Regulation of Bacillus subtilis macrofiber twist development by D-alanine

Complex spatial distribution and dynamics of an abundant Escherichia coli outer membrane protein, LamB

Advanced techniques for observing protein localization in live bacteria show that the distributions are dynamic. For technical reasons, most such techniques have not been applied to outer membrane proteins in Gram-negative bacteria. We have developed two novel live-cell imaging techniques to observe the surface distribution of LamB, an abundant integral outer membrane protein in Escherichia coli responsible for maltose uptake and for attachment of bacteriophage lambda. Using fluorescently labelled bacteriophage lambda tails, we quantitatively described the spatial distribution and dynamic movement of LamB in the outer membrane. LamB accumulated in spiral patterns. The distribution depended on cell length and changed rapidly. The majority of the protein diffused along spirals extending across the cell body. Tracking single particles, we found that there are two populations of LamB--one shows very restricted diffusion and the other shows greater mobility. The presence of two populations recalls the partitioning of eukaryotic membrane proteins between 'mobile' and 'immobile' populations. In this study, we have demonstrated that LamB moves along the bacterial surface and that these movements are restricted by an underlying dynamic spiral pattern.

A continuum of anionic charge: structures and functions of D-alanyl-teichoic acids in gram-positive bacteria

Teichoic acids (TAs) are major wall and membrane components of most gram-positive bacteria. With few exceptions, they are polymers of glycerol-phosphate or ribitol-phosphate to which are attached glycosyl and D-alanyl ester residues. Wall TA is attached to peptidoglycan via a linkage unit, whereas lipoteichoic acid is attached to glycolipid intercalated in the membrane. Together with peptidoglycan, these polymers make up a polyanionic matrix that functions in (i) cation homeostasis; (ii) trafficking of ions, nutrients, proteins, and antibiotics; (iii) regulation of autolysins; and (iv) presentation of envelope proteins. The esterification of TAs with D-alanyl esters provides a means of modulating the net anionic charge, determining the cationic binding capacity, and displaying cations in the wall. This review addresses the structures and functions of D-alanyl-TAs, the D-alanylation system encoded by the dlt operon, and the roles of TAs in cell growth. The importance of dlt in the physiology of many organisms is illustrated by the variety of mutant phenotypes. In addition, advances in our understanding of D-alanyl ester function in virulence and host-mediated responses have been made possible through targeted mutagenesis of dlt. Studies of the mechanism of D-alanylation have identified two potential targets of antibacterial action and provided possible screening reactions for designing novel agents targeted to D-alanyl-TA synthesis.

Helical growth and the curved shape of Vibrio cholerae

The curved, comma, or bent shape of Vibrio cholerae is attributed to, and explained by, the normal helical growth of the cell. The comma-like shape of V. cholerae is not due to an asymmetrical positioning of peptidoglycan such that some chains of peptidoglycan are placed so they are more spread out on one side of the cell and squeezed together on the other side.

Regulation of Bacillus subtilis macrofiber twist development by D-cycloserine

The effect of D-cycloserine on the establishment of twist states in Bacillus subtilis macrofibers was examined. Macrofibers produced in the presence of the drug differed in twist compared with those produced in its absence. The degree of twist alteration was dependent on the concentration of D-cycloserine in the growth medium. Macrofibers of different twist states representative of the entire twist spectrum from tight left-handedness to tight right-handedness were produced in strains FJ7 and C6D in four different ways: by control of the concentration of D-alanine, magnesium sulfate, or ammonium sulfate in the growth medium or by control of the growth temperature. The structures so produced were used to determine the effect of D-cycloserine on twist establishment starting from different twist states throughout the twist spectrum. In all but one case, twist resulting from growth in the presence of D-cycloserine was further towards the left-hand end of the twist spectrum than that produced in its absence, the exception being the unusual left-handed twist states produced in strains C6D and the closely related RHX 11S at high D-alanine concentrations described here. Studies of the interaction between D-cycloserine and D-alanine both used alone and used independently with the other twist-modifying systems (temperature, magnesium sulfate, and ammonium sulfate) revealed that changes in twist resulting from D-cycloserine were always in the opposite direction from those resulting from D-alanine. This antagonism suggests that the biochemical mechanism of twist regulation involves the metabolism of peptidoglycan, particularly reactions involving D-alanine or the dipeptide D-alanyl-D-alanine. This antagonism suggests that the biochemical mechanism of twist regulation involves the metabolism of peptidoglycan, particularly reactions involving D-alanine or the dipeptide D-alanyl-D-alanine. The possibility that peptidoglycan cross-linking is involved is discussed.