A polypeptide bacteriophage receptor: modified cell wall protein subunits in bacteriophage-resistant mutants of Bacillus sphaericus strain P-1

Bacillus sphaericus strain P-1 has previously been shown to have a tetragonally arrayed (T layer) protein which forms the outer layer of the cell wall. The T layer was quantitatively extracted from whole cells by 6 M urea, and the T layer subunits were purified by electrophoresis of the extracts on acrylamide gels containing 0.1% sodium dodecyl sulfate or 6 M urea. Using ethylene diacrylate cross-linked gels, the T layer was found to make up 16% of the total cellular protein. A virulent bacteriophage which is inactivated by purified T layer was isolated from soil. Twenty-four phage-resistant mutants were isolated, of which 17 had T layer subunits of increased mobility on sodium dodecyl sulfate acrylamide gels. No mutants devoid of T layer were found. Mutants were grouped into six classes according to the molecular weight of their T layer subunits. These ranged from that of the wild type, 150,000 down to 86,000. Two mutants from different classes were examined in detail. Cells of the mutant strains did not adsorb phage nor did cell walls isolated from these mutants inactivate phage. The amino acid composition of the T layers from mutants differed little from that of the wild-type T layer

A survey of defense mechanisms against distributed denial of service (DDOS) flooding attacks

Distributed Denial of Service (DDoS) flooding attacks are one of the biggest concerns for security professionals. DDoS flooding attacks are typically explicit attempts to disrupt legitimate users' access to services. Attackers usually gain access to a large number of computers by exploiting their vulnerabilities to set up attack armies (i.e., Botnets). Once an attack army has been set up, an attacker can invoke a coordinated, large-scale attack against one or more targets. Developing a comprehensive defense mechanism against identified and anticipated DDoS flooding attacks is a desired goal of the intrusion detection and prevention research community. However, the development of such a mechanism requires a comprehensive understanding of the problem and the techniques that have been used thus far in preventing, detecting, and responding to various DDoS flooding attacks. In this paper, we explore the scope of the DDoS flooding attack problem and attempts to combat it. We categorize the DDoS flooding attacks and classify existing countermeasures based on where and when they prevent, detect, and respond to the DDoS flooding attacks. Moreover, we highlight the need for a comprehensive distributed and collaborative defense approach. Our primary intention for this work is to stimulate the research community into developing creative, effective, efficient, and comprehensive prevention, detection, and response mechanisms that address the DDoS flooding problem before, during and after an actual attack. © 1998-2012 IEEE

Conditional mutants of Staphylococcus aureus defective in cell wall precursor synthesis

Temperature-sensitive (ts) mutants of Staphylococcus aureus with defective cell wall biosynthesis have been differentiated from other ts mutants by their ability to grow at the restrictive temperature (43 C) in the presence of 1 m NaCl. Under all conditions they possess normal colonial and cellular morphology at the level of resolution of the light microscope and are, therefore, not protoplasts. However, differences between mutant and wild-type cells can be seen by scanning electron microscopy. Many of the mutants contained concentrations of nucleotide precursors of peptidoglycan synthesis in excess of those present in wild-type cells, at both 30 and 43 C. The types of peptidoglycan precursors accumulated by six of the mutants have been determined, and specific enzymatic defects in three of these have been identified

Elastic fibers: The missing key to improve engineering concepts for reconstruction of the Nucleus Pulposus in the intervertebral disc.

The increasing prevalence of low back pain has imposed a heavy economic burden on global healthcare systems. Intense research activities have been performed for the regeneration of the Nucleus Pulposus (NP) of the IVD; however, tissue-engineered scaffolds have failed to capture the multi-scale structural hierarchy of the native tissue. The current study revealed for the first time, that elastic fibers form a network across the NP consisting of straight and thick parallel fibers that were interconnected by wavy fine fibers and strands. Both straight fibers and twisted strands were regularly merged or branched to form a fine elastic network across the NP. As a key structural feature, ultrathin (53 ± 7 nm), thin (215 ± 20 nm), and thick (890 ± 12 nm) elastic fibers were observed in the NP. While our quantitative analysis for measurement of the thickness of elastic fibers revealed no significant differences (p < 0.633), the preferential orientation of fibers was found to be significantly different (p < 0.001) across the NP. The distribution of orientation for the elastic fibers in the NP represented one major organized angle of orientation except for the central NP. We found that the distribution of elastic fibers in the central NP was different from those located in the peripheral regions representing two symmetrically organized major peaks (±45⁰). No significant differences in the maximum fiber count at the major angles of orientation (±45⁰) were observed for both peripheral (p = 0.427) and central NP (p = 0.788). Based on these new findings a structural model for the elastic fibers in the NP was proposed. The geometrical presentation, along with the distribution of elastic fibers orientation, resulting from the present study identifies the ultrastructural organization of elastic fibers in the NP important towards understanding their mechanical role which is still under investigation. Given the results of this new geometrical analysis, more-accurate multiscale finite element models can now be developed, which will provide new insights into the mechanobiology of the IVD. In addition, the results of this study can potentially be used for the fabrication of bio-inspired tissue-engineered scaffolds and IVD models to truly capture the multi-scale structural hierarchy of IVDs. STATEMENT OF SIGNIFICANCE: Visualization of elastic fibers in the nucleus of the intervertebral disk under high magnification was not reported before. The present research utilized extracellular matrix partial digestion to address significant gaps in understanding of nucleus microstructure that can potentially be used for the fabrication of bio-inspired tissue-engineered scaffolds and disk models to truly capture the multi-scale structural hierarchy of discs

Inhibition of messenger ribonucleic acid synthesis in Escherichia coli by thiolutin

Thiolutin, at concentrations of 5 to 40 mug/ml, inhibited the induced synthesis of beta-galactosidase in Escherichia coli CA8000. Thiolutin had no effect on the rate of in vitro hydrolysis of o-nitrophenyl-beta-d-galactoside by purified beta-galactosidase. Examination of the effects of thiolutin on the kinetics of appearance of beta-galactosidase in the presence and absence of rifampin in induced E. coli cells indicated that thiolutin interferes with the transcription process at the level of elongation of messenger ribonucleic acid (mRNA) chains. The data indicated that, in the presence of thiolutin, beta-galactosidase mRNA has a half-life of 1.6 min and that the first completed beta-galactosidase mRNA is produced about 1.5 min after induction. These data are consistent with estimates of transcription time and messenger half-life obtained by conventional means, and suggest that thiolutin does not affect translation of mRNA or its breakdown in vivo. After removal of thiolutin, cells fully regained the ability to be induced for synthesis of beta-galactosidase within 10 min, but mRNA which was incomplete at the time of thiolutin addition did not subsequently become functional

Advanced Strategies for the Regeneration of Lumbar Disc Annulus Fibrosus.

Damage to the annulus fibrosus (AF), the outer region of the intervertebral disc (IVD), results in an undesirable condition that may accelerate IVD degeneration causing low back pain. Despite intense research interest, attempts to regenerate the IVD have failed so far and no effective strategy has translated into a successful clinical outcome. Of particular significance, the failure of strategies to repair the AF has been a major drawback in the regeneration of IVD and nucleus replacement. It is unlikely to secure regenerative mediators (cells, genes, and biomolecules) and artificial nucleus materials after injection with an unsealed AF, as IVD is exposed to significant load and large deformation during daily activities. The AF defects strongly change the mechanical properties of the IVD and activate catabolic routes that are responsible for accelerating IVD degeneration. Therefore, there is a strong need to develop effective therapeutic strategies to prevent or reconstruct AF damage to support operational IVD regenerative strategies and nucleus replacement. By the way of this review, repair and regenerative strategies for AF reconstruction, their current status, challenges ahead, and future outlooks were discussed

Acid-soluble spore proteins of Bacillus subtilis

Acid-soluble spore proteins (ASSPs) comprise about 5% of the total protein of mature spores of different Bacillus subtilis strains. They consist of three abundant species, alpha, beta, and gamma, four less abundant species, and several minor species, alpha, beta, and gamma make up about 18, 18 and 36%, respectively, of the total ASSPs of strain 168, have molecular weights of 5,900, 5,9000, and 11,000, respectively, and resemble the major (A, C, and B) components of Bacillus megaterium ASSPs in several respects, including sensitivity to a specific B. megaterium spore endopeptidase. However, they have pI\u27s of 6.58, 6.67, and 7.96, all lower than those of any of the B. megaterium ASSPs. Although strains varied in the proportions of different ASSPs, to overall patterns seen on gel electrophoresis are constant. ASSPs are located interior to the cortex, presumably in the spore cytoplasm, and are synthesized during sporulation and degraded during germination