Measurements identify attachment process of E. coli eating bacteria

Joe Naiman

Village News Reporter

Control of E. coli bacteria could possibly be accomplished by the introduction of predatory bacteria such as Bdellovibrio bacteriovorus, and the Aug. 1-5 SPIE optical science conference at the San Diego Convention Center included a presentation by State University of New York at New Paltz associate professor Catherine Herne on microscopy measurements of B. bacteriovorus attaching to and devouring Escherichia coli.

The Aug. 3 presentation Measuring Bacterial Attachment Forces addressed the interaction between Bdello and E. coli. Herne, who teaches in the Department of Physics at SUNY New Paltz, collaborated with Max Hartman and Carrie Smithing from the SUNY New Paltz physics department and Megan Ferguson from the Department of Chemistry at SUNY New Paltz.

Bdellovibrio bacteriovorus is an antimicrobial agent. The potential benefits of B. bacteriovorus include clearing environmental pathogens, antibacterial treatment and periodontal health. Bdellovibrio bacteriovorus preys on other bacteria.

“When it finds a prey its prey is pretty defenseless,” Herne said.

“The bacteria finds a prey, burrows into it,” Herne said. “In the first 10 minutes it will attach to its prey and start to burrow in.”

The B. bacteriovorus then replicates. “It bursts out after three or four hours,” Herne said.

Although B. bacteriovorus is only between 0.5 microns and 1.0 microns long, it can travel up to approximately 200 microns (one-fifth of a millimeter) per second. “It swims really fast,” Herne said.

The E. coli bacteria length is usually between 1 and 2 microns. The interaction between B. bacteriovorus and E. coli has previously been measured using atomic force microscopy.

The term “optical tweezers” refers to an instrumentation system with a focused laser beam which can hold and move a microscopic object. “What we are focusing on is the first attachment process,” Herne said.

Many bacteria - including B. bacteriovorus - have appendages known as type IV pili. The B. bacteriovorus attaches to its prey through the pili. The SUNY New Paltz work traps a B. bacteriovorus cell in a single trap, moves that cell close to a surface with E. coli, and moves the B. bacteriovorus cell away from the surface after increasingly long periods of time.

“We know the attachment time,” Herne said. “The question we’re asking is does the Bdello stay with the E. coli or does the Bdello stay in the trap.”

The attachment force was measured. “We do this multiple times with different time spacing,” Herne said.

The pili usually ruptures at forces between 50 and 200 piconewtons with the majority of the measured ruptures occurring at approximately 100 piconewtons.

Joe Naiman can be reached by email at [email protected].