Bacillus anthracis physiology and genetics

Koehler, Theresa M.

doi:10.1016/j.mam.2009.07.004

Cited by 133 publications

(126 citation statements)

References 138 publications

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“…This decision is based on the growth characteristics of strains included in test development and evaluation. The growth rates of the strains used in this study were similar to previously reported doubling times for B. anthracis (22) and B. pseudomallei (16) growing in rich media at similar temperatures. The growth rate for Y. pestis strain DSJB001 was comparable to the previously reported rate for Y. pestis, although the doubling time for strain A1122 was more rapid (23).…”

Section: Discussionsupporting

confidence: 86%

Rapid Antimicrobial Susceptibility Testing of Bacillus anthracis, Yersinia pestis, and Burkholderia pseudomallei by Use of Laser Light Scattering Technology

et al. 2016

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Rapid methods to determine antimicrobial susceptibility would assist in the timely distribution of effective treatment or postexposure prophylaxis in the aftermath of the release of bacterial biothreat agents such as Bacillus anthracis, Yersinia pestis, or Burkholderia pseudomallei. Conventional susceptibility tests require 16 to 48 h of incubation, depending on the bacterial species. We evaluated a method that is based on laser light scattering technology that measures cell density in real time. We determined that it has the ability to rapidly differentiate between growth (resistant) and no growth (susceptible) of several bacterial threat agents in the presence of clinically relevant antimicrobials. Results were available in <4 h for B. anthracis and <6 h for Y. pestis and B. pseudomallei. One exception was B. pseudomallei in the presence of ceftazidime, which required >10 h of incubation. Use of laser scattering technology decreased the time required to determine antimicrobial susceptibility by 50% to 75% for B. anthracis, Y. pestis, and B. pseudomallei compared to conventional methods. In the event of a deliberate release of or accidental exposure to potential bacterial agents of bioterrorism, determining phenotypic susceptibility to antimicrobials is essential for the selection of effective treatment or postexposure prophylaxis (1). Several methods can be used to determine antimicrobial susceptibility, although the gold standard is the conventional broth microdilution (BMD) method. Based on guidelines from the Clinical and Laboratory Standards Institute (CLSI), this method requires an incubation period of 16 to 20 h for Bacillus anthracis and Burkholderia pseudomallei and 24 to 48 h for Yersinia pestis (2). Other commonly used methods for antimicrobial susceptibility testing (AST) of bacteria are agar dilution, Etest, and disc diffusion. There are several peer-reviewed publications that describe the use of these methods for biothreat (BT) bacteria (3-6). However, these alternative methods require incubation times that are similar to those of the BMD test since visible growth is required for interpretation of results (3-6).Rapid methods to determine antimicrobial susceptibility of BT bacteria are highly desirable to reduce the morbidity and mortality associated with the diseases caused by B. anthracis (anthrax), B. pseudomallei (melioidosis), and Y. pestis (plague). While genetic susceptibility tests have been described as more rapid than conventional methods, the genetic approaches have disadvantages since the presence of a resistant gene or a mutation does not necessarily result in phenotypic resistance (7). For example, B. anthracis has two ␤-lactamase genes, bla1 and bla2, on the chromosome, but this species is rarely resistant to ␤-lactam antimicrobials such as penicillin. Phenotypic susceptibility of most strains is due to a mutation(s) in the regulatory genes that prevent induction of ␤-lactamase gene expression (8, 9). Another issue associated with the use of genetic analysis to predict antimicrobial ...

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Section: Discussionsupporting

confidence: 86%

Rapid Antimicrobial Susceptibility Testing of Bacillus anthracis, Yersinia pestis, and Burkholderia pseudomallei by Use of Laser Light Scattering Technology

et al. 2016

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“…The spore-forming bacterium B. anthracis is the cause of the acute and often lethal disease anthrax (45). B. thuringiensis is well known as a source of insecticidal proteins and is therefore employed in agriculture (36).…”

Section: Resultsmentioning

confidence: 99%

Resistance Phenotypes Mediated by Aminoacyl-Phosphatidylglycerol Synthases

et al. 2012

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The specific aminoacylation of the phospholipid phosphatidylglycerol (PG) with alanine or with lysine catalyzed by aminoacylphosphatidylglycerol synthases (aaPGS) was shown to render various organisms less susceptible to antibacterial agents. This study makes use of Pseudomonas aeruginosa chimeric mutant strains producing lysyl-phosphatidylglycerol (L-PG) instead of the naturally occurring alanyl-phosphatidylglycerol (A-PG) to study the resulting impact on bacterial resistance. Consequences of such artificial phospholipid composition were studied in the presence of an overall of seven antimicrobials (␤-lactams, a lipopeptide antibiotic, cationic antimicrobial peptides [CAMPs]) to quantitatively assess the effect of A-PG substitution (with L-PG, L-PG and A-PG, increased A-PG levels). For the employed Gram-negative P. aeruginosa model system, an exclusive charge repulsion mechanism does not explain the attenuated antimicrobial susceptibility due to PG modification. Additionally, the specificity of nine orthologous aaPGS enzymes was experimentally determined. The newly characterized protein sequences allowed for the establishment of a significant group of A-PG synthase sequences which were bioinformatically compared to the related group of L-PG synthesizing enzymes. The analysis revealed a diverse origin for the evolution of A-PG and L-PG synthases, as the specificity of an individual enzyme is not reflected in terms of a characteristic sequence motif. This finding is relevant for future development of potential aaPGS inhibitors.

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“…The major virulence gene regulator of Bacillus anthracis, AtxA, positively affects transcription of the anthrax toxin and capsule biosynthetic genes (11,12,14,22,27,31,44,57,58). AtxA has motifs associated with DNA binding, phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) regulation domains (PRDs), and multimerization (24,26,56,58), but the precise molecular mechanism by which AtxA impacts transcription is not clear. Nevertheless, steady-state levels of AtxA are critical for optimal transcription of the anthrax toxin and capsule genes, and an atxA-null mutant is avirulent in a murine model for anthrax (8, 10-12, 23, 58).…”

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confidence: 99%

cis -Acting Elements That Control Expression of the Master Virulence Regulatory Gene atxA in Bacillus anthracis

et al. 2012

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Transcription of the Bacillus anthracis structural genes for the anthrax toxin proteins and biosynthetic operon for capsule is positively regulated by AtxA, a transcription regulator with unique properties. Consistent with the role of atxA in virulence factor expression, a B. anthracis atxA-null mutant is avirulent in a murine model for anthrax. In culture, multiple signals impact atxA transcript levels, and the timing and steady-state level of atxA expression are critical for optimal toxin and capsule synthesis. Despite the apparent complex control of atxA transcription, only one trans-acting protein, the transition state regulator AbrB, has been demonstrated to interact directly with the atxA promoter. Here we employ 5= and 3= deletion analysis and sitedirected mutagenesis of the atxA control region to demonstrate that atxA transcription from the major start site P1 is dependent upon a consensus sequence for the housekeeping sigma factor SigA and an A؉T-rich upstream element for RNA polymerase. We also show that an additional trans-acting protein(s) binds specifically to atxA promoter sequences located between ؊13 and ؉36 relative to P1 and negatively impacts transcription. Deletion of this region increases promoter activity up to 15-fold. Site-directed mutagenesis of a 9-bp palindromic sequence within the region prevents binding of the trans-acting protein(s), increasing promoter activity 7-fold and resulting in a corresponding increase in AtxA and anthrax toxin production. Notably, an atxA promoter mutant that produced elevated levels of AtxA and toxin proteins during culture was unaffected for virulence in a murine model for anthrax.

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Bacillus anthracis physiology and genetics

Cited by 133 publications

References 138 publications

Rapid Antimicrobial Susceptibility Testing of Bacillus anthracis, Yersinia pestis, and Burkholderia pseudomallei by Use of Laser Light Scattering Technology

Rapid Antimicrobial Susceptibility Testing of Bacillus anthracis, Yersinia pestis, and Burkholderia pseudomallei by Use of Laser Light Scattering Technology

Resistance Phenotypes Mediated by Aminoacyl-Phosphatidylglycerol Synthases

cis -Acting Elements That Control Expression of the Master Virulence Regulatory Gene atxA in Bacillus anthracis

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