Genetic Diversity of Bacillus sporothermodurans Isolated in Africa and Europe

Introduction: Bacillus sporothermodurans is a psychrotolerant, mesophilic, aerobic endospore-forming bacteria which may produce extreme heat-resistant spores. Their spores have been found to be more resistant than other heat resistant spores at temperatures above 130°C with D₁₄₀ ranging from 3.4–7.9 s. The heat resistance in some strains is as a result of a heat resistant clone (HRS clone). The spores may contaminate milk and milk products and some processed soup products and their presence in foods may cause spoilage and contravenes good manufacturing practice.  However, presence of the heat resistant clone may be location or matrix specific hence the importance to access the genetic relatedness of isolated strains isolated from different locations and food matrices.

Purpose: To confirm the presence of heat resistant clones of strains of Bacillus sporothermodurans and to determine their relatedness through GTG₅ fingerprinting.

Methods: Genomic DNA was extracted from bacterial cells grown on brain heart infusion agar and amplified through PCR using the BSPO and HRS primers, to confirm B. sporothermodurans and heat resistant clones, respectively. The GTG5 fingerprinting technique was performed using the GTGGTGGTGGTGGTG primer. Phylogenetic analysis was preformed to compare relatedness of strains isolated in Africa and Europe.

Results: In the present study approximately 37.5% of B. sporothermodurans strains confirmed were positive for the HRS clone. The South African strains clustered away from each other but still showed between 85 and 93% similarity level. Some strains isolated from different matrices in Europe clustered together; generally exhibiting a 95 % similarity level.

Significance: There is gradual increase in the prevalence of B. sporothermodurans in especially milk products. Identifying genetic differences would help inform technologies on the inactivation of B. sporothermodurans and to subsequently reduce spoilage and economic losses in the dairy industry.