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Molecular and Genomic Characterization of PFAB2: A Non-virulent Bacillus anthracis Strain Isolated from an Indian Hot Spring

[ Vol. 20 , Issue. 7 ]

Author(s):

Aparna Banerjee, Vikas K. Somani, Priyanka Chakraborty, Rakesh Bhatnagar, Rajeev K. Varshney, Alex Echeverría-Vega, Sara Cuadros-Orellana and Rajib Bandopadhyay*   Pages 491 - 507 ( 17 )

Abstract:


Background: Thermophilic bacilli in both aerobic or facultative anaerobic forms have been isolated for over a hundred years from different mesophilic or thermophilic environments as they are potential source of bioactive secondary metabolites. But the taxonomic resolution in the Bacillus genus at species or at strain level is very challenging for the insufficient divergence of the 16S rRNA genes. One such recurring problem is among Bacillus anthracis, B. cereus and B. thuringiensis. The disease-causing B. anthracis strains have their characteristic virulence factors coded in two wellknown plasmids, namely pXO1 (toxin genes) and pXO2 (capsule genes).

Objective: The present study aimed at the molecular and genomic characterization of a recently reported thermophilic and environmental isolate of B. anthracis, strain PFAB2.

Methods: We performed comparative genomics between the PFAB2 genome and different strains of B. anthracis, along with closely related B. cereus strains.

Results: The pangenomic analysis suggests that the PFAB2 genome harbors no complete prophage genes. Cluster analysis of Bray-Kurtis similarity resemblance matrix revealed that gene content of PFAB2 is more closely related to other environmental strains of B. anthracis. The secretome analysis and the in vitro and in vivo pathogenesis experiments corroborate the avirulent phenotype of this strain. The most probable explanation for this phenotype is the apparent absence of plasmids harboring genes for capsule biosynthesis and toxins secretion in the draft genome. Additional features of PFAB2 are good spore-forming and germinating capabilities and rapid replication ability.

Conclusion: The high replication rate in a wide range of temperatures and culture media, the nonpathogenicity, the good spore forming capability and its genomic similarity to the Ames strain together make PFAB2 an interesting model strain for the study of the pathogenic evolution of B. anthracis.

Keywords:

Bacillus anthracis, avirulence, comparative genomics, pangenomics, pathogenesis, secretome analysis.

Affiliation:

UGC-Center of Advanced Study, Department of Botany, The University of Burdwan, Golapbag, Burdwan, West Bengal, Molecular Biology and Genetic Engineering Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi 110067, UGC-Center of Advanced Study, Department of Botany, The University of Burdwan, Golapbag, Burdwan, West Bengal, Molecular Biology and Genetic Engineering Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi 110067, Centre of Excellence in Genomics, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Centro de Investigación en Estudios Avanzados del Maule (CIEAM), Vicerrectoría de Investigación y Posgrado, Universidad Católica del Maule, Talca, Facultad de Ciencias Agrarias y Forestales, Centro de Biotecnología de los Recursos Naturales, Universidad Católica del Maule, Talca, UGC-Center of Advanced Study, Department of Botany, The University of Burdwan, Golapbag, Burdwan, West Bengal

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