Biomedical subjects

Adam Driks

Publications and source records attributed to Adam Driks.

6 recordsLinked to original sources

PubMed2004

Role of commensal bacteria in development of gut-associated lymphoid tissues and preimmune antibody repertoire.

Intestinal bacteria are required for development of gut-associated lymphoid tissues (GALT), which mediate a variety of host immune functions, such as mucosal immunity and oral tolerance. In rabbits, the intestinal microflora are also required for developing the preimmune Ab repertoire by promoting somatic diversification of Ig genes in B cells that have migrated to GALT. We studied the mechanism of bacteria-induced GALT development. Bacteria were introduced into rabbits in which the appendix had been rendered germfree by microsurgery (we refer to these rabbits as germfree-appendix rabbits). We then identified specific members of the intestinal flora that promote GALT development. The combination of Bacteroides fragilis and Bacillus subtilis consistently promoted GALT development and led to development of the preimmune Ab repertoire, as shown by an increase in somatic diversification of VDJ-C micro genes in appendix B cells. Neither species alone consistently induced GALT development, nor did Clostridium subterminale, Escherichia coli, or Staphylococcus epidermidis. B. fragilis, which by itself is immunogenic, did not promote GALT development; hence, GALT development in rabbits does not appear to be the result of an Ag-specific immune response. To identify bacterial pathways required for GALT development, we introduced B. fragilis along with stress-response mutants of B. subtilis into germfree-appendix rabbits. We identified two Spo0A-controlled stress responses, sporulation and secretion of the protein YqxM, which are required for GALT development. We conclude that specific members of the commensal, intestinal flora drive GALT development through a specific subset of stress responses.

Animals↗

PubMed2003

The dynamic spore.

Explore the source record for details and available documents.

Bacillus thuringiensis↗

PubMed2003

Morphogenesis of bacillus spore surfaces.

Spores produced by bacilli are encased in a proteinaceous multilayered coat and, in some species (including Bacillus anthracis), further surrounded by a glycoprotein-containing exosporium. To characterize bacillus spore surface morphology and to identify proteins that direct formation of coat surface features, we used atomic-force microscopy (AFM) to image the surfaces of wild-type and mutant spores of Bacillus subtilis, as well as the spore surfaces of Bacillus cereus 569 and the Sterne strain of Bacillus anthracis. This analysis revealed that the coat surfaces in these strains are populated by a series of bumps ranging between 7 and 40 nm in diameter, depending on the species. Furthermore, a series of ridges encircled the spore, most of which were oriented along the long axis of the spore. The structures of these ridges differ sufficiently between species to permit species-specific identification. We propose that ridges are formed early in spore formation, when the spore volume likely decreases, and that when the spore swells during germination the ridges unfold. AFM analysis of a set of B. subtilis coat protein gene mutants revealed three coat proteins with roles in coat surface morphology: CotA, CotB, and CotE. Our data indicate novel roles for CotA and CotB in ridge pattern formation. Taken together, these results are consistent with the view that the coat is not inert. Rather, the coat is a dynamic structure that accommodates changes in spore volume.

Bacillus↗

PubMed2003

Proteomic analysis of the spore coats of Bacillus subtilis and Bacillus anthracis.

The outermost proteinaceous layer of bacterial spores, called the coat, is critical for spore survival, germination, and, for pathogenic spores, disease. To identify novel spore coat proteins, we have carried out a preliminary proteomic analysis of Bacillus subtilis and Bacillus anthracis spores, using a combination of standard sodium dodecyl sulfate-polyacrylamide gel electrophoresis separation and improved two-dimensional electrophoretic separations, followed by matrix-assisted laser desorption ionization-time of flight and/or dual mass spectrometry. We identified 38 B. subtilis spore proteins, 12 of which are known coat proteins. We propose that, of the novel proteins, YtaA, YvdP, and YnzH are bona fide coat proteins, and we have renamed them CotI, CotQ, and CotU, respectively. In addition, we initiated a study of coat proteins in B. anthracis and identified 11 spore proteins, 6 of which are candidate coat or exosporium proteins. We also queried the unfinished B. anthracis genome for potential coat proteins. Our analysis suggests that the B. subtilis and B. anthracis coats have roughly similar numbers of proteins and that a core group of coat protein species is shared between these organisms, including the major morphogenetic proteins. Nonetheless, a significant number of coat proteins are probably unique to each species. These results should accelerate efforts to develop B. anthracis detection methods and understand the ecological role of the coat.

Bacillus anthracis↗

PubMed2002

Maximum shields: the assembly and function of the bacterial spore coat.

Spores produced by bacilli and clostridia are surrounded by a multilayered protein shell called the coat. As the armor-like appearance of the coat suggests, this structure, along with others within the spore, confers the remarkable resistance properties that make Bacillus anthracis spores such potent biological weapons. Here, I review recent studies of coat assembly in the model organism Bacillus subtilis, and explore the implications of these findings for coat assembly in B. anthracis and for defense against biological weapons.

Bacillus anthracis↗

PubMed2002

FtsA mutants of Bacillus subtilis impaired in sporulation.

Spore formation in Bacillus subtilis involves a switch in the site of cell division from the midcell to a polar position. Both medial division and polar division are mediated in part by the actin-like, cytokinetic protein FtsA. We report the isolation of an FtsA mutant (FtsA(D265G)) that is defective in sporulation but is apparently unimpaired in vegetative growth. Sporulating cells of the mutant reach the stage of asymmetric division but are partially blocked in the subsequent morphological process of engulfment. As judged by fluorescence microscopy and electron microscopy, the FtsA(D265G) mutant produces normal-looking medial septa but immature (abnormally thin) polar septa. The mutant was unimpaired in transcription under the control of Spo0A, the master regulator for entry into sporulation, but was defective in transcription under the control of sigmaF, a regulatory protein whose activation is known to depend on polar division. An amino acid substitution at a residue (Y264) adjacent to D265 also caused a defect in sporulation. D265 and Y264 are conserved among endospore-forming bacteria, raising the possibility that these residues are involved in a sporulation-specific protein interaction that facilitates maturation of the sporulation septum and the activation of sigmaF.

Amino Acid Sequence↗