Biological Characterization of the Biocontrol Agent Bacillus amyloliquefaciens CPA-8: The Effect of Temperature, pH and Water Activity on Growth, Susceptibility to Antibiotics and Detection of Enterotoxic Genes

• Published in: Current microbiology 2017-09, Vol.74 (9), p.1089-1099
• Main Authors: Gotor-Vila, Amparo, Teixidó, Neus, Sisquella, María, Torres, Rosario, Usall, Josep
• Format: Article
• Language: English
• Subjects: Amplification; Anti-Bacterial Agents - metabolism; Antibiotics; Bacillus amyloliquefaciens; Bacillus amyloliquefaciens - drug effects; Bacillus amyloliquefaciens - growth & development; Bacillus amyloliquefaciens - metabolism; Bacillus amyloliquefaciens - radiation effects; Bacteria; Bacterial Toxins - genetics; Biological control; Biological effects; Biology; Biomedical and Life Sciences; Biotechnology; Cinnamates - metabolism; Drug Resistance, Bacterial; Enterotoxins - genetics; Foodborne diseases; Gene expression; Genes; Genes, Bacterial; Glucose; Glycerol; Hydrogen-Ion Concentration; Hygromycin; Hygromycin B - analogs & derivatives; Hygromycin B - metabolism; Illnesses; Life Sciences; Microbial Sensitivity Tests; Microbiology; Polymerase chain reaction; Temperature; Temperature effects; Temperature tolerance; Toxicity; Water; Water - chemistry; Water activity
• ISSN: 0343-8651; 1432-0991
• DOI: 10.1007/s00284-017-1289-8

This work focuses on the biological understanding of the biocontrol agent Bacillus amyloliquefaciens CPA-8 in order to accomplish the characterization required in the registration process for the development of a microorganism-based product. The tolerance of CPA-8 to grow under different pH–temperature and water activity ( a w )–temperature conditions was widely demonstrated. Regarding the pH results, optimum growth at the evaluated conditions was observed at 37 °C and pH between 7 and 5. On the contrary, the slowest growth was recorded at 20 °C and pH 4.5. Moreover, the type of solute used to reduce a w had a great influence on the minimum a w at which the bacterium was able to grow. The lowest a w values for CPA-8 growth in media modified with glycerol and glucose were 0.950 and 0.960, respectively. Besides, the lowest a w for CPA-8 growth increased when the temperature decreased to 20 °C, at which CPA-8 was not able to grow at less than 0.990 a w , regardless of the type of solute. Antibiotic susceptibility tests were carried out to determine which antibiotic could affect the behavior of the bacteria and revealed that CPA-8 was clearly resistant to hygromycin. Finally, a PCR amplification assay to detect the presence of enterotoxic genes from Bacillus cereus in CPA-8 was also performed. CPA-8 gave negative results for all the genes tested except for nheA gene, which is not enough for the toxicity expression, suggesting that fruit treated with this antagonist will not be a potential vehicle for foodborne illnesses.