DNA or by DNA from related $\text{Neisseriae}$, but not by high concentrations of heterologous DNAs. Gonococci were capable of adsorbing large quantities (up to about 50 μg per 10⁸ cells) of both homologous and heterologous DNA, which could not be eluted by strong shearing forces. Treatment with externally added DNase removed virtually all the heterologous DNA while a small fraction of the homologous DNA, not influenced by the presence of excess heterologous DNA, remained cell-bound in a form resistant to nuclease treatment. Competing homologous DNA suppressed nuclease-resistant binding. These findings suggest that gonococci have two types of DNA binding components at their surface. Competence of gonococci for genetic transformation undergoes a rapid decay if the cells are incubated with homologous (but $\text{not}$ with heterologous) DNA.     

Calcium-requiring step in the uptake of deoxyribonucleic acid molecules through the surface of competent pneumococci.

The conversion of surface-adsorbed deoxyribonucleic acid (DNA) molecules to a state in which they are inaccessible to exogenous deoxyribonuclease requires specifically calcium ions; magnesium ions cannot replace calcium ions. Virtually maximal levels of nuclease-resistant DNA binding and genetic transformation can be obtained in media free from magnesium and containing only calcium ions. It is suggested that the calcium-requiring process is the transport of DNA molecules across the plasma membrane. Magnesium ions stimulate both the loss of surface-adsorbed DNA to the medium and the extracellular degradation of DNA.     

Nucleoside 5''-phosphordiamidates, synthesis and some properties.

A simple way of preparing nucleoside 5'-phosphordiamidate is described. The procedure is based on the ammonolysis of nucleoside 5'-phosphordichloridates by dilute aqueous ammonium hydroxide. The behaviour of nucleoside phosphordiamidates under acidic and alkaline conditions is also reported. Alkaline hydrolysis results in the formation of the parent nucleoside, whereas one amide group can be removed selectively by mild acid hydrolysis. This property of nucleoside phosphordiamidates served as a basis for the elaboration of a simple synthesis of nucleoside phosphoramidates starting from nucleosides.     

Cu(II)-Binding N-Terminal Sequences of Human Proteins

Proteins anchor copper(II) ions mainly by imidazole from histidine residues located in different positions in the primary protein structures. However, the motifs with histidine in the first three N-terminal positions (His¹, His², and His³) show unique Cu(II)-binding properties, such as availability from the surface of the protein, high flexibility, and high Cu(II) exchangeability with other ligands. It makes such sequences beneficial for the fast exchange of Cu(II) between ligands. Furthermore, sequences with His¹ and His², thus, non-saturating the Cu(II) coordination sphere, are redox-active and may play a role in Cu(II) reduction to Cu(I). All human protein sequences deposited in UniProt Knowledgebase were browsed for those containing His¹, His², or His³. Proteolytically modified sequences (with the removal of a propeptide or Met residue) were taken for the analysis. Finally, the sequences were sorted out according to the subcellular localization of the proteins to match the respective sequences with the probability of interaction with divalent copper.     

IGFs and IGF-Binding Proteins in the Synovial Fluid of Patients with Rheumatoid Arthritis and Osteoarthritis

International Journal of Peptide Research and Therapeutics - The progressive damage of human articular cartilage is associated with loss of integrity of its extracellular matrix components. Their...     

Innate immunity orchestrates the mobilization and homing of hematopoietic stem/progenitor cells by engaging purinergic signaling—an update

Purinergic Signalling - Bone marrow (BM) as an active hematopoietic organ is highly sensitive to changes in body microenvironments and responds to external physical stimuli from the surrounding...