Predation on bacterial pathogens by predatory bacteria of sewage origin: three days prey-predator interactions.

Background: Predatory bacteria are Gram-negative microorganisms that grow within and lyse their bacterial prey. As bacterial predators have potential applications in medicine and biotechnology, the aim of this study was to isolate and identify predators from environmental samples. Therefore, three environmental bacteria belonging to the genus Bdellovibrio were isolated and characterized.

Results: The predator isolates tolerated pH range from 5 to 9 well, and were killed at pH ranges of 2 and 12. They survived best at 4 °C and 29 °C, tolerated to some extent -20 °C and even -80 °C, and were completely killed at 60° C. Furthermore, the host range analysis of the predator isolates was carried out on five Gram-negative (Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Salmonella enterica) and two Gram-positive bacteria (Staphylococcus aureus, and Enterococcus faecalis). The environmental predator isolates inhibited Gram-negative preys more efficiently than Gram-positive. Predators inhibited S. enterica the most (70.48%) and P. aeruginosa the least (3.84%) among Gram-negative preys. The best inhibitory effect among Gram-positive preys was observed for S. aureus (29.83%).

Conclusions: The isolates showed broad-range predation on diverse preys under various pH and temperature conditions. Therefore, the predator isolates identified in here may be suitable choices for controlling the population of Gram-negative bacteria in different fields.