A mycobacteriophage Ms6 strong promoter region (P lys ) was isolated by using transcriptional fusions with the lacZ reporter gene. Two tandem 70 -like promoter sequences (P1 and P2) were found in this region. DNA sequencing of the promoter downstream region revealed a 214-bp leader sequence followed by five adjacent coding regions of 231 bp (ORF1), 1,152 bp (ORF2), 996 bp (ORF3), 231 bp (ORF4), and 372 (ORF5). ORF1 has the potential to encode a 77-amino-acid protein which revealed similarity to mycobacteriophage TM4 gp90, a predicted protein with unknown function. ORF2 encodes a 384-amino-acid protein which is related to several bacteriophage amidases. This protein induced cell lysis upon addition of chloroform, confirming its mureinolytic activity. ORF3 encodes a 332-amino-acid protein which is related to TM4 gp30, a protein with sequence similarity to amidases. ORF4 encodes a 77-amino-acid holin-like protein with significant similarity to the holin of Lactococcus lactis r1t bacteriophage. ORF5 encodes a 124-amino-acid protein which is related to mycobacteriophage L5 gp30, a protein with unknown function. These data indicate that the promoter region P lys drives the transcription of the Ms6 lysis genes. An intrinsic transcription termination signal was identified in the leader sequence. Experiments using lacZ fusions showed that ␤-galactosidase synthesis is inhibited when this transcription termination signal is present in the leader sequence. In conclusion, mycobacteriophage Ms6 cell lysis genes are expressed by their own promoter region, independently of virion structure and assembly protein genes. Moreover, an antitermination mechanism might be involved in their transcription regulation. Double-stranded DNA (dsDNA) bacteriophages synthesize a mureinolytic enzyme, known as an endolysin, during late gene expression of the replication cycle, enabling the release of phage progeny. Phage-encoded lysins have several kinds of mureinolytic activities directed against the covalent linkages that maintain the cell wall integrity: (i) glycosylase and transglycosylase activity, targeting the glycosidic linkages; (ii) Nacetylmuramoyl-L-alanine amidase activity; and (iii) endopeptidase activity targeting the oligopeptide cross-links (17, 31).To degrade the cell wall of the host, a second factor, designated holin, is required. The holin is a hydrophobic membrane protein that forms pores or lesions in the cell membrane through which the murein hydrolase is released to the periplasm and gains access to the peptidoglycan substrate. Such a dual-component lysis system has recently been discovered in many bacteriophages of both gram-negative and grampositive bacteria (15,17,22,25,27,32). The synthesis of the bacteriophage holin (protein S) is tightly controlled at the transcriptional, translational, and posttranslational levels because it determines the time of lysis. In phage , the lysis genes are the first genes of the late operon, which also encodes the structural proteins of the phage particle. Transcription of the cell lysis...

Abstract-One of the key benefits of using intrusion-tolerant systems is the possibility of ensuring correct behavior in the presence of attacks and intrusions. These security gains are directly dependent on the components exhibiting failure diversity. To what extent failure diversity is observed in practical deployment depends on how diverse are the components that constitute the system. In this paper we present a study with operating systems (OS) vulnerability data from the NIST National Vulnerability Database. We have analyzed the vulnerabilities of 11 different OSes over a period of roughly 15 years, to check how many of these vulnerabilities occur in more than one OS. We found this number to be low for several combinations of OSes. Hence, our analysis provides a strong indication that building a system with diverse OSes may be a useful technique to improve its intrusion tolerance capabilities.

One of the key benefits of using intrusion-tolerant systems is the possibility of ensuring correct behavior in the presence of attacks and intrusions. These security gains are directly dependent on the components exhibiting failure diversity. To what extent failure diversity is observed in practical deployment depends on how diverse are the components that constitute the system. In this paper, we present a study with operating system's (OS's) vulnerability data from the NIST National Vulnerability Database (NVD). We have analyzed the vulnerabilities of 11 different OSs over a period of 18 years, to check how many of these vulnerabilities occur in more than one OS. We found this number to be low for several combinations of OSs. Hence, although there are a few caveats on the use of NVD data to support definitive conclusions, our analysis shows that by selecting appropriate OSs, one can preclude (or reduce substantially) common vulnerabilities from occurring in the replicas of the intrusion-tolerant system. ‡ A specific type of bug, regarding security, is usually called a vulnerability. Once a vulnerability is discovered, it can be maliciously exploited. If the exploited vulnerability leads to the software system deviating from its intended requirements or security policy, then the system is deemed to have failed. The system can fail on a single or combination of the following security properties: confidentiality, availability, and integrity. In the rest of this paper, we will use the terms fault and vulnerability interchangeably. 736 M. GARCIA ET AL.faulty. To satisfy this provision, system components need to exhibit failure diversity, that is, the probability that a majority of components fail at the same time should be negligible (or else the system as a whole will fail). This failure diversity assumption is easier to justify when one is concerned with accidental faults, such as power outages, disk crashes, or message corruption due to noise in communication lines. However, for design faults of any kind, including security vulnerabilities, the assumption is difficult to guarantee. If multiple components contain the same vulnerabilities, then a single attack can compromise all of them, therefore defeating the aim of intrusion tolerance system in providing improved security.To reduce the probability of vulnerabilities existing in more than one component, design diversity [3] can be employed: each component uses diverse software to perform the same functions, with the expectation that the differences will reduce the occurrence of common vulnerabilities, that is, vulnerabilities that exist in more than one system. Byzantine fault-tolerant replication often suggest the use of replica diversity (e.g., [4][5][6][7][8][9][10][11][12][13][14]), under the (sometimes implicit) assumption that they exhibit failure diversity. In this work, we want to empirically assess to what extent failure diversity is exhibited in a complex category of OTS software, namely operating systems (OSs).We focus our study on OS because they are a...

This document defines an architecture framework and functional requirements for transport of signaling information over IP.

A system for the controlled expression of a foreign gene in cultured tobacco cells (Nicotiana tabacum, BY2) by temperature shift was constructed. A 925-base-pair (bp) DNA fragment containing the 5'-flanking region of a low-molecular-mass heat-shock protein gene (HSP18.2) of Arabidopsis thaliana was inserted upstream of the beta-glucuronidase reporter gene (GUS). The resulting HSP18.2-GUS construct was introduced into BY2 cells by electroporation or Agrobacterium-mediated transformation. Transient expression of the HSP18.2 promoter in protoplasts was very low regardless of the heat shock. Although expression of the HSP18.2-GUS chimeric gene in the stable transformants of BY2 was hardly detected in culture at 25 degrees C, the expression increased rapidly on the transcriptional level when the incubation temperature was shifted to 35-37 degrees C. The optimal temperature for heat-shock induction was 37 degrees C. After a 2-h incubation at 37 degrees C, GUS activity was about 1000-fold greater than that before heat shock. The amount of GUS mRNA was maximum 2 h after heat shock, and then decreased gradually.

A system for the controlled expression of a foreign gene in cultured tobacco cells (Nicotiana tabacum, BY2) by temperature shift was constructed. A 925-base-pair (bp) DNA fragment containing the 5'-flanking region of a low-molecular-mass heat-shock protein gene (HSP18.2) of Arabidopsis thaliana was inserted upstream of the beta-glucuronidase reporter gene (GUS). The resulting HSP18.2-GUS construct was introduced into BY2 cells by electroporation or Agrobacterium-mediated transformation. Transient expression of the HSP18.2 promoter in protoplasts was very low regardless of the heat shock. Although expression of the HSP18.2-GUS chimeric gene in the stable transformants of BY2 was hardly detected in culture at 25 degrees C, the expression increased rapidly on the transcriptional level when the incubation temperature was shifted to 35-37 degrees C. The optimal temperature for heat-shock induction was 37 degrees C. After a 2-h incubation at 37 degrees C, GUS activity was about 1000-fold greater than that before heat shock. The amount of GUS mRNA was maximum 2 h after heat shock, and then decreased gradually.

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